Abstract
The use of awkward wrist postures and unskilled techniques might induce lateral epicondylitis. This study thus investigated the effects of wrist deviation combined with extension and movement velocity on the dynamic performances of the wrist muscles during the coupling posture via a custom-made bi-planar isokinetic dynamometer. Thirty subjects were recruited to perform the isokinetic testing. We measured the muscle strengths and activities for the wrist extensors and flexors during concentric and eccentric contractions at three movement velocities, 30°s-1, 90°s-1, and 180°s-1, combined with three wrist postures, neutral position (NP), radial deviation (RD), and ulnar deviation (UD). The root mean square (RMS) of the electromyographic signal in the extensor digitorum communis (EDC), normalized peak torque of extensors, and ratio of normalized peak torque between wrist extensors and flexors, were all greater in the NP than RD and UD in both contractions. The ratio of RMS between EDC and flexor digitorum superficialis (FDS) had a significantly greater value in RD than UD during the concentric contraction. The EDC showed significantly higher activity at the fast velocity in both contractions. Nevertheless, a significantly higher RMS of the electromyographic signal between EDC and FDS and the ratio of strength between wrist extensors and flexors were found at slow velocity in both contractions. The wrist deviation combined with extension and movement velocity of the wrist joint should thus be considered as influential factors which might alter the dynamic performances, and may result in further injury of the elbow joint.
Highlights
Lateral epicondylitis results from various factors, such as repetitive stressful tasks, overuse and poor posture [1, 2], and usually causes chronic pain over the upper limbs as well as functional disabilities
The assessment of isokinetic strength has been widely used to investigate the changes in strength in patients with lateral epicondylitis [8], but there are few studies presenting information on such dynamic performances based on isokinetic testing with eccentric and concentric contractions at different movement velocities and coupling postures in the wrist joint
The data on dynamic performances that is obtained from isokinetic testing, such as muscle strength and activity at the wrist joint with different coupling postures, can provide information to assess the severity of lateral epicondylitis, as well as improve rehabilitation interventions
Summary
Lateral epicondylitis results from various factors, such as repetitive stressful tasks, overuse and poor posture [1, 2], and usually causes chronic pain over the upper limbs as well as functional disabilities. The measurement of isokinetic contraction can provide information about muscular performance in a specific movement velocity and adaptations of muscular strength in sports activities, working movements, or rehabilitation interventions. The assessment of isokinetic strength has been widely used to investigate the changes in strength in patients with lateral epicondylitis [8], but there are few studies presenting information on such dynamic performances based on isokinetic testing with eccentric and concentric contractions at different movement velocities and coupling postures in the wrist joint. The data on dynamic performances that is obtained from isokinetic testing, such as muscle strength and activity at the wrist joint with different coupling postures, can provide information to assess the severity of lateral epicondylitis, as well as improve rehabilitation interventions
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