I would caution trainees to not abandon (or supplement) exercises withOUT actual weight. Resistance Exercise must resist weight … not immovable stops. True and Effective inroad must have a constant backloading affect that removes any inclination to stop/hold/pause a hold or motion. A resistive WEIGHT will always keep the muscle active. Unless, of course, one is moving too fast! This means NO Bullworkers, NO Apollo (remember those), NO Hydraulics, NO Pneumatics, NO Motors, NO Bands, NO Pressure Plates, NO Vibrating Rods, NO Springs, NO Bows, etcetera. Additionally there is a Central Nervous System feedback from a weight that involves spatial orientation (implies our head should be above our center mass). This CNS feedback loop has yet to be adequately explained (to my knowledge), but the experience shows it is an issue. I am looking forward to Dr. Darden’s “Backloading” Book as I suspect it will address a major factor of ASSURING A MUSCLE is LOADED throughout an exercise motion/hold. When we use an Exercise Device we must be Resisting Weights from Falling. In my opinion a static or an ultra slow negative is the only way to assure this. Once trainees start moving a weight in a positive direction it is far too easy to unload a muscle, unless to motion is ultra ultra ultra slow.
Much appreciation to Dr. Darden and his progression of the (HIS) science.