Average optimal minimum velocity threshold: A practical variable to increase the accuracy of one-repetition maximum estimation during the free-weight back squat

The prediction of one-repetition maximum (1RM) using the submaximal load-velocity relationship (LVR) is highly relevant for the field of strength and conditioning. The optimal minimum velocity threshold (MVT) was recently proposed to increase the accuracy of 1RM predictions. However, using the average optimal MVT would allow for more practical estimations. LVRs of the free-weight back squat were obtained in 53 participants, throughout 2 sessions. LVRs were obtained using the multi- and two-point methods. Estimations of 1RM were made based on the average actual MVT (1RM velocity) and the average optimal MVT. The accuracy of 1RM predictions was examined using absolute-percent error and Bland-Altman plots. Cross-validation was performed using a leave-one-out approach. The number of selected loads did not affect the slope, y-intercept, optimal MVT or the accuracy of 1RM predictions. Predictions based on the average optimal MVT displayed greater accuracy than those obtained with the average actual MVT (~6% vs. ~8% absolute-percent error, respectively). However, wide 95% limits of agreement (LoA) were found between actual and estimated 1RM using both approaches (~13%1RM). The average optimal MVT offers more accurate 1RM estimations than the average actual MVT. However, errors prove substantial, making it challenging to precisely track minor changes in 1RM.