Heel-striking and a brief history of the modern running shoe

Recently, Rick asked me to act as judge in a debate with a friend, who works in a store that sells running shoes, about heel-striking versus mid-foot landing.  

At first sight, it does seem rather amazing that the manufacturers of  running shoes continue to emphasize the virtues of cushioning and stabilization (to reduce pronation – the ‘natural’ tendency to roll from outside edge of the foot towards the medial edge as the longitudinal arch absorbs the energy of footfall)) five decades after Gordon Pirie trenchantly pointed out to Adi Dassler, the founder of Adidas, the reasons why the leading principle in running shoe design should be  ‘less is more’.   But the story has some interesting twists and turns.

Pirie argued that the arch of the human foot is well designed to absorb the stress of footfall provided the runner lands on the forefoot.  In chapter 3 of his book ‘Running Fast and Injury Free’ Pirie cites two observations to support his argument.  The first was the set of video recordings of 100 elite athletes at the 1972 Montreal Olympics, by Bill Toomey (winner of the decathlon gold medal in Mexico City in 1968).  According to Pirie, all 100 elite athletes filmed by Toomey were fore-foot strikers.  The second observation was more anecdotal: Pirie himself ran more recorded miles than any other human being (around 216,000 miles in 40 years) and suffered minimal injuries.  He attributes this to his forefoot running style. 

 

Zatopek and Dassler shoes

However, more recently video analyses reveal that a large number of elite and sub-elite are heel strikers.  What has changed?  I think the seeds were sown two decades before Montreal.  In Helsinki in 1952, Emil Zatopek won gold medals in the 5,000m, 10,000m and marathon, wearing Dassler shoes.  As far as I know, the shoes worn by Zatopek in Helsinki were in fact rather light-weight, though he is reputed to have trained in army boots.  However the more relevant fact is that at around that time, Dassler added the famous three stripes to Adidas shoes to stabilize the mid-foot.  As far I can see, that was the point at which engineering and marketing formed an alliance and abandoned the ‘less is more’ principle.  Fueled by Zatopek’s achievement, Adidas rapidly came to dominate the market.  Ultimately, the engineering led to more cushioned soles and marketing managers persuaded runners that cushioning and stability were crucial.  With heavy cushioning, it was no longer essential to land in a way that absorbed the energy of impact in the longitudinal arch of the foot, and eventually, many runners accepted heel striking as the norm.

In recent times, several schools of thought (most notably Pose and Chi) have resurrected Pirie’s ideas about efficient running, and there has been a resurgence of interest in minimalist shoes.  Nike, which grew from the foundation provided by Bill Bowerman’s famous waffle iron technique for fabricating a durable sole, and went on the eclipse Adidas, have recently capitalized on the minimalist trend with the Nike Frees.  Nonetheless, Nike are currently putting a lot of resources into promoting the Lunarglide, a lightweight shoe designed to combine cushioning and stability, and are targeting their marketing at female athletes.  Whatever the merits of the engineering, marketing has now made it almost impossible to draw any useful conclusions about how it is best to run from observations of elite and sub-elite athletes.

However, neither can we draw reliable conclusions from idealized accounts of ‘primitive’ tribesmen who are reported to achieve phenomenal long distance feats running barefoot or in rudimentary shoes.   Running a 10K in less than 27 minutes, or a marathon in just over two hours, are quite different from pursuing a wild animal for hour after hour across the African savanna or the North American prairies.  Drawing on arguments based on the evolution of the human foot to guide us about the most efficient way to run competitively might not be the best way to settle the question of how to run fast on road or track.

     

Short time on stance is crucial

One thing is fairly clear.  The fastest runners spend a short time on stance.  Studies by Peter Weyand and colleagues at Harvard University have demonstrated convincingly that the feature that distinguishes the fast runners from slower runners is a short time on stance (Journal of Applied Physiology, volume 89, pp 1991-1999, 2001).  A short time on stance necessarily entails a very strong push against the ground, resulting in powerful upwards propulsion, a long stride and relatively high cadence.

Schools of efficient running such as Pose also emphasize a short time on stance.  However, the theory of Pose promulgated by Dr Nicholas Romanov rather misleadingly  implies that the runner becomes airborne due to un-weighting of the foot as a result of gravitational torque, and a hamstring contraction that pulls the foot from the ground.  I believe that it is impossible to become airborne by this means.  A runner who spends 20% of the gait cycle on stance must necessarily exert an average downwards force on the ground that is 5 times body weight. 

Unfortunately, I do not know of any force-plate data that confirms that this is the case for a Pose runner.  I was a little disappointed when I attended a weekend Pose course with Dr Romanov, at Loughborough University (the home of Sport Science in the UK), and none of the Pose experts present showed any inclination to arrange a force-plate recording session.  Nonetheless, the Law of Conservation of Momentum requires that the impulse generated by ground reaction force must balance the downwards impulse generated by gravity acting on body weight, and hence the force exerted by the foot on the ground averaged over the entire gait cycle must be equal to body weight. 

A short time on stance not only ensures a powerful push against the ground, but also necessitates landing only a short distance in front of the centre of gravity, with the foot traveling backwards relative to the body’s centre of gravity at footfall.   This is most easily achieved with a forefoot or mid-foot landing.  Thus simple mechanical principles support Pirie’s argument for a forefoot landing.  However, it would be foolish to under-estimate the forces involved. 

 

Risks of minimalist shoes and forefoot landing

I was interested to note that Dallas Pose coach and stalwart of the PoseTech forum, Jack Becker, suffered a metatarsal stress fracture about two years ago.  While I have a great respect for Jack’s thoughtfulness, and I am personally grateful for advice that he once gave me regarding choice of shoes, I am inclined to think that his enthusiasm for minimalist Puma H-street shoes may have contributed to his stress fracture.  It is an interesting side-issue to note that Puma was founded Rudolf Dassler, brother of Adi – perhaps Rudolf took more note of Gordon Pirie’s opinions.  On balance, I am a little cautious about minimalist shoes, but certainly believe that cushioned heels, and heel striking, are undesirable.  It might be argued that it is better to train the intrinsic muscles of the feet to distribute the load along the arches of the foot rather than to allow these muscles to atrophy within heavily cushioned shoes.

There have been very few studies that have directly compared the benefits and risks of fore-foot, mid-foot and heel striking.  Perhaps the best known is the study by Arendse and colleagues from Tim Noakes’ laboratory in Capetown (Medicine & Science in Sports & Exercise: Volume 36,  pp 272-277, 2004).  The fore-foot landing group was instructed by Nicholas Romanov.  The main finding reported in the published paper was significantly decreased stress on the knee joint in the fore-foot runners compared with the heel-strikers.   However, forces around the ankle were noted to be higher, and Ross Tucker, who assisted Dr Romanov, reports on the Science of Sport blog that calf and Achilles problems were common in the fore-foot group.

 (http://scienceofsport.blogspot.com/2007/09/running-technique-part-ii-scientific.html )

In fact since the publication of the Arendse study, many Pose coaches have reduced the previous emphasis on a ball-of-the foot landing with marked plantar flexion of the ankle.  At least some Pose coaches acknowledge that the heel should be allowed to touch the ground lightly, to relieve the strain on the plantar fascia and Achilles tendon.

 

Conclusion

A short time on stance is essential if you want to run really fast, and this is most easily achieved with a forefoot or mid-foot landing. However the ground reaction forces are necessarily large, and landing on the ball of the foot with ankle plantar flexed places a great strain on the feet, ankles and calf muscles.  At least during long races, it is probably best to let the heel lightly touch the ground, to minimize risk of injury to the plantar fascia and Achilles tendon and perhaps even, risk of metatarsal stress fracture due to bone fatigue resulting from repetitive impact.