Selective training of the vastus medialis muscle using EMG biofeedback.

The purpose of this study was to investigate if, in three weeks, the vastus medialis muscle could be trained to contract independently of the vastus lateralis muscle. Ten subjects attended electromyographic biofeedback training sessions five days a week for three weeks for one half hour each day. During the first two weeks the subjects concentrated on decreasing the activity level of the vastus lateralis muscle, and during the final week they tried to increase the vastus medialis muscle activity level. Significant differences were found in the change in muscle activity level of the vastus lateralis muscle over the first two weeks, in the change of muscle activity level of the vastus medialis muscle over the third week, and in the difference between vastus medialis and vastus lateralis muscle activity levels from the first to the third weeks.