Relationship between the observation of types of scapular dyskinesis and peak muscle activity of the scapular stabilizing muscles

Purpose. To investigate the relationship between the peak activity of the three main scapular stabilizing muscles and identifying types of scapular dyskinesis.;Problem. There has been a strong correlation shown between scapular dyskinesis and resulting impingement.1-6,22 Resulting kinematic changes from impingement and altered scapular movement has been linked with a decrease in serratus anterior muscle activity, an increase in upper trapezius muscle activity, or an imbalance between the upper and lower parts of the trapezius muscle.22 This decrease in activity may result in a relationship between scapular stabilizing muscle activity and types of scapular dyskinesis. There has not yet to be research done looking at the scapular stabilizer activity and if an imbalance will lead to scapular dyskinesis occurring.;Method. This study was an observational descriptive study design investigating physically active, injury-free individuals. Testing took one day with an observation of scapular dyskinesis occurring first,then the electromyography data was collected. For the dyskinesis observation subjects were asked to hold either 3 lb. or 5 lb. dumbbells while performing four arm movement; sagittal plane, frontal plane, and 45? with thumbs up and 45? with thumbs down. While performing the arm movements the subjects were instructed to move at a three beat up and three beat down rhythm, provided by the metronome. After the observation electrodes were placed on the upper trapezius, lower trapezius, and serratus anterior. These electrodes were connected to the Biopac MP150 electromyography machine the data was managed using AcqKnowledge Software. Before performing the exercises of low- row and push-up-plus the subjects were instructed to warm up on a green resistance Theraband? doing low-row, frontal plane, sagittal plane, humeral abduction, and humeral extension each performed fifteen times. After warm-up the subjects were verbally instructed on how to perform each exercise for five repetitions and to be done on the same three beat up and three beat down rhythm with the metronome as before. The subjects were allowed to practice this until they were comfortable with the exercise. A peak activation measurement was taken for each muscle during the five repetitions. For each muscle the data's absolute value was taken and smoothed.;Findings. The data was analyzed by using a factorial 4x2 MANOVA. There were no significant differences found with the peak muscle activity with the two exercises (&agr;=0.246). There was no significance found between peak muscle activity and types of scapular dyskinesis observed (&agr;=0.181). There were trends found however between types of scapular dyskinesis and activity of the three scapular stabilizers.;Conclusion. From this study a trend was found between the relationship of identifying scapular dyskinesis and muscle activity. Future testing should investigate the effects of this relationship.