Sit-to-stand and stand-to-sit crutch use for lower extremity powered exoskeletons

Lower extremity powered exoskeletons are assistive devices that aim to improve rehabilitation for people with lower limb paralysis and provide upright mobility in the community. Sit-to-stand and stand-to-sit movements are important since a controlled and safe transition to standing is needed to begin exoskeleton use and sitting is needed to conclude and doff the exoskeleton. Ideally, sitting and standing methods minimize upper body contributions for balance and propulsion. This study analyzed crutch-assisted exoskeleton sit- to-stand and stand-to-sit to characterize crutch loads and motions. Five sit-to-stands and stand-to-sits were recorded for three spinal cord injured participants using a 10 camera Vicon motion analysis system, AMTI and Bertec force plates, and strain gauged forearm crutches that measured axial force. Joint kinematics, movement timing, and crutch kinetics were calculated. Participants employed different crutch techniques when sitting or standing. Crutch impulse was lower when the crutch angle from vertical was greater, at standing push-off or start of sitting. Quickly moving the centre of mass over the ankles during standing reduced crutch impulse by allowing the exoskeleton to lift the body with less upper limb force.