Affiliations: [a] University Outpatient Clinic, Sports Medicine and
Sports Orthopaedics, University of Potsdam, Germany
Note: [] Address for correspondence: Steffen Mueller, University
Outpatient Clinic Potsdam, Sports Medicine and Sports Orthopaedics, Am Neuen
Palais 10 - Haus 12, D-14469 Potsdam, Germany. Tel.: +49 331 977 1161; Fax: +49
331 977 1296; E-mail: stefmue@uni-potsdam.de
Abstract: Isokinetic dynamometry is a standard technique for strength testing
and training. Nevertheless reliability and validity is limited due to inertia
effects, especially for high velocities. Therefore in a first methodological
approach the purpose was to evaluate a new isokinetic measurement mode
including inertia compensation compared to a classic isokinetic measurement
mode for single and multijoint movements at different velocities. Isokinetic maximum strength measurements were carried out in 26 healthy active subjects.
Tests were performed using classic isokinetic and new isokinetic mode in random
order. Maximum torque/force, maximum movement velocity and time for
acceleration were calculated. For inter-instrument agreement Bland and Altman
analysis, systematic and random error was quantified. Differences between both
methods were assessed (ANOVA α = 0.05). Bland and Altman analysis showed the highest agreement between the two modes for strength
and velocity measurements (bias: < ± 1.1%; LOA: < 14.2%)
in knee flexion/extension at slow isokinetic velocity (60°/s). Least
agreement (range: bias: −67.6% ± 119.0%; LOA: 53.4%–69.3%)
was observed for shoulder/arm test at high isokinetic velocity
(360°/s). The Isokin_{new} mode showed higher maximum movement
velocities (p<0.05). For low isokinetic velocities the new mode agrees
with the classic mode. Especially at high isokinetic velocities the new
isokinetic mode shows relevant benefits coupled with a possible trade-off with
the force/torque measurement. In conclusion, this study offers for the first
time a comparison between the 'classical' and inertia-compensated isokinetic
dynamometers indicating the advantages and disadvantages associated with each
individual approach, particularly as they relate to medium or high velocities
in testing and training.
