Affiliations: [a] Institute of Movement and Neuroscience, German Sport University, Cologne, Germany | [b] Olympic Centre Westphalia, Department of Motion Analysis and Biomechanics, Dortmund, Germany | [c] SPRINZ Sport Performance Research Institute of New Zealand, Auckland University of Technology, Auckland, New Zealand
Correspondence:
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Corresponding author: Tobias Alt, Institute of Movement and Neuroscience, German Sport University, Am Sportpark Müngersdorf 6, 50933 Cologne, North Rhine-Westphalia, Germany. Tel.: +49 221 4982 3322; Fax: +49 221 4973454; E-mail: tobi.alt@web.de.
Abstract: BACKGROUND: Isokinetic dynamometry is widely considered the gold standard in mechanical muscle performance testing. Invariably, the moment-position raw data obtained from the dynamometer is directly analysed although kinematic inaccuracies may inherently exist. OBJECTIVE: To quantify the differences between two processing methods of isokinetic raw data: one based on the device’s own software and one using a hybrid kinematic procedure. METHODS: Seventy-six healthy male participants performed unilateral concentric knee extensor (Qcon) (90∘ ROM) and eccentric knee flexor (Hecc) tests (110∘ ROM) at 150∘/s. The knee angles were recorded by two high-speed cameras per body side. RESULTS: Compared to isokinetic data, kinematic analysis revealed reduced knee ROM of 17∘ for Qcon and of 21∘ for Hecc. Thus, the mean ‘isokinetic’ angular velocity declined to 121 and 122∘/s, respectively. The angles of peak moment changed significantly (-5∘ for Qcon, +20∘ for Hecc). Contractional work decreased (-20%) only for Qcon. The moments and angles derived from analysis of the DCR at the equilibrium point (DCRe) rose by 7% and 20% respectively when the isokinetic raw data were linked with kinematic data. The comparison of both processing methods revealed very high (R2= 91%) and high (R2= 69%) relationships for DCRe moments and angles. CONCLUSIONS: Isokinetic raw data comprise kinematic inaccuracies caused by axis misalignment, evasive movements and anatomical features. Although a hybrid kinematic procedure is more time-consuming, it may enable a more valid clinical interpretation of the test findings.
