Experimental protocol. Subjects spent 5 minutes in a sitting position and this was followed by a 5-minute quiet standing period with a 1-minute transition period for postural change between sitting and standing. Thereafter, the subjects underwent 25-minute rhythmic PWM or 25-minute quiet standing. A commercially available device was used for PWM and quiet standing. The device enables subjects to change their posture from sitting to standing by pulling a built-in hydraulic lever. Standing posture is stabilized by fixing the trunk, pelvis and knees using front, lateral and back trunk pads, lateral pelvic pads, and kneepads. Bilateral handles located in front of the trunk are linked to the footplates, thus allowing one leg to move forward while the other moves back by pushing and pulling the handles alternately. PWM: passive walking-like leg movement.