Reps in Reserve (RIR) is a useful concept when performing compound movements because it helps manage training intensity and fatigue while promoting consistent progress. Compound exercises, such as squats, deadlifts, and bench presses, involve multiple muscle groups and joints, making them more complex and demanding. Leaving 1 to 3 reps in reserve—meaning stopping a set when you feel you could still do a few more reps with good form—can reduce the risk of injury and excessive fatigue compared to training to failure[1].
Using RIR in compound lifts allows you to maintain higher training frequency and better recovery. Training to failure on these big lifts often leads to greater fatigue and longer recovery times, which can limit how often you train and potentially slow progress. By stopping short of failure, you can perform more total reps over time, which is beneficial for strength and muscle gains without overtaxing your body[1]. For novice lifters, aiming for an RIR of 1 to 2 on compound movements is recommended to balance effort and safety[1].
In contrast, isolation exercises or machine-based lifts, which are less complex biomechanically, can be taken closer to failure since they carry a lower injury risk and generate less systemic fatigue[1]. This distinction highlights how RIR can be tailored depending on the type of exercise.
Overall, incorporating reps in reserve into your training plan for compound movements helps optimize intensity, manage fatigue, and support long-term progress. It encourages training with enough effort to stimulate adaptation but not so much that recovery or technique suffers.
Sources
https://rippedbody.com/rpe/
https://betterme.world/articles/building-a-workout-plan/amp/
https://www.womenshealthmag.com/uk/fitness/a69069732/training-formula-for-women-strength-longevity/
