INTRODUCTION: Force-Velocity profiling (FVP) is a popular tool for measuring physical performance and monitoring training adaptations in winter-sports [1]. Although useful, there are conflicting views on the reliability of FVP parameters, especially theoretical maximum velocity at zero force (V0) [2]. Critically, the reliability of the input profiling parameters (mean force and mean velocity Fmean, Vmean) is a critical determinant of the reliability for the overall profile. Therefore, the purpose of the current study was to evaluate within-test reliability of individual FVP parameters in elite winter-sport athletes using the Lifter (Intelligent Motion, Wartburg an der Krems, Austria) device. Additionally, as the input parameters Fmean and Vmean are sensitive to the determination of the start and stop thresholds [2], therefore the current study also compared various methods to calculate profiling parameters and timepoints, as well as the resulting FV profiles to determine optimal methods for use on the Lifter device. METHODS: As part of routine testing between 2022 - 2024, 18 athletes (world-class alpine, cross country, biathalon, and ski jumping athletes) underwent FVP profiling using loaded jumps on the Lifter. Participants completed four repetitions at loads between 40-100% body weight. Profiling parameters for each repetition were calculated using the estimated force and velocity curves and various triggers of the start and end timepoints, as well as the method proposed by Samozino et al [3]. Within-session reliability for Fmean, Vmean,and Pmean was assessed using coefficient of variability (CV) and intra class correlation coefficients. FVP profiles were calculated for each method (F0, V0, Pmax, Sfv, r2). RESULTS/DISCUSSION: All selected methods presented strong ICC`s (Pmean 0.93 -0.97, Vmean 0.95- 0.98, Fmean 0.89 - 0.99) and acceptable CV`s (Pmean 3.0-6.5%, Vmean 2.4-4.6%, Fmean 0.7-3.5%). As all methods displayed high ICC`s, the method with the lowest CV for Pmean was the Samozino method, using maximum velocity as the end (for the calculation of jump height) and the first velocity over 0.03 m/s as the start(to set push-off height) (3.03 ± 1.55%). Despite high within session reliability, estimated FVP parameters for the same test varied up to 180% of the average value depending on the method used (ex. V0 2.55 - 15.88 m/s for one athlete with r2 > 0.88 for all methods - mean, 0.96). While all triggering methods present high reliability, the resulting output parameters do not produce the same profiling results This method displayed the lowest FVP Pmax however, highlighting the need for further work to identify the method with the best combination of reliability and accuracy. CONCLUSION: When using the Lifter, all of the selected methods displayed acceptable reliability, however large differences in the resulting FVP profiles were observed. Special care must be given to choosing which methods to use during FVP, as the output parameters are extremely sensitive to the variation of the input parameters, despite the appearance of high reliability.
© Copyright 2025 10th International Congress on Science and Skiing, January 28 - February 1, 2025, Val di Fiemme, Italy. All rights reserved.