title: Validity and Reliability of Two Field-Based Leg Stiffness Devices: Implications for Practical Use.
abstract: Leg stiffness is an important performance determinant in several sporting activities. This study evaluated the criterion-related validity and reliability of 2 field-based leg stiffness devices, Optojump NextR (Optojump) and Myotest ProR (Myotest) in different testing approaches. Thirty-four males performed, on 2 separate sessions, 3 trials of 7 maximal hops, synchronously recorded from a force platform (FP), Optojump and Myotest. Validity (Pearson's correlation coefficient, r; relative mean bias; 95% limits of agreement, 95%LoA) and reliability (coefficient of variation, CV; intraclass correlation coefficient, ICC; standard error of measurement, SEM) were calculated for first attempt, maximal attempt, and average across 3 trials. For all 3 methods, Optojump correlated highly to the FP (range r = .98-.99) with small bias (range 0.91-0.92, 95%LoA 0.86-0.98). Myotest demonstrated high correlation to FP (range r = .81-.86) with larger bias (range 1.92-1.93, 95%LoA 1.63-2.23). Optojump yielded a low CV (range 5.9% to 6.8%), high ICC (range 0.82-0.86), and SEM ranging 1.8-2.1 kN/m. Myotest had a larger CV (range 8.9% to 13.0%), moderate ICC (range 0.64-0.79), and SEM ranging from 6.3 to 8.9 kN/m. The findings present important information for these devices and support the use of a time-efficient single trial to assess leg stiffness in the field.
authors.affiliation: Department of Medical and Sport Sciences, University of Cumbria, Lancaster, United Kingdom.
authors.forename: Luca
authors.initials: L
authors.lastname: Ruggiero
authors.forename: Susan
authors.initials: S
authors.lastname: Dewhurst
authors.forename: Theodoros M
authors.initials: TM
authors.lastname: Bampouras
mesh_terms: D054874:Athletic Performance / Q000502:physiology*; D005080:Exercise Test / Q000295:instrumentation*; D006801:Humans; D035002:Lower Extremity / Q000503:physiopathology*; D008297:Male; D009068:Movement / Q000502:physiology; D018482:Muscle, Skeletal / Q000503:physiopathology*; D015203:Reproducibility of Results; D019876:Sports Equipment; D055815:Young Adult