Should you train your sets to the limit (failure) for optimal muscle growth, or is it better to keep a few repetitions ‘in the tank’ (Reps In Reserve)? A much-discussed topic in the locker room, on which new research has been published.

For this study, in which muscle growth expert Brad Schoenfeld also participated, the issue was investigated in 31 men and women who engaged in strength training over a period of ten weeks.

The participants were randomly assigned to one of two groups: a group that maintained a constant high effort, where all sets were performed with an RIR of 1, and a group that maintained a variable effort, where the target RIR was gradually reduced from 4 to 1 over the course of the weeks. Both groups performed the same exercises in a four-day-per-week strength training program.

The results showed no statistically significant differences between the groups regarding muscle growth or strength gain. However, the group with variable RIR reported significantly lower perceived exertion during the training program, despite comparable muscle adaptations.

The findings suggest that consistently training very close to the point of muscle failure in all sets may not be necessary to maximize short-term muscle adaptations. You can safely keep a few reps in the tank. Brad Schoenfeld on this:

You don’t necessarily have to train every set to the limit. By varying how close you get to the point of muscle failure, you may be able to achieve similar results with less exertion, which can make the training more sustainable in the long run.

We previously advised training with 1-2 RIR for isolation exercises and 2-3 RIR for compound exercises. Another option is to work in training blocks and gradually train towards a smaller RIR within them.

Please note: training intensity and training volume are incompatible. If you have little time to train, a high training intensity (for example, training everything to muscle failure) combined with a low training volume (for example, only 5 sets per week) can be the solution.