…only the lower-threshold motor units are recruited and fatigued by lower-movement speed exercise…the fact is that more muscle tissue is recruited and worked by higher-velocity movement than by slow exercise speeds.
When I did experiments with my surface EMG on bench press movements at 225lbs (repping out to exhaustion) the readings were lower at the initial, faster reps, and higher at the slower latter reps. The electrodes were placed on the pectoral muscles. When we did the same movement putting the electrodes on the anterior deltoids, the signal was more stable across the reps, but still were higher for the last few reps (struggling).
I don’t believe this would be the across the board for all muscle groups and through different exercises (i.e. Olympic lifts). I wish I had the time to go through all of them. Interesting issue though.
No Charlie. I realized after I wrote it that there was no context.
But the context is relative to weight lifting. Parts are: There is a persistent belief among the public, trainers, some coaches, and even among many exercise scientists, that weight training exercises must be done slowly
He’s establishing his view that “power production” is better for athletes than the slower lifting protocols. Here it is:
[i]A slow cadence increases the time under tension (how long the muscle spends contracting) and is thereby thought to increase the amount of work the muscles do and the resulting amount of muscular development. An examination of the physiology of power production, though, is enlightening. The vast majority of research demonstrates a clear relationship between high movement speed and the ability to generate power both at that speed and at all slower speeds. Conversely, exercising at a slower speed develops strength only at that speed and does not improve power at faster movement speeds. Complete power development across the whole range of movement speeds requires high-velocity loaded movement.
This is because high power production depends on the recruitment of a maximum number of motor units to generate the high amount of force necessary to produce that power. More power requires an increased efficiency in the number of motor units firing during contraction and - most importantly for the person interested in more muscle- resulting increase in the actual amount of muscle tissue involved in the work. As more high-threshold motor units are recruited to generate more power through increased force production, more of the muscle fibers in the muscle go to work, using more ATP that must be replaced through active metabolic recovery processes. Studies have found that longer duration repetitions, with a longer time under tension, actually result in a significantly lower oxygen debt (a measure of how much metababolic work was done) when compared to the fast moving repetitions. This is because only the lower-threshold motor units are recruited and fatigued by lower-movement speed exercise. It is true that fatigued motor units generate lactic acid in the 8 to 12 rep range, and lactic acid “burns,” even if it is being generated only by the low-threshold motor units. But the fact is that more muscle tissue is recruited and worked by higher-velocity movement than by slow exercise speeds. In the interests of both muscle mass and power training, higher velocity works better.[/i]