Reliability of the 8-repetition maximum test in men and women

Objective: The 8-repetition maximum test has been recommended as a method of prescribing an intensity for resistance training in healthy adults, athletes, and patients with health conditions. Yet, limited research related to the reliability of 8-repetition maximum testing has been conducted. The purpose of this study was to determine the reliability of the 8-repetition maximum test in men and women. Design: Test–retest reliability study. Methods: Twenty-eight people (14 males, 14 females, mean age = 23.0 years [standard deviation = 1.3]) with no exercise contraindications participated in this study. After familiarization, each participant underwent 8-repetition maximum testing using 4 different exercises. For all participants, the 8-repetition maximum test was performed during 2 sessions with 2–3 days between sessions. The intraclass correlation coefficient (ICC[1,2]), typical error as the coefficient of variation (TECV), and the Bland–Altman plot were used to assess reliability. Unpaired t-test was used to determine the influence of gender on differences between initial test and retest values. Results: Excellent reliability of the 8-repetition maximum test was found for all exercises (ICC[1,2] > 0.9). The range of TECV values was 3.4–10.4%. The Bland–Altman plot illustrated that 27 out of 28 data points for total 8-repetition maximum scores were within the 95% limits of agreement. Unpaired t-test indicated no significant difference between men and women in variations between initial test and retest 8-repetition maximum scores. Conclusion: The findings of this study suggest that an 8-repetition maximum test protocol that includes familiarization is reliable in men and women.