Abstract
Purpose: It is known from the literature that gripping, which is commonly used in various work-related, sport-related, and daily activities, activates both wrist extensors and flexors. Pain aggravation occurs during grip due to over-exertion of the extensor muscle group in lateral epicondylitis and grip strength is reduced. Of grip strength studies, few studies have simultaneously investigated muscular response using electromyography as a method of monitoring muscular fatigue or muscular activity of forearm muscles. The fatigability and activity of wrist antagonistic muscles in patients with lateral epicondylitis has not been previously investigated.
Methods: 16 tennis elbow patients (Tennis Elbow Group) and 16 healthy volunteers (Control Group) were participated in this study. In both groups, local muscular fatigue and muscular activity were measured for 3 forearm muscles contributing to the wrist extension and 2 muscles contributing to the wrist flexion using EMG and during gripping at 50% maximum voluntary contraction (MVC). Fatigability and activity of muscles then were compared between control and tennis elbow groups.
Results: Grip strength was significantly lower in tennis elbow group than that in control group (p < 0.05). Median frequency (MDF) and root mean square (RMS) of electromyographic signals were used as parameters to measure muscular fatigue and muscular activity, respectively. Further analysis showed no significant difference in the fatigability of forearm muscles between two groups. The activity of Extensor Carpi Radialis (ECR) showed statistically significant reduction in tennis elbow group compared to the control group (p < 0.05).
Conclusion: This is the first study to simultaneously investigate the fatigability and activity of the forearm antagonistic muscle groups in patients with lateral epi-condylitis. The fact that ECR showed similar level of muscular fatigue to other muscles despite decreased muscular activity may indicate of higher fatigability of this muscle in tennis elbow. Furethermore, decreased muscular activity of ECR may be a part of mechanism to protect the muscle from further injury in tennis elbow patients.
Correspondence should be addressed to Mr Carlos Wigderowitz, Senior Lecturer, University Department of Orthopaedic and Trauma Surgery, Ninewells Hospital and Medical School, Dundee DD1 9SY.
