In a study comparing human walking and running motions — and whether the hips, knees or ankles are the most important power sources for these motions — researchers at North Carolina State University found that the hips generate more of the power 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, according to Dominic Farris, PhD, biomedical engineer, North Carolina State University and Gregory Sawicki, PhD, biomedical engineer, North Carolina State University. Sawicki and Farris are part of NC State’s Human Physiology of Wearable Robotics (PoWeR) Lab.
The study found that hips generate more power when people walk. That is, until humans get to the point at which they are speed walking at two meters per second. Hips generate 44% of the power when people walk at a rate of two meters per second, with ankles contributing 39% of the power.
When people start running at this two-meter-per-second rate, the ankles provide 47% of the power compared to 32%for the hips.
“There seems to be a tradeoff in power generation from hips to ankles as you make the transition from walking to running,” Sawicki stated in a press release.
Both researchers are interested in how the study can help people who need assistance walking and running. Knowing which part of the lower limbs provide 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.
“Assistive devices, such as an exoskeleton or prosthesis may have motors near both the hip and ankle,” Farris stated in a press release. “If a person will be walking and then running, you would need to redistribute energy from the hip to the ankle when the person makes that transition.”
The study examined walking and running on level ground in order to gauge the differences brought about by increased speed. Walking and running on inclined ground is fundamentally different than walking and running on flat ground, according to the researchers and would likely skew the power generation results toward the hips and knees.