Which produces more muscle growth: relatively slow reps or fast reps? New research provides insight.
The study in question compared two training protocols: bench press with sets of 12 repetitions with 3 seconds repetitions (concentric-eccentric: 1.5-1.5) and sets of 6 repetitions with 6 seconds repetitions (3-3)? Everything else in the training program was equal, including training intensity.
The result? No difference in muscle growth or strength development of both the chest muscles and the triceps. That’s in line with the general scientific understanding of lifting tempo thus far: it’s a relatively insignificant training variable.
TIME UNDER TENSION
The groups trained with the same loads for the same Time Under Tension (TUT) per set. This means that the total accumulated mechanical tension – which is the primary stimulus for muscle growth – was the same for both protocols, hence the same results.
TUT does not seem to matter as much for muscle growth as often thought. If you slow down your reps you won’t be able to do as many of them or you’ll have to cut the weight, so you’ll have to compromise on the tension to get more TUT. Most studies find that manipulating total rep time does not affect muscle growth.
However, avoid super slow eccentrics, i.e. extremely slow eccentric reps (e.g. 6 seconds): this will be too much at the expense of the number of stimulating reps you can do per set.
Coach Menno Henselmans recommends Compensatory Acceleration Training to clients: explosively lift the weight but lower it under control (ie a few seconds) (eg 1-2). For example, for bench presses, this means that you quickly press the bar up and then slowly lower it.
In the long term, this seems to be the best strategy when it comes to optimal muscle growth, Henselmans says.