How Does Load Selection and Sex Influence 1RM Prediction Using the Minimal Velocity Threshold During Free-Weight Back Squat?

: The aim of the present study is to predict a 1RM through the load-velocity relationship using the minimum velocity threshold (MVT) in a free-weight back squat. Twenty-five males and twenty-five females performed a 1RM test during a free-weight back squat, based on which individual load-velocity relationships were created. Ten regression models to predict the 1RM were developed. The models included a two-point (mean propulsive velocity (MPV) ≈ 1 m·s-1; MPV ≈ 0.50 m·s-1) and a three-point linear equation (MPV ≈ 1 m·s-1; MPV ≈ 0.75 m·s-1; and MPV ≈ 0.50 m·s-1) with an MVT of 0.3 m·s-1 and 0.4 m·s-1 and, additionally, an MVT of 0.25 m·s-1 for females. The repeated measures ANOVA revealed no significant differences between the predicted and measured 1RM in males using an MVT of 0.30 m·s-1 and in females with an MVT of 0.25 m·s-1. In contrast, models using an MVT of 0.30 m·s-1 in females underestimated the measured 1RM, as did those using an MVT of 0.40 m·s-1 in both sexes. It appears possible to accurately predict the 1RM during a free-weight back squat using the load-velocity relationship. However, it is important to avoid using loads with velocities higher than 1 m·s-1 for the regression models and to use different MVTs for males and females.