Walking With Shakira

Shakira is right: Hips don’t lie. At least when they’re used for walking.

In a study comparing the power generated by hips, knees and ankles when humans walk and run on level ground, hips provided more of the power when humans walk at speeds up to 2 meters per second – a rate equated with speed walking – according to Drs. Greg Sawicki and Dom Farris in NC State’s Human PoWeR (Physiology of Wearable Robotics) lab.

When speed walking transitioned into running, however, the researchers found that a different portion of the leg provided more power: the ankle.

Knees came in a distant third in lower-limb power production – they provided only about 20 percent of the power when humans ran or walked on level ground. Sawicki and Farris say the knees come into play more when humans walk or run on an incline. (This may be good news to people like me who are reminded of a breakfast-cereal slogan – snap, crackle, pop – when they bend their knees.)

Why is this important? If you’re trying to build the next generation of prosthetics or assistive devices for anyone from stroke victims to injured soldiers, you need to know which parts of the body need more power – and when – as people walk and run at different speeds.

The study is published in Interface, a Royal Society journal.