Validity of the individualized load-velocity profile to predict one-repetition maximum on a pneumatic leg press device in adults aged 55-81 years

Abstract

Introduction: Resistance exercise is the primary strategy to counteract age-related declines in muscle function. Training loads are typically prescribed relative to an individual's one-repetition maximum (1-RM), but direct 1-RM testing is time-consuming and may increase injury risk in older adults. Because movement velocity can predict relative load, this cross-sectional study examined the accuracy of 1-RM estimation from individual load-velocity (L-v) profiles. Methods: Ninety-six participants (60 males, 36 females; 69 +/- 5.8 years) performed unilateral explosive repetitions on a pneumatic leg press at five submaximal loads to generate individualized L-v equations, followed by single repetitions to determine 1-RM. The group's sex-specific average measured velocity at 1-RM (V1RM; males: 0.17 +/- 0.08 m center dot s(-1), females: 0.18 +/- 0.09 m center dot s(-1)) was defined. A corrected V1RM, which accounted for non-linearity of the L-v relationship near maximal load, was also calculated (males: 0.31 +/- 0.15 m center dot s(-1), females: 0.33 +/- 0.12 m center dot s(-1)). To estimate 1-RM, measured V1RM and corrected V1RM values were input into the individual L-v equations. Results: Estimates based on measured V1RM overestimated 1-RM (mean difference = -7.7 +/- 7.4 kg; d = 1.05) and did not achieve statistical equivalence. Estimates using corrected V1RM more closely matched measured 1-RM (mean difference = -0.4 +/- 6.8 kg; d = 0.06) and demonstrated statistical equivalence, with the 90% confidence interval contained within predefined equivalence bounds (+/- 7.2 kg). Conclusion: Although 1-RM estimates derived from the corrected V1RM showed minimal average bias, interindividual variability persisted across both estimation methods, limiting the accuracy of 1-RM predictions at the individual level.