Electromyographic activity of scapular muscles during diagonal patterns using elastic resistance and free weights.

Purpose/background: Abnormalities in glenohumeral rhythm and neuromuscular control of the upper trapezius (UT), middle trapezius (MT), lower trapezius (LT) and serratus anterior (SA) muscles have been identified in individuals with shoulder pain. Upper extremity diagonal or proprioceptive neuromuscular facilitation (PNF) patterns have been suggested as effective means of activating scapular muscles, yet few studies have compared muscular activation during diagonal patterns with varying modes of resistance. The purpose of this study is to determine which type of resistance and PNF pattern combination best elicits electromyographic (EMG) activity of the scapular muscles.

Methods: Twenty one healthy subjects with no history of scapulohumeral dysfunction were recruited from a population of convenience. Surface electrodes were applied to the SA, UT, MT and LT and EMG data collected for each muscle as the subject performed resisted UE D1 flexion, UE D1 extension, UE D2 flexion and UE D2 extension with elastic resistance and a three pound weight.

Results: No significant differences were found between scapular muscle activity during D1 flexion when using elastic resistance and when using a weight. UT, MT and LT values were also not significantly different during D2 flexion when using elastic resistance vs. using a weight. The activity of the SA remained relatively the same during all patterns. The LT activity was significantly greater during D2 flexion with elastic resistance than during the D1 flexion and D1 extension with elastic resistance. MT activity was significantly greater during D2 flexion with elastic resistance as compared to all other patterns except D2 flexion with a weight. UT activity was significantly greater during flexion patterns than extension patterns.

Conclusions: The upper extremity PNF pattern did significantly affect the mean UT, MT and LT activity but was not found to significantly affect SA activity. The type of resistance did not significantly change muscle activity when used in the same diagonal patterns.