Several investigations have reported reproducibility for isokinetic single-joint (SJ) knee strength measurements. However, to date, only a few studies have concentrated on multi-joint (MJ) leg strength measurements. OBJECTIVE: This study is the first to investigate reproducibility for MJ leg strength measurements using the IsoMed 2000-system, which recently was introduced into the market. METHODS: Peak Force (PF) of forty-one healthy male subjects (mean age: 24.4 years) performing concentric and eccentric MJ leg extension at standardized mean knee-joint angular velocities 40 and 80°/s (i.e. individual linear foot velocities of 0.12-0.19 and 0.24-0.38 m/s, respectively) was measured in three identical sessions (T1-T3), separated by 10-14 days. Repeated measures analysis of variance (ANOVA) was applied for detection of systematic errors over sessions. Reproducibility was calculated between consecutive pairs of sessions (T1-T2; T2-T3) using intra-class correlation coefficients (ICC 2,1) and standard error of measurement (SEM). RESULTS: Significant increases in mean measurement values of ˜ 2-4% from T1 to T2/T3 could be seen for concentric measurements at 40°/s and overall eccentric measurements. Reproducibility calculations revealed ICC-values of 0.823-0.956 and 0.911-0.978 with corresponding measures of SEM of 72.1-175.3 and 49.3-125.3 N for T1-T2 and T2-T3, respectively. CONCLUSIONS: Moderate to high reproducibility was shown for the IsoMed 2000-system in measuring PF during concentric and eccentric isokinetic leg extension. However, as data indicate the presence of an initial practice-based improvement, we recommend the consideration of a familiarisation session in practice.
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