The prototype transfers up to 80% of an 80-lb load, but there’s one catch: The device affects the user’s gait. The user places his or her feet in boots attached to a series of tubes running up the leg to the backpack. The person carrying the load also needs 10% more oxygen than normal for the extra effort needed to overcome gait interference.
Springs at the ankle and hip and a damping device at the knee let the exoskeleton approximate the walking motion of human legs, with a small external power input (one watt). Other loadbearing exoskeletons require larger power sources (in one case, about 3,000 W from a gasoline engine).
Hugh Herr, principal investigator of the Biomechatronics Group, envisions exoskeletons that could help people run or lessen the likelihood of leg and back injuries.