Human feet are much stiffer than those of other primates, which means they limit midfoot bending during walking. The evolutionary reasons for this are not entirely clear. One idea is that the features that stiffen the foot evolved to make upright walking less effortful.

To test this, Owen Beck and Hui Tang at the University of Texas at Austin developed a pair of foot-stiffening socks, as they detail in a paper published in the journal Proceedings of the Royal Society B: Biological Sciences. Along the way, they may have come up with a low-cost garment that makes walking easier.

The socks feature tightly knitted bands around the ball of the foot. When someone stands or walks, they restrict the foot from spreading out or widening under pressure, a condition known as foot splay. This, in turn, increases arch stiffness. What the researchers didn’t know, however, was whether this extra stiffness would actually conserve energy without interfering with the natural movement needed for push-off.