Affiliations: [a] Department of Exercise and Sport Science, Crewe and
Alsager Faculty, The Manchester Metropolitan University, Alsager, UK
Note: [] Corresponding author: Anna N. Iossifidou, Department of Exercise
and Sport Science, Crewe and Alsager Faculty, The Manchester Metropolitan
University, Alsager ST7 2HL, UK.
Abstract: Moment measurements in isokinetic dynamometry are influenced by
moments due to acceleration. The purpose of the present study was to examine
the inertial effects on peak moment, power and work during concentric
isokinetic knee extension at 60, 180 and 300 deg/s. Seven healthy young adults
participated in the present study. Angular displacement from the Biodex
software was used to calculate angular velocity and acceleration. A recursive
second-order Butterworth filter was applied on angular displacement data and a
cut-off frequency of approximately 5 Hz was used based on power spectrum
assessment. Finally the actual joint moment was calculated by taking into
account the moments due to acceleration of the limb-lever arm system. In
general the correlations between the examined parameters were not influenced by
inertial effects. A weak relationship between peak moment and power was found
at 300 deg/s. Furthermore the differences between dynamometer moment and the
moment corrected for the inertial effects increased as the preselected angular
velocity increased. At 300 deg s the dynamometer moment was 8.12% higher than
the calculated joint moment. Absolute values of work measurements were similar
before and after correction but work production was different during the
initial acceleration and the final deceleration periods. Based on our findings
it was concluded that corrections for inertial effects are essential during
moment, work and power measurements at high velocities in isokinetic
dynamometry. Finally, work and power should not be replaced by peak moment
because they depend on both the range of motion and the moment development
throughout the range of motion and therefore offer additional information
concerning muscle and joint function.
Keywords: isokinetic, power, work, acceleration, moment
