Force-velocity profiling in athletes: Reliability and agreement across methods.

Kolbjørn Lindberg,Sindre Østerås,Bent Rønnestad,Paul Solberg,Martin Thorsen Frank,Magnus Midttun,Gøran Paulsen,Christian Helland,Thomas Haugen,Thomas Bjørnsen,Fredrik Sæland,Morten Kristoffersen,Daniel Boullosa

doi:10.1371/journal.pone.0245791

Abstract

The aim of the study was to examine the test-retest reliability and agreement across methods for assessing individual force-velocity (FV) profiles of the lower limbs in athletes. Using a multicenter approach, 27 male athletes completed all measurements for the main analysis, with up to 82 male and female athletes on some measurements. The athletes were tested twice before and twice after a 2- to 6-month period of regular training and sport participation. The double testing sessions were separated by ~1 week. Individual FV-profiles were acquired from incremental loading protocols in squat jump (SJ), countermovement jump (CMJ) and leg press. A force plate, linear encoder and a flight time calculation method were used for measuring force and velocity during SJ and CMJ. A linear regression was fitted to the average force and velocity values for each individual test to extrapolate the FV-variables: theoretical maximal force (F0), velocity (V0), power (Pmax), and the slope of the FV-profile (SFV). Despite strong linearity (R2>0.95) for individual FV-profiles, the SFV was unreliable for all measurement methods assessed during vertical jumping (coefficient of variation (CV): 14-30%, interclass correlation coefficient (ICC): 0.36-0.79). Only the leg press exercise, of the four FV-variables, showed acceptable reliability (CV:3.7-8.3%, ICC:0.82-0.98). The agreement across methods for F0 and Pmax ranged from (Pearson r): 0.56-0.95, standard error of estimate (SEE%): 5.8-18.8, and for V0 and SFV r: -0.39-0.78, SEE%: 12.2-37.2. With a typical error of 1.5 cm (5-10% CV) in jump height, SFV and V0 cannot be accurately obtained, regardless of the measurement method, using a loading range corresponding to 40-70% of F0. Efforts should be made to either reduce the variation in jumping performance or to assess loads closer to the FV-intercepts. Coaches and researchers should be aware of the poor reliability of the FV-variables obtained from vertical jumping, and of the differences across measurement methods.

Highlights

Within strength and power training, force-velocity (FV) profiling has received increasing attention as a means to monitor training adaptations [1,2,3] and to serve as a basis for individual training prescriptions for athletes [3,4,5,6]
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The 5–10% CV in jump height observed in this study was not acceptable for accurately assessing the accompanying FV-variables V0 and slope of the FV-profile (SFV), regardless of measurement method, with a loading range of bodyweight to 80 kg

Summary

Introduction

Within strength and power training, force-velocity (FV) profiling has received increasing attention as a means to monitor training adaptations [1,2,3] and to serve as a basis for individual training prescriptions for athletes [3,4,5,6]. The concept of FV-profiling is based on the fundamental properties of skeletal muscles, where there is an inverse relationship between force and velocity [7]. Athletes can perform maximal efforts against different loads while force and velocity are measured during vertical jumping or similar multi-joint movements. Based on such data, one can draw a linear regression line and extrapolate the theoretical maximal force (F0) (i.e., force at zero velocity) and velocity (V0) (i.e., velocity at zero force). Controversy exists about the linearity of FV-relationships obtained from multi-joint movements [8]

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Conclusion