
0% read · 1 min left
The accurate term for free-weight and machine training where the external weight stays constant but the muscle force required varies through the movement.
The use of free-weight exercises and exercises on various weight-training machines, though usually considered isotonic, is not isotonic (same-tension) in nature. The force exerted by a muscle in the performance of such exercises is not constant, but rather varies with the mechanical advantage of the joint involved in the movement and the length of the muscle at a particular point in the movement.
A better definition for resistance-training exercise in which the external resistance (or weight) does not change during a lifting (concentric) and a lowering (eccentric) phase of each repetition is "dynamic constant external resistance" (DCER) training.
Using resistance-training systems is another approach for varying the intensity and volume during resistance exercise, done by combining sets of exercises. These systems did not evolve through scientific evidence determining which systems worked best, but through trial and error by weight lifters who saw results with them.
Educational content only — not medical advice. Always consult a qualified professional for individualized guidance, especially around injury, pregnancy, or medical conditions.