Sex Differences in the Back-Squat One-Repetition Maximum Estimation Accuracy Relying on the Average Optimal Minimum Velocity Threshold

Abstract Fitas, A, Gomes, M, Santos, P, Pezarat-Correia, P, and Mendonca, GV. Sex differences in the back-squat one-repetition maximum estimation accuracy relying on the average optimal minimum velocity threshold. J Strength Cond Res 40(2): 136–142, 2026—The prediction of 1-repetition maximum (1RM) using the submaximal load–velocity relationship (LVR) is highly relevant in the field of strength and conditioning. The average optimal minimum velocity threshold (MVT)—velocity that minimizes the differences between actual and predicted 1RM—was recently proposed to overcome the limitations inherent to the individual optimal MVT: necessity of 1RM direct determination and the lack of knowledge regarding its longitudinal reliability. However, 1RM estimation accuracy based on this methodology has yet to be tested in female subjects. Individual LVRs of the Smith machine pause back squat were obtained in 16 male subjects and 16 female subjects. Estimations of 1RM were made based on sex specific average actual MVTs (1RM velocity) and average optimal MVTs (mean value of the individual actual and optimal MVTs). The accuracy of 1RM predictions was examined using absolute percentage error and Bland–Altman plots. Cross-validation was performed using a leave-one-out approach. Relative 1RM, the slope of the LVR, and the optimal MVT were similar in both sexes. In male subjects, 1RM estimation accuracy was similar regardless of the MVT used. In female subjects, however, the average optimal MVT reduced the absolute percentage error from 8.7 to 6.4% compared with the average actual MVT. However, wide limits of agreement (LoA) were found between actual and estimated 1RM using both approaches (∼15 and ∼10 kg, for male and female subjects, respectively). The average optimal MVT improves female subjects' 1RM estimation accuracy. Despite these findings, the width of the LoA may result in misestimations that are unacceptable for practical use.