Repetitions In Reserve In Research: Analyzing The Relationship Of Strength And Loading Choices

Abstract

Repetitions (reps) in reserve (RIR) is a practical method of quantifying resistance training (RT) intensity by estimating proximity to failure as a number of reps on a given set. RIR has long been employed in practice by strength athletes and trainers. Recently, it has become a subject of research—with initial studies supporting its effectiveness. Still, RIR relies on estimation. Gaining a better understanding of the effects which an individual’s strength and experience may have on their loading choice when using RIR will help inform future RT protocols in a research setting. PURPOSE: To examine how relative (RS) and absolute strength—as 1-repetition maximum (1RM)—affect loading choices for a given RIR by athletes in a research environment. METHODS: 16 male (n=10) and female (n=6) athletes aged 25±6 y were recruited to participate in a 10-week hypertrophybased RT program (3 days/week, 60-120 min/d). Participants were stratified by previous RT history as experienced (EX) or inexperienced (IX). Body weight (BW) was measured before the intervention. 1RM was tested in the back squat (BS) and bench press (BP) on week 2 and 10. Sub-maximal loading (determined by RIR) and a rep-range of 8–12 were used for the study’s remainder to promote muscle hypertrophy. 2 RIR and 3 RIR loading (as % of 1RM) was then compared to RS as determined by 1RM/BW. RESULTS: The average loading used in the BS and BP for 2 RIR was 83±11% and 80±9%, respectively. For 3 RIR, the loading was the same for both lifts at 68±6%. The average RS for BS and BP was 1.23±0.33 and 0.9±0.29 respectively. RS was strongly associated with resistance loading for 2 RIR and 3 RIR, respectively, in the BS (r= -0.757, p=0.001; r= -0.640, p=0.008) and BP (r= -0.794, p<0.001; r= - 0.722, p=0.002). 1RM was also strongly associated with 2 RIR and 3 RIR loading, respectively (BS: r= - 0.738, p=0.002; r= -0.670 p=0.005; and BP: r= - 0.756, p=0.001; r= -0.660, p=0.005). There were no differences in strength between EX and IX groups. CONCLUSION: These data suggest there is a strong inverse relationship between resistance loading choices at 2 RIR and 3 RIR (at a rep range of 8-12) and strength (both RS and 1RM) in an athletic population. Researchers employing RIR should be aware that an athlete’s strength may influence their likelihood to over- or underestimate RIR.