Reps in Reserve (RIR) is a training concept that refers to how many more repetitions you could perform at the end of a set before reaching muscle failure. For example, if you finish a set and feel you could do two more reps with good form, that set was done at an RIR of 2. This method helps manage training intensity without pushing to complete failure every time.
For beginners aiming to build muscle, using RIR can be quite useful. Beginners often benefit from stopping their sets with a couple of reps left in the tank (around RIR 2) because it allows them to work hard enough to stimulate muscle growth while avoiding excessive fatigue and risk of injury. Training too close to failure can be very taxing and may hinder recovery, especially for those new to lifting. By leaving some reps in reserve, beginners can maintain better form, reduce soreness, and train more consistently over time, which is crucial for muscle growth in the early stages[1][2][4].
Additionally, beginners experience rapid muscle growth partly because their muscles are very sensitive to training stress initially. This means they do not need to train to failure to see gains. Using RIR helps them balance effort and recovery, allowing for steady progress without burnout. As they adapt, they can gradually adjust intensity and volume to continue growing[5].
In practice, a beginner might perform 3 sets of 8-12 reps with an RIR of 2, meaning they stop each set when they feel they could do two more reps. This approach provides enough mechanical tension and metabolic stress to promote hypertrophy while keeping training sustainable and safe[1][4].
Sources
https://betterme.world/articles/glute-building-workout-plan/
https://rippedbody.com/rpe/
https://www.menshealth.com/uk/building-muscle/a28433729/full-body-workouts/
https://bonytobeastly.com/newbie-gains-guide/
