Reps in Reserve (RIR) is a training concept that refers to how many repetitions you could still perform at the end of a set before reaching failure. For someone returning to exercise, using RIR can be very useful because it helps manage effort and fatigue safely while still promoting progress.
When you come back to training after a break, your strength and endurance might not be at their previous levels. By leaving a few reps in reserve—meaning you stop a set before complete muscle failure—you reduce the risk of injury and excessive soreness. This approach allows you to train hard enough to stimulate muscle growth and strength gains but without overdoing it, which is important for recovery and consistency. For example, stopping a set when you feel you could do 1 to 3 more reps is often recommended for compound exercises to balance intensity and fatigue management[1].
Training to failure can sometimes lead to greater muscle fatigue and longer recovery times, which might limit how often you can train. For someone returning to exercise, this could slow progress or increase injury risk. Using RIR helps avoid these issues by allowing you to adjust your effort based on how you feel each day, which can fluctuate due to stress or other factors outside the gym[1].
Additionally, learning to estimate your RIR accurately improves with practice and can help you tailor your workouts more effectively. This skill ensures you are pushing yourself enough to make gains but not so much that you burn out quickly. Some studies suggest that even training with moderate effort and leaving reps in reserve can lead to similar muscle growth compared to training to failure, but with better recovery and less fatigue[3].
In summary, for those returning to exercise, using reps in reserve is a practical way to control workout intensity, reduce injury risk, and promote steady progress. It encourages listening to your body and adjusting effort accordingly, which is crucial when rebuilding strength and endurance.
Sources
https://rippedbody.com/rpe/
https://www.mensjournal.com/health-fitness/what-is-escalating-density-training
https://www.womenshealthmag.com/uk/fitness/strength-training/a69105961/two-30-minute-workouts-build-strength-study/
