The Reliability of Individualized Load–Velocity Profiles

Purpose : To examine the reliability of peak velocity (PV), mean propulsive velocity (MPV), and mean velocity (MV) in the development of load–velocity profiles (LVP) in the full-depth free-weight back squat performed with maximal concentric effort. Methods : Eighteen resistance-trained men performed a baseline 1-repetition maximum (1-RM) back-squat trial and 3 subsequent 1-RM trials used for reliability analyses, with 48-h intervals between trials. 1-RM trials comprised lifts from 6 relative loads including 20%, 40%, 60%, 80%, 90%, and 100% 1-RM. Individualized LVPs for PV, MPV, or MV were derived from loads that were highly reliable based on the following criteria: intraclass correlation coefficient (ICC) >.70, coefficient of variation (CV) ≤10%, and Cohen d effect size ( ES ) <0.60. Results : PV was highly reliable at all 6 loads. MPV and MV were highly reliable at 20%, 40%, 60%, 80%, and 90% but not 100% 1-RM (MPV: ICC = .66, CV = 18.0%, ES = 0.10, SEM = 0.04 m·s −1 ; MV: ICC = .55, CV = 19.4%, ES = 0.08, SEM = 0.04 m·s −1 ). When considering the reliable ranges, almost perfect correlations were observed for LVPs derived from PV 20–100% ( r = .91–.93), MPV 20–90% ( r = .92–.94), and MV 20–90% ( r = .94–.95). Furthermore, the LVPs were not significantly different ( P > .05) between trials or movement velocities or between linear regression versus 2nd-order polynomial fits. Conclusions : PV 20–100% , MPV 20–90% , and MV 20–90% are reliable and can be utilized to develop LVPs using linear regression. Conceptually, LVPs can be used to monitor changes in movement velocity and employed as a method for adjusting sessional training loads according to daily readiness.