A portable passive clutch system for selective upper extremity movements

A portable passive clutch system was implemented to provide selective exercise movements. The clutch system, which acts parallel to the muscle responsible for the movement, was designed to provide resistance force when a spring was stretched by the movement. The device had two exercise modes, clutch and resistance modes. The clutch mode provided resistance when the target muscle was concentrically activated and a force was not applied when the joint angle exceeded a predefined value. Conversely, in resistance mode, an elastic force was applied to the target muscle when it was stretched beyond its initial state. The changes in muscle activations were measured for both the modes through surface electromyography of the four muscles on the forearm during wrist and elbow movements, respectively. The amount of target muscle activations increased proportionally with an increase in the spring stiffness coefficient for the four movements. This device can be used for upper extremity movements for rehabilitation and exercise.