ISEMPH Presentation: Daniel Lieberman
"An evolutionary medical perspective on shoes"
Although most people think wearing shoes is normal, humans were barefoot for millions of years before the relatively recent invention of footwear. This presentation will review laboratory and field studies on habitually barefoot and shod populations in Kenya, Mexico and the United States designed to test how shoes alter foot function during walking and running, and the trade-offs they provide in terms of comfort and performance relative to preventing injury. Modern, conventional shoes protect the foot and decrease the work foot muscles have to do. However, compared to habitually shod individuals, the feet of habitually barefoot or minimally shod individuals have significantly stiffer and stronger arches and a lower incidence of low or high arches. In addition, controlled experiments demonstrate that individuals who are barefoot or minimally shod employ a greater degree of variation in foot strike when running, with less reliance on rearfoot striking, which generates impact peaks with high rates and magnitudes of loading. Finally, heel cushioning causes an inevitable trade-off between the amount of energy absorbed during impact versus the rate of loading. Shoes therefore contribute to several mismatch conditions but also alleviate their symptoms, permitting the conditions to remain prevalent or even intensify.