Archive for the ‘Cross-training’ Category

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:

Cycling

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.

semimembranosis3

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.

Swimming

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   

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.

Conclusion

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.

 

Elliptigo.

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.

 

Conclusion

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.

Heart

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

 

Conclusion

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.

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.

IMG_2590.JPG

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.

HeptathlonEvents

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.

More thoughts on elliptical cross-training

February 16, 2009

In my post yesterday I suggested that although elliptical cross training might have many benefits for the runner, it might not be good for promoting the required neuromuscular coordination.  Ewen asks whether one factor is the lower cadence on the elliptical. In fact I aim for an elliptical cadence in the range 80-90 complete gait cycles per minute which is similar to my cadence when running (around 90 left steps and 90 right steps per minutes).  I did some testing of my efficiency (i.e. heart rate v power output) at different cadences and found that there is not a great deal of difference between 70 and 90 gait cycles per minutes.  Around 80 appeared marginally more efficient than  70 but not much different from 90.  However,as I mentioned yesterday, the striking difference between elliptical cross training and running is the amount of downwards push required, presumably due to the lack of elastic recoil on the elliptical.

 

Although the action of elliptical is intermediate between running and cycling insofar as the involvement of trunk muscles on the elliptical is similar to running (especially if you do not use the handles), the leg action on the elliptical feels somewhat similar to cycling.  I am not a triathlete, but I understand that for the first few minutes after the bike-to-run transition, running feels awkward, and that this awkwardness can be at least partially reduced by increasing cadence towards the end of the cycling.  I suspect that the awkwardness is due to the change  from recruitment of fast twitch fibres employed to power concentric contraction, to a greater dependence on slow twitch fibres and eccentric contraction.   (I would be interested to know what triathletes understand about this).

 

If the downwards push on the elliptical is similar to that of cycling, then an immediate transition from elliptical to running will have some of the problems of a bike-to-run transition.   As in the bike-to-run transition, the problem might be diminished by high cadence on the elliptical, but I suspect it will always be at least a minor problem.   I sometimes use the elliptical at high cadence and low resistance to warm up for running on very cold days.  I believe it does promote muscle blood flow and joint lubrication, but I have been surprised to find that I still need to do a running warm up before I can run fluently.  Whether or not elliptical training one day affects neuromuscular coordination the next day, I d not know, but in view of the theoretical possibility of interference, I would advise a good warm up for the running session to establish good neuromuscular coordination.

 

Related to the issue of the greater push on the elliptical is the likely greater development of fast twitch fibres.  Ewen asks how well these fibres can be recruited aerobically.  The distinction between aerobic and anaerobic function is not an all-or-nothing distinction.  I suspect a moderate degree of hypertrophy of fast twitch fibres is useful for all except ultra-marathon runners.  Whenever stride length increases beyond about 1 metre, a quite appreciable push is required to launch the body along the required trajectory, and as I mentioned yesterday, elastic recoil is not adequate to achieve this.  (Since passing age 60 I have become increasingly aware of the need to push to achieve a fast pace – maybe this would be heresy to the Pose School, but until I meet an elderly Pose runner who can run fast, I will be inclined to hold onto my current opinion). At cadence of 180 steps (i.e. 90 left, 90 right) per minute, paces faster than about 5.5 min/Km require a  stride length greater than 1 metre.   A pace of 5.5min per Km, which is only a moderate marathon pace, is below lactate threshold pace for many runners, so as far as I can judge, an appreciable concentric push is required even when running in the aerobic zone.  I suspect that this is best achieved using fast twitch fibres.

 

So in conclusion, I think that the greater amount of concentric push on the elliptical might cause neuromuscular coordination difficulties during an elliptical-to-run transition, but might produce greater fast twitch hypertrophy which would be beneficial provided it is not excessive.

 

Two days ago, Ewen asked if I thought that my decreased heart rate at a given power output on the elliptical might translate into a lower heart rate at lactate threshold when running.  I do not think this is likely.  Instead I would expect that an increase in mitochondria, increased capillary density, increased pumping capacity of the heart, and increased ability to metabolize lactate would all lead to a faster pace and an increased heart rate at lactate threshold.  I would regard this as a benefit.  I just hope it is true.

Transfer of the benefits of elliptical cross-training to running

February 15, 2009

As usual, Ewen raises the important question about my post yesterday about improvements in aerobic efficiency during 3 months of elliptical cross training.  He asks whether or not the observed improvement would be expected to result in a lower heart rate in the vicinity of lactate threshold when running.  Implied in this question is the more general question: will the observed improvement in aerobic fitness lead to improved performance when running.  I do not know.

 

The definitive proof of the pudding will come when I test myself in a race.  However, many factors affect race performance. In my case, my tendency towards asthma places me at the mercy of my only partially controllable bronchi, so a particular race might be more influenced by daily fluctuations in the irritability of my bronchi than by overall change in aerobic fitness.  Therefore I need a test that is relatively unaffected by variable outside air temperature and humidity, and the muddiness of the terrain; and furthermore, produces little DOMS so it can be applied fairly frequently, allowing averaging to minimize the effect of daily fluctuations.  That is why I developed this elliptical test for aerobic fitness.  The dilemma is that I can only speculate on the likelihood that the gains in aerobic fitness on the elliptical will transfer to fitness for running.  I am still evaluating the relevant evidence, but here are my currents thoughts.

 

The goals of aerobic conditioning for running are:

1)      Increasing the number of mitochondria in muscle fibres. The mitochondria contain the enzymes that carry out oxidative metabolism; that is the combining of glucose with oxygen to generate relatively large amount of energy.  Increasing mitochondria should increase the ability to generate energy efficiently, provide enough oxygen and glucose can be delivered to the muscles.

2)      Increasing the efficiency of the heart as a pump.

3)      Promoting development of new capillaries in muscle so that blood (and hence oxygen and glucose) can be delivered to muscle fibres at a higher rate.

4)      Increasing the ability to metabolise lactate.  When the rate of supply of oxygen is insufficient, energy is produced by anaerobic metabolism  in which glucose is converted to lactate.  Although  this process is the dominant process once the ‘anaerobic threshold’ is exceeded, in fact this threshold is not an all-or-nothing threshold.  In the upper part of the aerobic zone, when oxygen delivery is not quite adequate, a certain amount of lactate is produced.  Build up of lactic acid leads to eventual transition into the anaerobic zone that can only be sustained for a limited time before rising acidity impairs muscle function.  This build up might be delayed if the ability of muscles and perhaps other tissues to remove lactate, is increased. In fact, lactate is also oxidized in mitochondria, so enhanced mitochondrial function should help delay the build up of lactate.

5)      Improving neuromuscular efficiency – the ability of the central nervous system to recruit muscles in the most efficient manner.

6)      Re-modelling of tendons, ligaments and bones to withstand the stresses of running

7)      Hypertrophy of muscle fibres.  During aerobic conditioning, I believe that the main mechanism of increase in the strength of muscle is likely to be the increase in mitochondria and capillaries listed above; during anaerobic resistance training, hypertrophy is due to incorporation of additional protein into muscles.  It is nonetheless probable that some strengthening of contractile proteins occurs during aerobic conditioning.  The skinny legs of many elite distance runners suggests this strengthening makes only a minor contribution to fitness for distance running, but even a distance runner needs to be able to exert  at least a moderaltey powerful downwards push at the end of stance because elastic recoil is far from 100% efficient and therefore elastic recoil is unable to supply an adequate push to propel the body along the required trajectory in the airborne phase. 

 

So which of these processes is likely to be enhanced by elliptical cross training, which are likely to be unaffected and which might actually be harmed?

 

Development of the heart as a pump is likely to be similar for a similar work elliptical work load as for running.  Development of mitochondria and capillaries is also likely to be similar, though  there is a possibility that the development will be a little more focused on fast twitch fibres, because the concentric contractions characteristic of the elliptical training are a little to likely to recruit fast twitch fibres. The development of ability to metabolise lactate is likely to be similar for the two types of training.

 

Elliptical training is unlikely to be effective in fine tuning of neuromuscular coordination for running.  The ability to capture the gravitational energy associated with the vertical oscillations of running, in the from of elastic energy that can be recovered at lift-off, is a crucial factor in efficient running.  The elliptical does not develop the exquisite neuromuscular coordination required for this.  Similarly, elliptical cross training does not provide much stress on tendons, ligaments  and bones, and hence will not be very effective in remodeling these structures to withstand the stress of running.  On the other hand, as I discussed in my post about reactive oxygen on February 5th,  the benefits of running might be offset by permanent damage to muscle fibres.  Such permanent damage appears to be less likely with elliptical training on account of the lesser amount of eccentric contraction.

 

Finally, I suspect that elliptical training might actually produce greater hypertrophy of muscle due to incorporation of protein in the contractile machinery with the muscle fibres, than running.  Because there is minimal elastic recoil, the elliptical demands a stronger downwards push by the leg muscles. I suspect that this will be more effective in producing hypertrophy of fast twitch fibres.  Too much hypertrophy of fast twitch fibres might be harmful, though at least for oldies like myself, in whom deterioration of fast twitch fibres is likely to play a major part in the shortened stride that makes us slow, I think a moderate amount of development of fast twitch fibres is probably beneficial.

 

Summary

So in summary, elliptical cross-training is likely to increase the pumping capacity of the heart, increase mitochondria and capillaries in muscle and increase the capacity to metabolise lactate.

 

It is unlikely to do much to strengthen tendons, ligament ad bones, but on the other hand, is also much less likely to cause permanent damage to either these connective tissues or to muscles.  It will not refine the exquisite neuromuscular control required to capture gravitational energy as elastic energy, and to recover via recoil at lift-off when running.

 

It might promote a slightly greater degree of hypertophy of fast twitch fibres than an equivalent amount of running.  I am inclined to think that on balance this might be beneficial, especially for older runners.

 

As Ewen suggests, it might be useful to replace the training session the day before a high quality running session with an elliptical session to help ensure that the muscle are in good shape for the high quality session.  However, in the warm up for the quality session, it is probably all the more important to include some brief bursts of running at the quality training pace, so as to recover optimal neuromuscular coordination for running at that pace.

 

Most of this is speculation.  I hope that when the spring arrives my bronchi will allow me to assess the fruits of my elliptical sessions, in a 10K race.

Snow drops and improved aerobic fitness

February 14, 2009

I am just back from an easy 10K run in the woods and along the river bank. We are now at the mushy end of a thaw that set in two days ago. At the edge of the village, two slumping lumps of snow are all that remain of a snowman and his partner; a sad demise on St Valentine’s day.  In the woods a few drifts of mushy snow remain and some mini ice floes float in scattered puddles, but the paths are mainly mud. 

 

Staying upright is almost as difficult as it was on the sheets of icy snow last week.  Mud does not raise the spirits in the way that snow does.  However, the clumps of snow drops in full bloom provide some compensation and the thick green carpet of bluebell shoots indicate that spring is not too far away.

 

The River Trent is in spate, swollen with melt-water but still far from bursting its banks.  Nonetheless, the ancient mill race on the escarpment side of the riverside path, but connected to the river by a tunnel, is full of water.  On account of the mud it took some time before I developed a good rhythm, but in the final few Km I was running fluently and comfortably at about 5:30 min per Km.

 

In November, at the time when I decided to re-introduce several elliptical cross-training sessions into my weekly schedule, I had developed a simple test of aerobic fitness.  I record heart rate in the final 15 sec of a series of consecutive 2 minute intervals.  At the beginning of each interval I increase the resistance but maintain a constant cadence so that power output increases in a series of 7 steps spanning the aerobic zone.  Before my run today I did this aerobic test as a warm up, and was pleased to find that my heart rate at each level of the test is about 12 BPM lower than it was on November. 

 

In part this improvement is due to the fact that my asthma is much better today.  There was scarcely a trace of a wheeze. My performance on this test fluctuates day by day depending on how wheezy I am.  It is probable that I will not do as well in future on days when the wheezing is worse.  However even if I were to take the average the most recent three tests and compare with the average of three tests done in November to smooth out the daily fluctuations, there would still be a definite improvement, perhaps by around 5 BPM at each level. 

 

 

Heart rate v power on the elliptical cross trainer

Heart rate v power on the elliptical cross trainer

 

 

 

 

This improvement has occurred over a period of three months during which I have done 2 or 3 easy (or moderate intensity) running  sessions and 3 to 5 elliptical sessions per week, apart for a few weeks in which training was curtailed by injury.  The majority of the elliptical sessions have been in the upper part of the aerobic zone (30 – 35 sessions over the three months). I have done a total of 5 sessions in which I exceeded lactate threshold, and 4 sessions in the lower or mid aerobic zone. 

 

One good thing about elliptical training is that it does not produce any appreciable leg muscle soreness on subsequent days.  This is almost certainly because of minimal eccentric contraction.  The lack of eccentric contraction during the elliptical sessions will probably have resulted in some de-conditioning of my legs, and it is unlikely that I could run anywhere near my potential best over 10K or a half marathon at present.  The interesting question is how much running will be required to re-condition my leg muscles for running.  Whatever the answer to that question, it is pleasing to know that I have been able to improve aerobic fitness substantially without stressing my legs.  

Cross training

January 18, 2009

The past few days have not been kind to my lungs. My peak expiratory flow has fluctuated between 500 litres/min (fairly good) and 240 litres/min (a level at which even mild exercise causes me to wheeze). I am not sure why the situation has deteriorated, as the weather has been milder this week with air temperatures well above zero degrees C. Today I did 4x1Km aiming for mean heart rate 142. I found it more effortful than last week. I managed to keep the mean HR at 142.5, but my average time per Km was 4:24, compared with 4:21 last week, and 4:20 in early December before my current episode of respiratory problems began.

I have contemplated stopping training for a while, but I doubt that would help, as my respiratory problems usually tend to persist for months following a cold or flu. During my short-lived return to running in my late 50’s, I developed a cold and stopped running. I still had symptom three months later, and had lost most of my fitness. The current symptoms are mainly due to excessive reactivity of my airways to any irritation rather than persistent infection. Unless I develop clear signs of bronchitis, I will persist with light to moderate intensity training. At this stage I am undecided about the mile race next week. If there is no further deterioration I might run, but an M60 PB is unlikely.

Cross-training

Since the onset of my breathing problems I have been doing a moderate amount of indoor training on the elliptical cross-trainer to minimize exposure to the cold air that irritates my bronchioles. In a recent comment Ewen raised the question of whether or not low intensity running might be as beneficial as cross-training. As with most questions to do with the optimal way to train, the issue is debateable. Some of the relevant ‘facts’ are:

1) A previously fit runner who changes to a program of cross-training alone, will suffer a substantial deterioration in running performance.

2) A previously fit runner who adds cross-training to his/her current training program can achieve a worthwhile improvement in running performance.

3) High volume running produces short term damage to muscles which can promote improved performance after recovery.

4) High volume running can result in muscle damage which is more persistent than that due merely to over-training, and may be permanent, in at least some individuals.

Each of these ‘facts’ is supported by a substantial amount of scientific and anecdotal evidence, but I do not have time to address all of these issues today. Maybe in future posts I will look at the evidence for each of these statements in some detail. Today I want to address several speculative issues that are relevant to Ewen’s comment:

1) In races run at paces in the vicinity of lactate threshold pace (10K to marathon) the ability to remove lactate from the blood stream is as important as the minimization of lactate production.

2) Elliptical cross training (and cycling) might be more effective than low intensity running in engaging fast twitch fibres (which tend to work anaerobically and therefore produce more lactate) but does less damage to muscle than is typical of high intensity running. Therefore, elliptical cross-training might be a safer way to develop the capacity to remove lactate from the blood stream.

Increased removal v reduced production of lactate

A study by Tim Noakes and colleagues from Cape Town demonstrated that lower blood lactate values during exercise after training were due to diminished lactate production at low work rates but in contrast, were due to elevated removal of lactate higher work rates, (McRae et al, Effects of training on lactate production and removal during progressive exercise in humans, Journal of Applied Physiology, Vol 72, 1649-1656, 1992). Thus, when running at paces near or above lactate threshold, the ability to remove lactate appears at least as important as the ability to minimize production of lactate.

Engagement of fast twitch fibres during concentric contraction

Resistance training typically engages fast twitch fibres resulting in muscle hypertrophy, whereas high volume low intensity running engages slow twitch fibres resulting in improved endurance, but minimal hypertrophy. This is dramatically illustrated by the identical twins, Otto and Ewert, described by Mike Rennie in the GL Brown Prize Lecture on Physiology in 2005 (Rennie, M., Exp. Physiol vol 90 pp 427-436). Otto trained for endurance events and developed a lithe, endurance runner’s physique, Ewert trained for field events and developed the ‘walnuts in a stocking’ look that Arnold Schwarzenegger subsequently emulated. Depending on taste you might find Otto a little puny. (See http://www.arthurdevany.com/webstuff/images/Twins.tiff)

In examining the effects of resistance training on different muscle fibre types, it is important to take account of the differences between concentric contraction, in which the muscle shortens as it develops tension, and eccentric contraction, in which the muscle is required to develop tension while it is being stretched.  A study of the effects of a resistance training program involving eccentric and concentric muscle contractions compared with concentric contraction alone, conducted in Gary Dudley’s lab, demonstrated that the combined eccentric/concentric program produced hypertrophy of both fast twitch and slow twitch fibres, whereas the program that included only concentric contraction (but similar total workload) produced mainly hypertrophy of fast twitch fibres. (Hather et al, Acta Physiologica Scandinavica, Vol 143 , Pp 177 – 185, 1991). Thus, for maximal development of muscles fibres during resistance training, it is necessary to combine eccentric with concentric contraction.

It is also of interest to note that concentric training produced an increase in capillaries per fibre area for both fast and slow twitch fibres and that the increases in capillaries were maintained 4 weeks after discontinuation of training.

Differences between running and elliptical training

It is necessary to be cautious in applying any conclusions from a study of resistance training to either running or elliptical training. Nonetheless, it is noteworthy that running and elliptical training differ in the relative amounts of eccentric and concentric contraction. Running involves relatively more eccentric contraction. In the quadriceps, the majority of the work while running is eccentric contraction performed as the muscle is stretched at footfall. In contrast, elliptical cross-training involves a more sustained concentric push by quadriceps. Thus elliptical training would be expected to engage fast twitch fibres to a greater extent. This is consistent the observation that ventilatory threshold (and therefore, the lactate threshold) occurs at a lower heart rate and lower level of energy consumption on the elliptical. This implies a higher proportion of anaerobic contraction, which is characteristic of fast twitch fibres.

So elliptical training (and also cycling) apparently differs from running by relatively greater engagement of fast twitch fibres and greater lactate production at a given level of energy consumption. Elliptical training might therefore be useful for developing the ability to metabolise lactate. Is this likely to be a beneficial form of training for a runner? At first sight it appears to be a waste of time for a distance runner to miss an opportunity to employ eccentric muscle contractions which might be used to develop both slow and fast twitch fibres. It should be noted that, contrary to the teachings of Hadd, even at running paces that engage predominantly fast twitch fibres there is also at least some development of slow twitch fibres – (see Dudley et al. Influence of Exercise Intensity and Duration on Biochemical Adaptations in Skeletal Muscle,’ Journal of Applied Physiology, vol. 53, pp. 844-850, 1982). But running at paces fast enough to induce the enzymes that metabolize lactate is where the issue of muscle damage enters the equation.

I can do elliptical sessions including about 30 minutes at the ventilatory threshold on four consecutive days without noticeable muscle stiffness or pain, whereas two consecutive days of running at ventilatory threshold pace for 30 minutes leave me a bit stiff and sore – yet I have spent far more hours running than training on the elliptical and would therefore expect to be relatively better adapted to running.

In conclusion, the elliptical appears to offer the prospect of inducing production of the enzymes that metabolize lactate with minimal wear and tear on the muscles. This is a tentative conclusion based on a slender evidence base, and I will not be convinced that it will lead to more effective training until I have more experience of putting it into practice. Nonetheless, I think the evidence is good enough to justify a trial of mixing running and elliptical sessions.

So for the time being, I will continue with both running and elliptical sessions. The running will include low intensity sessions and a small number of moderate intensity sessions. The low intensity running sessions are designed to increase mitochondria in slow twitch fibres thereby decreasing lactate production, while also increasing ability to metabolise fat and strengthening connective tissues. The moderate intensity running sessions are designed to increase mitochondria in both slow and fast twitch fibres producing not only a decreased rate of lactate production but also increasing the ability to metabolise lactate. The elliptical sessions will be mainly of moderate to high intensity, with the goal of increasing the ability to metabolise lactate and also increasing capillaries per fibre, but with minimal risk of muscle damage. Thus each type of session has its own major goals. There is of course the risk that mixing the various types of sessions will be counter-productive, but that is another complex issue that will have to be deferred to another day.

Intervals again, and some thoughts about cross-training

January 10, 2009

Today I resumed moderate intensity running sessions after a period of lower intensity training due to a respiratory infection and its aftermath. I did a 4x1Km interval session on the riverside path, aiming for mean HR 142 (around 90% of HR maximum for an old-timer like me). On the first repetition, the breeze was behind me and I went too fast (4:13 per Km, with mean HR 145) but then settled down well to achieve mean HR 142 on the subsequent three repetitions, giving an overall mean HR of 143 and mean pace of 4:20 /Km. This is similar to my performance a week before I was smitten with a respiratory tract infection in early December, when I achieved a mean pace of 4:21 /Km at mean HR 142 in a 6x1Km session. Today’s session felt a little harder – probably because I had started too fast – but overall, I am pleased that I have not suffered any appreciable loss of fitness during my period of illness and convalescence. In fact I hope that my aerobic base fitness might actually have improved a little as a result of the relatively large volume slow running over the holiday season.

During my convalescence I have also done an increased amount of cross training on the elliptical cross trainer. The elliptical cross trainer is probably an excellent mode of exercise for non-athletes who wish to maintain a moderate level of aerobic fitness with minimal risk of injury. However, it is not clear how useful it is for runners. The available evidence is sparse. One study from the Human Performance Lab at Appalachian State University indicates that performance in a 3Km time trial deteriorated by 48 seconds during 5 weeks of elliptical training that included one lactate threshold interval session, one sprint session and 3 or 4 easier sessions per week, but no actual running. A comparison group who did ‘off season’ running training during the 5 weeks actually improved their 3K run time by a small amount (9 seconds – not a statistically significant improvement, but certainly not a deterioration). So it is unlikely that the elliptical alone is much use for preparing for a race (Honea and Dumke, http://www.osr.appstate.edu/present/documents/Honea-student_research_poster.ppt).

However, my own preliminary observations led me to wonder whether or not the elliptical might have a useful role. I found that I reached ventilatory threshold at a lower heart rate (and greater perceived effort) on the elliptical compared with running. My first impression was that this merely confirms that elliptical cross-training is a less enjoyable way of getting out of breath. This conflicts with the claims of the manufacturers who emphasize that perceived effort is less on the elliptical, but I think those claims mainly apply to non-runners working at a level well below lactate threshold, where the smoothness of the ‘ride’ is indeed quite relaxing.

But I was intrigued to understand why the ventilatory threshold appears to occur at a lower heart rate. This suggests that more lactate is produced at a given heart rate, implying that anaerobic metabolism of glucose kicks in at a lower heart rate.

To investigate this further I searched the sport medicine literature and found a recent study by Garlatz and colleagues from Western Washington University (The FASEB Journal. 2008;22:1175.2). In a group of trained distance runners they found that at 90% of Working Heart Rate Range, perceived effort was higher but oxygen consumption lower on the elliptical cross-trainer compared with the treadmill. This confirms my own observation, and strongly supports the hypothesis that there is a higher proportion of anaerobic glucose metabolism at this heart rate on the elliptical.

In retrospect this is easy to understand. The action of the elliptical involves a strong push, especially by quadriceps which are active though most of the gait cycle, whereas the quads are only active for a small part of the gait cycle when running.  However when running the quads suffer a lot of stress because they work hardest when being stretched at footfall – and this generates the micro-tears that might cause DOMS the next day. In other words, on the elliptical, the quads do more work but it is different in nature and potentially less damaging in comparison with running. It is likely that the additional work recruits a higher proportion of fast twitch fibres which tend to metabolise glucose anaerobically. Thus elliptical cross training might be a very good way to improve the body’s capacity to handle lactate with relative little damage to muscles.

If you want to run a fast 3K, you really need to train your muscles to cope with large eccentric loading. The elliptical is probably not much use for this but may nonetheless have a useful role to play in improving the capacity to metabolise lactate with minimal damage to muscles.