In those distant days when I was a fairly serious athlete, we did not think much about style. Emil Zatopek’s three gold medals in Helsinki a few years previously had suggested that training mattered far more than style. The ungainly tension in his neck and shoulders was an irrelevancy. We were much more interested in the word-of-mouth rumours of his prodigious training sessions. At the time, we debated the merits of Percy Cerutty’s advocacy of running up sand-hills in contrast to Arthur Lydiard’s advocacy of 100+ miles per week. Neither style nor injuries were a major preoccupation.
In contrast, during the past decade, running style has become a focus of attention among elite and recreational athletes. The focus of the elites is illustrated by Alberto Salazar’s efforts to improve Mo Farah’s efficiency prior to his attempt at the London marathon this year. But perhaps even more importantly, style has been a focus of attention of recreational runners concerned about repeated injury.
A decade ago, distance running had blossomed into a mass participation sport and injuries were rife. Marketing of running shoes had become a major commercial enterprise. The running world was primed to embrace the idea that running no longer came naturally to modern man. Was it a consequence of wearing shoes all day or sitting for hours at a desk? Maybe even it was the training shoes that large commercial companies encouraged us to buy.
The time was ripe for the emergence of gurus with messages about how to run naturally. Techniques such as Pose and Chi became popular. These techniques were embraced with almost religious fervour and many of the disciples found relief from their recurrent injuries. Unfortunately other novices came away from their flirtation with these techniques with new injuries, especially problems with the Achilles tendon. Now, a decade or so later, the reasons for these contrasting experiences are fairly easy to identify. Although a few important issues about running style remain unresolved, the decade of experience and of research has provide fairly clear answers to the major questions.
Natural running: forefoot or heel strike?
One of the most hotly debated issues has been the question of heel striking versus fore foot striking. In part, this debate arose from an idealistic quest to identify mankind’s natural running style, unsullied by the influence of modern life styles. I will focus predominantly on Pose because its strengths and weaknesses are fairly well documented in books, research papers and on the Pose Tech website. The second chapter of ‘Pose Method of Running’ (Pose Tech Corp, 2002) opens with an examination of images of runners on classical Greek pottery. One of the images is from an amphora depicting runners at the panthenaic games in 530 BC. The inventor of Pose, Nicholas Romanov writes: ‘Look at these drawings and you will see quite clearly that all the athletes run on the front part of the foot without landing on the heel. As barefoot runners this was the obvious technique for efficiency and to avoid injury. To my mind this barefoot running style of landing on the forefoot is the purest example of the proper nature of running….As the Golden Age of Greece passed mankind appeared to leave these values far behind’.
The appeal to a golden age of classical Greece subsequently received some support from rigorous science. Based on evidence that our distant ancestors living on the African Savanah around 2 million years ago were probably persistence hunters who relied on the their capacity to chase their prey to exhaustion, Daniel Lieberman and colleagues at Harvard University examined the foot strike pattern of barefoot runners in comparison with runners wearing modern running shoes. He found that barefoot runners tended to land on the forefoot or midfoot whereas runners wearing shoes tended to be heel strikers. The heel strikers experienced a more rapid rise in the loading of the legs in early stance, although Lieberman was careful to avoid claiming at that stage that fore-foot striking would result in a lower injury rate.
Further investigation casts some doubt on the conclusion that habitual barefoot runners are not heel strikers. A study of habitual barefoot runners from north Kenya by Hatala and colleagues did provide further evidence that forefoot strike reduces the magnitude of impact loading. However, these habitually barefoot Kenyan runners tended to land on midfoot or forefoot only when running at sprinting speed, where impact loading is high. The majority of them landed on the heel at endurance running speeds (5 m/sec or less). At their preferred endurance speed (average of 3.3 m/sec) 72% were heel strikers. Could it be that heel striking is actually more efficient at endurance paces?
Is heel striking more efficient at endurance paces?
Ogueta and colleagues from Spain compared efficiency in two well matched groups of sub-elite distance runners and found that heel strikers are more efficient than midfoot strikers, across a range of speeds. Heel strikers were 5.4%,, 9.3% and 5.0% more economical than mid-foot strikers at speeds of 11, 13 and 15 km/h respectively. The difference was statistically significant at 11 and 13 km/hr, but only showed a trend towards significance at 15 Km/hr. DiMichele and Merni from Italy, who tested runners only at a single speed of 14 Km/hour, found no significant difference in efficiency between sub-elite heel strikers and mid foot strikers. Overall, the evidence suggests that at paces typical of recreational endurance running, heel striking is more efficient but the advantage diminishes as pace increases. This is consistent with the observation that in most runners the point of contact at footfall moves forward along the sole of the foot as speed increases.
These studies were cross sectional studies comparing different runners. Indirect evidence of the effect of a change to forefoot landing within an individual is provided by the longitudinal study by Dallam and colleagues of 8 athletes who changed to Pose. They found that 12 weeks after changing to Pose, the athletes were on average of 7.6 percent less efficient than before the change. Perhaps 12 weeks is not long enough to achieve facility with a new style, but the consistency of the magnitude of the penalty associated with forefoot/midfoot striking in the study by Ogueta and the penalty attributable to Pose in the study by Dallam adds weight to the conclusion that heel-striking is more efficient at endurance paces.
With regard to risk of injury, the evidence is more complex. In a retrospective study of US collegiate distance runners, Daoud and colleagues found that habitually rear-foot strike had approximately twice the rate of repetitive stress injuries than individuals who habitually landed on the forefoot. Traumatic injury rates were not significantly different between the two groups. The sharp initial rise of ground reaction force observed with heel strikers is a likely factor in the risk of injures such as tibial stress fracture. It is noteworthy that during a session that included a total of approximately an hour of running at lactate threshold pace, Clansey and colleagues found that several kinematic variables, including rate of rise of ground reaction force in early stance, increased significantly, suggesting an increased risk of stress fracture with increasing fatigue.
However, mid-foot and forefoot strike have their own risks, especially for the muscles and connective tissues acting at the ankle, as indicated by the Capetown study of Pose. Consistent with this, Almonroaeder and colleagues found a 15% greater load (averaged over stance) and an 11% greater rate of rise of tension in the Achilles tendon in mid-foot and forefoot strikers compared with heel-strikers.
Should the push be conscious?
One of the features that appears to account for some of the success of Pose in reducing injury rates among its dedicated disciples is the avoidance of a conscious push against the ground. In reality, force plate data clearly demonstrates that runners do push against the ground, with peak vertical forces often exceeding three times body weight. A study by Weyand and colleagues demonstrates that faster runners push harder against the ground. Many elite sprinters, including Usain Bolt, report that they do consciously push. However, my own speculation is that for recreational distance runners, a conscious push can be harmful if it encourages a delay on stance, and an associated increase in braking. Paradoxically, since the delay decreases airborne time, a lesser vertical push is required to maintain the airborne phase, but a greater horizontal push is required to overcome braking. Excessive horizontal push is potentially harmful, as we will discuss in the section on risks of braking, below.
Perhaps serendipitously, Pose discourages this potentially harmful conscious push by investing faith in the illusion of gravitational free energy. According to Nicholas Romanov, one of the most important principles of Pose is the ‘Do Nothing Concept’ which he describes on pages 88 and 89 of Pose Method of Running: ‘We must learn to get out of the way and let gravity propel us forward while we preserve as much of our energy as possible by the simple act of picking our feet off the ground.’
In the words of Romanov and Fletcher: ‘Runners do not push off the ground but fall forwards via a gravitational torque’. Pose theory draws on the observation that pivoting forwards is an effective way to initiate the action of running to explain how gravitational free energy can allegedly be harnessed even during running at a steady speed. The theory proposes that this can be achieved by employing the sequence of Pose, Fall, Pull, in the period from mid-stance to lift-off. Romanov’s description of the Pose does in fact match the balance posture of many good runners at mid-stance: knees and hips are slightly flexed while the hips and shoulders are aligned over the point of support through which force is transmitted from foot to ground. However, the Fall, which Romanov claims provides gravitational free energy, simply does not occur.
The body’s mass rises rather than falls in the second half of stance. This is clearly predicted by computation based on the time course of ground reaction forces, and also clearly apparent from video clips. The Pose Tech website claims that Usain Bolt employs Pose style, yet examination of the stills from the video of Bolt winning the 100m World Championship in Berlin in 2009 depicted on the PoseTech site, indicates that his hips and torso rise about 7 cm between mid-stance and lift-off. The origin of Romanov’s erroneous concept of the fall is revealed in fig 7 from his paper published with Graham Fletcher in Sports Biomechanics in 2007. In that figure, the authors mistakenly assume that the vertical component of ground reaction force is equal to body weight whereas force plate data show that is several times body weight at mid-stance. I discussed this issue in greater detail in my post of 14 Feb 2010. And finally, it no is more possible to get airborne by pulling the foot towards the hips than it is to self-elevate by pulling on one’s boot straps.
However, despite being based on fallacious theory, Pose does offer some benefits to at least some recreational runners. The discouragement of harmful excessive conscious pushing is balanced by focus on drills such as Change of Stance that help develop the neuromuscular coordination required to get off stance quickly. However, a greater vertical push would be required to maintain the longer airborne time if stance time were to be decreased at constant cadence. Pose technique averts this problem by encouraging increased cadence. For recreational runners who tend to spend too long on stance and to run with cadence that is too low, Pose can be helpful. However, short stance and high cadence each create their own problems. A rational approach to the challenge of identifying the optimum foot-strike , duration of stance and cadence for an individual runner under particular circumstances requires an understanding of the benefits and risk associated with the three major energy costs of running: overcoming braking while on stance; getting airborne; and repositioning the swinging leg during the airborne phase.
Balancing the three main costs
It is clear that efficient running requires a trade-off between the three major energy costs of running: getting airborne, overcoming braking and repositioning the limbs. We can minimise the energy cost of braking by getting off stance quickly, but that creates a demand for greater energy expenditure to maintain a longer airborne phase, unless cadence is increased. However, as described in my post of April 2012, increased cadence demands more energy expenditure to reposition the swinging leg, so we need to find a compromise that minimses total cost. The optimum balance between the three costs depends on pace and other circumstances, such as level of fatigue. We also need to take account of the need to minimise injury.
Risks of getting airborne
Getting airborne demands a strong push against the ground. It appears at first sight plausible that the stronger the push the greater the risk of injury. Surprisingly, studies that compare injury rates between individuals who differ in the magnitude of the vertical push they exert against the ground do not consistently find a significant association with injury rate. This might well be because the strength that allows faster runners to push more strongly also helps protect them against injury. Thus comparison between different runners might obscure a relationship between intensity of push and injury risk for an individual.
Some studies, reviewed by Zadpoor, do demonstrate an association between rate of rise of the vertical forces and risk of injures such as tibial stress fracture. Rate of rise of force is related to both duration over which the force rises to a peak (determined largely by the type of foot-strike, with heel striking creating a steeper rise), and also by the magnitude of the average force (which is inversely proportional to the fraction of the gait cycle spent on stance). Thus it is likely that at high speeds a strong push combined with mid or forefoot landing produces optimum efficiency and safety, though forefoot landing is only safe if the Achilles is well enough conditioned to take the strain. For most runners it is probably safer to ensure that at least some of the load is taken on the heel in longer races. At slower speeds, efficiency is greater with heel striking, and the risk of injury depends on whether the individual is more prone to adverse effects of stress at the knee or the ankle. Stress on the knee is greater with heel-strike, but greater at the ankle with forefoot strike, as demonstrated in the Capetown study of Pose.
It should also be noted that precise timing of the vertical push is crucial. For many runners, attempting to control the push consciously is counter-productive. In contrast, most of us are capable of much more precise timing of hand movements. Arm and leg on the opposite side are linked in their representation in the brain, and also, more tangibly, by the latissimus dorsi muscle and lumbar-sacral fascia that link the upper arm to the pelvis on the opposite side. Therefore, conscious focus on a sharp down and backward movement of the arm can help ensure precise timing of the push by the opposite leg. This sharp downswing of the arm should be accompanied by conscious relaxation of the shoulders. I personally find this strategy more helpful than the cultivating an illusion of falling after mid-stance
Risks of braking
Braking generates both compression forces and shear forces at joints, and also increases stress on hip extensors which must overcome the excessive hip flexion associated with the forward angle of the leg at foot-strike. One possible consequence is pain at the point of attachment of the hamstrings to the pelvis. Therefore from the injury perspective excessive braking must be avoided but it is necessary to bear in mind that there is a trade off between the low braking costs of short time on stance and the costs of being airborne for a greater propotion of the gait cycle. If excessive braking is to be avoided, it is crucial to avoid reaching forwards with the swinging leg, and ensure that the foot lands only a short distance in front of the centre of mass. The jarring associated with braking can be reduced by ensuring that the knee is flexed slightly more than the hip at foot-strike, but the penalty is a loss of rigidity of the leg which might reduce the efficiency of the capture of elastic energy. As discussed above there is a trade-off between braking and getting airborne. Excessive braking demands excessive horizontal push after mid-stance, and an inevitable increase in total stance time. For a runner prone to spend too long on stance focus on a precise push off, governed by conscious down-swing of the opposite arm can promote a good balance between the cost of braking and the costs of getting airborne.
Repositioning cost and cadence
The third element, leg repositioning cost, increases with increasing cadence, but conversely, the energy cost of getting airborne decreases with increasing cadence. The stresses on the tissues of the body associated with getting airborne, and therefore, the likely risk of injury, decrease with increasing cadence. Therefore, many runners, both recreational runners and even some elites, including Mo Farah, might benefit from increasing their cadence, but not so far that the increased energy cost of repositioning become excessive. The optimum cadence depends on various circumstances. Based on observation of elite runners and the calculations presented in my blog posts in Feb and March 2012 suggest that optimum cadence is at least 180 steps/min at 4 m/sec, and 200 steps/min at 5.5 m/sec. However the precise optimum for each individual will depend on leg strength and elasticity. For runners with lesser power and elasticity it is probably best to employ higher cadence, thereby reducing the need for vertical push. As my leg muscle power and elasticity have deteriorated with age, I have been forced to increase cadence. Typically my cadence is around 200 even at a pace of 4 m/sec. This involuntary increase in cadence has helped minimise the risk of damage to my elderly legs, at the price of inefficient expenditure of energy on repositioning my swinging leg. I am therefore working on increasing power and elasticity so that I can push off more powerfully and thereby decrease cadence safely.
Perhaps the most serious error promulgated by gurus is the claim that there is a single best style that is most efficient and safest. The evidence regarding the greater efficiency of heel-striking at endurance paces, yet greater risk of at least some repetitive strain injuries with heel strike illustrates the fallacy of this claim. The most efficient foot strike pattern, time on stance and cadence vary with pace, and in addition, the risk of injury depends on factors that vary between individuals, such as strength of muscles, tendons, ligament and bones. Perhaps the most important strategy of all for minimising injury is building-up of training load slowly over time, and being aware of the effects of fatigue on form during demanding sessions.
Running style does play a crucial role but a much more nuanced approach based on an understanding of the costs and benefits of each aspect of form must be taken to identify what is best for each individual in their current circumstances. The debate and the scientific studies of the past decade have indeed provided us with much information to make these nuanced judgments.