The aim of this study was to investigate whether RIR can be used as a reliable tool to prescribe load for two commonly used strength exercises. It was hypothesized that the load corresponding to 1-RIR would exhibit very high test-retest reliability when used for deadlift and bench press sets comprising 3-, 5-, and 8-repetitions.
Previous research has demonstrated anchors can influence RIR. If you have never experienced training to failure, you are likely to underestimate your capacity. Without experience, your assumed RIR of 9-10 will likely fall in the 3-5 range. To establish a new and accurate anchor, the 15 participants (novice male lifters, mean age 17.6 years) performed multiple sets using three different repetition schemes (3-, 5-, and 8-repetitions) in random order. Each set progressed in load until the subjects felt they reached 1-RIR. The accuracy was also assisted through 1RM testing conducted 1 week prior to the familiarization session.
The participants performed two testing sessions. The initial set for each repetition scheme was 75%, 70%, and 65% 1RM for the 3-, 5- and 8-repetition schemes. After each set, the participants provided an RIR rating. They then left the room for the adjustment of the weight, blinding them to the load and reducing the chances of them determining an RIR prior to the lift. The weight progressed until the lifter reported an RIR of 1.
The test-retest comparisons demonstrated a high level of reliability (deadlift: ICC=0.95-0.99, CV=2.7-5.7% and bench press: ICC=0.97-0.99, CV=3.8-6.2%). For the deadlift, 1 RIR equated loads of 88.2%, 84.3%, and 77.2% 1RM, for 3-, 5- and 8-repetition sets. For the bench press, loads of 93.0%, 87.3%, and 79.6% 1RM equated 1-RIR for sets of 3-, 5- and 8-repetition sets.
This data supports the use of RIR provided the athlete or patient completes a familiarization period (unless they are used to training with RIR). Of note, this paper does not account for the potential confounder of pain. If pain is the limiting factor, you are unlikely to strive for hypertrophy and strength improvements will primarily result from a reduction in pain. In that case, RIR is unlikely to be a preferred method of measuring intensity.