ABSTRACT
JeDi'ey M SchiffinanJ, Karen N GregorczykJ, Leif HasselquistJ, Caro(yn K. BenselJ, John P. ObusekJ, David Gutekunst], Peter Frykman3
There is an emerging technology in wearable robots, or exoskeletons , some of which are being developed to assist in carrying loads. These devices are designed to reduce the vertical force of the load on the body and thus reduce the energy expended by the load carrier. This study investigated the effects on metabolic cost and gait biomechanics of walking at 4.8 krn·h-I with 20-, 40-, and 55 -kg loads while wearing a prototype exoskeleton (EXO). Data were also collected on two maximal performance tests conducted after 8-km marches with and without the EXO and on postural balance as affected by the EXO. Ten U.S . Army enlisted men served as test parlicipants . Using rate of oxygen uptake ( 1702 ) as an index of energy cost, mean V02 scaled to body mass and scaled to total mass were found to be s ignificantly higher when the EXO was worn during walking than when it was not. The biomechanical data revealed significant differences in gait patterns between the EXO and the No-EXO conditions, which may have contributed to the higher energy cost with the EXO. The speed maintained by the participants was lower and the
distance traversed shorter when the EXO was worn for the 8 -km march. Scores on the maximal performance tests were not affected by whether or not the EXO was worn during the march . Postural sway cxcursions during stationary standing were significantly reduced with the EXO, but there was a greater tcndency for body sway to occur without conective adjustments back to an equilibrium point, a less stable pattern than evidenced without the EXO. This study identified a number of design fcatures of the EXO prototype that contributed to the higher energy cost, changed gait pattems, and reduccd balancc stability.
