A muscle assistance device comprises a brace having a first portion and a second portion movably coupled to the first portion, the first portion configured to be fastened to a first part of a users body on a first side of a joint and the second portion configured to be fastened to a second part of the users body on a second side of the joint, a sensor adapted to detect muscle stress associated with motion of the joint, an actuator coupled to the brace, and a controller coupled to the actuator and responsive to muscle stress detected by the sensor to operate the actuator to oppose the motion of the joint.
