Validity and Test-Retest Reliability of Repetitions-In-Reserve Across Different Low-Loads in the Barbell Bench Press With Blood Flow Restriction.

Grant, WM, Goods, PSR, Wall, BA, Davids, CJ, Narang, BJ, Debevec, T, and Scott, BR. Validity and test-retest reliability of repetitions-in-reserve across different low-loads in the barbell bench press with blood flow restriction. J Strength Cond Res 39(10): e1218-e1225, 2025-Repetitions-in-reserve (RIR) allows the standardization of effort between individuals during resistance training. This study investigated the validity and reliability of predicting RIR during low-load resistance training with blood flow restriction (BFR). Twenty subjects were assessed for bench press one-repetition maximum (1RM), before 4 experimental trials (20, 30, 30, 40% 1RM) comprising 4 sets (30, 15, 15, 15 repetitions; 30 seconds rest) with continuous BFR at 60% arterial occlusion pressure. After 15 repetitions in the final set, subjects estimated RIR before continuing the set to failure. Differences between estimated RIR and actual repetitions to failure were calculated (RIR error ). Test-retest reliability of RIR error was determined from repeated 30% 1RM trials using intraclass correlation coefficients (ICC) and coefficients of variation (CV). Differences and associations were assessed by repeated measures ANOVA and correlational analyses. The fewest fourth set repetitions were performed at 40% 1RM (median [interquartile range] = 8 [5-16] repetitions), followed by 30% 1RM (30 [19-37]) and 20% 1RM (90 [53-114]). RIR error was significantly higher with 20% 1RM (52 [23-76]) than 30% 1RM (9 [2-15]; p < 0.001) but was not analyzed at 40% 1RM (because 14/20 subjects completed ≤15 repetitions). Repetitions-in-reserve predictions were moderately reliable (ICC: 0.980, CV: 13.6%), but with wide limits of agreement (-7 to 7 repetitions). Number of fourth set repetitions was almost perfectly correlated with RIR error ( R2 = 0.90-0.94). Repetitions-in-reserve should not replace 1RM training prescriptions for low-load BFR. Results suggest that 30% 1RM is an appropriate load to begin with for trained individuals using a 75-repetition BFR scheme.