Does shoulder impingement syndrome affect the shoulder kinematics and associated muscle activity in archers?

BACKGROUND Archery related injuries, such as shoulder impingement syndrome are caused by repeated motion of the shoulder. The aim of this study was to analyze differences in the shoulder kinematics and the associated muscle activity between archers with shoulder impingement and uninjured archery players. METHODS Thirty male archers, who were divided into an impingement group and an uninjured group, were included in this study. The angle of scapular elevation, shoulder joint abduction, horizontal extension, and elbow joint flexion as well as the electromyographic activity of the upper trapezius, lower trapezius, deltoid middle, deltoid posterior, biceps brachii, and triceps brachii muscles at the point of stabilization during shooting were measured. Variables differing between impingement and uninjured groups were identified, and a stepwise regression analysis was performed to identify a combination of variables that effectively impingement syndrome. RESULTS The results indicated that the angle of scapular elevation was significantly greater than that uninjured group (P<0.05). The angle of horizontal extension in the impingement group was significantly smaller than that in the uninjured group (P<0.05). The angle of elbow flexion in the impingement group was significantly smaller than that in the uninjured group (P<0.05). The levels of upper trapezius and deltoid middle muscle activity were significantly higher in the impingement group, while the level of lower trapezius muscle activity was significantly lower (P<0.05) when compared to the uninjured group. The impingement group had a greater angle of scapular elevation, smaller angle of horizontal extension, smaller angle of elbow flexion, higher the levels of upper trapezius, lower the levels of lower trapezius, higher deltoid middle muscle activity and higher UT/LT ratio (all differences were significant). A logistic model for predicting impingement syndrome showed that UT/LT ratio was significantly related impingement syndrome (P<0.05). CONCLUSION The authors concluded that archers with shoulder impingement syndrome exhibit different kinematics and muscle activity compared to uninjured archers. Therefore, in order to prevent shoulder joint impingement during archery, training is necessary what can make lower trapezius muscle activity increased to decrease the UT/LT ratio.