General minimum velocity threshold for one-repetition maximum prediction in two squat variations: does the load–velocity profiling approach matter?

Abstract

Purpose Most studies examining the predictive value of the load–velocity relationship in determining one-repetition maximum (1RM) in the back squat implemented its direct determination to enable testing movement velocity within a predetermined set of relative loads (e.g., 50, 60, 70, 80, and 90% 1RM). We determined whether a different approach of load–velocity profiling affects the accuracy of estimating 1RM. Methods Predictions based on a practical 2-point approach (no pre-determination of 1RM) were compared to those obtained with the conventional multipoint and 2-point approach (pre-determination of 1RM). 1RM was estimated relying on a reference minimum velocity threshold (MVT) of 0.3 ms−1. Analyses were conducted for separate back-squat variations (n = 13 Smith machine; n = 13 free-weight). Slopes and y-intercepts were compared. The accuracy of 1RM prediction was determined by contrasting actual vs. predicted 1RM values. Results The individual MVT did not differ from the general 0.3 ms−1 value in either back-squat variation. Slopes and y-intercepts were similar between all determination approaches. For the Smith machine, estimated 1RM did not differ from the actual value with either approach (mean misestimate: −1.83 to 0.02 kg). However, the limits of agreement were wide (~ 12 kg) and the absolute percent error was significantly different from 0 with all approaches (p < 0.05). Conclusion 1RM can be estimated with similar accuracy with all profiling methods, irrespectively of the back squat variation. However, the free-weight variation displays higher systematic and random errors. It can be concluded that the wide limits of agreement preclude accurate 1RM estimations on an individual basis.

Optimal Minimum-Velocity Threshold to Predict One-repetition Maximum for the Back Squat

“…Irrespectively of this, according to the available literature, both the general as well as the individual MVT provide poor 1RM estimations for the back squat [7,8]. However, it should be noted that, while small differences between actual and predicted 1RM have been reported for the Smith-machine back squat [6,[17][18][19], this is not the case for the free-weight back squat (i. e. absolute errors reaching 4.1, 7.3, 7.8, 8.6 and 20.2 kg and absolute percent errors reaching 8.2 and 10.6 %) [2,7,10,15,[20][21][22].…”