Reliability of the Squat Jump Force-Velocity and Load-Velocity Profiles

Kotani, Y, Lake, J, Guppy, SN, Poon, W, Nosaka, K, Hori, N, and Haff, GG. The reliability of the squat jump force-velocity and load-velocity profiles. J Strength Cond Res 36(11): 3000-3007, 2022-The purpose of this study was to investigate the between-session reliability of the squat jump force-velocity (FV) and load-velocity (LV) profiles. Eighteen subjects (age = 28.1 +/- 4.8 years; height = 1.7 +/- 9.7; body mass = 74.7 +/- 12.8) who could back squat >1.5 times body mass participated in this study. Each subject completed a familiarization session, followed by 2 experimental sessions each separated by 72 hours. Subjects performed a series of squat jumps on a force plate against external loads between 0 and 100% of their body mass in a quasi-randomized block order. Intraclass correlation coefficient (ICC) and coefficient of variation (CV) were used to examine the between-session reliability. Peak velocity (PV) and mean velocity (MV) at each load were highly reliable (ICC >0.80, CV% <7.41, SEM <0.13 m center dot s(-1), smallest detectable difference [SDD] <0.31 m center dot s(-1), ES <0.21). Force-velocity profiles created with peak force and relative peak force resulted in poor to excellent reliability (ICC = 0.34-0.92, CV% = 11.9-26.3). When mean and relative mean forces were used to create FV profiles, there was poor to good reliability (ICC = 0.03-0.85, CV% = 18.1-39.4). When the LV profile was calculated with PV (ICC = 0.60-0.90, CV% = 7.9-16.9) or MV (ICC = 0.49-0.91, CV% = 11.1-23.4), there was poor to excellent reliability. There was no time effect found between sessions for both FV and LV profiles. The squat jump FV and LV profiles established with a force plate are not reliable. Therefore, these profiles are not recommended to be used to inform programming decisions.