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foot injury, foot structure, sports injury rates, leg injuries

Foot injury and foot structure

Foot injury and foot structure - there's been considerable confusion concerning the effects of foot structure on injury rates. Some researchers - and large numbers of people in the population at large - believe that individuals with low-arched feet have weak foot structures and are more predisposed to injuries in the lower extremities.

In the United States, would-be recruits with low-arched feet have actually been denied the opportunity to serve in the U.S. Army, because it was believed that their risk of injury would be unacceptably high.

On the other hand, some scientists have suggested that low-arched feet may in fact be protective against foot injuries and that high-arched people are at higher risk, especially for problems such as stress fractures in the feet and legs. They theorise that low arched feet absorb more energy during footstrike and that high-arched trotters are so rigid that they transmit impact forces directly up the leg, increasing the risk of bone damage.

If low or high arches did actually increase the risk of injury for soccer players, walkers, tennis players, basketball enthusiasts, runners, etc., they would probably do so by increasing the impact forces passing through the lower parts of the legs each time the feet hit the ground. To determine whether those impact forces are significantly different between low- and high-arched people, scientists at the University of Calgary recently studied 18 female and 19 male adults as they ran at a pace of about seven minutes per mile.

Actual arch heights of the subjects ranged from 1.38 to 3.56 cm (about a half-inch to almost an inch and a-half), and 'arch flattening' (the degree to which the arch collapsed) during running ranged from .1 to .8 cm (from one twenty-fifth to one-third of an inch). However, there was no connection between arch height and arch flattening. In other words, high- arched people did not actually have more rigid arches, as many researchers have suggested.

Further, impact forces were identical in high-arched and low-arched people, indicating that shock absorption was similar in the two types of feet. Neither the low-arched or high-arched person seems more likely to send injury-producing shock waves through the legs.

Why were there no differences between low- and high-arched people? As the Calgary scientists pointed out, if when people run they first land on their heels as their feet hit the ground, the resulting impact forces tend to be transmitted directly up through the heel bones into the lower part of the leg. In other words, the arch region plays little role in modulating impact forces. In fact, many people are indeed 'heel strikers.'

True, it seems likely that the impact forces for midfoot strikers (people who land on the middle of the foot with each step) would be affected by arch height. However, arch flattening would influence these forces, and neither low- or high-arched people are better at arch flattening, according to the Calgary research. In addition, other factors unrelated to arch height, including knee flexion during footstrike, ankle supination (the degree to which the foot rolls outward during footstrike), and pronation velocity (the speed with which the foot rolls inward during footstrike), also have an effect on impact forces and may override any specific effects of arch height.

So if your shoe salesperson tells you that you need extra shock absorbancy in your athletic shoes because you have high (or low) arches in your feet, be wary. Scientific research just doesn't support the idea. In fact, as the Canadian researchers pointed out, 'arch height can not be used clinically to define a general foot type that is at risk to injury.'

Another time-honored belief that individuals who pronate (roll their feet inwards) excessively during running are also at greater risk of injury - recently took a beating in research carried out by the same Calgary investigators. In a prospective study, the researchers were able to show that runners with high degrees of pronation in fact did not injure themselves during training more frequently than individuals who pronated very little.

This latter finding casts new light on efforts by running-shoe companies to produce running shoes which control pronation or, as the running shoe companies like to call it, 'excessive motion'. If higher amounts of pronation don't in fact produce higher injury rates, why does pronation need to be control led? ('Effects of Arch Height of the Foot on Ground
Reaction Forces in Running, ' Medicine and Science in Sports and Exercise, vol. 24(11), pp. 1264-1269, 1992)

foot injury, foot structure, sports injury rates, leg injuries