Conscious Correction of Scapular Orientation in Overhead Athletes Performing Selected Shoulder Rehabilitation Exercises: The Effect on Trapezius Muscle Activation Measured by Surface Electromyography
De Mey K, Danneels LA, Cagnie B, Huyghe L, Seyns E, Cools AM. J Orthop Sports Phys Ther. 2012 Nov 16
Once generally overlooked, the role of the scapula has become the focus of many injury prevention and sports performance programs. In order to achieve neuromuscular control and dynamic stability, programs call for some level of conscious scapular neutral positioning prior to exercise. However, it is unclear if this affects the main scapular rotators (trapezius muscles) during loading. Therefore, the purpose of this study was to examine the effect of conscious scapular positioning on upper (UT), middle (MT) and lower trapezius (LT) activity during 4 loaded exercises performed by overhead athletes presenting with scapular dyskinesis. Thirty participants were recruited for this study and demonstrated altered scapular resting positions as well as altered scapular dyskinesis upon dynamic clinical exam. Scapular dyskinesis was categorized as Type 1- prominence of the inferior medial scapular angle, Type 2 – the entire medial border or Type 3 – the superior border of the scapula. Each subject participated in one of the following overhead sports: volleyball, swimming or badminton. Electromyography was recorded for the UT, MT and LT. Each participant performed baseline testing consisting of prone shoulder extension, side-lying external rotation, side-lying forward flexion, and prone horizontal abduction with shoulder external rotation; without conscious scapular positioning. Each exercise was performed with a hand weight as determined by a gender and body-weight scale. Five 3-second concentric bouts were performed for each exercise with 3 seconds rest between each bout. The participants were given 2 minutes of rest between each exercise. For the test conditions, the participants underwent visual, auditory, and kinesthetic training based on their scapular dyskinesis category until they could satisfactorily hold a scapular neutral position for 5 seconds. The same 4 exercises were then randomized and repeated. Because participants were unable to consciously correct scapular patterns over a total range of motion, the exercises were limited to 90 degrees. When scapular neutral positioning became impaired, the participants were given appropriate verbal cues. Results showed significant levels of increased muscle activation in all 3 areas of the trapezius for prone extension and side-lying external rotation when consciously correcting scapular position versus baseline. Conversely, there was no significant interaction between scapula orientation and muscle activity for side-lying forward flexion and prone horizontal abduction with external rotation.
Although adjusting scapular orientation during shoulder exercises to improve neuromuscular control has become more common place in our rehabilitation efforts, these results demonstrate that it is exercise dependent. One short coming of this study is the 2 testing conditions (baseline and conscious correction). While the baseline tested UT, MT, and LT activity across a full range of motion, the experimental conditions did not. Cutting the test exercises off at 90 degrees of their respective range of motions does not accurately portray a sport-specific scenario. Overhead athletes typically engage in their respective sporting tasks well above 90 degrees of abduction. For the testing conditions to have been more relevant to the sporting world, measuring the muscle activity at higher degrees of abduction would be necessary. Conversely, many therapeutic exercises occur at 90 degrees of abduction and below, so the utility of these findings is not lost. The question remains, “Should we continue with scapular repositioning for all exercises to elicit increased muscle activity, or should we be more selective of the exercises when applying conscious repositioning techniques”? What are your thoughts on this study? What is your philosophy on scapular repositioning when comes to your injury prevention and/or rehabilitation efforts?
Written by: Mark Rice
Reviewed by: Stephen Thomas