Abstract: An actively controlled orthotic device includes active components that dynamically change the structural characteristics of the orthotic device according to the orientation and locomotion of the corresponding body part, or according to the changing needs of the subject over a period of use. Accordingly, the orthotic device can be effectively employed to provide locomotion assistance, gait rehabilitation, and gait training. Similarly, the orthotic device may be applied to the wrist, elbow, torso, or any other body part. The active components may be actuated to effectively transmit force to a body part, such as a limb, to assist with movement when desired. Additionally or alternatively, the active components may also be actuated to provide support of varying rigidity for the corresponding body part.