Reliability of leg press power-force-velocity profiling outcomes using the IsoMed 2000 dynamometer

INTRODUCTION: Vertical jump power-force-velocity profiling (P-F-v) is considered a time-efficient method to estimate the theoretical lower
limbs maximum force (F0), velocity (v0), power (Pmax), and the slope of the force-velocity relationship (SFV). However, the latest research
found limited reliability and advised caution – at least when testing athletes not highly familiar with vertical jumps.(1,2) Switching to the
coordinatively less challenging leg press movement might be a solution. Actually, a recent study found acceptable reliability for leg extension
P-F-v profiling outcomes in elite athletes from a wide variety of sports using a protocol for a pneumatic Keiser leg press device.(1)
Here, we examined the reliability of P-F-v profiling outcomes for the first time using a protocol for an isokinetic leg press, specifically the
IsoMed 2000 leg press device.
METHODS: Forty-five elite athletes (22 female) from various sports and all familiar with isokinetic testing participated in 3 identical sessions
(T1–T3), separated by 7 days. In each session, subjects completed an isokinetic leg press (IsoMed 2000; D&R Ferstl GmbH) P-F-v profile
consisting of maximum concentric leg extensions at 0.1, 0.3, 0.7 and 1.2 m/s (ROM at tension: ~80–170º). At each velocity, 4 trials were
performed. Mean force and mean velocity throughout the whole ROM were calculated. The trial with the highest mean force of each
velocity condition was used to create the P-F-v profile (F0, v0, Pmax, SFV). Reliability statistics were done between consecutive pairs of
sessions (T1–T2, T2–T3): Two-tailed paired samples t-tests were applied for detection of systematic errors. Intraclass correlation coefficients
(ICC(3,1)) and coefficients of variation (CV) were used to estimate relative and absolute reliability, respectively.(3)
RESULTS: No systematic errors were found over sessions. Values of ICC(3,1) ranged from .90 to .98 for T1–T2 and from .88 to .99 for T2–T3.
Corresponding CV-values ranged from 2.6 to 5.8% for T1–T2 and from 1.9 to 5.4% for T2–T3.
CONCLUSION: Overall good to excellent relative and acceptable absolute reliability was found for P-F-v profiling outcomes using the
IsoMed 2000 isokinetic leg press. These results are in line with the findings of Lindberg et al. using a pneumatic Keiser leg press. The better
reliability of the pneumatic leg press compared to vertical jump profiling outcomes was partly attributed to a shorter extrapolation distance
to the axis interceptions.(1) However, the extrapolation distance to the x-axis was considerably longer in the present study. Consequently,
we attribute our results mainly to the better standardization and the lower coordinative demands of the leg press movement
compared to vertical jumps, which leads to more reproducible force and velocity input data for the individual P-F-v profiles.
References
1. Lindberg et al., PLOS ONE, 2021
2. Fessl et al., Int J Sports Physiol Perform, 2022
3. Hopkins, Sports Med, 2000
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