Crazy heart rhythms

There is little doubt that the balance of benefits and risks to the well-being of the heart arising from regular running favours the benefits.  The risk of heart attack following a marathon is small but real, though it is generally accepted that this risk often arises from underlying heart abnormality.  However there is one heart problem that is relatively common and might arise largely from factors related to fitness itself.  That is atrial fibrillation.

Atrial fibrillation is a disturbance of heart rhythm in which the electrical events that initiate contraction do not arise in a regular manner from the sinoatrial node embedded in the muscle of the right atrium of the heart, but instead arises in a chaotic manner from a variety of different sites in the walls of the atria.  Instead of a well organized contraction of the  atria followed by a regular contraction of the ventricles, the walls of the atria contract in a poorly coordinated manner and blood is not transferred to the ventricles in a way that ensures efficient filling of the ventricles before ventricular contraction ejects the blood into the pulmonary artery (that connects the right ventricle to the lungs) and the aorta (that carries blood from the left ventricle to the rest of the body).  Usually a person with atrial fibrillation feels fatigued and may be aware of palpitations – an irregular heart beat.

The evidence for increased risk in endurance athletes

Many studies report that atrial fibrillation is more common in endurance athletes.  In a 5 year follow-up of 146 young elite athletes from a larger sample 1772 elite athletes who had been found to have heart rhythm disturbances, 13 (9%) had atrial fibrillation (Furlanello et al Atrial fibrillation in elite athletes. J Cardiovasc Electrophysiol. 1998;9(8 Suppl):S63-8.)    In 5 of the these 13 young athletes, an underlying heart abnormality was found (most commonly abnormality of the  electrical conduction path from atria to ventricles known as the Wolf-Parkinson-White syndrome, but in 8 athletes, no underlying cause was detectable. 

In a meta-analysis that examined pooled data from 6 previously published studies comparing a total of 655 athletes with 985 age and sex matched non-athletes (with all members of both groups drawn from clinic attenders), there were 147 cases of atrial fibrillation among athletes and 116 among the non-athletes  (Abdulla J, Nielsen JR  Is the risk of atrial fibrillation higher in athletes than in the general population? A systematic review and meta-analysis. Europace. 2009;11(9):1156-9.).  Mean age was 51+/-9 years and 93% were men. The authors concluded that the risk of atrial fibrillation is significantly higher in athletes compared with non- athletes, but that this finding should be confirmed further in large-scale prospective longitudinal studies.

In a prospective longitudinal study, individuals representative of the group of interest  (eg male endurance athletes) are recruited before they are known to have any abnormality and followed over a period of years.  This provides an estimate of the risk that members of that group will develop the problem over the number of years of the follow-up.  Such a prospective longitudinal study, of long distance skiers, has just been published this month  (Grimsmo J, Grundvold I, Maehlum S, Arnesen H. High prevalence of atrial fibrillation in long-term endurance cross-country skiers: echocardiographic findings and possible predictors–a 28-30 years follow-up study. Eur J Cardiovasc Prev Rehabil. 2010 Feb ;17(1):100-5.)   Grimsmo and colleagues studied cross-country skiers with a long history of training, from three different age groups, identified on the basis of participating in the Birkebeiner ski marathon, an annual 54 Km cross-county race from Rena to Lillehammer, in Norway. 122 individuals entered the study in 1976 and of these 78 were available for the follow-up assessment in 2004-2006.   12.8% of those followed up over the period of 28-30 years had ‘lone’ atrial fibrillation that was not accounted for by any other underlying heart abnormality.  The mean age of onset of the atrial fibrillation was 58 years.  Although atrial fibrillation is quite common among the elderly, occurring in about 5% of men over the age of 65, 12.8% is a very high rate to find among relatively young middle aged men.   There seems little doubt that male endurance athletes have a substantially increased risk of atrial fibrillation.

Is endurance training the cause of the problem?

In the study by Grimsmo and colleagues, the factors that were associated with the development of atrial fibrillation were a long interval between the p wave and the q wave in the electrocardiogram (this indicates a long conduction time between atria and ventricles); a slow heart rate; and a large left atrium.  Slow heart rate and enlarged left atrium are features produced by endurance training. So it is plausible that the endurance training plays a causal role in the problem.   It is well known that both excess parasympathetic activity (which is responsible for low resting heart rate) and excess of sympathetic activity can predispose to atrial fibrillation, with the parasympathetic form more common in individuals without other evidence of heart disease (Coumel P. Autonomic influences in atrial tachyarrhythmias. J Cardiovasc Electrophysiol. 1996;7(10):999-1007.)   While there is a widespread belief that the increased parasympathetic activity associated with endurance training is a good thing, the link to atrial fibrillation should give us pause for thought.

It is also possible that the mechanism involves atrial scarring.   In general, training effects arise as a result of transient damage to muscle that leads to compensation – this is well established for skeletal muscle and is likely to occur in heart muscle as well.  If the transient damage results in scars (residual fibrous tissue) then these scars might be expected to interfere with the coordinated conduction of electrical signals through the muscle.

What are the consequences of atrial fibrillation?

In the short term, atrial fibrillation usually results in fatigue and limitation of athletic performance.  The evidence for serious long term adverse effects is less straightforward.   The chaotic contraction of the atria can result in clotting of blood within the atria creating a risk that the clots might break free and be transported via the large arteries and produce blockage in the smaller diameter peripheral arteries.  One possible serious consequence is a stroke due to blockage of arteries in the brain.   In a 9 year follow-up study between 1993 and 2002, of 30 athletes with atrial fibrillation, Hoogsteen and colleagues found that by 2002, 3 (10%) were dead; paroxysmal atrial fibrillation continued in 15 (50%) ; permanent atrial fibrillation emerged in 5 (17%) ; and 7 (23%) of them showed no further atrial fibrillation.   Thus at least in this group of athletes, the outcome was worrying.  However it should be noted that these were not specifically described as cases of ‘lone atrial fibrillation’ and hence in at least some cases it is possible that there were other underlying heart abnormalities.

A personal note

Not only do atrial hypertrophy and over-activity of either the parasympathetic or sympathetic divisions of the autonomic nervous system appear to increase the risk of atrial fibrillation but there is also evidence that inflammation can increase the risk.  In the presence of inflammation, the body produces a protein known as C-reactive protein.   A meta-analysis of the relationship between C-reactive protein and recurrence of atrial fibrillation in patients under medical treatment found evidence suggesting that baseline C-reactive protein levels predict the long-term risk of recurrence of atrial fibrillation (Korantzopoulos P, Kalantzi K, Siogas K, Goudevenos JA Long-term prognostic value of baseline C-reactive protein in predicting recurrence of atrial fibrillation after electrical cardioversion. Pacing Clin Electrophysiol. 2008 ;31(10):1272-6.).

Recently I suffered an episode of inflammatory arthritis and as a precaution I cut back on training.  On 13^th February, about two weeks after the worst of the joint pain, I did my regular test of aerobic fitness on the elliptical cross-trainer.  In this test, I record heart rate during 2 minutes on each of a series of steps of increasing power output in the range 30 to 232 watts. In recent months, my heart rate at 232 watts is usually around 146-148 which I regard as just a little above my anaerobic threshold.  I can comfortably maintain a breathing rate of 40 breaths per minute, at this heart rate but if I increase further, then my breathing rate increases rapidly up to around 80 per minute.   On 13^th Feb, I noted that my heart rate was typically around 5 beats per minute higher than usual on each of the lower steps and by the final step at 232 watts, it settled at 150 beats per minute.  I did not feel stressed, so I simply assumed that I had lost a little fitness in the preceding three weeks of reduced training. 

I examined the Poincare plot which provides an indication of function of the autonomic nervous system.  The plot for the final 1 minute at power output of 232 watts is shown in figure 1. 

Poincare plot during the final minute at a power output of 232 watts

As I have discussed in previous postings the spread of points across the 45 degree line denotes high frequency heart rate variability and is an index of parasympathetic activity, though there is some controversy about the details of the interpretation of the Poincare plot during upper-aerobic exercise.  The measurement that represents the amount of spread at right angles to the 45 degree line (sd1) is 3.9ms, while the quantity presenting spread along the 45 degree line (sd2) is 3.3 ms.  This is fairly typical of what I usually observe when maintaining a constant power output at the upper end of the aerobic range.  

Last summer, when I developed parasympathetc overactivity as I increased training during recovery from my episode of illness, the spread of points across the line was far greater (up to 12 ms).  The only minor feature of note in figure 1 is that there is one point well away from the cluster above the 45 degree line and a matching aberrant point below the line.  These two points indicate that one beat was initiated about 10 milliseconds earlier than might have been expected and was followed by a corresponding lengthening of the next inter-beat interval before normal sinus rhythm resumed.  This 10 ms advance is a trivial advance of the usual beat rate though it might indicate that a location outside of the sinoatrial node had captured the role of initiating that beat.  However I would regard one slightly early beat among around 150 beats as utterly trivial, and therefore I had no qualms about setting off for an easy 8Km run in the lower aerobic zone.  I maintained an easy pace of around 5:30 minute  per Km, which would normally be associated with a heart rate of around 118 bpm.  Because I did not have any concerns, and I felt quite comfortable running, I did not take much notice of my heart rate as I ran. I was therefore amazed when I examined the beat by beat variation afterwards (figure 2.).

Crazy heart rhythm during an easy lower aerobic run

As expected, my heart rate rose steadily over the first two minutes to about 117 bpm but then within the next 6 minutes there were 7 strikingly premature beasts, typically occurring 150-200 milliseconds early.  If this is not an artifact due to monitor malfunction, it suggests that a rogue site was capturing the role of initiating the beat.  Furthermore during that period the heart rate fluctuated a lot more than usual, though it tended mostly to be in the range 100-120 bpm. However, those fluctuations were nothing compared with what happened after around 9 minutes.  The rhythm went haywire, and did not settle until I got home, at around 45 minutes.  The heart rate then settled rapidly reaching around 75 bpm with only modest (and potentially healthy) amount of beat by beat variability, 4 minutes after I stopped running.  What might this mean?  My first conclusion is that my monitor had malfunctioned.  I still do not have any firm evidence to rule out this possibility.  The other possibility is that I experienced about 30 minutes of atrial fibrillation.  However the amazing thing is that I felt quite comfortable running.  Perhaps the run felt slightly more effortful than usual for a lower aerobic run, but after a few weeks of reduced training, that would not have been surprising.

I have not yet resumed full training but have done a number of 8-10Km lower aerobic runs and about 10 sessions on the elliptical cross trainer, since mid February.  There has been no further sign of this crazy rhythm.  Typically, when running my heart rate has been around 620-650 beats/Km, which indicates scarcely any loss of aerobic fitness since mid January.  My observed heart rate during elliptical sessions has been back to normal, and my resting heart rate is around 46 bpm which I regard as healthy.

So at this stage I plan to build up my training cautiously.  As the unusual rhythm occurred when running at any easy pace, I think that long easy runs during which parasympathetic activity would be expected to be higher, might actually be riskier than shorter faster runs, but nonetheless, I will be very cautious about any sessions that might be stressful.

With regard to the longer term, I will simply have to wait and see.  I still have no clear evidence that it was not simply a malfunction of my monitor, and I would be interested to know if others have observed similar patterns with the Polar RS800CX.  Although I do not entirely trust the monitor, I am nonetheless very glad that I have it, as it gives me confidence that if in fact I am developing atrial fibrillation, I will be able to detect it.  The chance of detecting it during a planned clinical ECG recording would be very low at present.  Whatever the eventual outcome, it has confirmed that running when exhibiting any signs of inflammation is probably not a good idea.  On the other hand, I suspect that my life expectancy will be greater if I remain fit, so I am quite happy to keep on running while I monitor the situation.  As for my plan to run a good marathon in 2012, only time will tell.

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Barefoot running and foot dynamics

In a review article published in the journal Nature in 2004 (vol 432, pp 345-352) Bramble and Lieberman from Harvard University compared the efficiency of human running with the running of other mammals.  They concluded that it was likely that the human musculo-skeletal system had evolved in a manner that allowed our forebears to run for long distances in pursuit of game, in the distant past before the development of spears or guns.  Unlike the lioness which relies on a sprint of a few hundred metres to capture her prey, it appears that our forebears relied on endurance rather than speed; perhaps they pursued some ungulate for hour after hour until their quarry was exhausted.  Clearly one of the major adaptations is the ability to get airborne and to land in way that captures gravitational energy as elastic potential energy.  The quads and calf muscles are well suited to this purpose.  But what about the feet?   In an era long before the engineers from companies such as Adidas and Nike developed the heavily padded running shoe that makes heel-striking feasible – humans ran barefoot. A more recent study of habitual barefoot runners by Lieberman demonstrates clearly what many had expected: habitual barefoot runners land on the fore-foot or mid-foot, and that this style of landing does not produce the sharp initial rise in ground reaction force that is seen when the runner lands on the heel (Nature, 463: 531-565; 2010).

The design of the human foot

It is scarcely surprising that barefoot runners land on forefoot or mid-foot because the design of the human foot is well suited to such a landing.  The two most striking features are the longitudinal arch which extends from the metatarsal heads at the front of the foot to the heel, and subtalar joint that allows the movements known as pronation and supination. 

The longitudinal arch

The longitudinal arch is most pronounced along the medial (inside) border of the foot.  It is a spring-like structure well suited to absorbing impact, storing the energy of impact as elastic energy distributed within the connective tissue of the foot, the Achilles tendon and the calf muscles, and then releasing this energy as the body is propelled upwards by the recoil.

The subtalar joint

The subtalar joint is a compound joint involving the head of the talus (the bone within the ankle that links the long bones of the lower leg with the rest of the foot); the calcaneus (the heel bone located beneath the body of the talus) and the navicular bone (one of the major tarsal bones that acts as the keystone of the medial longitudinal arch).  The anatomy of the sub-talar joint is rather complex, but the crucial point is that it allows the foot to rotate onto its inner edge, locking the medial arch so that it can support the weight of the body.  This movement is known as pronation.  Rotation in the opposite direction around the subtalar joint rolls the foot onto its outer edge and takes the weight off the longitudinal arch

Foot dynamics when running

Because a runner’s swinging leg must move towards the midline of the body as it descends  towards footfall, the natural tendency for a barefoot runner is to land on the outer edge of the foot.  As the weight is taken up, the subtalar joint allows pronation which transfers the load to the longitudinal arch.  As the Achilles tendon and calf muscles take up the strain the heel drops towards the ground.  Provided the calf has not been maintained in an artificially tense state, by midstance the heel will be on the ground and the arch will be spring-loaded, exerting pressure of the ground.  The ground reaction force drives the body upwards and as recoil occurs, the foot tends to supinate transferring the load towards the outer edge of the foot so that it is distributed across the metatarsal heads immediately before lift-off.

Thus, within a period of duration in the range 80-200 milliseconds, the foot has undergone a complex series of movements.  Not only is there the hinge-like transition from slight plantar flexion of the ankle at footfall to marked dorsiflexion at mid-stance and plantar flexion at lift off, but also the inward roll (pronation) and the final outward supination.    A moderate degree of pronation (typically up to 15 degrees) is a crucial feature of distributing the load onto the longitudinal arch. 

Torque at hip and knee

The way the foot lands has a substantial influence on the twisting forces at hip and knee.  In a comparison of the torques occurring at the various joints of the leg during running during barefoot running compared with running in typical trainers with a padded heel, Kerrigan and colleagues demonstrated greater torques at hip and knee during shod running (PM &R: The Journal of Injury, Function and Rehabilitation, Vol. 1, pp 1058-1063, 2009).  The magnitude of the torques during running in shoes were in fact greater than those observed during walking with high heels.   The barefoot runners were observed to adopt a shorter stride length, which would be expected to result in lower ground reaction forces, but only a small proportion of the relative reduction torque when barefoot could be accounted for the reduced stride length.  It is likely that the altered distribution of load on the springy longitudinal arch was a major factor in the lower torques when barefoot.   

Is it the shoes or running style?

The main focus in the studies of Lieberman and of Kerrigan is on the differences of between barefoot running and shod running, but the issue is confounded by the differences in foot dynamics.  As about 20-30% of shod runners land on forefoot or mid-foot, it is important to know whether the apparent advantages of barefoot running are primarily a consequence of the being unshod or, instead, a consequence of the style of landing.  

One of the striking differences between the barefoot runner landing on the forefoot and shod heel-striker is the sharp rise in ground reaction force shortly after impact.  Although no study has demonstrated that this sharp spike is responsible for increased risk of injury, it is a prime suspect, as it would be expected to initiate a jarring impulse that would be transmitted up the leg to the knee, hips and spine.   It is easy to envisage how landing on the heel would result in an abrupt braking action that would generate the sharp spike of ground reaction force (GRF).  The role of the running shoe in causing or ameliorating this sharp spike is less clear. 

In fact, force plate data recorded during heel striking with and without shoes, which Lieberman and colleagues present on their website, demonstrates that shoes reduce the initial spike, but do not abolish it (http://barefootrunning.fas.harvard.edu/).  However, comparing barefoot heel striking with barefoot forefoot demonstrates that forefoot landing produces a far greater reduction in the initial spike.  Thus there is little doubt that the style of landing plays the major role in reducing the initial spike in GRF.  As expected, shoes are potentially helpful rather than harmful for the heel-striker.

However, the cardinal comparison of interest is that between barefoot and shod forefoot landing.  In fact the force plate data indicates that for forefoot runners, the initial sharp spike is virtually entirely abolished for both barefoot and shod running. Furthermore, there is very little difference between fore-foot striking in racing flats compared with conventional running shoes.  Thus, at least as far as the potentially harmful initial spike of GRF is concerned, there is little evidence of difference between barefoot and shod running with a fore-foot landing.

Non-conscious adaptation

One feature of particular note about the data presented by both Lieberman and colleagues and by Kerrigan and colleagues is that barefoot runners automatically adjust their running style to adapt to the lack of protection.  Not only do they tend to change from heel-strike to forefoot or mid-foot strike, but they also shorten their stride.  This has several implications.

First of all it demonstrates that the neuromuscular system acts automatically to adjust running action so as to minimize risk of injury.  This might be advanced as an argument in favour of running barefoot as it suggests that the bare foot is more responsive to the running surface whereas shoes dull this sensibility.  The automatic shortening of stride might also be regarded as an advantage in at least some circumstances.  The impact forces will be less, and in addition, running with a shorter stride and a higher cadence is more efficient, simply because less work is done against gravity in a larger number of shorter strides that cover the same distance.  However, shortening stride improves efficiency only up to a certain point beyond which it becomes less efficient (as discussed in my post on 31^st Dec 2009.

In his book ‘Programmed to Run’ , Tom Miller reports data recorded by Buckalew in the US Olympic women’s marathon trial is 1984.  They recorded cadence and stride length in 40 women early in the race and again late in the race.  They compared the 10 women who achieved the fastest finishing times with the 10 who recorded the slowest finishing times.   Early in the race there was no difference between the two groups of women, but late in the race, the slower women exhibited a shorter stride despite maintaining the same cadence as the faster woman.  This loss of stride length despite maintenance of cadence is similar to that observed as runners grow older.  Thus, the decrease of stride when running barefoot might potentially impair performance unless an effort is made to ensure that cadence is maintained. 

Is it worth abandoning your shoes?

Despite the evidence from Lieberman’s studies indicating that the initial sharp spike of GRF is similar for a fore-foot runner whether running barefoot, in racing flats, or in conventional running shoes, a thick padded heel actually makes it more difficult to land on the fore-foot.  Furthermore, rigid motion control that prevented adequate pronation would hinder the transfer of load to the medial longitudinal arch, and built-in arch support might hinder the natural flattening of the arch as it takes up the load, thereby impeding the storage of elastic energy.  These considerations provide reason to consider abandoning shoes with heavily padded heel, arch support and rigid control of pronation. However, even before making a change such as this, it should be noted that the connective tissues supporting longitudinal arch, the Achilles tendon and calf muscle will be at risk of injury unless these structures have been adequately prepared for the task of capturing and storing the energy of impact, and the required neuromuscular coordination has been developed.

If a lifetime of wearing shoes has caused atrophy of tissues and loss of the required strength and sensitive neuromuscular coordination, then any transition to a more minimal shoe should be done gradually.

 The question of whether it is worth taking the further step of abandoning a minimal running shoe once one has acquired the strength and coordination to run comfortably and safely with fore-foot or mid-foot landing, is less easy to answer.  I am not aware of any evidence that indicates that this extra step is worthwhile. On the other hand, it would carry some risk: not only the risk of laceration or bruising of the foot on sharp objects, but also the possibility that stride would automatically decrease as an unconscious protective measure. This might be especially troublesome in the later stages of a long distance race.

There is one additional issue to consider.  Several studies have demonstrated that running barefoot uses about 5% less energy than shod running ( e.g. Squadrone and Gallozzi, J Sports Med Phys Fitness. 49(1):6-13; 2009.).  However it is not clear whether that is mainly accounted for by the weight of the shoe or the mechanics of running.  A study by Divert and colleagues (Int J Sports Med. 29(6):512-8, 2008) concluded that the soft padding of the shoe might result in a decrease of the storage and restitution of elastic energy capacity which could explain the lower net efficiency reported in shod running. 

For some people the feeling of freedom and the satisfaction of running naturally might be adequate justification for running barefoot.  However, I am inclined to regard shoes as the product of a natural phenomenon: the inventiveness of mankind.  I am as happy to celebrate human inventiveness as I am to celebrate primitive naturalism.  As I sit here typing, I am very pleased that human inventiveness had produced reading glasses. 

While there might be some satisfaction in running as our remote ancestors did, I suspect that if I had been born on the African savanna a million years ago, I would not be spending the few weeks before my 64^th birthday contemplating how to maximize the chances that I will still be enjoying running in 10 years time.  It is more likely I would be worrying about how to avoid becoming a gristly morsel for some predatory feline within the next 10 days, if that fate had not already befallen me.  So I am perfectly happy to live in the modern era and to celebrate the inventiveness of my forebears.  However I hope I am wise enough to recognize when inventiveness has become counter-productive. I think the modern running shoe might be an example of counter-productive invention

 

Reminiscences

In my youth I initially ran in sandshoes, but in the late 1960’s I bought an expensive pair of Adidas shoes – I do not remember the model – they had arch support and heavy padding especially under the heel.  In the shop they felt luxurious, so I eagerly bought them, took them home and set out on a trial run.  I could scarcely believe how uncomfortable they were.  Because I couldn’t believe it, I did not take them back, but persevered with them, but they did not get much better.  My next shoe purchase was a pair of Onisuka tigers; very lightweight racing flats which I wore for many years. I ran all my best marathons in my tigers.  Even now I regret that during one of the many house moves over the past four decades I jettisoned these dilapidated old friends.   The Onitsuka Company eventually became Asics, and I recently bought a pair of Asics hyperspeeds.   The hyperspeeds are lightweight and have a fairly minimal sole, though not quite as minimal as my old tigers.  I am enjoying running in them – but they have one irritating feature. Unlike the slightly rippled undersurface of the tigers, the hyperspeeds have a criss-cross pattern that is ideal for trapping small stones.   So I will be true to my age and murmur nostalgically that running shoes were far better when I was a lad.

The mind and brain of the runner

Mind and brain are two sides of one coin: the mind is the subjective experience of the activity in a complex network of brain cells that receive sensations from the external word and the internal milieu, interpret those sensations, and in turn transmit commands back to the muscles, hormone secreting glands, and viscera that carry out the functions of the body. 

If you are a runner, there are at least three things it is worth knowing about your mind and brain.

• What you believe affects the way your body works.  A group of hotel cleaners was informed 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.  (Crum and Langer, ‘Mind-Set Matters: Exercise and the Placebo Effect’, Psychological Science, vol 18: pp165-171; 2007)  Athletes who have faith in an inspiring coach often outperform those who do not have an inspiring coach.  What can the self-coached runner do to maximize the effectiveness of his or her training?

 

• Non-conscious mechanisms act to limit damage to body tissues.  While the details of the role of the central governor, which Tim Noakes proposes acts to limit work output before we do serious damage to heart or muscles, remain controversial, there is little doubt that there are non-conscious mechanisms that adjust our actions to minimize harm.  Barefoot runners tend to run with a shorter stride and land on forefoot or mid-foot rather than heel (Lieberman et al, ‘Foot strike patterns and collision forces in habitually barefoot versus shod runnersNature vol 463: pp 531-535, 2010).  These adaptations are the likely reason that they experience less torque at knee and hip joints (Kerrigan et al, ‘The Effect of Running Shoes on Lower Extremity Joint Torques’PM &R: The Journal of Injury, Function and Rehabilitation, Vol. 1, pp 1058-1063, December 2009).  The softer landing of the barefoot runner may have equipped our forebears to pursue game across the African savanna, but is not necessarily the most efficient way to run 10Km on a road.  However, an appreciation of how the human body was designed to run (by evolution or by God) is a good starting point in the quest to determine how to run fast and injury free.

 

• The brain codes whole actions.  The gunslinger who draws his gun in a reflex response to the action of an assailant takes about 20 milliseconds less to draw  than the assailant who made a conscious decision to draw.  This is probably not a big enough difference to save the ‘good guy’ in a gun fight, but nonetheless demonstrates that complex, well rehearsed actions can be performed more rapidly under automatic non-conscious control than  under deliberate conscious control (Welchman et al. ‘The quick and the dead: when reaction beats intention.’ Proc Roy Soc B Pub on-line Feb 2010; http://dx.doi.org/10.1098/rspb.2009.2123).    When running it is generally best to avoid attempting conscious micro-management of the muscles.  Changes in running style cannot be implemented efficiently by conscious change in the actions of specific muscles.  A more efficient action is likely to emerge as a consequence of drills, strengthening of the necessary muscles, and guidance by a mental image of the goal rather than the specific details of the action.

 

Faith and Pose

I have been pondering these issues in recent weeks in relation to the Pose Method of Running.   In my recent posts I have reviewed what I regard as the good features and the bad features of Pose.  My overall conclusion is that Pose technique works reasonably well, at least for amateur athletes, despite quite serious flaws in the  biomechanical theory on which is based. In part it works because it espouses several very sound principles including the recommendation that cadence should be at least 180 steps per minutes, and that time on stance should be as short as possible.  In part it works because the Pose ‘pull’ facilitates a short time on stance despite appearing remarkably like trying to get airborne by pulling on one’s own bootstraps.  Thirdly, I think Pose works because its adherents invest an almost religious faith in it.  My own belief is that it would better to put one’s faith in a method that is biomechanically sound as this might combine the benefits of faith with the benefits of sound biomechanics, but it is not easy for a skeptic to have faith.

The Psychology of Pose

Nonetheless, I do believe many aspects of the psychology of Pose are helpful.  The aspect that I think is most helpful is the subtle way in which it encourages mental images.  Here is an example posted by jonp in response to a query from Gerry G about the distinction between ‘landing on’ and ‘landing over’ the ball of the foot in the thread devoted to discussion of my blog (post 42; Canute’s Efficient Running Site):

‘I would describe it as a distinction between “landing on the ball of foot” and “keeping bodyweight over the ball of foot”.
“Landing on” may emphasise actively putting the leg/foot to the ground before your mass is ready to be supported.
“Bodyweight over” emphasises a full body lean position over your ball of foot so that when your mass arrives on support (creating bodyweight) it will also be supported by the ball of foot.
Basically we don’t want to emphasise/focus on landing.’

Much of what appears arcane and even pedantic about Pose arises from the attempt to create images of what is required.   At times the creation of the image is at the expense of a realistic description of the action that occurs.  This is most clear in the case of the concept of the pull.  The pull is a hamstring contraction that lifts the foot towards the buttocks after un-weighting at the end of stance.  Pose theory explicitly denies the role of pushing and the associated ground reaction force in getting airborne, as is illustrated in the erroneous figure 7 in the article ‘Runners do not push off the ground but fall forwards via a gravitational torque’ by Romanov and Fletcher in Sports Biomechanics, 2007.    However in practice, a good Pose runner does get off stance quite rapidly. And I believe this is because Pose encourages focusing attention during stance on a rapid pull. Up to a point, this is useful. However it might become unhelpful if it encourages the runner to spend more time on strengthening the hamstring for the concentric pull than on conditioning the quads and calf muscles for sustaining the eccentric contraction that is the cardinal requisite for capturing the elastic energy that drives the push.

Religious fervor

On the whole, I think the religious fervor of Pose disciples is less helpful.  This fervor is easily visible on the PoseTech forums (which unfortunately are pass-word protected though it is easy for an interested person to join).  As I have mentioned previously, I was amused by the posting on the PoseTech thread devoted to my blog that simply stated ‘Burn the heretic’ (post 2: Canute’s Efficient Running Site’).   There have been many subsequent reasonable and interesting postings on that thread, but also quite a lot that is less reasonable.  

Where does this religious fervor come from?  A clear illustration was provided at the Pose clinic with Dr Romanov in Loughborough in March 2008.  Much of the event appeared orchestrated to establish the Pose mystique.  The first session commenced with an admonition from Dr Romanov that we must not question his authority.  For almost all of the practical demonstrations throughout the weekend he picked on the youngest member of our group, a personable but potentially impressionable young man.  For example, to illustrate the power of the mind, he had this young man bend to touch his toes.  He encouraged him to reach lower and lower by focusing his mind, over a period of about a minute.  Not surprisingly, the young man’s fingers reached lower as the protective stretch reflex generated in the muscle spindles relaxed.  While I strongly believe in the role of the mind in governing the body, there is not need to invoke arcane mental processes to understand a mechanism that is mediated by a simple neural circuit from muscles to spinal cord and back.   The next morning, Dr Romanov instructed him to close his eyes as he took his wrist and led him up a grassy hill, running Pose style.  When the young man opened his eyes, he was incredulous how easy it had been to run uphill.  Later we were all given the opportunity to share this experience, led by one of the Pose coaches.  The trick is that the leader slows down on the ascent to maintain an approximately constant effort level. It has virtually nothing to do with running style.  By end of the two days, the effect of these tricks, together with the group bonding that occurs when a group of like-minded people meet for a weekend to focus on a shared goal, helped produce a  group of committed Pose disciples.

Followers, Leaders and Self-belief

We are faced with the challenge of remaining sufficiently skeptical to avoid being led into error, yet benefiting from the power of faith.  Fortunately, the way the human mind works suggests that there is a way of combining skepticism with faith.  Humans have evolved as social creatures and it is probably beneficial to the species as a whole that the majority are prepared to put faith in a leader.  However, it also often the case that the person most capable of moving mountains is the leader him (or her)self.  Truly exceptional performances are often based on strong self-belief.  I suspect this reflects another characteristic of the human mind.  Despite a fascination with mysticism, humans are inherently scientists insofar as we try to understand our world by making predictions about the consequences of our actions and observing the results.   When our predictions are confirmed, we invest faith in the prediction and in ourselves.  Our goal as athletes is to develop a style of running and a method of training on the basis of careful observation and then be prepared to invest faith in it. 

This does not mean investing a blind faith in one style of good running or one training method.  In fact the evidence suggests that many aspects of any running style have advantages and disadvantages.  It is also clear that approaches to training methods as different as those of Lydiard and Furman can achieve successful results.  Belief that there is only one path to success is a very brittle foundation on which to build.  My belief, based mainly on observation but partly also on faith in the rationality of the human mind, is that we should use our powers of observation and reasoning to identify the style and training plan that appears to best suit our circumstances and goals.  We need to be able to recognize the strengths and potential weaknesses of our plan and then invest faith in our own judgment.

Problems with Pose

In my post on 8^th Feb I described how the Pose Method of Running  has strongly influenced my understanding of running style.  In that post I focused mainly on the features of Pose that I have found helpful.  Here is a summary of those features:

1)      Running style matters for all runners; amateurs whose major goal is to enjoy running injury free and elites who are eager to maximize their speed and efficiency.

2)      High cadence, at least 180 steps per minute, is efficient

3)      Short time on stance maximizes both speed and efficiency; short time on stance demands landing only a short distance in front of the centre of gravity

4)      Landing on the ball of the foot is efficient and can reduce risk of injury to joints, especially hip and knee.

5)      When making changes to running style, it is sensible to employ drills to make the new style habitual and exercises to develop the strength required to sustain the new pattern of motor activity.

I will return to consider most of these positive features in greater detail in the future, but now it is time to address what appear to me to be negative or misleading aspects of Pose. 

The metaphor of gravity as the source of energy

The role of gravity is central to the theory of Pose, but it is not all that easy to determine what Dr Romanov believes about gravity.  In the first chapter of Pose Method of Running he states that we should use gravity as the source of energy.   Elsewhere he talks about gravity providing propulsion for running.  The statement that gravity is the source of energy must be taken as a metaphor: words that invoke an image rather than words that are literally true.  This image might well be useful, but confusing metaphor with reality can be misleading.  Gravity can be a source of kinetic energy only if the centre of gravity of the object falls.  Over the course of the gait cycle, the body does not fall so gravity provides no net energy. 

At Loughborough in 2008 when I had endeavored to engage him in discussion about the role of gravity, Dr Romanov had been unwilling to discuss this issue, but by 2009 he was prepared to acknowledge explicitly that gravity is not literally the source of energy for running.  In a presentation on accelerated running presented at the 22^nd ISBS conference in Limerick, Ireland, in 2009, Dr Romanov and his colleagues acknowledged that: ‘Gravity completes no net work during stance in constant speed running,’  [This paper is available at http://w4.ub.uni-konstanz.de/cpa/article/viewFile/3291/3092]

Dr Romanov further obscures the meaning of the statement in chapter 1 of Pose Method of Running that gravity is the source of energy, by use of misleading analogies.  In chapter 12 (page 64) he compares the deflection of the vertically acting force of gravity to provide horizontal propulsion for the runner with the way a yachtsman sets the sails to utilize the wind to propel a boat into the wind.  However, this analogy is misleading and largely irrelevant because the pressure of wind on the sails imparts energy to the boat; the setting of the sails deflects the direction of the force, but the crucial issue is that the wind provides energy.  Elsewhere in Pose Method of Running (page 210) he uses the illustration of a lumberjack felling a tree on a hillside so that it falls in the uphill direction as a description of how Pose allows a runner to use gravity to propel him or herself uphill, but fails to point out that the felled tree ends up with its centre of gravity lower after being felled, whereas the uphill runner must raise his or her centre of gravity.  So these analogies do not explain how gravity might provide the energy for running.

Pose, fall, pull

Behind the smokescreen of misleading analogies and motivational material such as accounts of the achievements of Tiger Woods and Lance Armstrong, Pose Method of Running does provide a description of the core of the Pose technique, which can be summarized in three words: ‘pose, fall, pull’.  At mid-stance, for a brief instant, the Pose runner adopts the posture which Dr Romanov calls the pose.  This is a position in which the ankle, hips and shoulder are aligned.  The knee is slightly flexed so the legs and torso form a shallow S shape.  Although momentarily in balance, this posture is poised on the brink of instability.  Slight forward movement results in a face forward-and-downwards fall, driven by gravity.  As the body rotates forwards and down, the weight is taken off the foot, allow the pull: a swift hamstring contraction that pulls the foot towards the buttocks.    The body is now airborne and moving forwards towards the point at which the other foot is allowed to drop to the ground virtually under the centre of mass, with the point of support under the ball of the foot; and from footfall the body moves to the next pose, fall and pull.  At first sight this might seem plausible.

The common-place experience of leaning forwards from a standing position to commence running makes the sequence of pose, fall and pull appear plausible.  Indeed the Pose description does capture some of the features of accelerated running moderately well, though even in accelerated running gravity is a stimulus to promote muscle contraction rather than a source of free energy.  But when it comes to running at a steady speed on a level surface, the sequence of pose, fall and pull does not describe the essence of how we run.

What is missing from pose, fall, pull?

First of all, the unbalancing after midstance is due mainly to momentum. In fact, once one is up to speed, momentum carries us forwards, as dictated by Newton’s first law of motion.  Forward propulsion is only required to overcome wind resistance and to compensate for the braking that occurs in early stance.  The major energy consuming actions of running are getting airborne and swinging the leg forward fast enough so it is ready to support the body at the next footfall.  By focusing on the proposed role of gravity in providing forward propulsion when running at constant speed, Pose focuses on one of the aspects of running that consumes relativley little energy, apart for the situation when there is a very strong headwind.  Furthermore, in attributing the forward propulsion to gravitational torque, Dr Romanov is almost certainly wrong.  Gravitational torque in late stance generates a forward-and-down rotation, not a forward linear motion.  If a face-down crash is to be avoided, this rotation must be corrected at some other point in the gait cycle. 

At least part of the cancellation of the head forward-and-down rotation is provided by the oppositely directed gravitational torque that acts in early stance.  A calculation based on force plate data acquired by Cavanagh and Lafortune which I performed during my debate with Simbil in the comment section of my post on Feb 24^th, 2009, demonstrated that about 2/3 of the head forward-and-down rotational momentum was cancelled by the oppositely directed gravitational torque acting  in early stance.  I consider it probable that the remaining one third of the rotational momentum in that instance was cancelled by the wind resistance, but in the absence of a precise measurement of wind resistance, that remains speculation.  Nonetheless, the central issue is that gravitational torque cannot generate forwards linear momentum. According to Newton’s second law of motion, linear acceleration in a forward direction at any instant is proportional to the forward directed forces acting on the body at that instant.  Apart from wind, the only horizontal force is the horizontal component of ground reaction force (GRF), and that must be the source of forward propulsion. 

It should be noted that recording of the electrical signals associated with muscle contractions demonstrate that the major extensor muscles of the leg which might be expected to push against the ground to generate the forward ground reaction force are largely silent in late stance.  However force plate data (eg Cavanagh and Lafortune, Journal of Biomechanics, 1980) clearly demonstrated that there is a forward directed horizontal GRF in the second half of stance.  The push that generates this is the elastic recoil of muscles that had been subjected to eccentric contraction in early stance.  The Pose emphasis on gravitational torque fails to acknowledge the role of horizontal GRF in providing the forward propulsion that is required when maintaining a constant speed.

A further illustration of Dr Romanov’s under-estimation of the role of horizontal GRF is provided in the paper by Fletcher, Dunn and Romanov on accelerated running presented in the ISBS conference in Limerick in 2009.  In that paper the authors present data which they claim shows that maximum horizontal acceleration of the centre of mass (COM) occurs before maximum horizontal GRF.  They conclude that acceleration of the COM occurs via a gravitational torque with GRF being the consequence of, not the cause of these movements.   In contrast, equation 1a in that same paper correctly shows that the horizontal acceleration at any instant in time is proportional to horizontal GRF (in accord with Newton’s second law) and hence the maximum horizontal acceleration must occur at the same time as the maximum horizontal GRF.  The author’s conclusion appears to be in direct contradiction to equation 1a and to Newtonian mechanics.

Getting airborne

As stated above, when running, the issue of horizontal propulsion is not the major issue.  From the point of view of energy consumption, getting airborne is a bigger issue.   Pose theory emphasizes the role of a pull by the hamstring that pulls the foot towards the buttocks.  I find this concept of the pull interesting and believe that conscious focus on producing the pull as recommended by Dr Romanov is indeed very helpful.  However, a hamstring pull cannot lift the body – that would be like lifting oneself by one’s own bootstraps.  The force that gets us airborne is the vertical component of GRF.  Force plate data demonstrates that through most of the stance period vertical GRF is much greater than body weight – typically 2 or 3 times body weight.  In late stance, the silence of the extensor muscles implies that GRF is maintained by elastic recoil of muscles and tendons that had been subjected to eccentric contraction in early stance.

Dr Romanov’s serious under-estimation of the magnitude of GRF is illustrated in figure 7 in the article by Romanov and Fletcher in Sports Biomechanics, 2007 (volume 6, pp 434-452) entitled: ’Runners do not push off the ground but fall forwards via a gravitational torque.’   Figure 7 illustrates the forces acting during the part of stance after the centre of mass (COM) has passed over the point of support.  The authors conclude that the resultant force acting on the body is equal to the component of gravity at right angles to the line from point of support to the COM.  They base this conclusion on the statement that the component of gravitational force along the axis from support to COM  is equal and opposite to the ground reaction force vector.  Force plate data such as that presented by Cavanagh and Lafortune clearly demonstrate that this is simply wrong.  Throughout most of stance GRF is much greater than body weight, and it is the vertical component of this GRF that gets us airborne.   

Forces Acting on a Runner After Midstance

In the figure showing forces acting on a runner after mid-stance, diagram (a) depicts fig 7 in Romanov & Fletcher (Sports Biomechanics, 2007).  GRF is cancelled by the opposing component of gravity. The resultant force (thick black arrow) is equal to the forwards and downwards component of gravity. Diagram (b) is based on a more realistic estimate of GRF (from Cavanagh & Lafortune, Journal of Biomechanics, 1980).  GRF exceeds the opposing component of gravity. The resultant force (thick black arrow) is directed forwards and upwards. 

Insofar as Pose theory encourages an under-estimation of the magnitude of ground reaction forces, it creates an illusion that puts us at risk of failing to develop adequate strength of muscle and sinew to withstand forceful eccentric contraction, and thereby to store adequate elastic potential energy which can produce the recoil required to generate both the horizontal GRF that provides the required horizontal propulsion and the even larger vertical GRF that is required to get us airborne.  Failure to develop the required strength will result in sub-optimal performance and might place us at risk of injury.

Physics is not the only science

On the other hand, it is not purely a matter of physics.  In fact the human brain processes intended whole actions rather than muscle contractions.  With its focus on a rapid pull, the imagery (and drills ) of Pose can facilitate a remarkably rapid lift off from stance without any conscious awareness of the push against the ground.  While the notion that this is achieved purely by a pull is as fanciful as the idea of lifting one by one’s own bootstraps, Pose does encourage a fairly efficient take-off with minimal conscious muscular effort.  I was fascinated at Loughborough to see just how quickly jonp could get off stance.   So despite rather questionable theoretical underpinning, in practice Pose works fairly well.  Nonetheless, I am inclined to think that an elite athlete, especially a middle distance runner, would probably be well advised to work more explicitly on developing the strength and coordination to capture and release the maximum amount of elastic energy. I doubt if Pose drills augmented by hamstring exercises are adequate. 

It might be that Pose enthusiasts will complain I have mis-represented the actions involved in the sequence pose, fall, pull.  If so, I will gladly listen to their criticism and hope to improve my understanding.  There is a certain mysticism in the way that Pose is described and in my attempt to provide a concise, concrete account I have omitted some of the subtleties.  Nonetheless, I am quite confident that Dr Romanov’s exposition of the mechanism violates the laws of physics, as is illustrated both in the paper in Sports Biomechanics in 2007 and the paper presented at the ISBS conference in 2009. 

Are there practical problems with Pose?

While I have little faith in the theory of Pose, that in itself would not necessarily undermine the practical utility of the Pose technique.  After all, many of the images created in the Alexander technique such as imagining the neck extending or the back broadening have relatively little correspondence to what actually happens to the relevant part of the body during practice of the Alexander technique.  Yet there is little doubt that Alexander technique promotes good posture. In many circumstances the image is more important than the precision of the anatomical description.

Unfortunately, I believe that Pose has not only theoretical problems but also some practical problems, most importantly in regard to foot dynamics.  The most extensive scientific study of the effectiveness of Pose technique was the study performed in Tim Noakes laboratory in Capetown in 2002 and published in the Journal Medicine and Science in Sports and Exercise by Arendse and colleagues in 2004.  The investigators examined the stresses acting at knee and ankle during Pose running compared with mid-foot running and heel striking.  Dr Romanov was the coach who instructed the Pose runners, so we can assume that the teaching was in accord with Pose principles at the time.    The measurements revealed less stress around the knee joint in the Pose runners – a credible and important finding which has been strongly proclaimed in subsequent literature promoting Pose. The study also showed that Pose was associated with greater stress around the ankle joint – a warning of risk of injury to Achilles tendon, calf muscles and plantar fascia, unless special precautions are taken.  This adverse finding of the study has received much less prominent publicity in the Pose literature.

I suspect this problem arose because prior to the Arendse study, orthodox Pose teaching placed too much emphasis on maintaining the foot in plantar flexion while on stance.  This potentially damaging foot posture is still shown in a very large number of the illustrations in the 2004 edition of the Pose Method of Running. That edition does at least acknowledge in the text that the heel might brush the ground, but the reasons for this are not discussed.  I suspect that currently, many Pose coaches do adjust their teaching to minimize the risk of stress around the ankle, though I know from talking to beginner Pose runners that Achilles problems still occur, and I consider that Dr Romanov should have been more active in emphasizing the risks.   

There is another topic that I have touched on indirectly above: the psychological effects, good and bad, about the way Pose is taught and marketed.  In my next post I will discuss these, before returning to the topic which I regard as one of the most important aspects of running style: how to achieve a short time on stance while minimizing stress on muscles and joints.  That topic will include a discussion of foot dynamics taking account of some of the recent studes that have compared shod and barefoot running.

The dangers of the modern running shoe and some thoughts on Pose

The past few months has seen the publication of some interesting evidence regarding the disadvantages of the modern running shoe.  First there was the paper by Kerrigan and colleagues showing that, in comparison with running bare-foot, modern running shoes generate greater torque at knee and hip joints (The Effect of Running Shoes on Lower Extremity Joint Torques, PM &R: The Journal of Injury, Function and Rehabilitation, Vol. 1, pp 1058-1063, December 2009).  The torques generated during shod running exceeded even those recorded in women wearing high heeled shoes.  Then at the end of January 2010, a paper by Dan Lieberman of Harvard University, was published in the highly prestigious journal ‘Nature’, reporting evidence that modern running shoes are associated with potentially damaging rapid rises in ground reaction force, in contrast with barefoot running.  The fact that Dr Lieberman’s research is funded partly by the manufacturers of Vibram Five Fingers is a reason for listening with some caution to ‘barefoot professor’ Lieberman’s persuasive presentation on the promotional video produced by ‘Nature’  (http://www.youtube.com/watch?v=7jrnj-7YKZE ).  Nonetheless, the evidence demonstrating that the modern running shoe is harmful is becoming compelling.  In the near future I plan to post a review of this of evidence regarding running shoes.

Optimum running style

But before examining foot dynamics during running, it is probably best to review the more general question of optimum running style.  My thinking on this topic has been strongly shaped by my experience of the Pose style developed by Dr Nicolas Romanov (http://www.posetech.com/ ).  I had initially looked into Pose in 2004 during my first middle-aged dalliance with running, and decided that it had many worthwhile features, though I was a puzzled by some peculiarities of the biomechanical theory on which Pose was based.  After taking up running more regularly in 2007, and participating in a very informative discussion of the various schools of efficient running on the Fetch Efficient Running thread throughout that year, I was delighted to have the opportunity to attend a two day course with Dr Romanov  in Loughborough in March 2008. 

That two-day course was enough to confirm my suspicion that some details of Dr Romanov’s grasp of biomechanics were not sound, and also gave me some insight in the psychological strategies used to market Pose, but in addition provided me with two very positive experiences.   First, observation of Pose coach Jon Port (aka jonp) in action demonstrated that Pose can produce a highly developed ability to get off stance quickly.  Secondly, discussion with Pose coach Mark Hainsworth (aka Cabletow) re-assured me that it is acceptable to allow the heel to brush the ground in mid-stance.  I had been concerned about the risk of Achilles strain arising from the plantar flexion of the foot at mid-stance illustrated in much of the Pose literature (e.g. Pose Method of Running, 2^nd Edition, Romanov and Robson, 2004).  As I will discuss subsequently, I think that official Pose teaching is still reluctant to address this issue adequately, but Cabletow’s advice was re-assuring.   So I set about developing a style of running which incorporated what I regarded as the good features of Pose while ignoring the bad.

Style matters

Let us start with the good features.  First, Dr Romanov deserves credit for championing the idea that running style is worth thinking about.  While it is probable that many elite runners have managed to find a style that works for them without a great deal of theorizing, it is equally clear that a very large number of runners, including even some elite runners, suffer injury. Poor running style almost certainly contributes to the risk of injury.  It is also likely that many runners could run somewhat faster if they removed inefficient features of their style.  As discussed in my posting on 29^th November 2009, I think that the analysis of Paula Radcliffe’s running style by physiotherapist, Gerald Hartman was an important factor in taking her from 4^th place in the 10,000m in the Sydney Olympics in 2000, to a cross-country  world championship victory in 2002 and to her spectacular world record in the marathon in 2003.  Paula did flirt at  least briefly with Pose, though that is not the main issue.  Dr Romanov has perhaps done more than any other coach in recent times to champion the idea that running style matters to all runners, whether amateur or elite.

High cadence

Secondly, Pose emphasizes a high cadence.  Getting airborne is the essence of running, but getting off the ground consumes energy.  As demonstrated in the calculation page in the side bar to this blog, the total amount of work done against gravity in a series of short fast strides is less than that during a smaller number of longer strides producing the same speed.  In general, high cadence is beneficial, though there comes a point, perhaps around 200 steps per minute, where any further increase results in loss of efficiency (as discussed on in my posting on stride length and cadence on 31st Dec 2009.)   Of course, Dr Romanov is not the only theorist to propose a high cadence.  Gordon Pirie advocated a rapid turnover in his book, ‘Running Fast and Injury free’, and many others have reiterated this principle.  Nonetheless, the Pose recommendation of a cadence of at least 180 steps per minute is sound.

Short time on stance

Third, Pose promotes a short time on stance. Since time stance is inevitably associated with a braking effect due to a backward directed ground reaction force in early stance, and furthermore, the longer the time on stance, the greater this braking effect, spending a long time on stance is inefficient.  Pose achieves a short time on stance by encouraging footfall only a short distance in front of the centre of gravity, and by promoting a rapid pull of foot from stance.  In fact I believe that the theory advanced by Dr Romanov to underpin the Pose mechanism for achieving a short time on stance is largely wrong, but the end result is beneficial.  This illustrates the fact that having a good mental image of the end result of a complex muscular action that entails coordination of many muscles is far more important than attempting conscious micro-management of each contributing muscle.  I will return to a more detailed consideration of this subsequently.

Forefoot landing

Fourthly, Pose promotes landing on the forefoot.   As originally proposed, Pose advocates footfall with the ankle plantar flexed.  I believe that maintaining this planar flexion through midstance as shown in much of the Pose literature, is potentially dangerous.  However, Dr Lieberman’s recent comparison of barefoot running with shod running confirms that forefoot (or at least mid-foot landing) is desirable.  We will return to this issue again later.

Drills and exercises

Finally, Pose provides a framework that includes specified drills and strengthening exercises, together with the recommendation that when changing one’s running style, it is crucial to use these drills and exercises to develop the appropriate actions and the required muscular strength before attempting to run for long distances in the new style.  This is very sound advice, though this is an area where the commercialization of Pose potentially creates problems.  The commercialization has led to a down-playing of the risks of Pose style, and in my opinion, this creates a situation in which athletes who are eager to minimize the reduction in training volume during a change of style, are at risk of injury.  Again, this is an issue to which we will return.

These are what I consider to be the five major positive aspects of Pose style.  My next posting will examine what I consider to be the negative features of Pose.