An exercise is much more than a start position and a finish position. The outcome of an exercise is only as beneficial (or costly) as the precision with which the motions/positions are performed. It all boils down to the quality of the individual rep. Explore the influence of controlling mechanical factors such joint position, joint forces, inertia and active vs. passive support/restraint, as well as intention-based cuing. Learn to alter your clients' exercise experience. They'll be telling you, "I never felt it like that before!"