Abstract: An arm muscle developing device for selectively exercising the triceps or biceps of the arm. The device includes a substantially rigid panel having a first surface, a second surface, a first end, a second end, a first side edge, and a second side edge. A frame includes a first elongate member, a second elongate member, a third elongate member and a fourth elongate member. The first and second elongate members are orientated parallel to each other. The third elongate member is hingedly coupled to the first end of the panel. A first securing member removably secures the upper portion of the arm to the panel. A second securing member removably secures the lower arm. Each of a plurality of loop members is attached to the frame and the panel. A plurality of biasing members bias the loop members attached to the frame toward the loop members attached to the panel.