Feasibility of the 2-Point Method for Determining the 1-Repetition Maximum in the Bench Press Exercise

Abstract

Purpose: This study compared the concurrent validity and reliability of previously proposed generalized group equations for estimating the bench press (BP) 1-repetition maximum (1RM) with the individualized load-velocity relationship modeled with a 2-point method. Methods: Thirty men (BP 1RM relative to body mass: 1.08 [0.18] kg.kg(-1)) performed 2 incremental loading tests in the concentric-only BP exercise and another 2 in the eccentric-concentric BP exercise to assess their actual 1RM and load-velocity relationships. A high velocity (approximate to 1 m.s(-1)) and a low velocity (approximate to 0.5 m.s(-1)) were selected from their load-velocity relationships to estimate the 1RM from generalized group equations and through an individual linear model obtained from the 2 velocities. Results: The directly measured 1RM was highly correlated with all predicted IRMs (r = .847-.977). The generalized group equations systematically underestimated the actual 1RM when predicted from the concentric-only BP (P< .001; effect size = 0.15-0.94) but overestimated it when predicted from the eccentric-concentric BP (P< .001; effect size = 0.36-0.98). Conversely, a low systematic bias (range: -2.3 to 0.5 kg) and random errors (range: 3.0-3.8 kg), no heteroscedasticity of errors (r(2) = .053-.082), and trivial effect size (range: -0.17 to 0.04) were observed when the prediction was based on the 2-point method. Although all examined methods reported the 1RM with high reliability (coefficient of variation <= 5.1%; intraclass correlation coefficient >=.89), the direct method was the most reliable (coefficient of variation < 2.0%; intraclass correlation coefficient > .98). Conclusions: The quick, fatigue-free, and practical 2-point method was able to predict the BP 1RM with high reliability and practically perfect validity, and therefore, the authors recommend its use over generalized group equations.