Threshold training: integrating mind and body

February 5, 2017

There is little doubt that ability to minimise acid accumulation in muscle and blood while running at race pace is a major determinant of performance at distances from 5K to marathon.  However the question of how best to train to achieve this ability is less clear.

This ability depends on several different physiological capacities. On the one hand, there are capacities such as cardiac stroke volume, capillary supply to muscles, and aerobic enzymes in the mitochondria that contribute to the overall capacity to generate energy aerobically, and thereby minimise production of lactic acid.  On the other hand are the physiological capacities that determine the ability to transport and utilise lactic acid. These include the transport molecules located in cellular membranes that transport lactic acid out of the fibres, especially type 2 fibres, where it is generated.  After transport out of type 2 fibres it can be taken up into type 1 fibres with the same muscle where it can be used as fuel, or carried via the blood to other organs such as the heart where it can be also used as fuel, or to the liver, where it can be converted by the process of gluconeogenesis into glucose and thence stored as glycogen.   All of these physiological capacities contribute to the ability to minimise lactic acid accumulation at race pace and all can be trained, to at least some extent,  by sustained running at threshold pace.

 

Specificity v Variety

Many coaches and athletes, including renowned coach Jack Daniels, have argued that the optimum form of training to minimise lactic acid accumulation at race pace is threshold training (i.e. sustained running at a pace in the vicinity of the threshold at which lactic acid begins to accumulate rapidly) or cruise interval sessions, in which epochs of moderate duration at a pace a little above lactate threshold alternate with recovery epochs at a lower pace to allow some dissipation of the acidity.  Threshold training is consistent with the principle of specificity: namely that the most efficient way to enhance the ability to sustain race pace is to train at a pace near to race pace.

However, there are several reasons to question the principle of specificity  Perhaps most important is the likelihood that if you rely on running near threshold pace as the main way to enhance this ability, your body will make use the physiological capacities that are already well developed to achieve the target pace during training sessions.    If some of the required physiological capacities are less well developed, it might be more efficient to spend time training is a manner that challenges those less developed physiological capacities.  For example, if ability to transport and utilize lactic acid is relatively weak, high intensity intervals will generate large surges of lactic acid and will challenge the mechanism for transporting and utilizing lactic acid.

As discussed in a recent post, many different types of training session, ranging from long runs at a moderate aerobic pace; threshold runs; to high intensity intervals can help develop the various physiological capacities required to minimise acid accumulation while running at race pace.  In general, it is likely to be best to employ a varied training program that utilises all of these types of training to promote that all of the required physiological capacities.  The proportion of the different types of training should be adjusted according to the athlete’s specific needs and also to the goals of the phase of training. During base building, when a substantial volume of training is required to build overall resilience while also building a large aerobic capacity, it is best to place the focus on lower intensity running to avoid accumulation of excessive stress. Nonetheless, some more intense training should be included in the phase, in part because it is an efficient way to develop aerobic capacity (as demonstrated by the many studies of high intensity interval training) and also because a judicious build-up of intensity develops the resilience of tissues to cope with high intensity in the pre-competition and competitive seasons.

To minimise risk of injury, there should be a gradual build of the intensity of the sessions training during base-building; intense training should generally be avoided when tired; and within any intense session, thorough warm up is crucial.  As discussed in my recent blog post, there are some grounds for proposing that risk of injury might actually be higher during sustained running at threshold pace than during more intense interval sessions provided you take adequate precautions to minimise risk of injury.  Nonetheless, there is little doubt that threshold sessions have an important part to play in the training of a distance runner. But rather than regarding such sessions as the universal answer to the question of what session to do to enhance the ability to sustain race pace, it is more sensible to utilise these sessions to achieve more specific goals.

One of the truly specific roles of the threshold session is training the body to integrate all of the physiological capacities required for distance racing.   The human body is a multi-organ system in which each individual organ, especially heart, lungs, muscles and brain, but also other organs such as liver and adrenal glands, plays a specific role in distance running performance.  Threshold training promotes the required integration of this diverse orchestra of organs.  For the most part, this integration occurs unconsciously.  We do not need to think about it.  This truly amazing integration of different physiological processes occurring in different organs is achieved by an intricate network of nerves, hormones and other signalling molecules, without the need for conscious intervention.  Indeed attempts to intervene consciously often led to less efficient integration, as is indicated by the finding that in some instances, runner who focus on internal processes such as breathing run less efficiently than runners who focus on things in the external world.

Brain and mind

The brain via its role as the central processing unit of the nervous system and also as a high level regulator of the endocrine system, plays a cardinal role in this integration.  For the most part, the brain carries out its integrating role non-consciously, but we would be missing out on two of the very valuable features of threshold training if we ignored its value in training conscious brain processes.

The first of these is the development of the confidence that butresses the self-talk that is sometimes necessary to overcome a self–defeating internal dialogue during a hard race.   In general I try to avoid doing demanding threshold sessions when I am tired or stressed because of the risk of injury at such times, but sometimes a scheduled hard session cannot reasonably be deferred.  This is the time to make a virtue of necessity and use the session as an opportunity to prove to your doubting mind that you really are capable of pushing through pain.  In fact quite often it is helpful to reframe the word ‘pain’ in such circumstance, because what our mind might tend to interpret as pain during a threshold session on a stressful day should more accurately be described as a level of effort that we are not confident that we can sustain for more than another few minutes.  Almost invariably we can sustain this level of effort for longer.  Demonstrating this provides evidence to buttress the self-talk we might require in a subsequent occasion in a hard race.

In my view, even more important than the development of mental strength to deal with hard races is the opportunity that threshold training offers to facilitate the ability to get into that almost magical state known as the zone.  When we are in the zone running seems almost effortless.  We feel exhilarated, in control, and above all, confident.  The zone is a state of consciousness, but it is not a state that we can easily adopt consciously.  When it occurs it can feel like a state of grace endowed upon us by something outside of ourselves.  Nonetheless we can facilitate it.  Threshold running can provide great opportunities for developing the ability to facilitate it.

In my younger days, for several years I lived in a house facing the beach in Brighton, a sea-side suburb of my home town, Adelaide.  My favourite Sunday morning run took me from sea level to the summit of Mount Lofty, the highest point in the Adelaide Hills.  I ran up the gorge of Sturt Creek and through Belair National Part to the summit.  My return journey started with a steep descent of Waterfall Gully, followed by an almost level run on pavement via the eastern and southern suburbs of the city, back to my sea-side home. The total journey was around 25 miles.  It was my version of the run that Lydiard’s athletes did regularly on Sunday morning in the Waitakere Hills above Auckland, though perhaps a little more demanding in both terrain and distance.   My ascent of more than 2000 feet was often quite a slog, but the descent though Waterfall Gully was exciting.

waterfallgully

Waterfall Gully (photo: Nabo.co.au)

Nowadays there is a well-made walking path from the lowest waterfall to the summit, but in those days, almost fifty years ago, the gully was wild.  In many places the most feasible route involved hopping from rock to rock in the bed of the stream itself.   On a good day, when my legs felt strong and sure as I leapt nimbly from rock to rock, I emerged onto the road below the lowest waterfall thoroughly exhilarated.  On such days, I ran a large portion of the remaining distance at a fast tempo, around 10K race pace, aided by the slight descent with average slope of about 1% to sea level.  Even now, decades later, I have a clear memory of the sense of power and confidence as I ran.   Around that time I was able to recreate the same sensation of power and confidence during several races. Those races are among the most cherished memories of my running career.

Even in a polarised training program that places the main emphasis on a high volume of relatively  low intensity training with a small amount of high intensity training, there is a place for threshold training, perhaps around 10% of total training.    Those sessions have a crucial role to play in training the body to integrate the diverse physiological capacities required for distance running, and in particular, provide a valuable opportunity for training the brain to achieve integration of mind and body.

Polarized Training and Injury Prevention

December 29, 2016

Avoiding injury is one of the major goals of training for distance running.  On account of the impact forces experienced at footfall on every stride, runners are uniquely prone to injury.  However, effective strategies for preventing injury are elusive.  In recent years, advocates of techniques such as Pose have claimed that injuries are largely due to poor running technique, and have promised that the problem can be overcome by proper technique.  In particular, they have identified heel striking as a cardinal problem.  However, there is very little evidence to support this claim.   Others have advocated stretching during warm-up as a strategy to reduce risk of injury, though the evidence provides little support for this claim.  Advocates of barefoot running have proposed that running shoes are the problem, but again there is little evidence to support the claim that running barefoot or in minimalist shoes reduces risk of injury.  Conversely, the manufacturers of running shoes have placed blame on foot orientation problems such as over-pronation and claimed that motion control shoes can reduce this risk.  Yet again, the evidence is slight, though at least one study had found that over-pronation is associated with increased risk of injury.

It is likely that a wide variety of factors contribute to injury in different individuals.  Meta-analyses that pool the findings of many studies are only likely to identify risk factors that are common to many athletes.  Two risk factors emerge consistently: a history of previous injury; and a large weekly volume of training.   Lisa Callaghan has provided an up-to-date review of the evidence.

Prior injury

A history of previous injury might predispose to subsequent injury simply because the athlete has not corrected problems that contributed to the first injury.  It is also possible that unsatisfactory recovery from the previous injury plays a role.  Muscles, tendons and other connective tissues tear when subjected to force that exceed the limits of their resilience.  A cardinal factor in the resilience of connective tissues is the elongated spring-like structure of collagen fibres, making them resilient against forces acting along the direction of the fibre.  During the initial stages of repair following injury, collagen is laid down with random orientation providing a framework for tissue renovation, but full resilience requires remodelling such that the collagen fibres become aligned in the required direction.  Therefore effective recovery requires early mobilization to promote the laying down of appropriately aligned fibres, perhaps augmented by slow stretching.

Training volume

Observational studies report that training volumes of 65 Km (40 miles) or more per week are associated with higher rates of injury [Fields et al; van Ghent et al].   In part these observations might simply reflect the greater duration of exposure to risk of injury, though it is likely that fatigue plays an important role.   In particular fatigue impairs neuromuscular coordination increasing the likelihood of poor coordination between different types of muscles fibres within a muscle and poor coordination between muscles that act as agonists and antagonists, resulting in excessive local forces within tissues.

Polarized training

Simply limiting training volume is unlikely to be a satisfactory strategy for many runners, making it desirable to identify alternative strategies to reduce the damaging effects of fatigue.  As the forces exerted increase with increasing pace, it might be expected that injury risk would be greater at faster paces. However the observation by Van Middelkoop and colleagues that among marathon runners, those who do interval training have a lower risk of knee injury raises an intriguing question.  Could it be that interval training provides greater protection than training at   somewhat lesser paces in the vicinity of lactate threshold?   Interval training, in which short efforts at fast but sub-maximal pace are separated by recovery periods, tends to promote the development of neuromuscular coordination with relatively mild muscle fatigue.  As discussed in my recent post, interval training is likely to promote a favourable balance between anabolic and catabolic hormones, leading to strengthening of tissues. In contrast, running for a sustained period at threshold pace might produce fatigue with the associated risky deterioration of neuromuscular coordination during the session, and also tip the balance towards the catabolic effects of cortisol, promoting subsequent breakdown of tissues.

Even more speculatively, the viscoelastic character of the musculotendinous unit might result in a peak risk of damage to muscles and tendons at threshold paces. Viscoelastic materials offer strong resistance to brief sudden onset forces but less resistance to sustained forces.  Although force is greater at sprinting pace, time on stance decreases.  At speeds above LT there is actually a decrease in the impulse acting through the foot at each step because the increased force is more than compensated by  reduction in time on stance.  The product of forces x time on stance actually decreases, as illustrated in figure 1 based on data from the study by Weyand and colleagues.

ImpactForce&Impulse

Figure 1. Upper panel: the average vertical force (expressed relative to body weight) during stance as a function of running speed. Lower panel: the vertical impulse (average force x duration of stance) transmitted through the leg during stance as a function of running speed.

Thus, it is possible that the risk of tissues tearing is actually less at sub-maximal paces substantially above LT than in the vicinity of LT.   Nonetheless, it is crucial to prime the requisite neuromuscular coordination during the warm-up (for example by moderate intensity strides) and it is generally desirable to avoid absolutely maximal effort that taxes neuromuscular coordination to the limit, during training.

The other pole of polarised training is low intensity running.  This has the potential to build resilience of the muscles, tendons and the other connective tissues engaged during running by repeated application of moderate forces.   Provided training volume is built-up gradually and excessive fatigue is avoided, the risk of injury is low.

Conclusion

While the predisposing and precipitating factors causing running injuries remain controversial, consistent evidence indicates that a high weekly training volume increases the risk.  In contrast, the observation that interval training provides some protection suggests that polarised training might diminish the risk.  Observational evidence and also speculation based on principles of biomechanics and physiology suggest that high intensity sessions have the potential to build effective neuromuscular coordination, while low intensity training would be expected to enhance the resilience of muscles, tendons and other connective tissues with relatively little risk.  Nonetheless, as with any type of training, it is important to build up the training load gradually, and to warm up for each session in a manner the primes the requisite neuromuscular coordination.

How does polarised training minimise lactate accumulation?

December 23, 2016

My previous post discussed evidence indicating that training in the vicinity of lactate threshold (LT) can lead to sustained elevation of cortisol which has the potential to damage to the neuromuscular system and suppress immune responses.  In particular, the study by Balsalobre-Fernandez indicates that frequent training at or a little above lactate threshold is more damaging than a lesser amount of training at a higher intensity.   This might be the key to understanding why a growing body of evidence favours polarized training, which includes a large volume of low intensity training, a small amount of high intensity training and a similarly small amount of threshold training,  in preference to a training program with a higher proportion of threshold training.

As distance races from 5 Km to marathon are raced in vicinity of lactate threshold, pace at LT is a crucial determinant of performance.  Enhancing the ability to delay the onset of lactic acid accumulation as pace increases is one of the key goals of training.   The effectiveness of polarised training raises the question of how a program with only a small about of threshold training might nonetheless be effective in enhancing ability to minimise lactate accumulation.

Lactate accumulation might be minimised by decreasing the rate of production and /or increasing ability to remove it.  The rate of production can best be minimised by increasing the capacity to generate energy aerobically, which in turn might be enhanced by increasing the capacity of aerobic enzymes in mitochondria and/or increasing delivery of oxygenated blood to muscles.

Developing Aerobic Capacity

While a large volume of low intensity running would be expected to increase the aerobic enzymes in slow twitch fibres, the more challenging question is how to enhance the aerobic capacity of fast twitch fibres.  Low intensity running beyond the point of exhaustion of slow twitch fibres might help achieve this, but frequent very long runs create the risk of excessive stress.   For many years followers of Arthur Lydiard’s approach to periodization, in which the base-building phase is almost exclusively devoted to relatively low intensity aerobic running, have  maintained that when you bring speed work into the program, you halt the development of aerobic enzymes. The size of the engine is now fixed; the task of speed work is to tune this engine.

This claim was associated with a widespread belief that the acidity generated above LT prevented development of aerobic enzymes, and perhaps even damaged them.   This belief is ill-founded.  Extensive research into high intensity interval training (HIIT) in recent years has demonstrated that HIIT is a very efficient way to increase the capacity of aerobic enzymes.  The available evidence indicates that HIIT achieves the enhancement of mitochondrial enzymes via the increasing the activity of the messenger molecule, PGC-1alpha, the same messenger as  appears to mediate mitochondrial development in response to lower intensity endurance training

HIIT research is largely focussed on comparing high intensity training with low intensity training and has not so far investigated the potential benefits of a polarised approach.  It would be anticipated that in a polarised approach the rate of gain in aerobic capacity would not be a rapid as with HIIT, but it is scarcely credible that diluting the high intensity session with low intensity sessions would abolish  the aerobic gains of the high intensity sessions, provided there is adequate opportunity for recovery.

Not only does HIIT produce efficient development of aerobic enzymes, but it is also effective in enhancing the development of the enzymes that metabolise fats, thereby promoting the generation of energy from fat, a processes that does not generate lactate

With regard to increasing the supply of oxygenated blood to muscle, sprint interval training is as  effective as endurance training in promoting development of capillaries.  Although the effect of HIIT on development of cardiac output has been less thoroughly studied, it is noteworthy that the Gerschler’s rationale for the introduction of interval training was the stimulation of cardiac output.  In his word interval training provides “a stimulus particularly powerful to reach the heart.”

Transport of lactate

The alternative approach to minimizing lactate accumulation is removal of lactate from muscle and blood.  With regard to the relative efficacy of polarised training compared with threshold training, the important issue is whether or not this is better promoted by brief surges of intensive lactate production or by sustaining a moderate level of lactate.   The mechanisms by which lactate is removed from muscle include the transport of lactate from fast twitch fibres, where it is produced, to slow twitch fibres, which have the capacity to metabolise the lactate; the transport to other organs such as heart muscle which are well adapted to metabolising lactate; or transport to the liver where the process of glycogenesis converts lactate to glucose and subsequent storage in the form of glycogen.

The transport of lactate across cell membranes is mediated via a set of transport molecules, the monocarboxylate transporters (MCTs) that transport lactate together with protons.  Transport by MCT’s involves diffusion and the rate is determined by the transmembrane gradient of either lactate or acidity (protons).  It is likely that under most conditions, lactate flux is determined mainly by the gradient produced by metabolism-driven uptake, while the availability of MCTs is rate-limiting only after the establishment of large transmembrane gradients.   Therefore, the first goal in enhancing the capacity to clear lactate during distance running is enhancing the ability to metabolise lactate. In heart and slow twitch fibres, this is achieved by enhancing vascularization and aerobic enzyme activity.  The evidence discussed above suggests that polarized training is an effective way to do this.  Nonetheless, it is desirable to ensure that MCT’s are maintained at an adequate level. Because  MCT-mediated transport is rate-limiting only in the presence of large transmembrane gradients, it would be expected that brief surges of lactate  will be more effective in promoting development of MCTs than sustained moderate levels.

Buffering of acidity

The role of acidity in stimulating training effects is ambiguous.  On the one hand rising acidity eventually halts metabolism in muscle, but on the other, some degree of stress is likely to be necessary to promote adaptation.   Ingestion of sodium bicarbonate (baking soda) which neutralises acid has been shown to diminish the secretion of anabolic hormones, such as growth hormone, following intense exercise. Thus rise in acidity appears to facilitate at least some of the desired effects of training.  In contrast, sodium bicarbonate ingestion augments the increase in activity of the messenger molecule PGC-1alpha in skeletal muscle during recovery from intense interval exercise in humans, and therefore might promote the development of mitochondria.

This raises the question of the role of natural buffering mechanisms in the blood.    During intense exercise there is a transient rise in the body’s natural buffers, phosphate ions and bicarbonate ions, that helps neutralise the rise in acidity despite the rise in lactate concentration.  Thus it is plausible that one of the advantages of interval training compared with threshold training is that the transient natural buffering during interval training allows more intense exercise and hence allows greater lactate production without excessive acidity.    Perhaps this would act as a greater stimulus to PGC-1 Alpha activity and perhaps MCT production as well. On the other hand, natural buffering might diminish the potentially beneficial increase growth hormone activity.  Overall, on account of the competing antagonistic effects, I doubt that buffering is an important adjunct to training.   The issue is similar to the debate about the value of cold baths to reduce inflammation after training.

Nonetheless, the possibility that buffering might increase tolerance of lactate production, together with the substantial evidence for improved endurance performance in rats and humans, reviewed  McNaughton and colleagues, has led to the proposal that bicarbonate doping might enhance race performance.  I am intrinsically opposed to the ingestion of substances in marked excess of the amounts present in a normal healthy diet for the sake of enhancing performance, but some athletes might argue that provided it is not illegal it is acceptable.   However, the dose required to produce an appreciable effect (20-30 gm) can cause vomiting or diarrhoea.  I would regard this is too great a risk to take.

Long term improvement

It is clear that many of the physiological adaptations required to minimise the rate of accumulation of lactate can be achieved very efficiently by HIIT.  This evidence undermines the principle that enhancement of the ability to handle lactate is achieved most effectively by specific training in the vicinity of LT.

Unfortunately, most of the HIIT research so far has focussed on the contrast of HIIT with lower intensity training, delivered over a time scale of several weeks.   There is some evidence  that the benefits of HIIT do plateau after a period of a few months.   The study by Stoggl and Sperlich demonstrated that for athletes who have a history of regular training, polarised training produces greater benefits than either threshold training or predominantly high intensity training.  It is plausible that the adaptations produced by HIIT can also be achieved, perhaps more gradually but with the potential for steady improvement over a prolonged period, by a polarised program.  Hitherto there have been too few studies that have examined the development of physiological capacities such as aerobic enzymes, delivery of blood to muscle and the transport of lactate, during training programs sustained over a full season or longer.

Injury prevention

Injury is an issue of perennial importance to athletes.  In general, muscle injury is likely if a large force is exerted unexpectedly, or if muscles are fatigued.  Protection against injury is minimised by the strengthening promoted by anabolic hormones on the one hand, or diminished by the breakdown of tissues promoted by sustained elevation of catabolic hormones such as cortisol.  In the next post in this series, I will address the question of whether injury is more or less likely with a polarised program than with threshold training.

Is threshold training over-rated? Stephen Seiler v Jack Daniels

December 19, 2016

In the early years of a runner’s career, almost any reasonably sensible training plan with a gradual build-up of training load will produce improvement.  However, once a runner has reached a plateau of performance, the challenge is to identify the type of training that offers the best chance of further improvement.   Races ranging from 5K to marathon are run at paces in the vicinity of lactate threshold (LT).  Race performance is largely determined by the fact that as pace rises above lactate threshold, acid accumulates in muscles and blood, eventually resulting in an enforced slow-down.  Thus, one of the major goals of training is increasing pace at lactate threshold, as this will allow increased race pace.  The principle of specificity of training suggests that the optimum training program will include a large amount of running near lactate threshold to enhance capacity to prevent accumulation of acid.  Indeed, this is the approach adopted by many recreational runners.

Polarized training

However, the evidence from examination of the training logs of elite endurance athletes, reviewed comprehensively in a lecture by Stephen Seiler in Paris in 2013, indicates that many elites adopt a polarised approach  that places emphasis on the two extremes of intensity. There is a large amount of low intensity training (comfortably below LT) and an appreciable minority of high intensity training (above LT).  Polarised training does also include some training near lactate threshold, but the amount of threshold training is modest; typically the proportions are 80% low intensity, 10% threshold and 10% high intensity.

As reviewed in my previous post on the topic, several scientific comparisons  of training programs have demonstrated that for well-trained athletes who have reached a plateau of performance, polarised training produces greater gains in fitness and performance, than other forms of training such as threshold training on the one hand, or high volume, low intensity training on the other.

The specificity principle

Nonetheless many  coaches and athletes who advocate specific training paces to achieve the various required adaptations required for distance running, maintain a firml belief that threshold training is the best way to increase the pace at lactate threshold, and should form a substantial component of a distance runner’s training program.  Jack Daniels, doyen among coaches advocating specific paces for specific adaptations, has argued that because stress level rises rapidly at paces exceeding threshold there is a sweet spot in the vicinity of lactate threshold that achieves sufficient stress to promote adaptation while avoiding the danger of excessive stress.

Evidence from laboratory studies of rats appears to provide some support for this view.  While it is necessary to be cautious in using evidence from studies of rats to inform training of humans, the basic physiology of rat muscle is similar to that of human muscle.  They share with us an aptitude for running at aerobic paces. The evidence from the well-controlled systematic studies that are feasible in rats is potentially useful in establishing principles that apply across species.  Dudley’s studies in which he measured changes in aerobic enzymes produced by a variety of different training intensities and durations in rats (all training for 5 days per week for 8 weeks) demonstrated that running beyond a certain duration produced no further increase in aerobic enzymes.   Furthermore, the duration of running beyond which there was no further improvement is shorter at higher training intensity.  This suggests that at any given intensity, training runs beyond a certain duration  will produce no further increase in aerobic capacity though there might of course be other gains, for example increase resilience of bones, muscles, ligaments, tendons and also the mind.  But there is also likely to be an increase in overall stress.  At very high intensity the duration limit is so short that the overall gain in aerobic fitness is less than can be achieved by longer session at lower intensity. The greatest overall increase in aerobic enzymes in muscles with predominantly red (aerobic) fibres, was achieved by an intensity that led to maximum gain at around 60 minutes.  Thus in Dudley’s rats, there appeared to be a sweet spot in intensity for optimum development of aerobic capacity.  Although Dudley did not measure lactate levels, it is plausible that this intensity corresponds roughly to lactate threshold in humans.

Hormones and training

However even if we accept that Dudley’s studies support Jack Daniel’s argument for a sweet spot, it is crucial to note that Dudley assessed the effects of training over a total duration of only eight weeks.  The important issue for the athlete who has reached a plateau is the likely consequences of training over a longer time-scale than 8 weeks.  It is probable that the crucial issue is the balance between catabolic and anabolic effects of training.  During a training session, the catabolic hormones cortisol and noradrenaline are released into the blood stream to mobilise body resources, especially glucose, required to meet the demands of training.  The release of catabolic hormones also triggers the subsequent release of anabolic hormones, such as growth hormone, that promote repair and strengthening of body tissues.    As training intensity rises above lactate threshold the release of catabolic hormones and the associated release of anabolic hormones increases sharply (as illustrated by Wahl and colleagues).  Thus the potential stimulus triggering the benefits of training rises sharply as intensity exceeds lactate threshold.  The accumulation of cortisol also increases with increased duration of running.  For example, Cook and colleagues report that salivary cortisol increases steadily during a marathon, typically achieving a fourfold increase at 30 minutes after completion of the race compared with the level prior to the start.

While a transient rise in cortisol tends to be beneficial, sustained elevation of cortisol is potentially harmful because cortisol promotes the breakdown of body tissues.  Cortisol levels in hair samples provide an indication of cortisol level sustained over a period of weeks or months.   Skoluda et al measured cortisol levels in hair in a group of distance runners over a season. They reported that these runners had abnormally high cortisol levels over a prolonged period, raising the possibility of adverse sustained catabolic effects, including suppression of the immune system.  Skoluda concluded that repeated physical stress of intensive training and competitive races is associated with potentially harmful sustained elevation of cortisol.  However, they did not explicitly compare different training programs.

There is no published evidence of differences in medium or long term catabolic/anabolic balance between polarised training and threshold training.  Furthermore, because gradual increase in training load leads to a blunting of the sharp rise in catabolic hormones produced by training in the vicinity of LT, a fully informative study would need to take careful account of the structure of the training program over a sustained period.  Nonetheless a study of high level distance runners by Balsalobre-Fernandez and colleagues does provide relevant information.  They recorded training, performance and salivary cortisol level in 15 high-level middle and long-distance runners from the High Performance Sports Center, Madrid, throughout a period of 10 months.  The group comprised 12 men and 3 women, mean age 26.4 years, with personal bests in 1500-metres between 3:38–3:58 (men) and 4:12–4:23 (women). They rated training in three zones: zone 1 included long-distance continuous training, or interval training with long sets (4–6 km), at relatively relaxed paces; zone 2 included of intervals with sets of 1–3 km at approximately 5 K pace , likely to be moderately above lactate threshold; zone 3 included short-distance and sprint interval training at paces ranging from around 1500m pace to full sprint. Thus zone 1 and 3 roughly correspond to low intensity and high intensity zones of a polarised program, while zone 2 sessions are a little more intense but less sustained than a typical threshold training session in the mid-zone of a typical polarised program.

During the winter months, the athletes did a substantial amount of low intensity (zone 1) training.  The 25 weeks of spring and summer training was dominated by zone 2 training.  For 15 weeks within this 25 week period, the average training zone was in the range 1.75-2.25, indicating a large proportion of zone 2 training; while for 3 weeks the average was above 2.25, indicating an appreciable amount of training in zone 3 in addition to zone 2.

In addition to recording race performance, Balsalobre-Fernandez and colleagues regularly assessed vertical counter-move jump height (CMJ) as a measure of neuromuscular performance.  Averaged over the entire season, the runners with higher long-term cortisol levels has significantly lower CMJ scores, confirming that sustained elevation of cortisol is associated with poor neuromuscular performance.  However, analysis of correlations between weekly average cortisol and CMJ values revealed that higher CMJ scores were recorded in weeks with higher cortisol levels, indicating that transient elevation of cortisol is associated with better neuromuscular performance.  The weeks with higher CMJ performance were weeks with lower training volume but higher training intensity (i.e. more Zone 3 sessions).  Finally, CMJ scores were significantly higher in the week before the season’s best competition performance

In summary, the evidence from the study by Balsalobre-Fernadez and colleagues confirms that sustained elevation of cortisol is harmful and favours a lower volume of higher intensity training rather than moderately large volume a little above lactate threshold.  This might be a key to understanding why polarised training might be superior to threshold training.   In my next post, I will examine the mechanisms by which the training adaptations required for distance running might be best achieved using a polarised approach.  In particular I will discuss the ability of negative ions such as phosphate and bicarbonate in the blood to provide temporary buffering of the acidity associated with lactate production.  This buffering might allow transient surges of lactate produced by brief high intensity exercise to produce beneficial enhancement of the transporter molecules that facilitate transport of lactate from type 2 to type 1 muscle fibres in which it can be used as fuel, and also the transport of lactate from muscles to liver and heart, without the potentially damaging effects of increased acid levels associated with sustained increase in level of lactate.

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:

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.

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.

GH&IGF

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.

Conclusion

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.