When doing barbell exercises is there an effect of the speed that a rep is completed on hypertrophy?

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    My impression is that slower reps are better for sarcoplasmic hypertrophy since they increase time under tension, and faster reps are better for myofibrillar hypertrophy and strength performance (particularly because faster reps recruit fast twitch fibers too). Commented Aug 23, 2023 at 5:25

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Specifically for hypertrophy, researcher Chris Beardsley states:

... we observe hypertrophy after any workout in which effort is high (since effort determines motor unit recruitment) and bar speed is slow (since slow speeds permit muscle fibers to produce high forces, which produce the high levels of mechanical tension).

In other words, the weight needs to be heavy enough for the muscle to exert full force in order to move the resistance. You need high motor unit recruitment.

Moving a weight slowly with increased time under tension won't necessarily stimulate muscle growth, and moving a weight really fast won't either.

He gives the example of walking. Walking technically is a constant tension resistance exercise which you can do for hours. The effort for every step is extremely low, but the speed is also really low. You could walk for hours every day and not see an ounce of muscle growth in the areas that are pushing your body.

Consequently, jumping may be pushing the resistance really fast, but the tension is really low. So box jumps are not really good for hypertrophy (at least up to a point).

So he puts it simply, the "stimulating reps" of a set is when the weight starts to move slowly; not because you purposely slow it down, but because you have no choice.

Now there are other reasons besides hypertrophy to slow down the weight. It's safer. It helps prevent form breakdown. You don't rely on momentum which increases muscular tension on the muscle you're trying to work. Those on itself will not cause hypertrophy.

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