PACK POINTS
The power of walking – and running
In a first-of-its-kind study comparing human walking and running motions, engineers at NC State showed that ankles and hips equally contribute to power generation when people walk, but the ankles generate more of the power when humans run. Knees provide approximately one-fifth or less of walking or running power.
The research could help inform the best ways of building assistive or prosthetic devices for humans or constructing next-generation robotics, said NC State biomedical engineers Drs. Dominic Farris and Gregory Sawicki, the co-authors of a study on the mechanics of walking and running. The two researchers are part of NC State’s Human PoWeR (Physiology of Wearable Robotics) Lab.
The study is the first to zoom in on the mechanical power generated by specific lower-limb joints in a single comprehensive study of walking and running across a range of speeds, Sawicki said.
The study shows that, overall, hips generate slightly more power when people walk. That is, until humans get to the point at which they’re speed walking – walking so fast that it feels more comfortable to run – at 2 meters per second. Hips generate 44 percent of the power when people walk at that rate, with ankles contributing 39 percent of the power.
When people start running at this 2-meter-per-second rate, the ankles really kick in, providing 47 percent of the power compared to 32 percent for the hips. Ankles continue to provide the most power of the three lower-limb joints as running speeds increase. Switching to a run may be a strategy that allows people to make more use of the long elastic Achilles tendon at the ankle joint to recycle the body’s mechanical energy.
Knowing which part of the lower limbs provides more power during the different activities can help engineers figure out how, depending on the person’s speed and gait, mechanical power needs to be distributed for people who need help walking and running. 