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

Abstract

The reliability of the squat jump force-velocity and loadvelocity 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 5 28.1 6 4.8 years; height 5 1.7 6 9.7; body mass 5 74.7 6 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•s 21 , smallest detectable difference [SDD] ,0.31 m•s 21 , ES ,0.21). Force-velocity profiles created with peak force and relative peak force resulted in poor to excellent reliability (ICC 5 0.34-0.92, CV% 5 11.9-26.3). When mean and relative mean forces were used to create FV profiles, there was poor to good reliability (ICC 5 0.03-0.85, CV% 5 18.1-39.4). When the LV profile was calculated with PV (ICC 5 0.60-0.90, CV% 5 7.9-16.9) or MV (ICC 5 0.49-0.91, CV% 5 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.

Is the Concept, Method, or Measurement to Blame for Testing Error? An Illustration Using the Force-Velocity-Power Profile

“…In contrast, 3 recent studies have reported poor reliability of FvP profile outputs (notably v 0 and S Fv ) obtained during jumping using various methods, including computation-based and reference methods. [2][3][4] The interpretations and conclusions provided by the authors clearly challenge both the methods and the FvP concept relevance: "The squat jump Fv [ : : : ] profiles established with a force plate are not reliable. Therefore, these profiles are not recommended to be used to inform programming decisions," 4 and "Coaches and researchers should be aware of the poor reliability of the Fv variables obtained from vertical jumping," 2 or "Fv variables [ : : : ] seemed to present a low between-day reliability."…”

“…[2][3][4] The interpretations and conclusions provided by the authors clearly challenge both the methods and the FvP concept relevance: "The squat jump Fv [ : : : ] profiles established with a force plate are not reliable. Therefore, these profiles are not recommended to be used to inform programming decisions," 4 and "Coaches and researchers should be aware of the poor reliability of the Fv variables obtained from vertical jumping," 2 or "Fv variables [ : : : ] seemed to present a low between-day reliability." 3 Unfortunately, input measurement reliability and questionable testing procedures are largely overlooked as a potential cause of error in the "take-home" messages and conclusions.…”

“…If not, the potential gain in information will be overpassed by the magnified error, as this seems to be the case in the different studies that concluded that FvP relationships are unreliable in general. [2][3][4] The problem is not the FvP relationships themselves or the methods used but an unfavorable balance between measurement variabilities and levels of insight targeted.…”

“…This is a pertinent focus given the increasing use of the century-old force-velocity (Fv) relationship concept and associated variables in research 1 and the fact that 3 recent studies have challenged the reliability and subsequent utility of FvP profiling. [2][3][4] Unfortunately, these studies give little to no consideration in their conclusions to an obvious source for their insufficient low measurement reliability or procedures standardization. Are FvP relationships and associated individual "profile" concepts fundamentally flawed and the associated testing methods unreliable (as often concluded in these studies), or is it also (and to what extent) an issue with the input data measurements?…”

Measurement Agreement Between Samozino's Method and Force Plate Force-Velocity Profiles During Barbell and Hexbar Countermovement Jumps

“…This may have affect results and agreements between methods in the calculation of the intercepts of the linear F-v relationship, F 0 (N•kg 21 ) and v 0 (m•s 21 ). Therefore, for a given body mass, 1 subject jumped against a higher relative load than the next subject, thereby potentially affecting the slope of the F-v relationship (30,52). The intercepts are extrapolated from the data points along the slope and are essentially estimates of theoretical maximal values, although frequently discussed as determinants of jump performance.…”