Fig. 1

VariLeg exoskeleton with user (motor complete thoracic SCI). A variable stiffness actuator (VSA) in the knee joint can mimic the stiffness modulation observed in individuals with unimpaired gait (M2/M1). The hip joint is actuated conventionally with an electric motor and a reduction gear box (M3). Cuffs on the leg and a torso orthosis fix the exoskeleton to the user. The user balances using crutches that also serve to pilot the device through push buttons (e.g. triggering steps). Left inset: Details of the foot interface including a spring-loaded passive ankle and ground contact sensing