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

Abstract

BACKGROUND: Although the reliability of isokinetic strength tests of knee flexors (flex) and extensors (ext) has been examined several times, statistical evidence about the influence of internal and external factors is missing. OBJECTIVE: This study aims to examine the impact of familiarisation, muscle group, contraction mode, angular velocity and test parameters on the reproducibility of findings derived from an isokinetic dynamometer (IsoMed 2000). METHODS: Thirty-three male subjects (mean age: 22.3 years) with no prior experience of isokinetic exercise participated in three identical test sessions (T1, T2, T3), each separated by 48-72 h. Peak moment (PM), angle of peak moment (APM) and contractional work (CW) were determined unilaterally (left and right) during maximum concentric (con) and eccentric (ecc) knee flexion (abdominal position) and extension (supine position) at 30, 90 and 150 • /s, respectively. An ANOVA with repeated measures confirmed systematic bias. Reproducibility of consecutive tests (T1-T2, T2-T3) was assessed by calculating the intra-class correlation coefficient (ICC 2,1) (relative reliability) as well as the standard error of measurement (SEM) (absolute reliability). ICC values were averaged according to respective factors (Fisher's z-transformation) and tested for significant differences by Steiger's formulas. RESULTS: PM and CW demonstrated a high absolute reliability (SEM: 4.7-10.5%). Relative reproducibility varied considerably (p 0.05) between muscles (ecc flex > ecc ext), contraction modes (con ext > ecc ext) and test parameters (PM = CW > APM), but did not depend on angular velocity (30 = 90 = 150 • /s). Due to familiarisation the reliability of PM obtained from eccentric knee extensions significantly increased (T2-T3 > T1-T2). CONCLUSIONS: These results improve the development and execution of reliable isokinetic strength testing protocols for unilateral knee flexion and extension together with the interpretation of different test parameters.

The Effects of Angular Velocity and Training Status on the Dynamic Control Equilibrium

“…3b). This physiological discrepancy of APM is wellknown [3,4,36] and queries the calculation and meaningful interpretation of 'functional' H:Q ratios. To avoid the comparison of moments that are generated at different joint angles [14,36], Coombs & Garbutt [13] introduced the DCRe as a diagnostic parameter for more functional analyses of reciprocal thigh muscle performance (▶ Fig.…”

“…To obtain reliable data, each participant performed 2 familiarisation sessions followed by a testing session which were all separated by 48-72 h [4]. All 3 sessions were performed in a performance laboratory and consisted of the same procedure.…”

“…For each condition, both concentric and eccentric movements were conducted at 2 different angular velocities (30 and 150°/s). The reliability of this protocol and the derived parameters has been previously assessed as high [3,4]. To attain the largest possible isokinetic range of motion, a very quick acceleration and a hard deceleration were chosen.…”

“…Hand grips beside the hip provided sufficient stability [5,22]. In order to examine the largest range of the respective condition, the degree of movement differed between knee flexion and extension [3,4] (▶Fig. 1).…”

“…The major disadvantage of the DCR is that it compares moments that never act in conjunction with each other. It is well known that peak moments of eccentric flexion and concentric extension emerge at considerably different knee flexion angles of 12 and 59 ° [3,4,36]. Thus, the 'functional' H:Q ratio (DCR) reflects a situation that never occurs during everyday movements.…”