Background and purpose: This was a descriptive and exploratory study of electromyographic (EMG) activity of wrist extensor musculature specific to the extensor digitorum (ED), extensor carpi radialis brevis (ECRB) and flexor carpi radialis (FCR) in individuals with a medical diagnosis of the common work associated complaint of lateral epicondylitis (LE). The purpose was to evaluate and compare the EMG activity of the selected forearm muscles during three different types of resistive (strengthening) therapeutic exercises (rubber ball, theraputty, and "make-it-disappear" (MID) sponge) in participants with LE.
Participants: Five individuals between the ages of 44 and 55 years of age diagnosed with lateral epicondylitis by a physician were recruited on a voluntary basis from a local outpatient clinic.
Methods: The participants completed 1 min. of each of the resistive exercises, which were assigned randomly. Muscle activity was collected simultaneously by 3 surface electrodes (4/18/16 DE-2.3 silver surface EMG electrodes, Delsys Inc, Boston, MA) and recorded on an EMG Myomonitor-4 (Delsys Inc, Boston, MA) utilizing EmgCE software (Delsys Inc, Boston, MA). The raw EMG signal was converted to a root mean square (RMS) at each 0.0625 second interval during the full 60 second recording using EMGWorks, (Delsys, Inc, Boston, MA). The data were pooled, and the mean RMS was then determined as an overall measure of activity for each muscle during the 60 recording.
Results: A 1-way ANOVA with Tukey's post-test was completed using Prizm Software (Graph Pad Software, Inc, San Diego, CA) for a comparison of the mean RMS values of each muscle during each activity. Statistically significant between group differences were noted for all muscles, among all exercises. Relative activity was noted to be greatest for ED and FCR during MID exercise, and for ECRB during putty exercise.
Conclusion: All three exercises represent different patterns of muscle activity, for the muscles observed. The possible differences in the recorded activity may be consequent to the specific positioning and movement requirements involved in the performance of the distinct exercises. Practitioners may find the evidence of this study helpful in designing rehabilitation programs for those affected with lateral epicondylitis.