Reps in Reserve (RIR) is a way to measure how many more repetitions you could perform before reaching muscular failure during a set. Using RIR helps adjust training day by day by allowing you to control effort and fatigue more precisely. Instead of always pushing to failure, you leave a certain number of reps “in the tank,” which helps manage fatigue and recovery while still providing enough stimulus for muscle growth and strength gains.
By tracking RIR, you can tailor each workout based on how you feel that day. For example, if you feel strong, you might train closer to failure (RIR 0-1), but if you feel tired or sore, you can back off slightly (RIR 2-3) to avoid overtraining. This flexibility helps maintain consistent progress without excessive fatigue or injury risk.
RIR also improves programming because coaches and lifters can prescribe specific intensities, such as “3 sets of 8 reps at RIR 2,” which is clear and actionable. Different exercises benefit from different RIR targets: heavy compound lifts like squats and deadlifts are safer and more effective when stopping 1-3 reps before failure, while machine or isolation exercises can often be pushed closer to failure due to lower injury risk.
Managing RIR across sets is another way to optimize training. A common approach is to start sets with higher RIR (e.g., 2-3) to conserve energy, then gradually reduce RIR in later sets (down to 0-1) to maximize effort and muscle stimulus without excessive fatigue early on.
Overall, using RIR daily helps balance training intensity and recovery, allowing for better long-term progress and reduced injury risk by adjusting effort based on how you feel each session.
Sources
https://www.minimumviablepump.com/guides/rir
https://rippedbody.com/rpe/
https://www.empower.physio/blog-all/rpe-vs-rir-1
