Hill sprints

December 3, 2016

In recent days there has been an interesting discussion on the Fetcheveryone ‘Polarised training’ thread about the value of the short intense hill sprints that Renato Canova and Brad Hudson recommend for distance runners.

Typically these take to form of 6 or more short (6-8 second) intense uphill sprints with adequate recovery between each sprint.  They can be done at either the beginning or end of a training session.   Canova recommends them up to twice a week. I have never done them more frequently than once per week.   Although 6 hill sprints do not add greatly to the training load of a ‘serious’ athlete, I have always been concerned to avoid the risk of excessive stress.   It is more important to maintain good form that promotes optimum muscle fibre recruitment

One of the immediate benefits is a feeling of speed in your legs that can make subsequent fast pace running feel relatively easy.   Some athletes do intense hill sprints in the 24 hours before a race for this purpose.  Although I have not habitually done this, I usually do  ‘bounding’ drills during the taper for a target race to achieve a similar result.  In fact hill sprints are probably safer than bounding drills as they present little risk of injury provided you warm up adequately.

I think that the feeling of ‘having speed in your legs’ is based largely on the sensation of recruiting fast twitch fibres.  However, you might wonder why this is helpful for a long distance runner, since fast twitch fibres are poorly adapted for aerobic metabolism.  I suspect the reason is that fast twitch fibres are good at capturing the energy of impact at footfall as elastic energy.  Provided you have developed the ability to recycle lactate from fast-twitch fibres to slow twitch fibres that can use the lactate as fuel, the fast twitch contractions do not lead to increase in blood acidity.

Non-weight-bearing aerobic cross training

September 11, 2016

All forms of low-impact aerobic cross training provide the opportunity to enhance some aspects of fitness while reducing risk of injury due to lack of the impact at footfall.  As described in my previous post, cross-training that entails weight-bearing enhances endurance of the postural muscles that provide a stable core to support the driving force exerted by the legs.  For this reason, most of my cross-training is weight-bearing.  However under some circumstances, non-weight bearing training is preferable.

If the main goal is recovery, non-weight-bearing cross-training minimises stress on the musculo-skeletal system.    In particular, swimming has been shown to produce more effective recovery than complete rest after heavy training.  It is probable that when swimming the increased blood circulation promotes removal of the debris resulting from the muscle damage during heavy training.   If the goal is maintaining fitness while recovering from injury, avoidance of weight bearing might be essential in the early phase of recovery, and a judicious combination of weight bearing and non-weight-bearing training cross-training subsequently introduced as the injury heals.  Emily Infeld’s log of her training after suffering a hip stress fracture three months before the US Trials for the Rio Olympics is a very informative description of judicious integration of non-weight bearing and weight-bearing cross training.  Finally, non-weight bearing cross training such as cycling or swimming might be preferable simply because these activities are enjoyable and mentally stimulating.

Let us consider several of the most popular forms of non-weight bearing cross training in greater detail:


One of the great virtues of cycling is that with a few precautions and a gradual build up, you can cycle for many hours with minimal risk of injury.  It also offers great opportunities for an enjoyable alternative to running.  It is therefore a great way to develop cardiac output and endurance.   However, a crucial question is whether or not it is a good way to build up the leg muscles that are most important for running.   Like all other forms of low impact cross training, it does not condition the muscles to cope with the eccentric contractions at footfall.  Nonetheless, as in running, the main generators of power in cycling are the extensors of hip and knee, with a contribution form calf muscles in the final stage of the down-stroke.  At low and moderate intensities cycling has the potential for developing important features such as fat burning, capillary supply and the ability to shuttle lactate between type 2 and type 1 fibres, in these muscles, while at high intensity it can enhance their power.

However, the notorious challenge of the transition from bike to run in the triathlon raises the possibility that cycling might use these muscles in a different manner that is actually antagonistic to running.   Although I am not a triathlete, for more than sixty years the bike has been my major means of transport for local travel, including travelling home from work before an  evening training session and even more critically, for travelling to and from races. My experience leaves little doubt that in the short term, cycling does impede running.  What causes this and does it have implications for longer term influence of  cycling on running?  Unfortunately, I have never been able to get a convincing answer to this question in my discussions with triathletes, but I have developed some speculations based on my own experiences and on the anatomy of the hip and knee extensors.

The first point to note is that the range of hip extension differs between running and cycling.  When running, the hip extensors come into play in arresting the flexion of hip and knee in late swing (initially an eccentric contraction) and continue to act until late stance, by which stage the hip is extended beyond the neutral position and the leg is angled downwards and back.  During late stance, the hip extensors undergo concentric contraction, though the fact that the fact that the hamstrings cross both hip and knee complicates matters; we will return to the implications of this later.   When cycling the hip extensors are passively streched during the upstroke and contract concentrically throughout the down-stroke. The hip extension ends with the foot below the torso and the hip still slightly flexed. Thus, throughout the period of extension the hip is actually in a state of full or partial flexion.  Although the hip extensors are not subject to active stretching during the down-stroke, the extensors are nearly fully stretched at the beginning of the down-stroke and remain slightly lengthened relative to the neutral position at the end of the down-stroke.

Thus, despite the fact that cycling avoids the potentially seriously eccentric contraction that occurs during running, the hip extensors are at least somewhat lengthened relative to neutral and the flexors slightly shortened throughout the stroke, and there is a risk that protracted periods of cycling will lead to a tendency for shortening of hip flexors and stretching of hip extensors.  For a person with a desk job, this exacerbates the tendency for shortening hip flexors induced by hours of sitting.   Such a tendency for shortened hip flexors and stretched extensors might impede the extension of hip and knee in later stance that is crucial for powerful running.

However, the situation is actually a little more complex. The major hip extensors are the gluteus maximus and the hamstrings.  The long hamstrings cross both hip and knee, acting as flexors of the knee in addition to extending the hip.  During both cycling and running, the knee and hip extend together, so the length of the hamstrings changes relatively little.  The issue of shortened hip flexors and stretched extensors appears at first sight to apply only the flexors and extensors crossing a single joint (psoas and gluteus maximus).  However, the picture is even more complex, because the hamstrings, apart from the short head of biceps femoris, take their origin from the ischial tuberosity which is below and slightly behind the hip joint, exacerbating the tendency for stretching as the hip flexes, while most of the fibres of the long head of biceps femoris and semimembranosis are inserted only a short distance below the knee joint, such that knee flexion produces little tendency towards shortening.  The net effect of the location of the origin and insertions of the various components of the hamstrings is that both semimembranosis and the long head of biceps femoris are stretched passively during the hip and knee flexion during the upstroke of cycling.


Illustration of the passive stretching of semimembranosis muscle as the hip and knee flex to approximately 90 degrees. The muscle is about 6 cm shorter than the femur in the neutral position, but only 2-3 cm shorter during flexion. In this illustration the pelvis remains neutral. When cycling, forward lean of the trunk displaces the ischial tuberosity backwards, adding to the stretch of semimembranosis.

Overall, there is a tendency for shortening of psoas, a hip flexor,  and lengthening of gluteus maximus and two major components of the hamstrings. At least in the short term this will impede the powerful extension of the hip in late stance required when running.   If cycling forms a large part of training, it might produce a sustained imbalance between hip flexion and extension, resulting in sustained impediment of the hip extension crucial for powerful running.

I think there are two ways of minimizing the risk of impeding hip extension.  First of all, it is probably useful to stretch the hip flexors after cycling. Static stretching should only be done while the muscles are warm. I rarely engage in passive stretching. However I regularly do dynamic hip swings (standing on one leg, swinging the other leg forward and back, with knee extended, emphasising on a good back-swing.  If I ever do a triathlon, I will be inclined to spend 30 seconds in the second transition mobilizing the hip.  The second strategy for reducing the problem of dominance of flexion over extension is cycling at a high cadence.  This favours the development of muscle properties such as capillary supply and fat metabolism rather than the building up of powerful type 2 fibres, thereby reducing risk of developing a strong imbalance between flexors and extensors.

Yet another potentially important factor is the type and fitting of the saddle.  On my commuter bike I have a saddle that is wide enough to support both ischial tuberosities (the ‘sit bones’).  On one of the few occasions when I have cycled vigorously for a sustained period, I was amazed to find that that on dismounting I could scarcely walk, let alone run. It appeared that my hamstrings were partially paralysed.  This was almost certainly due to pressure on the upper part of the hamstrings, which are attached to the ischial tuberosities.  The problem was only transient but emphasized to the importance of a well fitted saddle of the correct width.

In summary, cycling is a potentially valuable form of cross training. It is possible to cycle for far longer periods than feasible when running; it is good for developing cardiac endurance and also for the attributes of skeletal muscles important for running in the aerobic zone, but it is necessary to avoid developing an imbalance between hip flexors and extensors. This might be achieved by cycling at high cadence and at doing dynamic stretching of the hip flexors for least a short period afterwards.


Over the years I have only swum sporadically, though for several months after I had injured the lateral ligaments of my left knee in a cycling accident last year, swimming became the mainstay of  my cross training.  I consider that the front crawl is the most useful stroke because the flutter kick and core strength required for a well-balanced position in the water help maintain the endurance of the gluteals and trunk muscles engaged during running.

Unless you devote some attention to swimming technique, front crawl can become an anaerobic activity (despite a relatively low heart rate). It is noteworthy that in the study led by Peter Peeling at University of Western Australia, in which a recovery session including 2 km of moderate intensity swimming produced more effective recovery than passive rest of similar duration after intense running interval sessions, the participants were triathletes.  I doubt that swimming would produce such a beneficial recovery in runners who were not technically accomplished swimmers.

For most people, and especially for male distance runners, the centre of mass of the body is near to the hips while the centre of buoyancy is in the chest.  As a result the body tends to rotate to a feet- down, head-up position in the water, increasing drag and tending to make swimming an anaerobic activity. The streamlined position necessary for a sustained aerobic front crawl requires a flutter kick and engagement of trunk muscles, actions which in themselves are directly beneficial to the distance runner.  I consider the Swim Smooth site is a very helpful source of guidance on front crawl technique.


Aqua jogging using a flotation belt for buoyancy, or deep water running, involve similar neuromuscular action to running, with zero or minimal impact.  However, the relative activity in the quads and hamstrings differs between different styles of deep water running, and is also likely to differ from ‘on land’ running.   For example, Mercer and colleagues demonstrated that when running at a stride frequency that the runners had self-selected during ‘on land’ running, activation of quads and hamstrings was lower during a high knees style of deep water running than a ‘cross-country’ style.  However, the high knees style produced greater activation of hamstrings that a body weight-supported treadmill with either 60 or 80% support, but similar activation of quads.  Furthermore, it is subjectively harder to achieve a given heart rate, and maximum achievable heart rate tends to be lower during aqua jogging or deep water running than when running on land.  This might be because of greater venous return of blood to the heart and consequently increased stroke volume, though I am not aware of direct evidence for this.

Overall the evidence indicates that aqua jogging or deep water running can produce useful gains in fitness in previously untrained individuals, and can help maintain fitness in injured athletes, but it should not be assumed to be very similar to ‘on land’ running  in either the relative activation of different muscle groups, or in cardiovascular responses.

In light of the greater perceived effort required to achieve a given heart rate, and also the potential for boredom, I consider that aqua jogging and deep-water running lend themselves better to interval style sessions, if the goal is to increase fitness. On the other hand, if the goal is recovery after hard training, aqua aerobics (perhaps best done in a group led by an enthusiastic leader and accompanied by lively music) might be enjoyable and relaxing.

Similar to the evidence that swimming can promote better recovery than passive rest after intense running, Takahashi and colleagues demonstrated that 30 minutes of walking, jogging and jumping in water daily for three days following a down-hill running session produced better recovery of muscle, evidenced by less soreness and stiffness, than were observed in a control group.


Body-weight-support treadmill

In the so-called anti-gravity treadmill, the lower body is encased in an airtight bag.  Air-pressure in the bag is increased thereby tending to lift you off the treadmill.  The principle is similar to aqua-jogging but with the advantage that the reduction in effective body weight can be set at any desired level from 0 to 80%.  In both principle and practice, this is can be an effective device for promoting recovery from injury, though accessibility is limited and the cost is probably prohibitive for use simply as a form of cross training.


Low impact, aerobic cross training is a useful way in which to increase volume of training, with beneficial effects on features such as capillary supply to heart and skeletal muscle, ability to metabolise fats, ability to shuttle lactate between type 2 and type 1 fibres, endurance of postural muscles and other aspects of fitness relevant to distance running.  It greatly reduces the risk of injury arising from impact at foot fall, but conversely, cannot enhance the ability to cope with the eccentric contraction of leg muscles at footfall that plays a cardinal role in getting airborne.  Furthermore different forms of cross training achieve the various physiological goals of cross-training to differing degrees.   The optimum choice between them depends on the specific training goals and on other circumstances.

In general, I favour weight-bearing cross training over non-weight-bearing on account of the benefits to postural muscles, bones and other connective tissues. In particular, I favour the elliptical cross trainer used in the hands-free mode, because it provides a very effective workout for postural muscles and upper body actions that are relevant to running.  However, many individuals find it boring and would prefer to be out-doors.

If you have a large amount of time available and enjoy being out-doors, walking, especially hill-walking is a good option for conditioning the legs.  Similarly, cycling is potentially a great form of cross training on account of the fact that, after adequate preparation, you can cycle virtually all day with minimal risk of injury.  However, as discussed in my speculative account of the differences in neuromuscular activity between running and cycling, I think prolonged cycling creates a risk of shortening of hip flexors and stretching of hip extensors, that might impede the hip extension in late stance that plays a key role in running.  This risk might be diminished by cycling with a high cadence and by regular hip-mobility exercises.

If the primary goal is promoting recovery from a hard session, or during the initial phases of mobilisation after injury, swimming, aqua jogging or aqua aerobics might be preferable.   Other devices such as the zero-runner or the anti-gravity treadmill are potentially useful because they allow a pattern of muscle recruitment that more closely resembles that of running. However limited accessibility and cost might be limitations for many runners.

Low impact weight-bearing aerobic cross training

August 24, 2016

Running itself is the cardinal component of the distance runners program, though a large volume of running at race pace is definitely not desirable: it creates substantial stress, generating a catabolic state and a high risk of injury. The optimal program incorporates a high volume at low intensity and a small volume of high intensity training.  If your goal is to achieve longevity as a successful distance runner, it is essential to have a strategy that allows a high volume of training without accumulating too much damage to the body, especially to the leg muscles and joints.  Some runners can achieve the required  high volume of low intensity training purely with low intensity running.  For many, the optimum strategy includes a substantial amount of low-impact aerobic cross training.

The principle virtue of low impact cross training is that it avoids the potentially damaging eccentric contraction at foot-fall.  This allows large volume with minimal risk of injury.  The limitation is that it fails to develop the powerful eccentric contractions that are essential for getting airborne, a cardinal feature of running.    In contrast, plyometric cross-training is designed specifically to  generate eccentric contractions and is even more effective than running itself for developing the type 2 a fibres that play a major role during eccentric contraction, but it carries even greater risk of injury.

Forms of aerobic cross training

Aerobic cross training can take many forms.  One important distinction is the distinction between weight-bearing exercise, such as  elliptical cross training, stair-stepping or various devices designed to closely mimic the action of running, such as the Zero Runner and Bionic Runner; or non-weight bearing exercise such as cycling, aqua-jogging and swimming.  Another distinction is based on intensity: ranging from the low aerobic zone via the upper aerobic to the anaerobic zone.  I will focus on weight-bearing aerobic cross training, with the main emphasis on training in the  low aerobic zone, but I will include some comments on moderate and  high intensity cross training.

The specific goals of low intensity aerobic cross training are:

  • Enhancing fat metabolism, through development of the enzymes that perform beta-oxidation of fat.
  • Enhancing the shuttling of lactate between type 2 muscle fibres and type 1 fibres which have a large capacity to utilise lactate as fuel. Note that even in the low aerobic zone, lactate is produced in type 2 fibres, but because it is taken up into type 1 fibres it does not spill over into the blood stream.
  • Developing capillary supply to muscle.
  • Developing cardiac endurance.
  • Strengthening connective tissues and bones providing protection against injury.
  • Development of postural muscle endurance.

Although weight-bearing offers beneficial musculo-skeletal strengthening that helps protect against injury this can be  a  disadvantage during recover from injury, and in such instances either cycling, aqua jogging or swimming might be preferable. I will discuss these forms of cross-training in a subsequent post.


Elliptical Cross trainer

The elliptical cross-trainer is designed such that the two feet follow an elliptical trajectory  while pressing on two moving platforms to drive a flywheel, and the legs move in manner that is somewhat similar to the action of running.   The main driving power is generated by extension of hips and knees, as in running.  However the degree of flexion of hips and legs is less than when running at moderate or fast paces.  There is little or no plantar flexion of the ankle or rotation of the hips.   Nonetheless the elliptical does help develop the hip and knee extensors that are the powerful drivers of running.   There is potential for development of capillaries, fat metabolism and the shuttling of lactate between type 2 and type 1 fibres in these muscles, with minimal risk of damage.

Although it is possible to use the arms to assist in driving the flywheel via two handles, I prefer to avoid using the handles, except when aiming for very high power output.  I aim to swing the arms in the same manner as when running, thereby using the upper body to help generate the force exerted through the legs, in the same manner as when running.  This promotes development of the core muscles required to maintain a good running posture.

As with all forms of low impact cross training, the elliptical has the potential to develop cardiac output and cardiac endurance.

One potential disadvantage of a stationary elliptical is boredom, though in fact I find that low intensity elliptical sessions create a  positive meditative state and foster a helpful awareness of the relationship between breathing and the rhythmic action of the legs.

I use the elliptical regularly as an adjunct to my training. During base-building, typically 30% of my training is on the elliptical. On one occasion, over a decade ago, when I had done only a very small amount of training in the preceding 6 months, I did 6 weeks of training exclusively on the elliptical.  I did 6 half-hour sessions per week, including a mixture of low aerobic and mid-aerobic sessions.  Before the start of the 6 week elliptical block I had done a timed 6 Km run at lactate threshold pace. I repeated this running session after the block of elliptical training and was pleased to note that my pace was 12% faster and average heart rate slightly lower than before the elliptical training.  It appears that at least under some circumstances exclusive elliptical training can result in a substantial improvement in running speed at lactate threshold.  However at that time, I was quite unfit and I would have anticipated an appreciable improvement in running performance from virtually any systematic program of aerobic training.

I also employ the elliptical for high intensity interval training.  Even when starting from a fit baseline, I have experienced substantial gains in aerobic capacity when elliptical HIT sessions have been my only form of high intensity training.   In fact since injuring my knee in an accident a year ago I have been forced to restrict the amount of high intensity running I do, and have found the elliptical invaluable for high intensity training.

There are noteworthy examples of elite athletes employing elliptical training during recovery from injury.  In the months prior to the Beijing Olympics Paula Radcliffe was unable to run on account of a stress fracture of her femur, and used the elliptical on account of its low impact. In the Olympic marathon she maintained a place in the leading group until 30 Km, demonstrating that her aerobic fitness was good, but beyond that point her legs gave way, causing her to drop back to a disappointing 23rd place,  confirming that elliptical cross-training does not condition the legs adequately to sustain a high level of performance for the entire duration of the marathon.

More recently, 10,000m runner  Emily Infeld experienced  a stress fracture of her left hip three months before the  US trials for the Rio Olympics.  She employed a seven week program of cross training that included elliptical training and swimming, before resuming regular running.   In the trials, she was second to Molly Huddle , in 31:46.1.  Six weeks later, in Rio, Molly was 6th and Emily 11th in 31:26.9.



The Elliptigo is an elliptical cross trainer on wheels. It provides very similar fitness benefits to those proved by the elliptical, with the added advantage of being outdoors on the open road.   Its main disadvantage compared with the elliptical is the cost.

Elites including Dean Karnazes and Meb Keflezighi have used it to augment their training.  Both have been sponsored by the manufacturer of Elliptigo.  Following his victory in the 2014 Boston Marathon, Meb reported that the Elliptigo was a useful way to maintain fat burning capacity, with minimal stress on his legs.    In the 2016 US Olympic marathon trials, Meb finished second in 2:12:20 behind Galen Rupp, and made it to his 4th Olympics at age 40. In Rio, he finished in 33rd place, in 2:16:24.  This can be compared with his silver medal performance of 2:11:29 in Athens, 12 years earlier.  He considers that Elliptigo cross-training has contributed to his remarkable longevity at elite level.


Zero runner

The Zero runner is a stationary machine, somewhat like the elliptical, but with several extra hinges, including hinges at knee height in the rods from which the foot platforms are suspended.   The hinge allows a much greater flexion of the knee than the elliptical, and thus provides an action that more closely resembles the movements of running.  Dean Karnazes reports that the motion is smooth and natural and feels just like running, but without the impact.  As with the Elliptigo, the disadvantage is cost.


Bionic Runner

The Bionic Runner employs an action designed to mimic the action of running, but without impact, perhaps even more closely than the Zero-runner.  It has the added advantage that it is not stationary and is intended for outdoor use.  It has two wheels like a bicycle but is ridden standing up. The cranks are constructed in manner that achieves a foot trajectory very similar to the trajectory when running. In particular, the ratio of swing to stance duration mimics the shorter stance phase typical of moderate or fast paced running.  The recruited muscles are similar to those recruited when running, though it appears to me that the balance of work done by the extensors of the knee relative to the extensors of the hip is somewhat greater for the Bionic Runner than for running.  It also places a substantial demand on the postural muscles of the torso.  It lends itself naturally to moderately intense aerobic training.  (I am grateful to Ewen for drawing my attention to the Bionic Runner)


Kick-bike Scooter

The kick-bike scooter is a two-wheeled device propelled by pushing against the ground with a single leg, with an action that engages many of the muscles employed in running.  The range of motion at the hip is potentially large, thereby providing a good work-out for the hip extensors, especially gluteus maximus.   It also provides far greater exercise for the calf than the elliptical.  Because it engages a large number of muscles, it tends to encourage a more vigorous workout than many other forms of low impact aerobic cross-training.


Stair stepper

A stair stepper offers  the advantages of hill training with minimal impact.  It provides a vigorous workout for the glutes, quadriceps, hamstrings and calf muscles, and also for the heart. Kelly Holmes made great use of a stair stepper in preparing for her double victory in the 800m and 1500m in the Athens Olympics.



All forms of weight-bearing, low impact cross training offer the possibility of enhancing cardiac and leg muscle function in a manner that minimises risk of musculo-skeletal damage.  Some forms, such as the Bionic Runner, kick-bike scooter and stair stepper are more readily adaptable to enhance muscle power and cardiac output, while others such as the elliptical, Elliptigo and Zero-runner lend themselves to developing endurance, though these differences are only a matter of degree.   In practice, the optimum choice of type of aerobic cross training is likely to depend on issues of preference and convenience, such as the choice between indoor and outdoor, and on practical issues such as the cost or availability of the equipment.

In general, weight-bearing forms of cross training provide a good opportunity to develop endurance of the core muscle essential for good running posture. The elliptical, the stair-stepper and perhaps the Zero runner allow an upper body action that closely resembles the upper body action when running, but in all forms of weight bearing cross training, it is important to focus on good posture for maximum benefit.


Cross Training

June 19, 2016

There is little doubt that if you wish to run well, a large part of your training should involve running.  Running requires a specialised pattern of muscle activity that must be practised.  It also subjects the body to unique stresses to which the body must adapt.  Gradual build-up of running itself is almost certainly an imporant part of acquiring the skill and adapting to the unique stresses.   In other words, training should be specific.  However, the principle of specificity has important limitations.  You do not become a good marathon runner merely by running marathons at your best race pace repeatedly.   This will merely lead to exhaustion.  The principle of specificity does not extend to exclusive training at race pace over the relevant distance.  We need to build up a variety of strengths and abilities and training should be adapted in a manner that allows the development of each of these strengths and abilities to the full extent without exhausting the body.  This leads to the question of whether it is more effective to include some cross-training activities other than running, in order to build specific strengths with minimal stress, and if so, what proportion of training should be cross-training.

The first point to make is that the answer almost certainly  depends on the individual.  Some individuals have achieved superlative performances with little or no cross training.   Among these is Ed Whitlock, undoubtedly the most successful elderly distance runner the world has seen; holder of more than 45 age-group world records, spanning distances from 1500m to marathon, in age groups ranging from  65-69 to 85-89. His training consists of low-intensity running for several hours each day, together with fairly frequent races at shorter distances.  He does no cross training at all.

However, if one examines Ed’s training in more detail, it is clear that he has crafted it carefully in a way that scrupulously avoids the stress of extensive amounts of running at or near race pace.  He describes his training pace a glacial.  He shuffles along with a short stride, scarcely becoming airborne, for the explicit purpose of minimising impact stresses on his legs.  Despite the fact that all of his explicit training is actually running, it is running in manner so different from his race pace and gait that one might almost be tempted to call it cross-training.  Nonetheless, it does involve the essential elements of running, albeit with one of running’s defining features, getting airborne, almost entirely removed.

At the other extreme is Dean Karnazes, ultra-distance runner famed for prodigious feats of endurance such as the Badwater Ultramarathon, which he won in 2004.  In his own words, he is very eager to try any form of cross training that presents itself.  At various times he has advocated the elliptigo, an elliptical cross-trainer on wheels designed to mimic the movements of running but with no impact forces, and more recently, the Zero Runner, in which the mounting rods of the platforms that you stand on are hinged at the level of foot and knee.  The leg action even more closely resembles that of running, yet impact forces are abolished.  Karnazes also emphasizes the importance of whole body training, including a wide range of strength exercises

There are few noteworthy examples of elite runners who have been forced to rely almost entirely on cross training.   Three months out from the Beijing Olympics, Paula Radcliffe suffered a stress fracture of her femur and was forced to rely heavily on elliptical cross training and pool running.  She did complete the race in 23rd place, in a creditable but intensely disappointing time of 2:32:38.  The images of her struggling after the first 19 miles of the race are almost as pitiful as the pictures of her sitting beside the road in Athens 4 years previously when she dropped out of a race that many expected would be the crowning glory of a phenomenal few years in which she had taken ownership of the women’s marathon.    The fact that in Beijing Paula was able to keep up with the leading pack for the first 19 miles indicates that her cross training produced impressive aerobic fitness, but the cross-training was inadequate to condition her legs to withstand the repeated trauma of impact.  In her words: ‘My calf stiffened up and the pain went all the way up my leg.  By the end, I was running on one leg’.


It is clear that different athletes have incorporated cross training into their training routines for various reasons and to a varying extent, with varying levels of success.  In my recent series of articles on strategies for enhancing longevity as a runner, I had concluded that the evidence suggested that cross training has an important role to play.  I will finish this article with an overview of the aspects of a runner’s physiology that might be developed effectively by cross-training, and in subsequent articles, will examine the virtues and limitations of a range of different forms of cross training, including resistance exercises and plyometrics; elliptical cross training, cycling, walking and swimming.


The heart’s capability to pump a large volume of oxygenated blood via arteries to muscles, together with the ability to sustain high cardiac output over prolonged periods, are key components of aerobic fitness.  Virtually all forms of cross training enhance the pumping capacity of the heart.  The various forms of low-impact aerobic exercise, especially cycling, elliptical cross training, aqua jogging and swimming offer the possibility of maintaining a high cardiac output for sustained periods with minimal trauma to the musculo-skeletal system. They contribute to the development of cardiac endurance by mechanisms such as increasing the capacity of heart muscle to utilise fats, while also enhancing capillaries within cardiac muscle itself that are essential for delivering oxygen to the heart muscle fibres.    Low-impact aerobic training can also be incorporated in high intensity interval training, providing a time-efficient way of increasing cardiac output, largely by increasing stroke volume.

Skeletal muscle

As in the case of heart muscle,  long duration aerobic cross-training develops the ability of skeletal muscle to metabolise fat and also enhance the capillary supply to the muscle fibres  Resistance training can be used to develop skeletal muscle strength and power in an efficient manner by employing loads that exceed those involved in running. Plyometric training is a very efficient way of enhancing power of eccentric contraction and developing resistance to damage from eccentric contraction, but unlike low-impact forms of cross training, plyometric exercises carry a serious risk of trauma to muscles, tendons and ligaments.  Hence plyometrics should be incorporated in a training program cautiously, gradually build-up of the intensity of the eccentric contractions.  However provided build-up is gradual it is possible to apply far greater forces than occur during running itself.  This generates reserve capacity to manage eccentric contraction, resulting in a more powerful running action together solid protection against injury

Systemic metabolism and hormones

Both long duration low intensity aerobic cross training and short duration high intensity cross training promote many of the metabolic and hormonal responses that are crucial for endurance running and for the repair of tissues. For example, low impact cross training in the mid to upper aerobic zone is potentially an effective way to enhance the capacity of the lactate shuttle that transports lactate to liver where it is converted back to glucose and stored as glycogen.  High intensity cross–training  can enhance the capacity to transport potassium that is released from muscle during contraction, back into muscle, thereby making the muscles more resistant to fatigue.   Both aerobic exercise and resistance training can promote growth hormone release, though in general résistance training is more effective for stimulating growth hormones and other anabolic hormones.

Enhanced recovery

A moderate body of evidence indicates that low intensity activity following strenuous training promotes potentially beneficial physiological changes, such as a decrease in blood levels of reactive proteins  that are marker for inflammation.  However the evidence that such changes actually enhance subsequent performance is sparse.   Perhaps the most convincing evidence comes from the study led by Peter Peeling at University of Western Australia,  in which nine triathletes performed an intense running interval session on two separate  occasions followed 10 hours later by either a swim recovery session (consisting of 20 × 100 m at 90 % of 1 km swimming time-trial speed), or a passive recovery session of similar duration.  On each occasion, on the day following the interval session, they performed a high-intensity treadmill run to fatigue to assess the degree of recovery of running performance.  The athletes were able to run for an average of 13 minutes, 50 seconds after swimming  recovery compared to only 12 minutes, 8 seconds after lying still for recovery.  Furthermore, the swimming  recovery was associated with significantly lower levels of c-reactive protein 24 hours after the interval run. Thus the swimming recovery was not only associated with reduction in a protein marker of inflammation but also with enhanced performance in the treadmill running test, 24 hours later.  Peeling and colleagues speculated that the non-weight bearing character of the swimming recovery was likely to be an important factor in the benefit



Overall, the various different forms of cross training can enhance the capacity of many of the physiological functions that are essential for distance running, while minimising the damage from impact at foot fall that is inevitable during running itself.   The diversity of different benefits from different forms of cross training make it possible to target specific weaknesses where  necessary.  Alternatively, incorporating a diverse range of cross training activities in your training program can deliver benefits in a wide range of physiological functions while minimising the accumulation of stress on the body.

The experience of Paula Radcliffe in Beijing suggests that a distance runner must nonetheless do a substantial amount of actual running.  On the other hand, a broader perspective on her career raises a more challenging question. Despite standing head and shoulders above all female marathon runners in history, her career was blighted by injury.  Would a more judicious balance between running and cross-training throughout her career have allowed her not only to set an astounding world record far beyond the reach of all others in the current era, but perhaps she might also have won an Olympic medal.

Achieving longevity as a distance runner: twelve principles.

April 27, 2016

In the past seven posts I have addressed the challenge of maximising longevity as a distance runner.  For many of us, age appears to offer the prospect of inexorable decline.  In contrast, a few individuals achieve performances in their 70’s or 80’s that would be a source of great satisfaction for many runners 30 years younger.  Ed Whitlock recorded a time of 2:54:48 in the 2004 Toronto Waterfront Marathon at age 73 and as recently as a week ago, set an M85 half-marathon world record of 1:50:47 in the Waterloo half-marathon.  Even Ed is slowing as the years pass, but he has transformed our understanding of what an elderly distance runner can achieve.

In a previous blog post I attempted to tease out the secrets of Ed’s phenomenal longevity.  I concluded that his remarkably high maximum heart rate, determined largely by his genes, was one of the key elements that made him truly phenomenal, but his life-style and training allowed him to realise the potential offered by his genes. A central feature of his training has been frequent long, slow runs of up to 3 hours duration, often up to four or five times in a week.  This high volume of low intensity running is augmented by moderately frequent races, typically over distances of 5-10Km.

For most of us, merely attempting to emulate Ed’s training would be impractical, either on the grounds of lack of time, or because our bodies could not cope with the volume of training.   However, I believe that if we examine the anecdotal evidence provided by the training of Ed Whitlock and augment this with evidence that is emerging from current scientific studies of aging itself and of the way in which the aging body reacts to training, we can begin to formulate some general principles that will help maximise the chance of achieving the potential longevity offered by our genes.   It is also encouraging that the rapid accumulation of scientific knowledge offers the prospect of even better guidance in the future.

Meanwhile I have assembled a set of 12 principles that encapsulate much of the material presented in the past seven posts.  In this summary, I will not present the evidence justifying these principles. That evidence is presented in the preceding articles. Here are the 12 principles:

  1. Continue to run regularly. The evidence indicates that continuing to run, at least into the seventh and eight decades decreases risk of disability and death. However, by virtue the stressful effect of the impact at foot-strike, and also because running tends to exacerbate the age-related shift of hormonal balance away from anabolism (building up of tissues) towards catabolism (break down of tissues), the risks associated with running are greater in the elderly than in young adults.  Greater care is required to minimise these risks.


  1. Increase training volume gradually. Gradual increase minimises the stress of training and decreases the risk of excessive rise in the stress hormone cortisol, and allows gradual building of resilient less injury-prone tissues.


  1. Recover thoroughly after strenuous training and racing. The major reason is to ensure that acute inflammation resolves rather than becoming potentially destructive chronic inflammation.  However to prevent the development of constrictive adhesions due to the deposition of collagen fibres, it is important to maintain mobility during recovery. This might be achieved by easy exercise – walking, jogging, or elliptical cross training. Perhaps stretching has a role to play though there is little compelling evidence in favour of stretching. There is substantial evidence in favour of massage.


  1. Do a substantial amount of low intensity training. Low intensity training promotes both mitochondrial biogenesis and fat metabolism, while also building the resilience of muscles, tendons, ligaments and bones.  Low intensity training enhances the ability to handle lactic acid by developing the ability to transfer lactate from fast twitch fibres into slow twitch fibres where it is consumed as fuel.


  1. Do a modest amount of high intensity training. High intensity training helps to sustain power (the ability to deliver force rapidly) while also being an effective way to enhance the mechanism for pumping calcium back into muscles. High intensity training enhances the ability to clear lactate from muscle and transport it to other tissues such as liver where it can be utilised.


  1. Optimise cadence. A relatively high cadence at a given pace requires a shorter stride length, thereby reducing peak airborne height (and reducing impact forces) while also reducing braking forces.  Overall, potentially damaging forces are reduced. However high cadence does increase the energy cost of repositioning the swinging leg, so very high cadence is inefficient.  The most efficient cadence increases with increasing pace.  Most runners increase cadence with increasing pace.  Nonetheless for the elderly runner, it might be best to maintain a quite high cadence during training even at low paces because minimising impact forces is more important than maximising efficiency.


  1. Engage in low impact cross training. Although running itself is the most effective way of getting fit for running, running is a very stressful form of exercise on account of the impact forces.  Many of the desired benefits of training, especially cardiac fitness, can be acquired through other forms of exercise. Low impact cross training, (elliptical, cycling, walking) provides substantial benefit with minimum damage.


  1. Do regular resistance exercise. Resistance exercises help maintain strength and power, while promoting anabolism, thereby correcting the age-related tendency towards an excess of catabolism over anabolism. There are many different forms of resistance exercise.  I do regular barbell squats and dead-lifts with quite heavy loads (typically 100Kg) and also do hang-cleans to enhance power in the posterior chain muscles (glutes, hamstrings, gastrocnemius).  These exercises enhance the recruitment of type 2 fibres.


  1. Consume a well-balanced diet. The question of the healthiest diet remains controversial, but there is no doubt that elderly individuals require a higher intake of protein to maximise tissue repair; variety, including bright coloured vegetables, helps ensure adequate intake of micronutrients. At least a moderate amount of omega-3 fats is required to promote repair of cell membranes, but a balance between omega-3 and omega-6 is probably necessary to promote acute inflammation with minimal chronic inflammation.


  1. Get adequate sleep. Sleep is a crucial element of recovery. It promotes a naturally regulated release of growth hormone and encourages tissue repair.


  1. Avoid sustained stress. The body is a dynamic system that requires a degree of challenge, and hence of stress, to prevent atrophy. The body responds to stress of any kind – physical or mental – by increasing release of the stress hormones, adrenaline and cortisol. In the short term this shifts the hormonal balance towards catabolism mobilising the energy required to respond to the stress, but if sustained it damages tissues, not only via break-down of body tissues, but also by promoting more subtle damage to DNA, as discussed in my post on ‘whole body factors’.  To achieve well-being in life and optimum benefit from training, any stress, from whatever cause, should be accompanied by a commensurate amount of recovery.  Measurements such a heart rate, heart rate variability, and blood pressure can provide useful warnings of harmful imbalance.  However, our brains are very well attuned to assessing our level of stress, and sensitivity to one’s own sense of well-being also offers useful guidance.


  1. Develop confidence in control over one’s life.  Scientific evidence from large studies demonstrates that a sense of control over one’s life promotes longevity, while abundant anecdotal evidence illustrates that confidence is a key element in athletic performance.  Good health and optimal performance are facilitated by minimising self-defeating thoughts.  Each individual needs to develop their own strategies for achieving this.


I have been pleased to see from the stats provided by Word-press that many readers from many parts of the world read my blog. There are typically around 30,000 page views per year from over 100 different countries.  I started this blog nine years ago with the aim of encouraging discussion and debate about efficient running and training. Over the years there have been some vigorous debates, mainly about the more controversial issues of running technique.   The challenge of achieving longevity as a distance runner has not aroused the same passions. In part this is because the evidence is less controversial, but nonetheless, some of the evidence could be challenged, and there are many areas in which it could be expanded.  Please let me know if you disagree with these principles or alternatively consider there are other important things to be taken into account.


The Longevity of the Long-distance Runner V : Whole Body Factors

April 16, 2016

In recent posts I have examined various the ways in which the body changes with age, with the aim of drawing some practical conclusions about lifestyle and training to maximize the chance of continuing to run well in old age.   After starting with anecdotal evidence drawn for the experiences and  the training of several of the world’s best elderly marathoners, and then examining some of the basic science, in the third and fourth articles in the series I addressed the effects of aging on heart muscle and on skeletal muscle.

However, the body functions as an integrated whole, due to the coordinating action of the nervous system and messenger molecules, such as hormones and cytokines, that circulate in the blood stream.  In this final article in the series I plan to examine ‘whole body’ factors that play a crucial role in how well we age.


Hormones: achieving a balance between catabolism and anabolism

Catabolic hormones, such as cortisol, promote the break down of tissues and the combustion of fuel to generate energy.  Anabolic hormones, including growth hormone and androgens promote the building up of tissues.

During distance running, cortisol plays an vital role in mobilising the glucose required to fuel muscle contraction, and  also to supply other crucial organs, especially the brain. However, the stress of regular training tends to create sustained elevation of cortisol thereby promoting a chronic catabolic state that favours the break down body tissues and might also impair immune defences.   A study by Skoluda and colleagues confirms that endurance athletes tend to have persistently high levels of cortisol. The increase is greater in those with higher training volume. Thus the regulation of cortisol is potentially of great importance, not only for ensuring that an athlete obtains benefits from training, but also for long term health

The balance between the beneficial role of short term increase in cortisol and the damaging influence of chronic elevation is illustrated in a study of distance runners by Balsalobre-Fernandez and colleagues. They measured salivary cortisol levels, neuromuscular effectiveness as indicated by counter-move jump height (CMJ) and various other measures throughout a 39 week running season..  As had been observed in previous studies, in this study CMJ was a predictor of an individual’s running performance, being highest before the season’s best and low before the season’ worst performance.  On a week by week basis, high cortisol correlated positively with CMJ height, but averaged across the entire season, there was a negative correlation between cortisol and CMJ height. In the short term, high cortisol is associated with good performance but in contrast chronic cortisol elevation is likely to impair performance.

Exercise, especially resistance exercise, also stimulates the release of anabolic hormones thereby promoting repair and compensatory strengthening of damages tissues, and helping restore a healthy balance between anabolism and catabolism.  With increasing age, the body becomes less responsive to anabolic stimuli and there is tendency for the balance to shift towards catabolism. Thus, for the elderly distance runner, avoiding excessive catabolism while promoting anabolism becomes important.

As illustrated in a study of older adults by Melov and colleagues, 6 months of resistance training can partially reverse muscle weakness, in parallel with a substantial reversal of the disadvantageous pattern of gene transcription and muscle protein synthesis associated with aging.

However it would be too simplistic to assume that artificially increasing the action of a specific anabolic hormone would lead to either longer life or greater longevity as a runner.  In fact there is only inconsistent evidence that levels of any one anabolic hormone are predictive of life-span.    The inconsistency of the evidence is probably due to the fact that hormones are subject feed-back control that moderates the effect of increase in level of a hormone, and furthermore there are complex interactions between hormones.  Nonetheless, the importance of addressing the tendency towards diminished anabolism with age is confirmed by the evidence that an overall decrease in anabolic effects due to a decrease of multiple anabolic hormones leads to shorter life expectancy and greater frailty.  For example, Maggio and colleagues found that low levels of multiple anabolic hormones are associated with increased and 6-year mortality in older men, while Cappola and colleagues  demonstrated that multiple deficiencies in anabolic hormones were associated with increased frailty in older women.

Growth Hormone

The inadequacy of augmenting a single anabolic hormone is illustrated well by the effects of altering levels of growth hormone.  Growth hormone is released by the anterior pituitary gland and acts on many tissues of the body to stimulate growth and cell regeneration.  It stimulates the liver to produce a messenger molecule, IGF-1 (Insulin-Like Growth Factor, type 1) that promotes hypertrophy while decreasing the formation of harmful free radicals and inhibiting cell death and slowing the atrophy of both skeletal and heart muscle (as illustrated in the figure).   It also raises the concentration of glucose and free fatty acids.  These multiple apparently beneficial effects initially led to enthusiasm for growth hormone supplementation as an anti-aging treatment.


Figure: The brain integrates information from the body and the external world, and when required sends signals to the pituitary gland at the base of the brain. The pituitary releases growth hormone which has multiple effects including stimulating the liver to produce IGF-1, which in turn stimulates repair and regeneration in muscle, bone and other tissues.

However despite some evidence of apparently beneficial changes, such as increased lean body mass and bone mineral density in elderly men reported by Rudman and colleagues, several meta-analyses that assembled the overall evidence from many studies failed to find clear-cut evidence of benefit.

Further light is cast on this paradox by evidence that in several species of animals ranging from nematode worms to mice, disruption of IGF signalling actually promotes increased life-span, by increasing the activity of several genes that promote longevity.   There is some evidence of similar effects in humans, especially among those reaching advanced old-age.  In a study of nonagenarians, Milman and colleagues demonstrated that low IGF levels were associated with increased survival in females.  Furthermore, in both males and females with a history of cancer, lower IGF-1 levels predicted longer survival.  It is possible that the observed beneficial effect of low IGF-1 levels on survival in humans is at least in part due to diminished cell production in individuals susceptible to malignant proliferation.

The paradoxical benefical consequences of diminished IGF-1 provide a strong warning against a simplistic approach based on supplementation of a single anabolic hormone.   Any such approach runs the risk of upsetting the balance in a finely tuned system of interacting hormone and messenger molecules.  However there are many ways in which we can promote the development of a beneficial balance between anabolism and catabolism by engaging the body’s more nuanced responses.  Exercise (especially resistance exercise); diet (rich in variety and with adequate protein); sleep (which promotes growth hormone release) and stress reduction (which reduces the sustained release of catabolic hormone) all shift the balance towards anabolism.


Damage produced by chronic inflammation

Inflammation is the cardinal mechanism by which the body repairs itself following injury.  It is also the mechanism by which many of the beneficial effects of training are achieved.  The stress of training induces microscopic trauma that triggers an inflammatory response that repairs and strengthens the body.  But chronic inflammation is harmful and plays a role in many of the diseases that that become more prevalent with increasing age, including diabetes, heart disease, stroke, cancer and Alzheimer’s  disease (reviewed in a readable article in U.S. News Health).

Within this series on the longevity of the long distance runner, we have already discussed the  adverse effects of chronic inflammation in the heart and in skeletal muscle.  While  many of the manifestations of inflammation are localised in a particular tissue, inflammation is mediated by messenger molecules that circulate throughout the blood stream and thus inflammation is a ’whole body’ issue.   Inadequate recovery from demanding exercise is likely to lead to circulating pro-inflammatory messenger molecules.   Although it is not proven, it is plausible that circulating pro-inflammatory messengers play a role in several of the harmful conditions that occur with increased prevalence in endurance athletes, such as asthma, cardiac rhythm disturbances, and more controversially, the increased atherosclerosis observed in elderly men who have competed in multiple marathon (discussed in my previous post in 2010),.

Diet can play an important role in increasing or decreasing the risk of chronic inflammation.  For example, omega-3 fatty acids tend to by anti-inflammatory while omega-6 fatty acids are pro-inflammatory. It is nonetheless important to re-iterate that inflammation has both beneficial and harmful effects, and in general, a healthy diet is a balanced diet.

As discussed in a more detail in a blog post in 2014, the three key things we can do to minimise the risk of damage are:

1)      Allow adequate recovery after heavy training and racing. Studies in animals and humans demonstrate that much of the fibrosis arising from chronic inflammation, resolves during an adequate recovery period.

2)      Build up training gradually. The tissue trauma that initiates the inflammatory process is less if the tissues have been strengthened by gradual adaptation. This is illustrated by the fact that DOMS is more marked if you suddenly increase training volume.

3)      Consume a diet that minimises chronic inflammation. Current evidence indicates that a Mediterranean diet, in which the pro-inflammatory omega-6 fats prevalent in the Western diet are balanced by omega-3 fats from fish and/or nuts and green leafy vegetables, is a heart-healthy diet.


Protecting our DNA

While variation in genetic endowment only contributes a minor fraction to the variation in longevity between individuals, our genes  nonetheless play a crucial in the functioning of the cells of our body throughout our lives.  The translation and transcription of the DNA strands that carry  the genetic code  generates  the RNA template required for building the proteins that are needed to sustain and repair bodily tissues.    Furthermore, the regeneration of cells via the process of cell division requires the duplication of the DNA so that each ‘daughter’ cell has the necessary complement of DNA. Thus the protection of the integrity of our DNA throughout our life-span is essential for repair and replacement of cells.

There are three main ways in which the integrity DNA can be compromised

  • Mutations, produced by radiation, environmental toxins or chance errors in duplication during cell division. Mutation change the sequence of the DNA base-pairs (A-T and G-C) thereby changing the code itself.  Mutations in sperm or eggs affect subsequent generations.  Mutation within other bodily cells are unlikely to have a widespread defect on the body, except in the situation where the mechanism that regulates cell division is damaged causing the affected cell becomes malignant.   A healthy immune system scavenges rogue cells that threaten to become malignant.  Moderate exercise and a well-balanced diet that promote a healthy balance between catabolism and anabolism help maintain a healthy immune system.


  • Certain locations on DNA are prone to undergo a chemical change known as methylation, in which a methyl group (-CH3) is attached to cytosine (the letter ‘C’ in the genetic code). Although this chemical change does not change the order of the DNA base-pairs and therefore does not change the genetic code itself, it can affect the readiness with which the DNA can be transcribed to produce protein when required. DNA methylation patterns change in a systematic way with aging.  Some of the variations are predictive of likelihood of dying within a given time-span.  So far there is no convincing evidence that change in specific DNA methylation patterns can extend lifespan.  Nonetheless, the rate of age-specific DNA methylation changes is dependent on a range of circumstances, including tissue inflammation; exposure to the stress hormone, cortisol; and nutrition. In a review of aging and DNA methylation, Jung and Pfeiffer conclude that intake of essential nutrients (including methionine, folic acid, and vitamin B12) involved in the metabolism of methyl groups, might be key factors in delaying the progressive deterioration of DNA methylation patterns, and hence may be important for healthy aging.


  • Each chromosome has a protective cap known as telomere at its end, but these telomeres become shortened as a result of repeated cell duplication. When the telomeres become very short, cell division can no longer occur and tissues can no longer be regenerated. However shortening of telomeres is not irreversible.  For example, Ramunos and colleagues report that RNA treatment of cultured human cells can produce lengthening of telomeres. Furthermore, Ornish and colleagues have reported  evidence indicates that telomeres can be lengthened by a balanced diet, exercise and stress reduction:


Overall, the evidence indicates that a balanced diet, exercise and stress reduction can help protect of DNA.  However the question of what constitutes a healthy diet remains controversial, The various different studies that have led to the conclusion that a healthy diet might protect DNA have differed in the details of the diet.  Nonetheless, the main features of a healthy diet are a modest amount of each of the major macronutrients (carbohydrates fats and protein) and a plentiful supply of diverse micronutrients (vitamins and trace elements).  In the elderly, utilization of dietary protein is less efficient the in the young, and a higher daily intake of protein is required


The Brain and its Mind

The forgoing discussion has emphasized the important of control of stress in promoting a healthy balance of anabolism and catabolism, minimization of chronic inflammation and protection our genes.   The central controller of stress is the brain and the mind it supports.

For the athlete, perhaps that most useful way to describe the role of the brain is in terms of the central governor.   The concept of the central governor was originally proposed by Tim Noakes to account for the observation that even when athletes exert themselves to their utmost, at the end-point there is still at least a small amount of energy in reserve.   This is illustrated by the fact than many marathoners can muster a sprint when the end is in sight despite being unable to increase pace when there is still a mile still to run.   It appears that the brain exerts a restraining influence to prevent us pushing ourselves into a dangerously stressed state.  This concept of the central governor as a controller that sets a limit on performance has been controversial.  An alternative view is that fatigue is determined by exhaustion of muscles rather than signals from the brain.  Whether or not all aspects of the concept as proposed by Tim Noakes are accurate, there is no doubt that the brain and its mind exert a strong influence not only over athletic performance, but over many aspects of how our bodies react to challenge.

It is almost certainly misleading to envisage the central governor as a small homunculus wearing a pilots cap and googles sitting in a cockpit located near the front of the brain with hand on the throttle to determine how fast we run.  In fact a network of circuits in the brain receive input from diverse regions of the body and from the external world, synthesize this mass of information and send messages not only to the muscles but to the endocrine glands that secret hormones and either directly via the nervous system or indirectly via hormones, to all organs of the body that determine how our body responds to the challenges currently facing it.    The way in which the brain syntheses the sensory information is guided by past experiences and by beliefs and goals.   I find it helpful to regard this network of brain circuits that integrate sensory information, past experience, belief and goals to generate messages that determine how our body responds to challenge as the central governor.

Training teaches us what we are capable of, but our beliefs also have immense capacity to influence the decisions of our central governor.    The power of belief in athletic performance is well demonstrated by numerous anecdotes; not least by the way in which Roger Banister’s sub-4 minute mile opened the gate to a stream (though not a flood) of subsequent sub-4 minute miles.  Belief also influences the way in which our bodies respond to training.   Crum and Langer informed a group of hotel cleaners that the work they did would make them fitter. Four weeks later they had lower blood pressure, less body fat and other signs of improved fitness compared with a matched group of colleagues who had done the same work but had not been advised about the health benefits of that work.   In medical practice, the placebo effect is one of the most powerful tools in the hands of a physician.

In the domain of aging, it is common to hear ‘you are only as old as you feel’.   This is a truism that might ring a little hollow in the minds of aging runners who observe the almost inexorable deterioration of their performances with the passing years.    However, despite the overall validity of the expectation that the passing years bring deterioration, we risk sabotaging our own prospects by accepting that year-on-year decline is an absolute certainty.  I find it helpful to hold in mind the fact that Ed Whitlock failed to break 3 hours for the marathon at age 70 but achieved the time of 2:54:48 at age 73.

With regards to the effect of age on general health, the evidence from the MIDUS study (a large study of Midlife Development in the U.S.) that higher perceived control over one’s life affects the expression of genes that modulate physical health.    Furthermore there appears to be a reciprocal relationship between mental and physical factors insofar as vigorous exercise promotes a sense of control over one’s life.  It is plausible that the reciprocal relationship between mental and physical adaptation to aging arises from the reciprocal relationship between adaptation to stress and metabolic efficiency mediated by nervous and endocrine systems.

Despite the strong evidence that the mind can exert an influence over matter, it is a challenge to find effective ways of enhancing our ability to harness this powerful influence.     My own experience has taught me that one effective approach is avoiding jumping to premature conclusions about the effects of aging, but instead examining the evidence, both scientific and anecdotal, and putting my predictions based on this evidence to the test in practice, bearing in mind that average outcome predicted for the entire population does not dictate the fate of the individual.


If we wish to maintain health in old age, and in a particular, extend our longevity as distance runners, we need to achieve an optimum balance between catabolism and anabolism; derive benefit from the repair and strengthening mediated by acute inflammation while avoiding the damage of chronic inflammation; and maintain our DNA in good condition.   A balanced diet; gradual build-up of training and good recovery after intense exercise; avoidance of undue stress; and maintaining confidence that we have control over our own fate all play a role in achieving these goals.

In previous articles in this series on longevity of the long distance runner, I have identified practical things that can be done to maintain the function of skeletal muscles and heart. In my next post I will provide a summary of the series, with a list of 12 recommendations for maximising longevity as a runner.

Longevity of a long-distance runner? Personal experiences

April 2, 2016

Before posting the final article in the series on the longevity of the long-distance runner, I will insert an account of my own recent experiences.  For the past year I had been planning a ‘heptathlon’ of activities for the week following my 70th birthday, in March this year.   It was a whimsical idea that had grown out of discussion on one of the social threads on the Fetcheveryone web-site for runners.  I did not intend to take it too seriously, but nonetheless, I did consider it a good opportunity to develop some new skills and broaden my range of cross-training activities, as part of an overall long-term goal to keep fit and active for as many years as possible.

I planned seven activities intended to test strength, power, balance, technical skill and endurance, with one activity each day, spread over the week. I set myself performance targets for the various events.  These were not intended to be extraordinary individual achievements for each event, but rather an overall test of my ability to achieve a modest level in a wide range of activities.

However my plans were seriously disrupted by a bicycle accident last July that left me with torn lateral ligaments in my left knee.   For several months I could not run at all.  The physio estimated recovery would take about a year and advised very gradual increase in activities.  During the final months of 2015 progress was very slow.  Nonetheless, I did establish that provided I ran slowly with a very short stride length to minimise impact forces, my knee could cope.  By the end of the year I built up to a level where I could run 10 Km slowly with few complaints from my knee.

At the end of December, I reviewed my heptathlon plan.  I decided it was feasible to attempt the heptathlon, but there was little prospect of achieving my former performance targets.  I therefore set some less demanding ‘B standard’ targets for the various activities.   The only activity that I had to change completely was the planned 100 metre sprint.  There was a serious risk that any attempt to sprint would jeopardise the recovery of the torn ligaments.  Therefore I replaced the planned sprint with a sprint on the elliptical cross-trainer.

My partially healed ligaments coped fairly well as I built up the volume of training for the various activities in January and February.  Surprisingly, cycling was the activity that caused the most pain in my knee, and I was forced to limit the amount of cycling.  Provided I continued to run with a very short stride length, running produced only occasional transient stabs of pain.   When I had set my B standard targets at the end of 2015, I had selected 20 Km as the target for the planned off-road run, as it appeared that this would be as much as I could reasonably expect my knee to cope with by March. In fact, by early February I was able to run 20Km without upsetting my knee, and by the end of February, I had done one long run of 39 Km.

I had also made good progress with most of the other events, and it appeared possible that I might be able to achieve the A standard targets  that I had originally set before the accident, in at least some of the activities.  Unfortunately, in early March my knee became a little more troublesome, making it necessary to cut back the volume of training to ensure that I would at least able to get the start of my planned heptathlon at the end of the month.  In particular I was unable to do any more longish training runs, and it appeared likely that lack of endurance would be an issue during the heptathlon.

A further scheduling issue created an additional problem.  I was scheduled to attend a two day academic conference in York in late March. When the conference dates were confirmed, it turned out to coincide with the first two days of my planned heptathlon.  Despite the anticipated lack of endurance, distance running is nonetheless my primary activity.   For the final heptathlon event, I had planned a 50K off-road ultra-marathon and this had to be on Easter Monday, so I could not defer the start.

Fortunately, the least demanding of the events, a test of balance that involved maintaining the Tree Pose, standing on one leg with arms extended above my head for 2 minutes on each leg, could be performed with minimal time commitment and at any location. I had originally planned that this non-demanding activity would be in the middle of the heptathlon to provide a recovery day, but I simply had to sacrifice the planned recovery day by doing this activity on the first day.  The second activity was a test of strength: the target was 5x100Kg barbell squats and 100 consecutive push-ups. Fortunately, I was able to do the push-ups in my hotel room before the second day of the conference and the barbell squats after returning home to Nottingham in the evening.

Once the first two days were behind me, the subsequent 5 days went very well, though there was an unexpected challenge on the final day.  Storm Katie swept across England on Easter Monday bringing high winds, heavy rain, sleet and snow, and causing quite a lot of damage.  For most of the first 20 Km of the 50 Km ultra I was struggling against a storm-force head-wind.  A few hours later, when running on the opposite direction, the fury of the storm had subsided, depriving me of the benefit of a strong tail-wind.  On numerous occasions throughout the run, I was sloshing through ankle deep water and mud.   I was very grateful that my friend Helen and her husband James joined me for a substantial part of the second half of the run.


Running beside Zouch Lock on the River Soar, with Helen, at 30Km (photo by James)

By the end I was utterly exhausted, more exhausted than I have ever been before, but very happy that I had completed the heptathlon.  I achieved six A standard and one B standard performance.  The performance targets and my actual achievements are shown in the table.


I had included two of the activities, the high jump and the swim, mainly because I wanted to learn the required techniques. As a youngster at school my friends and I sometimes did high-jumping during the lunch hour, using high jump uprights and bar in a corner of the school sports field.  We did not have a mat, so it was only feasible to do the scissors.  I did not have any special talent for jumping and my best performance in those days was only 3 feet 6 inches (106.7 cm).

About 10 years later, Dick Fosbury amazed the world by winning gold at the 1968 Olympics in Mexico City with his specular Flop technique.  The name ‘Flop’ is an appropriate description of the combined sideways and backwards somersault over the bar.  The thing that impressed me as a young physicist nearing the completion of my PhD was the fact that because the head and shoulders are already descending as the hips cross the bar, the centre of gravity is below the height of the bar at all times throughout the jump.   This appeared to be a magic trick.  However, by that stage of my life, I was a distance runner, so it did not occur to me to experiment with the technique myself at that time.

However, as I planned my 70th birthday heptathlon I recalled my previous fascination with the Flop and decided that I would learn the technique, with the aim of jumping higher that I had managed as a school boy about 57 years ago.   After the accident, the injury to my left knee forced me to change the take-off from my preferred left foot to the right. In addition, I had to restrict the run-up to a fairly slow approach of no more than 6 short steps to avoid stress on the left knee.  I was nonetheless delighted to clear 112 cm, a life-time personal best for the high jump by more than 5 cm.

Somewhat similarly in the case of swimming, despite learning to do the dog-paddle at age 6, in the subsequent 64 years I had only swum occasionally, usually for the purpose of enjoying being in the water, but I had not focused on technique.  I had no reason to learn how to coordinate breathing with my stroke, nor how to keep my legs from sinking.    Preparing for the heptathlon provided an opportunity to learn how to do the front crawl properly.

In fact swimming was the only activity in which I failed to reach my A standard, but I was nonetheless very pleased with the progress that I made with the technique.   I can now coordinate breathing-out while my head is under water and breathing in while the recovery of the arm on the breathing side passes close to my head, and I can keep my feet near the surface using a flutter kick from the hips.  At this stage, I feel I have mastered the rudiments of the technique.  The main thing I need to do in future is to make the action more automatic, allowing me to relax a little more, and swim comfortably for longer distances.

Overall, despite being a rather whimsical idea at first, the heptathlon has proven to be a very satisfying challenge.   Now, my most important goal is recovering my running speed, at least to the level near that I could achieve a year ago.  However, until my knee ligaments are strong, my stride length and pace will be severely limited.  I will have to be patient.  At least I have an interesting range of cross-training activities to help me sustain overall fitness without undue stress on my legs.

The longevity of the long distance runner, part IV: preserving muscle

March 7, 2016

I am afraid it has been a long time since my last blog post. I have been busy at work, though I have also made some progress in recovering fitness following my bicycle accident last summer.   Before the accident I had been planning a ’heptathlon’ of events, including running, jumping, swimming, cycling, lifting, and balancing, for the week of my seventieth birthday in late March of this year. Following the accident it appeared that the goals I had set were totally out of reach. In light of my rather slow recovery in the latter part of 2015, at the beginning of 2016 I had reset my targets for each event. However, although the torn ligaments in my left knee are still only partially healed, I have made substantial progress in the past 2 months and am now hopeful I will achieve my original targets in at least several of the events. I have had fun teaching myself the Fosbury Flop – despite having to adjust to taking-off from my non-preferred leg because of the damage to my left knee. Even when taking-off from the right leg I need to be very careful about foot placement during the run-up.   I have also taken the opportunity to learn the rudiments of a proper front-crawl swimming technique. But I will defer a more detailed account of my birthday heptathlon for a future post.

Now it is time to return to the issue of longevity of long distance runners. In previous posts I had addressed some of the basic science and had also examined the evidence regarding cardiac outcomes. In this post I will address the issue of deterioration of skeletal muscle, and what can be done to minimise it.


When a muscle is not used, signalling molecules within the muscle fibre initiate a sequence of events resulting in cessation of protein synthesis and increase in protein degradation.  In a world where cars and other mechanical devices have greatly reduced the need to use muscles vigorously, disuse is a major contributor to the loss of muscle and function with age, a condition known as sarcopenia.   However, even among those who continue to use their muscles, sarcopenia can only be held at bay, perhaps for decades, but eventually age extracts its remorseless toll.   For the general population, there is a simple public health message: exercise, along with a diet that includes adequate intake of protein and other nutrients, can slow the progression of sarcopenia.

However for the dedicated athlete the message is a little more complex.   Running itself can damage muscle both by direct mechanical trauma and also my biochemical trauma.   The question of what type and amount of exercise is most effective for ensuring longevity as a runner is challenging.   We should start by examining the mechanisms by which running itself might actually damage muscle.

Mechanical damage in skeletal muscle

The eccentric contraction of leg muscles at footfall results in stresses that pull muscle fibres asunder, especially at points where the contractile actin molecules attach to the structural framework of the muscle fibre.   This damage leads to an inflammatory response, in which fluid accumulates in the muscle, bringing with it the cells and nutrients required for repair and subsequent scavenging of debris. In the short term (over a time scale of hours) there is often a measurable increase in muscle size. As the repair proceeds a supportive mesh of collagen fibres are laid down. Initially this mesh is likely to prove a minor obstruction to smooth movement of the fibres.

Restricted movement leads to the accumulation of more fibre. Here is a quite intriguing short video by Gil Hedley about the fuzz that accumulates around muscle fibres that have become immobilised (illustrated in a cadaver, so do not watch it is you are squeamish). It is crucial to ensure tissues are mobilised during the recovery from a hard training session. While the most certain way to build up restrictive fibrous fuzz between muscles surfaces leading to restricted mobility in old age is a very sedentary lifestyle, but it is likely that years of training sessions which produce micro-trauma, without appropriate fuzz-clearing recovery is not much better.   It makes sense to me that a systematic strategy for mobilisation during recovery – be it massage, stretching or gentle movement – is crucial for longevity as an athlete. I have ready access to an elliptical cross trainer and my own preference is a relaxed elliptical session to maintain mobility of the fibres within my muscles. In addition I apply cross fibre friction massage (usually using my thumb) at focal sites of tenderness on tendons and other connective tissues to disrupt the formation of fuzz.

Biochemical trauma

Perhaps more insidiously, the very process that generates energy to fuel muscle contraction produces damage. Muscles generate energy by burning fuel, mainly glucose or fats, to generate the energy rich molecule, adenosine triphosphate (ATP). The energy contained in the phosphate bonds of ATP is the immediate source of energy the drives the ratchetting of actin over myosin molecules to produce muscle contraction.  A modest amount of ATP is produced during the early steps in metabolism of glucose via anaerobic glycolysis. Glycolysis converts glucose to pyruvate which is then converted to acetyl CoA provided oxygen is available. The early steps of fat metabolism also generate acetylCoA. In the presence of oxygen, acetylCoA is oxidised in mitochondria, via the Krebs (citric acid) cycle producing carbon dioxide and various molecules (such as NADH) that can act as electron donors. The most bountiful production of ATP during process of energy metabolism arises during the final stage: the electron transport chain.

In this final stage, electrons are transported along a chain of molecules embedded in the inner membrane of the mitochondria. In association with this transport of electrons, the charged protons that remain when an electron is removed from hydrogen, are transported into the space between the inner and outer membranes of the mitochondrion, setting up a voltage gradient, as depicted in figure 1.     This voltage gradient drives the protons back into the inner compartment of the mitochondrion via an ion channel though the enzyme, ATP synthase, embedded in the inner membrane, delivering the energy required to produce ATP.   However, this energetic process is almost literally playing with fire. In the process, electrons are stripped off oxygen atoms producing highly reactive positively charged oxygen ions that can leak out of the mitochondria and avidly bind to other molecules, producing irreversible oxidative damage.



Figure 1 The mitochondrial electron transport chain (by Fvasconcellos 22:35, 9 September 2007 (UTC) [Public domain], via Wikimedia Commons ) The oxidation of acetyl CoA via the Citric Acid Cycle generates electron donors such as NADH. The electrons pass along a chain of molecules embedded in the inner membrane of the mitochondria, tranferring hydrogen ions to the inter-membrane space. These ions are driven back to the matrix of the mitochondrion by the resulting electrical gradient, via a channel in the enzyme ATP synthase, thereby generating ATP.

Mitochondria become damaged; they typically have a half-life in the range 3 to 10 days. They must be replaced and the debris removed. Healthy aging requires the maintenance of efficient replacement, which is turn is dependent on the expression of the relevant genes as described in my recent post, and effective scavenging of debris. Damaged mitochondrial membranes are leakier, and are therefore more prone to release reactive oxygen ions and create greater damage within cells. In the elderly, mitochondria tend to be leakier.

There are also other metabolic mechanisms that result in exercise induced muscle damage. Although the details of the mechanism are debatable, exercising to the point where muscle glycogen store is seriously depleted also has the potential for damage. It is possible that glycogen depletion leads to serious depletion of ATP which is essential for most energy demanding intra-cellular processes, including the pumping of calcium. Calcium is released during muscle contraction and accumulates to damaging levels unless removed by ATP-fuelled pumping across the sarcolemma, the membrane that encloses each muscle cell membrane.   It is plausible that this is a major mechanism of muscle damage during the later stages of a marathon.


Minimizing damage from mechanical trauma

Gradual build-up

Although the inflammation induced by micro-trauma is a part of the mechanism by which the muscle is repaired and strengthened, at least in the elderly and perhaps in all athletes, it is almost certainly desirable to avoid excessive micro-trauma and subsequent accumulation of residual fibrous tissue as a by-product of the repair process. A sudden increase in training volume or intensity leads to Delayed Onset Muscle Soreness (DOMS) whereas more gradual increase is associated with minimal DOMS indicates that the first. This is a manifestation of the repeated bout effect, a protective adaptation against “maximal” eccentric contractions that is induced by submaximal eccentric contractions or a relatively small number of eccentric contractions. Perhaps the most important strategy for minimising accumulation of muscle damage with age is ensuring a gradual increase in training volume and intensity.  In a recent review, Nosaka and Aoki concluded that the magnitude of muscle damage can be attenuated by the use of the repeated bout effect more efficiently than any other prophylactic interventions.

Adequate recovery

While acute inflammation is largely a beneficial process that is essential for repair of tissues, if inflammation is sustained it becomes chronic, leading to long-lasting and perhaps permanent impairment of function. Therefore, adequate recovery after demanding training sessions and races is crucial.   Recovery does not necessarily demand absolute rest, as mobilization of tissues is important to minimise build of fibrous tissue – the fuzz described graphically in the video by Gil Hedley. The mobilization should be active enough to break down mis-oriented collagen fibres and to encourage blood flow, but not so vigorous as to cause new trauma. I favour low-impact cross training for this purpose.

Optimising cadence

For fast running, a strong push off from stance, mediated by an eccentric contraction is essential (as illustrated by Peter Weyand and colleagues). However, for a distance runner the goal must be to achieve peak efficiency in a manner that does as little damage to muscle s as possible.   In general, increasing cadence reduced impact forces, and for many recreational athletes, an increase in cadence actually improves efficiency. As I have discussed elsewhere, there is a limit to the benefits of increasing cadence. Nonetheless, for the elderly runner, during training it is probably advisable to aim for a short stride with relatively high cadence during long runs. This is a key feature of the training of Ed Whitlock.

Protein and amino acids

Repair requires amino acids which are the building blocks of the proteins that required to rebuild the components of muscle fibres.   The presence of amino acids in the blood stream acts as a stimulus to protein synthesis. Furthermore certain amino acids are critical, especially branched chain amino acids, which are essential in the sense that they cannot be synthesized within the body and therefore must be ingested. Howatson and colleagues demonstrated that following a session in which muscles were damaged by eccentric contraction during drop-jumps, 12 days of supplementation with branched chain amino acids produced significantly greater reduction muscle soreness and in levels of creatinine kinase in the blood (a measure of muscle damage) and significantly greater recovery of muscle strength than observed in a control group who received placebo.

Low-impact cross-training

Another useful strategy for minimising muscle trauma is low-impact cross training. I personally do about 30% of my training on the elliptical cross trainer.   Some of these sessions are recovery sessions, but I also do many of my high intensity sessions on the cross trainer as this allows me to increase aerobic fitness with minimal muscle trauma.

Resistance training

It might be expected that resistance training would enhance the longevity of a distance runner by virtue of delaying sarcopenia and increasing resistance to mechanical trauma. However until recently the picture has been confusing. Skeletal muscles exhibit quite different changes in physiology and metabolism in response to resistance training compared with endurance training. Endurance training promotes a development of type 1 (slow twitch fibres) at the expense of type 2 (fast twitch) fibres, and increases the number of mitochondria, but does not produce muscle growth. In contrast, resistance training mainly stimulates muscle protein synthesis resulting in muscle growth, achieved by fusion of satellite cells (a type of stem cell found in muscle) with existing muscle fibres. These differences in response to different types of exercise reflect different signalling processes within the muscle cells.

In a seminal study of isolated rat muscle, Atherton and colleagues demonstrated that low frequency simulation switches on a signalling pathway known as the AMPK-PGC-1α signalling pathway, which promotes aerobic metabolism and leads to the changes typical of endurance training, whereas high frequency stimulation which mimics the effects of resistance training, selectively activates the PKB-TSC2-mTOR signalling cascade causing changes consistent with increased protein synthesis and muscle growth. mTOR is a cardinal growth regulator that is switched on by various nutritional and environmental cues.

While the observation of mTOR activation provides a plausible mechanism by which resistance training increases muscle growth, it was at first unclear whether or not this would promote increased or decreased longevity. mTOR has opposite effects to another regulator, myostatin, which switches off muscle growth. Early evidence indicated that myostatin acts to increase longevity. This evidence was consistent with the puzzling but robust evidence that calorie restriction promotes longevity in laboratory animals. However more recent studies have demonstrated that the effects of myostatin are more complex than initially believed.   In fact, there is growing evidence that activation of mTOR and associated muscle growth is associated with longevity.

For example, Melov and colleagues examined the effect of six months of regular resistance exercise in a group of elderly participants. At baseline the elderly participants were 59% weaker than a young adult control group, but after the six months of resistance exercise their strength increased significantly such that they were only 38% lower than the young adults. The investigators also examined the degree of expression of genes before and after the 6 months of resistance training. At baseline there were a large number of genes that showed different levels of expression in the elderly group, but following exercise training the expression of most of the relevant genes returned to the levels observed in the young adults. Thus, resistance training not only achieves quite different changes in muscles compared with the effects of endurance training, but these changes appear to reverse features of age-related degeneration.  In a recent review, Sakuma and Yamaguchi concluded that resistance training in combination with amino acid-containing nutrition appears to be the best candidate to attenuate, prevent, or ultimately reverse age-related muscle wasting and weakness.


Stretching and massage

Despite the popularity of stretching, the evidence of benefits is minimal. It is probable that static stretching of cold muscles does more harm than good. However, as mentioned above, it makes sense to me that a systematic strategy for mobilisation during recovery after racing and training is worthwhile. Furthermore, there is growing evidence that massage can be helpful. For example, a study by Crane and colleagues at McMaster University in Ontario demonstrated that massage therapy attenuates inflammatory signalling after exercise-induced muscle damage. Studies in rabbits, reviewed by Alex Hutchinson, indicate that massage promotes muscle repair, and blood vessel formation, possibly by a mechanism initiated by stretch-sensitive receptors in muscles .


Minimizing damage from biochemical trauma

There is little direct evidence of effective strategies for minimising biochemical trauma, but our current understanding of mechanisms suggests several plausible approaches.

In light of the fact that damaged mitochondria are prone to leak potentially damaging reactive oxygen ions generated as a by-product of the electron transport that generates copious ATP, maintaining mitochondria is good condition is crucial for minimising damage. The maintenance of a healthy stock of mitochondria depends on a balance between the genesis of new mitochondria (biogenesis) and the removal of old mitochondria (mitophagy). The complex set of intra-cellular signalling processes that regulate this balance is described in a review by Palikaras. The signalling molecule, PGC-1α, is the core regulator of mitochondrial biogenesis. Signalling via PGC-1α is promoted by aerobic exercise.   One of the key benefits of relatively low intensity aerobic exercise is the promotion of mitochondrial biogenesis with relatively little risk of further damage.

There are other potential benefits of low intensity training. The evidence that impaired ability to pump the calcium released during muscle contraction back into muscle cells when glycogen is seriously depleted indicates that sustained running in the upper aerobic zone is potentially harmful.   One way of minimising glycogen depletion is enhancing capacity for fat metabolism. Perhaps relatively large volume low intensity running is the safest way to achieve this.

It should however be noted that the first stage of metabolism of fats leading to the production of acetyl CoA (beta-oxidation) generates less ATP per molecule of acetyl CoA produced than the corresponding stage of glucose metabolism (glycolysis), more oxygen must be consumed to generate a given amount of energy from fat than from glucose. Thus, fat metabolism actually makes relatively greater demands on the citric acid cycle and the electron transport chain that glucose metabolism for a given rate of energy production. Thus, fat metabolism leads to less efficient use of oxygen and it remains unclear whether or not fat metabolism is less stressful for mitochondria overall. However, the contrast between the body’s limited store of glycogen yet abundant store of fat means that at moderate paces, ability to use a higher proportion of fat in the fuel mix would be expected to place less overall stress on the body during sustained running at such paces.

In light of the potential damage produced by excess release of calcium fron muscle cells, it is also potentially helpful to attempt to enhance the capacity for calcium ion transport back into cells.  Interestingly, high intensity training (HIT) has the capacity to achieve this. In contrast to the possibility of damage from sustained upper aerobic exercise, HIT would be expected to produce surges of calcium release during the bursts of high intensity activity with an opportunity for reuptake during the recovery epochs.

Although this is speculative, I think that a polarised training program characterised by a large volume of low intensity running and a small proportion of high intensity interval running is potentially the optimum strategy for optimising longevity as a runner.


The evidence reviewed above leads to several recommendations for promoting longevity as a runner.

  • Gradual increase in training volume
  • Optimising cadence
  • Thorough recovery after strenuous events
  • Stretching and mobilization; massage
  • Low impact cross training
  • Low intensity running to promote both mitochondrial biogenesis and fat metabolism
  • Enhancing calcium pumping by High Intensity Training
  • Adequate protein intake, including adequate sources of branched chain amino acids.


So far in this series we have focussed largely on local effects in cardiac muscle and in skeletal muscle. However, there are also important mechanisms mediated by hormones and other signalling molecules in the blood stream, that play a role in damage, repair and protection. In the final post in this series we will examine these mechanisms.

The longevity of the long distance runner, part 3: Cardiac Outcomes

January 10, 2016

After examining the anecdotal evidence provided by elderly marathoners and then grappling with some of the basic science underlying longevity in recent posts, it is time to attempt to draw some practical conclusions about what can be done to optimise longevity as a runner.   While the unfolding science of the molecular mechanisms by which our bodies respond to wear and tear offers intriguing prospects of identifying strategies for promoting heathy aging, there are at this stage more questions than answers. However we each live only once and if we want to optimise our chances of running fluently in old age, we must make the most of the evidence that is currently available. Despite the uncertainties, the evolving science provides a framework for weighing up the value of the lessons that might be drawn from the anecdotes.

But it is necessary to be aware of the pitfalls if we are too simplistic in our interpretation of the science. For example, at first sight the fact that catabolic hormones such as cortisol promote the break-down of body tissues to provide fuel for energy generation in stressful situations, suggests that avoiding sustained elevation of cortisol is likely to promote longevity. Indeed this conclusion might be valid in some circumstances, but it is not a universal rule. The strategy that is most successful for promoting longevity in animals is a calorie restricted diet. This works for creatures as diverse as worms, fish, rodents and dogs, and there is some evidence for health benefits in primates. The mechanisms by which it achieves its benefits include an increase in resistance to oxidative damage to tissues by virtue of more resilient mitochondrial membranes. However calorie restriction is stressful and promotes long term elevation of cortisol. It appears that animals actually need at a least a moderate level of ongoing stress to encourage heathy adaptation. The goal is achieving balance between stressful stimuli and adaptive responses.   The balance point depends on individual circumstances, and is likely to shift as we grow older.

The nature of training

The basic principle of athletic training is stressing the body in order to encourage it to grow stronger. One of the key mechanisms by which this is achieved is inflammation, a process by which damage to tissues generates a cascade of responses mediated by chemical messenger molecules that circulate in the blood stream, triggering repair and strengthening but also leaving a trail of debris.

There is abundant evidence that running increases life expectancy. In a 21 year follow-up study of elderly runners Chakravarty and colleagues at Stanford University found that continuing to run into the seventh and eighth decades has continuing benefits for both life expectancy and reduction of disability. Death rates were less in runners than in controls not only for cardiovascular causes, but also other causes, including cancer, neurological disorders and infections. Nonetheless, unsurprisingly, Chakravarty reported that although the increase in disability with age was substantially less in runners than in non-runners, the runners did nonetheless suffer increasing disability over the follow-up period. This is of course what would be expected if the processes by which training strengthens the body also leave a trail of debris.

If our goal is to increase not only life expectancy but also to achieve healthy aging and longevity as runners, we need to look more closely at the mechanisms by which running damages tissues. Ensuring longevity as a runner requires training in a manner that ensures that the accumulation of debris is minimised.

Healthy aging is a process affecting all parts of the body. Nonetheless, for the runner, the cardiovascular system, musculoskeletal system, nervous systems and endocrine systems are of special importance. There is a large body of evidence about how these systems age and about both the beneficial and the damaging effects of running on these systems.   I will examine the evidence regarding cardiovascular system in this post, and draw some tentative conclusions about how we might train to achieve healthy aging of the heart. In my next post I will examine the evidence regarding the musculo skeletal system, for which much more detailed information about cellular mechanism is available due to the feasibility of tissue biopsy. This will allow us to extend and consolidate the conclusions regarding optimal training for maximizing longevity as a runner.    In the final posts in this series I will turn my attention to the nervous and endocrine systems, and speculate about the way in which optimal training might impact upon health aging of those crucial systems.

Cardiovascular changes

Running produces both short term and long term changes in the cardiovascular system, some beneficial, some potentially harmful. I have discussed many of these changes in several previous blog posts (e.g. ‘The athletes heart’; ‘Inflammation, heart-rhythms, training-effects and overtraining’; ‘Endurance training and heart health, revisited’) and will present a brief overview here.

In the medium term (over time scale of weeks) regular training leads to an increase in blood volume. This increases venous return to the heart. The stretching of the heart muscle leads to more forceful contraction and a greater stroke volume. The cardiac output for a given heart rate is increased. Resting heart rate decreases and the heart rate required to run at a particular sub-maximal pace decreases.

In the longer term, the heart muscle is remodelled, with an increase in overall volume and in thickness of the ventricular walls. This condition is known as ‘athletes heart’. The mechanism is mediated by the intra-cellular signalling pathway that engages an enzyme known as Akt, which promotes growth of both muscle cells and capillaries. This is usually regarded as a benign physiological adaptation. The enlargement of the heart that accompanies pathological conditions such as high blood pressure or obstruction of the heart valves is also mediated by the Akt signalling pathway, but in contrast to the benign enlargement of the athlete’s heart, the Akt signalling is accompanied by inhibition of a growth factor required for the development of capillaries. Thus, in the athlete’s heart the enlargement is accompanied by adequate development of a blood supply to the heart muscle, whereas in pathological conditions the blood supply is usually inadequate.

However, in some athletes the enlargement might have adverse effects. There is compelling evidence that endurance runners with a long history of substantial training have an increased risk of disturbances of heart rhythm, including both ‘supra-ventricular’ disturbances such as atrial fibrillation, and potentially more lethal ventricular disturbances. The cause of these rhythm disturbances is not fully established but it is probable that the re-modelling of the heart muscle in a way that alters electrical conduction pathways plays a role.  It is likely that residual fibrosis at sites where damaged muscle has been repaired also plays a role by producing local irritability of the cardiac muscle cells leading them to fire spontaneously.

During intense prolonged exercise the strength of ventricular contraction, especially that of the right ventricle, is diminished, a condition known as Exercise-Induced Right Ventricular Dysfunction. If the exercise is sufficiently intense and prolonged, cardiac enzymes can be detected in the bloodstream, indicating a least temporary structural damage to heart muscle.

In a study of forty highly trained athletes competing in events ranging from marathon to iron-man triathlon, LaGerche and colleagues from Melbourne found transient weakening of the right ventricle immediately after the event. This was more severe the longer the duration of the event. The transient weakness returned near to normal within a week. However in 5 of the athletes, there was evidence of long term fibrosis of the ventricular septum, indicating chronic damage. Those with evidence suggesting long term damage had an average age of 43 and had been competing for an average of 20 years. Those without evidence of chronic damage had an average age of 35 and had been competing for an average of 8 years.   The evidence suggests that duration of endurance competition is a strong predictor of chronic damage.

Although an enlarged athlete’s heart usually has a much better blood supply than the enlarged heart associated with high blood pressure or obstruction of the heart valves, there is disconcerting but controversial evidence of excessive calcification of the arteries in at least some athletes, especially in males in who run marathons over period of many years. The mechanism is uncertain, though sustained inflammation is a plausible mechanism.

Effects of the amount and type of training

Although an overwhelming mass of evidence demonstrates that runners have a longer life expectancy and in particular, a lower risk of death from heart attack or heart failure than sedentary individuals, several large epidemiological studies raise the possibility that adverse health effects (especially cardiac events) tend to be a little more frequent in those who engage in a large amount of exercise than in those who exercise moderately. The US Aerobic Longitudinal Study examined the associations of running with all-cause and cardiovascular mortality risks in 55,137 adults, aged 18 to 100 years (mean age 44 years) over an average period of 15 years and found a marked decreased in both cardiac and all-cause mortality in runners compared with non-runners, but the reduction in mortality was a little less in those training 6 or more times per week compared with those training 1-5 times per week. The Copenhagen City Heart Study followed 1,098 healthy joggers and 3,950 healthy non-joggers for a period of 12 years and found that 1 to 2.4 hours of jogging per week was associated with the lowest mortality. These ‘moderate’ joggers had a mortality hazard ratio of 0.29 compared with sedentary non-joggers.

But closer look at the evidence reveals a potentially informative detail. In a study of heart health of over a million women, Miranda Armstrong and her co-investigators from Oxford  found that among obese women, those who did a large amount of exercise suffered more heart problems than those who did a moderate amount. However, in contrast, among the women who had a Body Mass Index less than 25, those doing a large amount of exercise had fewer heart problems than those doing a moderate amount of exercise.   This suggests that if there is a risk in doing a large amount of exercise, it is mainly confined to those for whom the exercise is excessively stressful due to other risk factors that shift the balance towards harm rather than benefit.

Although the evidence from the large epidemiological studies remains a topic of debate because of issues such as possible bias in participant selection and the relatively small numbers of individuals in the category who take a very large amount of exercise, I think the balance of evidence does indicate that at least some individuals who take a large amount of exercise do have an increased risk of death, including death form cardiac events, within a given time period.   In my opinion, the important question is what determines which individuals will be harmed by a large amount of exercise, and whether there are ways in which we can minimise the risk of harm.

There is evidence that adequate prior training can protect against damage.   Neilan and colleagues studied non-elite marathoners runners completing the Boston Marathon and reported that right ventricle weakness was more pronounced in those who had trained less than 35 miles per week compared with those who had trained more than 45 miles per week.   The logical conclusion from studies such as the Oxford study of obese female runners and Neilan’s study of marathoners is that running in a manner that exceeds the individual’s current ability to cope with the stress increases the risk of damage.   This in turn suggests that building up gradually in a manner that ensures that training sessions are never excessively stressful is likely to be the safest approach.

Furthermore, it is likely that lack of adequate prior training or obesity are not the only factors that impair the ability to cope with the stress of demanding training and racing. Following a very demanding marathon or ultra-marathon, the evidence of damage remains detectable for a period of weeks. It is plausible that demanding training when the heart is in a weakened state will compound the damage. It is widely accepted in practice that recovery following intense racing or heavy training is crucial, but unfortunately there is relatively little scientific evidence addressing the question of whether or not the adverse cardiac effects of intense exercise resolve during a recovery period, or conversely, whether the adverse effects are compounded by repeated bouts of exercise.   We must therefore turn to evidence from studies of rats.

Benito and colleagues exercised rats on a treadmill for 60 minutes at a quite vigorous pace of 60 cm/s (achieved after 2 weeks of progressive training) 5 days per week for a total of 4 weeks, 8 weeks or 16 weeks. For a rat, 16 weeks of life is roughly equivalent to 10 years for a human. During the first 8 weeks there was relatively little evidence of damage, but prominent signs of damage emerged between 8 and 16 weeks. After the 16 weeks of exercise, the rats exhibited hypertrophy of the left ventricle and also the reduced function of the right ventricle, similar to the findings reported in humans. Furthermore the rats had marked deposits of collagen in the right ventricle, and messenger RNA and protein expression characteristic of fibrosis in both atria and the right ventricle. The exercised rats had an increased susceptibility to induction of ventricular arrhythmias. A sub-group of the rats were examined after an 8 week recovery period following the 16 weeks of exercise. Although the increased weight of the heart had not fully returned to normal level, all of the fibrotic changes that had been observed after 16 weeks of exercise had returned to the normal level observed in sedentary control rats. Thus, at least in rats, the adverse potentially arrhythmigenic changes produced by intense exercise over a 16 week period appear to be reversible after an adequate recovery period.    Thus the best available scientific evidence does support the accepted principle that recovery following intense racing or heavy training is crucial.


Proposed cardiac outcomes of long-term training. The size of the ellipses indicates cardiac fitness at each stage; colour indicates balance between recovery (blue) and stress (red)

In summary, the evidence regarding the cardiovascular effects of running suggests the following guidelines for healthy aging and longevity as a runner:

  • Continuing to run regularly, at least into the seventh and eight decades decreases risk of death and disability.
  • Training volume should be built up gradually.
  • Adequate recovery after demanding events, such as a marathon (or indeed, even after heavy training sessions) is likely to be crucial.

My next post will examine the evidence regarding the effects of training on the musculoskeletal system, and will both consolidate and extend these conclusions.

The longevity of the long distance runner, part 2: the basic science.

January 1, 2016

In my previous blog post I had posed the question: What determines the rate at which a runner’s performance declines with age?   As a prelude to addressing the scientific evidence, I had discussed anecdotal evidence gleaned from the family history, lifestyle and training of the two greatest veteran distance runners of all time: Derek Turnbull and Ed Whitlock. The anecdotal evidence suggested that genes, life-style and training all played a role. Especially in the case of Ed Whitlock, it is probable that having long-lived forebears; deferring very high volume training until after his retirement from work; and adopting a training program designed to minimise stress all contributed to his extraordinary longevity as a world-record breaking marathoner into his mid-eighties.   However, anecdotal evidence provides little basis for drawing general conclusions. What does science tell us?

At first sight, the answer appears to be that science provides a lot of obscure information that in practice offers us little guidance as to how we might adjust our life-style or training to maximise longevity, either as functioning living creatures or more particularly, as athletes. However, if we do not allow ourselves to be put-off by the apparent complexity of the story, it is possible to establish the basis for some simple speculations that might be useful in practice.

Although my primary focus is on longevity as a runner, longevity as a runner is very closely linked to healthy aging.   Healthy aging is not merely freedom from identified illnesses, though many illnesses are common in the elderly and unhealthy elderly people are often afflicted by multiple illnesses.  In fact it is probably more appropriate to consider that healthy aging is a state characterised continued good functioning of all systems of the body, that creates a low vulnerability to illness and is also a requirement for longevity as a runner.

Are there genes for longevity?

There have been several large studies of genes associated with longevity in the general population. These indicate that many genes contribute a small amount to longevity but few contribute an appreciable amount. In fact only one gene has emerged as a significant predictor of longevity in genome-wide association studies: the gene for apolipoprotein E (APOE).   Apolipoprotein E is a protein involved in the transport and metabolism of cholesterol and in several other metabolic functions. The E4 variant of the gene for APOE is associated with substantially increased risk of Alzheimer’s disease and also of heart disease and of increased rate of shortening of telomeres – the protective caps on the ends of chromosome that protect them from damage. Rapid shortening of telomeres is associated with decreased longevity.

We have two copies of each gene (apart from genes on the sex chromosomes), one copy inherited from each parent. In individuals in whom both copies of the APOE gene are the E4 variant, the risk of Alzheimer’s disease is around 15 times greater than in individuals who have two copies of the ‘neutral’ E3 variant, but fortunately very few individuals carry two copies of the E4 variant. However, almost 14% of the population carry one E4 variant. An individual with one copy of E4 together with a copy of E3 has a risk of Alzheimer’s that is about 3 times greater than that of a person with two copies of E3.   Similarly, carrying the unfavourable E4 variant of the gene for APOE does have an apprecibale effect on life expectancy, but even this ‘unfavourable’ gene accounts for only small amount of the variation in longevity in the population. It should also be noted that in contrast, the unfavourable E4 variant is associated with potentially beneficial higher levels of vitamin D which might explain why the gene has persisted in the population despite its unfavourable effects.

But the gene for APOE is the exception. Other genes that appear to contribute to variation in longevity in the population account for a much smaller proportion of the variation than the APOE gene. One other gene that warrants a passing acknowledgement is a gene with the whimsical name, FOXO3. It is a gene that plays a role in regulating gene transcription: the process by which the genetic code specified in our DNA is transcribed onto a temporary RNA copy in preparation for translation into the structure of the proteins that are the building blocks of our bodies. FOXO3 influences the process by which cells die naturally and also plays a role in defence against oxidative damage – a topic we shall return to later.   Its function suggests that FOXO3 is a candidate for an important role in determining longevity, but in fact its influence is not large enough to be discernible above the noise in the data obtained in large (‘genome wide’) studies of the association between genes and longevity.

Genetic variants with small effect

Most of the variants of the many genes that are associated with small alterations in longevity occur commonly in the population. Individually these genetic variants produce a slight perturbation of the structure or function of the body. The very fact that these variants are common demonstrates that individually they cannot have a devastating effect on structure or function, as variants with devastating effects are unlikely to get handed down through many generations.

At this stage it is worth pausing to look briefly at the nature of genetic variation and the mechanism by which it can affect the body’s structure or function. The genetic code is specified by the sequence of the molecular units that a strung together to form the double helical chains of DNA. There are only four of these elementary molecular units, which are assigned the labels A, T, G and C. (These labels are the first letters of the names of the purine and pyrimidine molecules that from part of these units.) DNA consists of a pair of intertwined chains, linked by the bonds that form between A and T or between G and C, at corresponding locations on the two chains Thus each element in the code is either an A-T pair or a G-C pair.  During the preparation for translation, the twinned DNA strands get copied as a single-stranded RNA molecule where each A,T,G, or C unit in one of the DNA chains is copied as a U,A,C or G.   Note that the elementary unit labelled as T (representing the pyrimidine, thymine) in DNA has been replaced by a slightly different molecular unit labelled U (representing the pyrimidine, uracil) in RNA. The crucial thing is that each possible triplet of three sequential units in an RNA chain is the code for a particular amino acid. Amino acids are the basic units that are assembled to form proteins. Proteins are the basic building blocks of the body, serving many specific purposes. Many are enzymes that catalyse the various metabolic processes in the body. Others, such as collagen, are structural elements. The contractile proteins, actin and myosin, enable muscles to do work.

The mechanism by which the genetic code gets transcribed and translated into protein is known as gene expression.  It is gene expression that shapes the structure and function of the body.  As we shall discuss later, many things can influence gene expression.


Figure 1: schematic illustration of gene expression. An extra-cellular signalling molecule (eg an inflammatory cytokine) binds to a specific receptor embedded in the membrane of the cell , triggering a cascade of signalling within the cell. This cascade involves messenger molecules such as cAMP and various effector proteins, including kinase enzymes which activate other proteins by attaching a phosphate group (‘phosphorylation’). When the CREB protein is activated it initiates transcription of DNA, producing an RNA molecule in which the order of the A, U, C & G units is the code for a specific protein. Each triplet of A, U, C & G units represents a particular amino acid. The code specified by the RNA template is translated into the sequence of amino acids that are assembled to make the specified protein. The process of assembling the protein is performed by a molecular construction device called a ribosome.



During the rough and tumble process of cell duplication that occurs regularly in living tissues, one letter of the code might get changed (‘mutated’). This is known as a point mutation, and the resulting variation is known as a Single Nucleotide Polymorphism (SNP). The mutation might be triggered by irradiation by radioactive materials, chemical assault by disruptive chemicals in the environment or the diet, or merely by random jiggling of units making up DNA as it is duplicated during cell division.   As a result of the change in one of the letters, a particular triplet in the code is likely to specify a different amino acid. When the mutant DNA is transcribed into RNA and subsequently translated into a protein, one amino acid will be replaced by another. Just as when a particular footballer is substituted during a football match, the substitution might have a dramatic effect, for better or worse, or alternatively, the team might continue to function with little overall change in effectiveness, in the case of amino acid substitution, there might be either a dramatic change in function of the protein if the substituted amino acid plays a cardinal role or merely a slight change in effectiveness of the protein. Because the sequence of amino acids in proteins has been shaped though many generations, most proteins in the body are well honed to fit their particular role. In the absence of major environmental change, mutations that substantially enhance the fitness of the body for its survival are extremely rare.   On the other hand, mutations that result in serious disruption of the function of the protein diminish fitness for survival, and therefore disappear from the population. The mutations that survive to become common in the population usually have only small effects on the function of the specified protein. In addition to the point mutations that generate SNPs, other types of variation are possible, but these are beyond the scope of this discussion

In summary, the commonly occurring variations in the genes that code for particular proteins usually have only minor effects on the function of those proteins. These functional effects might be helpful or helpful depending on circumstance. But the crucial thing is that it is likely that in most instances various other circumstances including life-style factors might over-ride the relatively minor effect of a specific genetic variant on the structure or function of the body. For most of us, our fate is not pre-ordained by these genes.

One might expect to find that that among the minority of exceptional individuals who live to a great age, the co-existence of many favourable genes each contributing a little, might make an appreciable contribution to their extraordinary longevity. While twin studies demonstrate that the genes contribute only about 25% to the probability of survival to age 85, studies of extremely elderly individuals, such as the study of 801 centenarians (with median age at death of 104 years) by Sebastian and colleagues,, demonstrate that genes play a substantially greater role in the longevity of these exceptional individuals. Similarly, for individuals who exhibit extraordinary longevity as athletes, it is probable that the co-existence of many favourable genes plays an appreciable role. When a large number of small nudges all push in the same direction, their combined effect is appreciable. However for the majority of us, who carry a mixed selection of mildly favourable and unfavourable genetic variants, it is plausible that if we could adopt a range of life-style choices (including appropriate training) that tend to enhance longevity in a consistent manner, we could engineer our fate in a way that swamps the potpourri of random minor influences arising from our genetic endowment.

Gene expression does matter

While the selection of minor genetic variants we happen to have been born with plays only a small part in life-expectancy for most of us, the manner in which our genes are expressed nonetheless plays a crucial role in determining how long we live and how well we continue to function in old age. Unlike an inanimate machine, such as a bicycle with parts that become abraded or degraded by friction and/or corrosion as it grows old, living creatures have inbuilt mechanisms for repair and for correcting internal imbalances that threaten their well-being. A bicycle eventually ceases to function because the abrasion or degradation causes a component to break or jam unless maintained and repaired by an external agency.   However, when a human is subject to wear and tear an elaborate self-repair mechanism is mobilised. The occurrence of damage triggers the release of signalling molecules, which travel via the blood stream to remote regions of the body to mobilise defences. The signalling molecules bind to specific receptors on the surface of the target cell, initiating a series of steps leading to the transcription and translation of DNA to produce proteins that replace or augment the existing proteins as required to repair or even enhance the functions of the body.

After the arrival at the cell surface of a signalling molecule indicating the need for repair or some other response to the external environment, the next step is a cascade of internal signalling within the cell which initiates the transcription of the DNA code onto a temporary RNA template (as discussed above in the review of the process by which the genetic code is expressed, and illustrated in figure 1).

There is a unique RNA template for each protein that is to be constructed. Therefore at any time, the profile of RNA in the cells of a particular tissue indicates which particular proteins are under construction at that time.   The RNA profile of a particular tissue at a particular time is in effect a snap-shot of the multiple building, repair and maintenance processes underway in that tissue at that time.

Environmental factors including life-style and training work in synergy with genes to maintain the body in good working order.   The expression of genes in muscle is not only of particular importance for athletes whose activities are depend on well-functioning muscles, but growing evidence indicates that the expression of genes in muscles is a marker for heathy aging throughout the body. Recent studies indicate that the RNA profile of muscle in late middle age might be a good predictor of the fitness not only of muscle but of other body tissues in subsequent decades.

For example, Sood and colleagues from Kings College, London, demonstrated that a particular RNA profile initially identified in muscle biopsies from a small sample of healthy individuals at age 65, could be used to predict subsequent health of kidneys and brain in several independent samples of elderly people. In one sample followed for 20 years, this profile proved to be a significant predictor of overall survival. Sood proposes that this RNA profile, initially identified in muscle, is a robust marker of healthy aging.

The finding that the state of gene expression in muscle at age 65 can be a good predictor of subsequent overall health is consistent with the observation that self-selected walking speed in late middle age is a strong predictor of survival, and is perhaps of special interest to dedicated runners, though we should not read too much into the fact that the investigators chose to examine muscle tissue. At this stage many question remain unanswered. Two key questions are: what does the set of proteins that are specified by the RNA profile identified by Sood tell us about the molecular processes that characterise healthy aging; and what are the factors that determine the RNA profile in muscle in middle age.

Examination of the list of proteins specified by the identified RNA profile provides few strong clues regarding the molecular processes that characterise healthy aging. Some of the proteins have a known role in cell survival. Perhaps disappointingly for anyone dedicated to running, none of the proteins are those known to be produced in response to vigorous exercise.   However, I am not greatly surprised by this. Although the sample of individual in who the RNA profile was initially identified were healthy and active, none were athletes.   Nonetheless even as a dedicated runner, I find it intriguing that there are features in the current internal state of muscle fibres, other than (or perhaps in addition to) the recognised consequences of vigorous exercise, that indicate current good health and predict future well-being. Vigorous exercise is not all that matters.

Furthermore, the identified RNA profile does not include diminished amounts of the RNA associated with the known risks for diabetes and cardiovascular disease, suggesting that there are aspects s of healthy aging that are not specifically associated with low risk of heart disease. This implies that current guidelines for a healthy lifestyle, which focus largely on known factors associated with cardiovascular health, might fail to include other important aspects of healthy aging.

Perhaps the most important practical issue is whether we can do anything to promote the development of a healthy RNA profile. In general, RNA profile is determined by a combination of genetic and environmental factors.   The fact that genes themselves are not a strong predictor of longevity (except in the small group of exceptional individuals who reach extreme old age) makes it plausible that environmental factors play a large role in promoting the identified healthy RNA profile in middle age. At this stage there is little reason to propose that these factors are uniquely related to muscle. It is possible that influences from elsewhere in the body, such as neural regulation by the brain, the action of hormones or effects produced by other signalling molecules circulating in the blood stream, might shape the RNA profile in muscle.

It is likely that the challenge of remaining a healthy athlete into old age is a ‘whole body’ challenge, and I therefore look forward to future studies that might indicate what can be done to promote the development of a healthy RNA profile in muscle in middle age, irrespective of whether the direct site of action is in muscle or elsewhere in the body.

What can we do now?

Studies such as that of Sood and colleagues provide a fascinating pointer towards future investigations that might enable us to improve our chances of aging in a healthy manner, but it is reasonable to ask what guidance science provides now. In fact there is a substantial body of existing evidence about the mechanisms of cellular repair, protection and maintenance that allows us to make intelligent guesses about what might be helpful.

At the heart of this self-repair mechanism is the process of inflammation. This mechanism is not only responsible for repair of overt damage, but is also the mechanism by which training makes an athlete stronger and fitter. But the mechanism for self-repair does not confer immortality for two reasons. First, inflammation itself can leave a trail of debris in the tissues of the body. The debris is at least partially removed by the crucial scavenging process known as autophagy, but ultimately the residual junk gums up the works. Secondly, it appears that there is a limit to the number of times that the cells of the body can divide to generate new cells to replace those that are worn out. The gradual shortening of the protective telomeres on the ends of chromosomes is a crucial factor in limiting the number of times that cells can divide.

Cardinal among the processes that regulate the maintenance of living tissues are processes mediated by hormones. In particular achieving a balance between catabolic hormones that promote the break-down of tissues, including the process of autophagy, and anabolic hormones that promote the building of tissues, is crucial.

Finally, in light of the fact that gene expression matters throughout life, the cellular mechanism for protecting and repairing DNA itself, are likely to play an important role in life-expectancy and in our longevity as runners.


Figure 2: Schematic illustration of the mechanisms involved in cellular repair. These mechanisms are central to the response to training and also to the responses various other types of cellular damage that are crucial for healthy aging.

Although there is still much to learn about all of these processes, there are things that we can do now that help harness inflammation constructively, achieve a good balance between catabolism and anabolism and perhaps even promote the protection and repair of DNA. But this post has already grown long. I will address these issues in greater detail in future posts