A Knitted Sock That Stiffens the Arch Cut Walking Effort in a Small Test

A sock that squeezes the ball of the foot can make walking slightly less tiring, according to a new study from the University of Texas at Austin. ScienceAlert reported that the socks stiffened the foot's arch and lowered the body's energy use with each step, which could one day help people walk farther with less effort.

The finding was a side effect of a different question. The team set out to probe an evolutionary puzzle: human feet are stiffer than those of other primates, and it has never been fully clear why. A leading theory holds that a stiff foot helps people walk upright with less effort. These experiments, published in Proceedings of the Royal Society B: Biological Sciences, support that idea, ScienceAlert said.

The key numbers behind the study

• 12 participants: The team recruited 12 healthy volunteers with an average age of 28. That is a small group, so the result is an early signal rather than a settled answer.
• 5-minute sessions: Each person walked on a treadmill for 5 minutes at a time, once in the custom socks and once in ordinary commercial socks for comparison.
• 2%: Walking in the foot-stiffening socks reduced whole-body metabolic rate by 2% compared with commercial socks, the researchers wrote.
• 2 kilograms (4.4 pounds): The researchers equate that 2% saving to taking a 2-kilogram weight off the waist, a difference a hiker would likely notice.
• 65%: The experiments showed the arch was stiffened lengthwise by 65%, yet the foot could still bend and push off with each step.

How the socks work

The design is a tight, knitted band around the ball of the foot, intended to stop the foot from splaying, or widening, under load. In the researchers' words, the custom socks pressed harder on the forefoot than commercial ones did, which stiffened the arch through a mechanical link between the two directions of foot movement.

Energy use was measured through breathing, by tracking how much oxygen the volunteers took in and how much carbon dioxide they exhaled. The team reported that the socks limited forefoot splay and stiffened the arch without apparently restricting the foot's mobility late in each step.

The researchers observed that the calf muscles pushed with a little more force but contracted more slowly, which takes less energy overall. ScienceAlert compared this to shifting into a higher gear on a bicycle. A stiffer foot also does more mechanical work in each step, the authors wrote, so the leg muscles have less work to do to keep a steady walking pace.

Why it matters for everyday walkers

Earlier attempts to show that a stiffer foot means more efficient walking had hit a wall. According to ScienceAlert, experiments with rigid shoe insoles and arch supports failed to cut energy use. The socks did, which the outlet described as evidence that the stiffer human foot evolved as a better way to push off between strides on two legs.

There is a practical angle too. The authors argue that rigid shoes cannot lower metabolic rate at realistic walking speeds, and that exoskeletons, while they offer larger benefits, are relatively expensive and hard to use through the day. They describe the socks as a cheap and readily adoptable technology that could reduce the energy cost of walking, and perhaps running.

ScienceAlert said the socks, or garments like them, might eventually help walkers build endurance and could make it easier for people of all levels of mobility to get around, in a simpler and cheaper way than other options. The outlet added that a patent for the design has already been filed.

What the study does not show

The results come from 12 healthy adults on a treadmill for short sessions. The study does not test older people, people with mobility problems, long hikes or running, and the benefits for those groups remain to be shown. The 2% reduction is modest on its own, and the real-world value of the socks will depend on follow-up work with larger and more varied groups of people.

Around Prague, based on reporting by ScienceAlert