Abstract
Objective. To study unintentional, spontaneous forces developed during isometric shoulder strength
testing.
Design. An experimental study.
Background. During torque measurements, subjects may apply forces in directions other than requested,
thereby obscuring the interpretation of the results.
Methods. A shoulder strength test was performed with a strength test device permitting measurements
of force in the requested direction as well as perpendicular to it. Nine fishermen
and nine welders performed isometric abduction and elevation with the arm held in
various angles. Moreover four rotational postures were investigated.
Results. Spontaneous force deviations from requested direction were found in almost all posture
tested, with errors––defined as 100 times the ratio of the magnitude of intentional
torque to the magnitude of unintentional (erroneous) torque generated perpendicular
to it––of more than 30% found for some postures. Abduction in 45° horizontal flexion
was better controlled than abduction in 90° horizontal flexion. Detailed analysis
indicated some groupwise differences between fishermen and welders. Also pairwise
comparison of handiness indicated some differences.
Conclusions. Considerable deviations from requested direction of action can arise during strength
tests. Thus, one must either monitor these deviations or minimize them by a proper
design of the examination to get relevant data. As the error can differ between certain
subject categories depending on posture this indicate a new tool for discriminating
between musculo-skeletal problems.Relevance
Muscle strength devices must be used with care as their measurement setups may mask
the true muscle action of the patients.
Keywords
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Article info
Publication history
Accepted:
April 9,
2002
Received:
March 29,
2001
Identification
Copyright
© 2002 Elsevier Science Ltd. Published by Elsevier Inc. All rights reserved.
