Abstract: Workout equipment that detects and adjusts the effective weight automatically, within individual repetitions and between sets. The equipment is able to vary the exercise resistance during the stroke to allow the user to push through a weak spot and gain the maximum benefit of exercising to their full range of motion. The equipment detects weakness preceding muscle failure by the speed at which the user is manipulating the device. Users are instructed to complete each repetition slowly, smoothly and to their fullest extension or flexion and to return to the starting position slowly and under control at all times. The equipment can detect when a user is slowing down and straining at a given level of resistance, or at a particular point in the stroke path, and it will automatically lessen the effective weight to allow the user to push through and complete the stroke.