A Comparison of the Effects of Two Therapeutic Exercises on the Muscle Action Potential of the Vastus Medialis

Electromyography was utilized to compare the effects of two therapeutic exercises at two work loads in knee extension on the muscle action potential in the vastus medialis. One exercise was extension to 180 degrees with a four second isometric hold and flexion to 90 degrees. The other exercise was extension to 180 degrees, 15 degrees flexion, 15 degrees extension and flexion to 90 degrees. Each exercise lasted for 10 seconds. The subjects in the study were 11 varsity female athletes from the fall and winter interscholastic athletic program at Eastern Illinois University. The subjects met for the first time to determine their work loads and to practice each exercise. The work loads were determined to be one-half and three-fourths of the maximum weight lifted to full knee extension. At a second meeting, data was collected from each subject for each exercise performed during two trials at two different work loads. The research design consisted of a single-group with two variables. The amplitude of the spikes was measured and the frequencies of the spikes on each interference pattern were counted. A quantitative figure was obtained by multiplying mean amplitude by frequency for each trial. This score was utilized with a multiple analysis of variance program by the Eastern Illinois University Data Processing Center. A null hypothesis was tested at the .05 level of significance. The null hypothesis stated: Exercising the quadriceps femoris through a full range of motion plus repetition of the last 15 degrees does not increase the muscle action potential of the vastus medialis when compared to a full extension and flexion exercise with the same time duration. Major findings of the study concluded that there was no difference in the muscle action potential in the two exercises. There was a significant difference in the muscle action potential due to the increase in weights between one-half maximum weight and three-fourths maximum weight