Abstract
BACKGROUND: Estimating repetitions in reserve (RIR) has been established as a valid and practical method for monitoring set configuration concerning proximity to failure in resistance training. However, factors such as sex and exercise equipment could interfere with the estimation process. Therefore, this study aimed to determine the influence of sex (female vs male) and exercise equipment (free-weight vs Smith machine) on the RIR estimation at different relative loads during the bench press exercise. HYPOTHESIS: Men would be more accurate than women in the RIR estimation, and participants would better perceive their actual effort at the Smith machine compared with the free-weight bench press exercise. STUDY DESIGN: Repeated measures design. LEVEL OF EVIDENCE: Level 3. METHODS: In a counterbalanced order, recreationally trained participants (12 female, 14 male) performed 2 identical sessions with the free-weight bench press exercise in 1 week and 2 identical sessions with the Smith machine bench press exercise in another week (first session for familiarization and second session for validity analysis). In each session, participants performed single sets of repetitions to failure against 3 relative loads (65%, 75%, and 85% of the 1-repetition maximum [1RM]). RESULTS: Results revealed a significant interaction between RIR and sex at 65% 1RM (P < 0.01; women: -1.2 [-1.7 to -0.6] repetitions; men: -0.1 [-0.6 to 0.3] repetitions), and between RIR and exercise equipment at 65% 1RM (P < 0.01; free-weight: -1.1 [-1.5 to -0.6] repetitions; Smith machine: -0.2 [-0.6 to 0.2] repetitions), but not at 75% and 85% 1RM. CONCLUSIONS: RIR estimation is a valid method for monitoring set configuration. However, this method tends to underestimate RIR at 65%1RM with female athletes and in the free-weight exercise for both sexes. CLINICAL RELEVANCE: Strength and conditioning coaches should help their athletes understand effort awareness in the aforementioned context.