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ELECTROMYGRAPHIC ANALYSIS OF THE UPPER TRAPEZIUS, PECTORALIS MAJOR, AND LATISSIMUS DORSI DURING SHOULDER EXERCISE

Abstract

R. Q. Quezada1, S. Simmons2

1Corban University, Salem, OR & 2Willamette University, Salem, OR

The purpose of this study was to determine if posture effects shoulder range of motion and position through an increase in maximal electromyographic (EMG) activity through electromyographic analysis. The human body is not symmetrical. The Postural Restoration Institute state that posture is a reflection of the position our body through the many systems it regulates. Due to this, limited functional patterns are created faulting our ability to either breathe, rotate, or rest in a symmetrical state. These limited functional patterns refer to a restriction of movement in certain directions or certain normal functional range. METHODS: 4 adolescent males (19.425 + 0.2) attending the university participated in this study. Maximal EMG testing was completed at Willamette University. Maximum Voluntary Isometric Contraction (MVIC) was used to determine a standardized method for muscle strength. MVIC and maximum EMG data were collected from 3 muscles; upper trapezius pectoralis major and latissimus dorsi. Maximum EMG analysis was recorded with subjects sitting in a chair with the right arm placed at 90 degrees of humeral abduction, and the elbow placed at 0 degrees of horizontal abduction, with subjects externally rotating the humerus to 90 degrees. 3 trials were given to each subject. After the initial test, the postural restoration corrective exercise; 90/90 hip bridge with ball and balloon was given. The exercise was chosen to enhance both posture and stability in order to improve function and/or decrease pain. 5 sets of 5 breathes (maximal inhalation, and exhalation) were given to each subject. 3 final trials were given to each subject to determine if maximum EMG activity has increased. RESULTS: A change in Maximum EMG activity will be measured with paired sample t test. There was an increase in EMG activity post postural restoration corrective exercises for each of the three muscles, with the Upper Trapezius increasing to statistical significance. Maximum Upper Trapezius EMG (pre = 713.598 + 206.435mV; post = 1339.750 + 84.240mV; t (3) = 4.308, p = .023). Maximum Pectoralis Major EMG (pre = 227.5350 + 12.21800mV; post = 299.9900 +51.78800mV; t (3) = 2.264, p = .109). Maximum Latissimus Dorsi EMG (pre = 207.1936 + 300.40960mV; post = 249.4150 + 241.59600mV; t (3) = 1.436, p = .247). CONCLUSION: Due to the natural asymmetry in our body, over dominance can occur. Reciprocal function is needed to maintain balance throughout the entirety of the body. The results of maximal EMG activity increase may be the cause of reduced system unilateral overuse and increase in balance needed to maintain proper muscle contraction.

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