Fig. 1. Joint powers in shoulder (A) and squat (B) movements. Both cyclic activities had positive and negative joint powers that were associated with lowering and raising either one upper extremity or all body mass above the ankles. (C) Total positive and negative joint work were virtually identical in the negative and positive phases of the shoulder and squat tasks (i.e. differences were less than 1%). These data strongly suggest that positive and negative joint and muscle work can be equivalent in certain uni- and multi-joint, cyclic movements.