Abstract: A golf swing aid apparatus (FIG. 1) a flexure sensing device (12) for an articulated member and a movement sensing device (13) for sensing angular movement of a limb relative to a body to which it is attached. The device (12) has supports (23a, 23b) attached to either side of the joint of the articulated member, a flexure sensor (12') extending between the supports and a transducer. The flexure sensor is capable of expanding from a first position to a second position and then to a third position in response to different degrees of flexure of the articulated member and contracting back to the second and first positions in response to straightening of the member. The transducer is driven by a circuit (14, FIG. 4) to generate a signal in response to a predetermined expansion of the sensor to the second position and cease generating the signal in response to further predetermined expansion to the third position.