One Repetition Maximum Test-Retest Reliability and Safety Using Keiser Pneumatic Resistance Training Machines With Older Women

ABSTRACT: Infante, MA, Harrell, GM, Strand, KL, Parrino, RL, and Signorile, JF. One repetition maximum test-retest reliability and safety using Keiser pneumatic resistance training machines with older women. J Strength Cond Res 35(12): 3513-3517, 2021-Chest press (CP) and leg press (LP) are the most common exercises used to assess strength in older persons; therefore, the reliability of these tests is critical to clinicians and researchers. Because women comprise the highest proportion of the older population, this study examined the test-retest reliability of Keiser A420 pneumatic machines during CP and LP 1 repetition maximum (1RM) testing in 23 older women on 2 separate occasions, trial 1 (T1) and trial 2 (T2), at least 72 hours apart. Significance was set at <0.05. CP1RM and LP1RM showed excellent test-retest reliability (intraclass correlation coefficient = 0.974, 0.972, respectively, p < 0.001) and low coefficients of variation (CP1RM = 5.28%; LP1RM = 6.32%). Standard error of measurement for CP1RM (0.97 kg) was lower than that of LP1RM (6.36 kg). The minimal detectable change (MDC) for the CP1RM and LP1RM was 2.69 and 17.63 kg, respectively. Bland-Altman plots revealed only 1 point outside of the 95% CI for comparison of T1 and T2 for either exercise, there was little systematic error across average values, both lines of equality fell within the limits of agreement (LOA), and the bias between T1 and T2 for both exercises was below 5% of the average 1RM. By contrast, the LOA for CP1RM and LP1RM are somewhat wide because they both exceeded their computed MDC values. Given the excellent test-retest reliability of the Keiser A420 pneumatic CP and LP machines with older women, clinicians and researchers can confidently and safely use these machines for 1RM testing after proper familiarization.