Quantifying EMG Activity of Trapezius Muscle during Empty Can & Full Can Tests

Study Design: Correlational design.

Purpose: To quantify the EMG activity of the three fibers of the trapezius muscle during empty can&full can shoulder exercises/ tests.

Setting: College electrotherapy laboratory.

Subjects: 50 healthy subjects, age group between 20-30 years.

Materials: Full scale goniometer, EMG equipment- NeuroTrac™ ETS C 0120, a laptop- Dell, Self adhesive electrodes.

Methods: Subjects fulfilling the inclusion criteria were taken into consideration. The procedure was explained to the subjects and a written consent was taken after explaining the benefits and clearing the doubts of the subject regarding study. After ROM and muscle tension evaluation using manual muscle testing (MMT), and goniometry of the cervical spine and shoulder, subjects were recruited and electrodes were placed accordingly, for recording the trapezius muscle activity. After electrode placement the subjects were asked to perform two shoulder rehabilitation exercises that is, empty can&full can exercises. The subjects were instructed to perform, each of the above mentioned exercises with, holding of the exercise position, for 30 seconds which was followed by a rest period, and performance of the test. Recording of the data was done, in between the exercise performance.

Data analysis: Mean and standard deviation were calculated from the EMG values, recorded for each fiber of the trapezius muscle during empty can and full can shoulder exercises/tests.

The coefficient of variation i.e. variability was computed using the statistical values (mean&standard deviation).

Result: The coefficient of mean variation ( variability) calculated was least for the lower trapezius muscle during the empty can shoulder exercise/test, it suggests that the EMG values for the lower trapezius muscle during empty can shoulder exercise/test is more compact,consistent, homogenous&is efficient.

Conclusion: The present study concludes that during the empty can&full can shoulder exercises/ tests a scapular stabilizing muscle i.e. trapezius was also activated along with the other rotator cuff muscles. Out of the two mentioned exercises/tests maximum activation was seen in the lower fibers of the trapezius muscle followed by upper & middle fibers during Empty Can exercise/test. However, during full can exercise, out of the three fibers of the trapezius muscle maximum activity was recorded from the lower fibers followed by upper&middle fibers.