Shoes that raise the toes make walking easier, according to a small study. The downside is that this might weaken the foot, increasing the risk of a common and painful condition known as plantar fasciitis.
When Freddy Sichting at the Chemnitz University of Technology in Germany went running with Daniel Lieberman of Harvard University 鈥� whose work helped popularise barefoot running聽鈥� the pair started talking about how shoes affect feet. In particular, they wondered about the way the sole of most shoes curves upwards under the toes, a feature called a toe spring.
鈥淚t is such an obvious feature of nearly every shoe,鈥� says Sichting. Despite this, he says, no one had studied its effect on the foot before.
Advertisement
So Sichting, Lieberman and their colleagues got 13 volunteers aged between 19 and 33 to walk on a treadmill while barefoot or wearing simple sandals with a toe spring angle of 10, 20, 30 and 40 degrees.
The researchers used sandals rather than shoes, so they could record the 3D motion of the foot, from which it was possible to work out how active the muscles in the foot were during walking. They didn鈥檛 test a sandal without a toe spring, as it is very different to walk in footwear with a completely flat sole.
The results show that the muscles in the feet have to do a little less work per step to stabilise the foot while walking in footwear with a toe spring, Sichting says, with higher toe spring angles increasing the effect.
鈥淭his sums up over thousands of steps, over days and years,鈥� he says. 鈥淚t鈥檚 this long-term effect that might be bad.鈥�
This could result in weaker foot muscles, which means there is more stress on other tissues such as the plantar fascia, a layer of connective tissue running under the foot from the toes to the heel. When people put a lot more stress on the foot than normal 鈥� when they go hiking, take up running, get a job that involves standing or put on weight 鈥� there is a higher risk of damaging the plantar fascia and developing plantar fasciitis, Sichting thinks.
However, the causes of plantar fasciitis are still debated, he acknowledges. The team will have to do further studies to confirm this idea.
If the team is right, regularly walking and running in minimal footwear should strengthen the feet and reduce the risk of plantar fasciitis. But any transition to this should be made gradually, cautions Sichting.
鈥淢ost feet are not used to doing all the work without the support of modern shoes,鈥� he says.
Scientific Reports
