Medical News
Health
26 June 2019
Tough but sensitive solesMahmoud Khaled/Anadolu Agency/Getty Images
By Michael Le PageThe thicker soles that develop on the feet of those who rarely or never wear shoes provide protection without reducing the foot’s ability to sense the ground beneath them – unlike cushioned shoes.
That’s the finding of a team led by evolutionary biologist Daniel Lieberman of Harvard University, who took up barefoot running a decade ago when he began studying it. His 2010 findings helped fuel the craze.
Lieberman noticed that as his calluses grew thicker, his feet got tougher without seeming to lose their ability to sense the surface beneath them. He and his colleagues have now confirmed this by studying the feet of around 100 people in Kenya and the US.
Advertisement
Those who usually went barefoot had calluses up to a third thicker, but could sense vibrations just as well as those with thinner calluses. The reason, the team think, is that hard calluses transmit forces without dampening them – unlike the foam or rubber soles of many shoes.
People who don’t have calluses are often very surprised by this, Lieberman says. But he points out that, for instance, guitarists also develop thick calluses on their fingers without losing sensitivity.
The team are now looking at whether shoes or sandals with thin, stiff, uncushioned soles that act more like calluses and allow people to get more information from their feet could have some benefits compared with highly cushioned footwear.
In particular, the team think this might help elderly people with their sense of balance, not least because feet become less sensitive with age. “Any way we could figure out to help people fall less would be useful,” says Lieberman.
Injury reduction
A 2003 study also suggested that athletes would suffer fewer injuries if they got more pressure cues from their feet.
Lieberman’s team also found that cushioned shoes prolong the impact when the foot strikes the ground. The peak force is reduced but the overall impulse – the force over time – is higher.
“Over millions and millions of steps, we wonder if this has some effect on joint disease,” says Lieberman, who points out that arthritis has become much more common over the past century or so even when adjusting for factors such as body weight.
“This is not about running, this is about walking,” he says. “A gait that is much more important for most of us most of the time.”
Journal reference: Nature, DOI: 10.1038/s41586-019-1345-6
More on these topics:
health