Shoulder muscle recruitment patterns and related biomechanics during upper extremity sports

Abstract

Understanding when and how much shoulder muscles are active during upper extremity sports is helpful to physicians, therapists, trainers and coaches in providing appropriate treatment, training and rehabilitation protocols to these athletes. This review focuses on shoulder muscle activity (rotator cuff, deltoids, pectoralis major, latissimus dorsi, triceps and biceps brachii, and scapular muscles) during the baseball pitch, the American football throw, the windmill softball pitch, the volleyball serve and spike, the tennis serve and volley, baseball hitting, and the golf swing. Because shoulder electromyography (EMG) data are far more extensive for overhead throwing activities compared with non-throwing upper extremity sports, much of this review focuses on shoulder EMG during the overhead throwing motion. Throughout this review shoulder kinematic and kinetic data (when available) are integrated with shoulder EMG data to help better understand why certain muscles are active during different phases of an activity, what type of muscle action (eccentric or concentric) occurs, and to provide insight into the shoulder injury mechanism.Kinematic, kinetic and EMG data have been reported extensively during overhead throwing, such as baseball pitching and football passing. Because shoulder forces, torques and muscle activity are generally greatest during the arm cocking and arm deceleration phases of overhead throwing, it is believed that most shoulder injuries occur during these phases. During overhead throwing, high rotator cuff muscle activity is generated to help resist the high shoulder distractive forces ≈80120 bodyweight during the arm cocking and deceleration phases. During arm cocking, peak rotator cuff activity is 4999 of a maximum voluntary isometric contraction (MVIC) in baseball pitching and 4167 MVIC in football throwing. During arm deceleration, peak rotator cuff activity is 3784 MVIC in baseball pitching and 8695 MVIC in football throwing. Peak rotator cuff activity is also high is the windmill softball pitch (7593 MVIC), the volleyball serve and spike (5471 MVIC), the tennis serve and volley (40113 MVIC), baseball hitting (2839 MVIC), and the golf swing (2868 MVIC).Peak scapular muscle activity is also high during the arm cocking and arm deceleration phases of baseball pitching, with peak serratus anterior activity 69106 MVIC, peak upper, middle and lower trapezius activity 5178 MVIC, peak rhomboids activity 4145 MVIC, and peak levator scapulae activity 3372 MVIC. Moreover, peak serratus anterior activity was ≈60 MVIC during the windmill softball pitch, ≈75 MVIC during the tennis serve and forehand and backhand volley, ≈3040 MVIC during baseball hitting, and ≈70 MVIC during the golf swing. In addition, during the golf swing, peak upper, middle and lower trapezius activity was 4252 MVIC, peak rhomboids activity was ≈60 MVIC, and peak levator scapulae activity was ≈60 MVIC. © 2009 Adis Data Information BV.