Abstract: Wearable devices protect against musculoskeletal injuries and enhance performance. Systems and methods provide wearable devices to assist with human motion during physical activities, such as performing movements (e.g., lifting) and holding static poses (e.g., crouching, or holding a tool while working overhead). Materials, constructions, and system architectures allow the wearable devices to be worn over, under, or integrated into clothing for extended periods of time to improve performance or reduce risk of injury. Sensors may be included in the wearable devices to detect various activities, motions, and postures of the wearer, and various active and semi-active controls approaches may leverage sensor information to provide tailored assistance to individual users. Various controls optimization techniques ensure the wearable devices operate at peak efficiency.