Abstract: Shoulder strengthening systems can provide multidirectional and dynamic resistance to shoulder movement of a user. A shoulder strengthening system can include a frame, a joint pivotably coupled to the frame, a resistance mechanism coupled to the joint, and a shaft coupled to the joint. Resistance mechanisms can include a first hydraulic member and a second hydraulic member. The first hydraulic member can be configured to restrict relative motion of the joint about a first axis and the second hydraulic member can be configured to restrict relative motion of the joint about a second axis. The shaft and the joint of a shoulder strengthening system can be configured to move together relative to the frame about the first and second axes.