A power generating leg, configurable to be coupled to a person's lower limb, comprising a thigh link, a shank link, a knee mechanism, a torque generator, and a power unit. The knee mechanism is connected to said thigh link and said shank link, and configured to allow flexion and extension movements of said thigh link and said shank link relative to each other. The torque generator is configured to generate torque between said shank link and said thigh link. The power unit is coupled to said torque generator, and configured to cause said torque generator to generate torque. When said power unit is in a power regeneration mode, said power unit causes said torque generator to generate a torque that opposes the angular velocity of said thigh link and said shank link relative to each other and said power unit converts a portion of the power associated with the product of said torque and said angular velocity of said shank link and thigh link relative to each other into electrical power to be stored in a storage device.