Stanford University engineers develop ankle exoskeleton to make running easier

Engineers at Stanford University have created a device that people could strap to their legs that makes running easier. The team of researchers has investigated a pair of different modes for running assistance. One of the methods was motor-powered assistance, and the other is spring-based assistance.

The team says that one goal is to help boost physical activity and potentially create a new mode of transportation. In testing, wearing an exoskeleton that was switched off increased the energy cost of running, making it 13 percent harder than running without the exoskeleton. When the exoskeleton was turned on, it was 15 percent easier than running without the exoskeleton.

The team also found that when the exoskeleton was powered to mimic a spring, there was an increase in energy demand for running, making it 11 percent harder than running without the exoskeleton and only two percent easier than the non-powered exoskeleton. The researchers say that future designs could reduce the energy cost of wearing an exoskeleton allowing runners to get a small benefit from spring-like assistance at the ankle.

The device attaches to the shoe with the rope under the heel and the carbon fiber bar inserted into the sole, near the toe. Motors were situated behind the treadmill rather than on the exoskeleton itself and produce the two modes of assistance studied. The spring-like mode mimics the influence of a spring running parallel to the calf, storing energy during the beginning of the step and unloading it as the post push off.

In powered mode, researchers connected a cable running from the back the exoskeleton from the front of the heel to the calf. With action like a bicycle brake cable, it's able to pull upward during toe-off to help extend the ankle at the end of a running step. Power assistance took a lot of energy burden off the calf muscles says the researchers. The team notes that it was very springy and bouncy compared to normal running. Researchers believe that this technology can help people in various ways.