Reproducibility of concentric and eccentric isokinetic multi-joint leg extension measurements using the IsoMed 2000-system

Abstract

BACKGROUND: 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 2000system, 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.

Factors influencing the reproducibility of isokinetic knee flexion and extension test findings

“…This is in accordance with recent research suggesting that a single habituation session is sufficient for inexperienced subjects to eliminate practice-induced improvements [2,27,28,30]. However, this was not applicable to eccentric flexion and extension revealing still significant increases after T1.…”

“…Although familiarisation is a well-known side effect of isokinetic knee testing impeding accurate assessment due to a practice-based improvement [2,[27][28][29][30][31], its impact on test-retest reliability has not been statistically analysed yet. Dirnberger et al [28] demonstrated high reliability of concentric and eccentric knee extensions as ICC values ranged from 0.907-0.955 and SEM indices from 7.4-19.1 Nm for T1-T2.…”

“…Familiarisation is a well-known side effect of isokinetic strength tests impeding accurate assessment of reliability because it induces a practice-based improvement, not only of the knee joint [2,[27][28][29]. A single habituation session lead to a 10% increase of concentric knee extensions' PM and CW [30].…”

“…In contrast to this recommendation, Lund et al [32] detected no learning effect within six isokinetic tests of concentric knee flexors and extensors. In general, at least a single habituation session should be executed to minimize accommodationrelated improvements in isokinetic strength diagnosis and to enhance the reproducibility [27][28][29].…”

Explosive Strength of the Knee Extensors: The Influence of Criterion Trial Detection Methodology on Measurement Reproducibility

“…For the present study, the more powerful dynamometer version E750-560 was used. Extensive information on the structure and performance characteristics of available versions of the IsoMed 2000 dynamometer, including the version relevant for the present study, can be found elsewhere (Dirnberger et al, 2013) and should not be duplicated here. Prior to each session, the dynamometer was calibrated according to the specific guidelines outlined in the service manual.…”