An Efficient and Accurate Approach for Estimating the Free-Weight Back Squat 1-Repetition Maximum Based on the 2-Point Method and Optimal Minimal Velocity Threshold.

Chen, Z, Xiao, F, Mao, Y, Zhang, X, and García-Ramos, A. An efficient and accurate approach for estimating the free-weight back squat 1-repetition maximum based on the 2-point method and optimal minimal velocity threshold. J Strength Cond Res XX(X): 000-000, 2024-This study aimed to compare the accuracy of nine 1-repetition maximum (1RM) estimation methods based on velocity recordings during the free-weight back squat. In a counterbalanced order, 39 resistance-trained male subjects performed 2 sessions against 6 loads (∼40, 50, 60, 70, 80, and 90% of 1RM) and 2 sessions against only 2 loads (∼40 and 90% of 1RM) followed by the actual 1RM attempts. The first session of each procedure was used for obtaining minimal velocity thresholds (MVTs) and the second session was used for 1RM estimation. Predicted 1RMs were calculated by entering 3 MVTs (i.e., actual MVT [i.e., the MVT associated with the actual 1RM], general MVT [i.e., 0.30 m·second-1], and optimal MVT [i.e., the MVT that minimizes the differences between the actual and predicted 1RMs]) into 3 load-velocity relationship (LVR) regression equations (multiple-point [i.e., using data of 6 loads from the multiple-point test], extracted 2-point [i.e., using data of the lightest and heaviest loads from the multiple-point test], and 2-point [i.e., using data of 2 loads from the 2-point test]). Alpha was set at 0.05. The main findings revealed that only the 1RMs predicted by the optimal MVT showed acceptable accuracy (raw errors ≤0.8 kg, absolute errors ≤4.0%) compared with the actual 1RM. The analysis of variance failed to reveal a significant main effect of the "type of LVR model" (p = 0.079). Therefore, we recommend using the 2-point method combined with the optimal MVT to obtain an efficient and accurate 1RM estimation during the free-weight back squat.