Correlations between one-repetition maximum weights of different back squat depths

BACKGROUND: Although squat depth determines the weight that can be lifted while squatting, it is unclear whether the One-repetition maximum (1RM) at one squat depth can be used to estimate the 1RM at another squat depth. OBJECTIVE: To determine the correlations between 1RM weights at different back squat depths (BSQs) in frequently trained male collegiate athletes. METHODS: This cross-sectional study included 26 male collegiate athletes. Body composition, lower extremity length, and 1RM of BSQ were measured. 1RM of BSQ was measured at three positions (quarter, half and parallel positions), defined as 45 degrees of knee flexion (quarter, Q-SQ), 90 degrees of knee flexion (half, H-SQ), and femur parallel to the ground (parallel, P-SQ), respectively. All testing was conducted by a certified strength and conditioning specialist. Pearson’s correlation analysis and Spearman’s rank correlation were used to examine the correlation between 1RM at each squat depth. RESULTS: There was a significant correlation between 1RM in the H-SQ and P-SQ positions (p< 0.001, r= 0.725, R2= 0.526, y= 1.0728x+ 24.641), but no significant correlation between 1RM of Q-SQ and P-SQ, and 1RM of Q-SQ and H-SQ. There were significant correlations between the 1RM of Q-SQ and height (p= 0.001, r= 0.594), and with the length of the lower extremities (p= 0.002, r= 0.586). CONCLUSIONS: Mutual estimation of the 1RM of H-SQ or P-SQ from the 1RM of the other squat position is possible. Estimation of the 1RM of Q-SQ from the 1RM of H-SQ or P-SQ is, however, difficult, and must be measured separately. Future studies should be conducted with larger sample sizes, in athletes of various sports, and in females.