This study aimed to assess the effect of lower trapezius (LT) weakness on humeral and scapular kinematics and shoulder muscle activity during the tennis serve.
Fifteen competitive male tennis players (age, 23.8 ± 3.4 yr; height, 182.8 ± 6.7 cm; mass: 76.6 ± 8.7 kg; tennis experience: 15.6 ± 4.9 yr) performed two tennis serves before and after selective fatigue of the LT (25-min electric muscle stimulation). During each tennis serve, racket, humeral and scapular kinematics and the activity of 13 shoulder muscles were recorded using an optoelectronic system synchronized with indwelling and surface electromyography. The serve was split into five phases, that is, early and late cocking, acceleration, early and late follow-through.
Selective fatigue led to a 22.5% ± 10.4% strength decrease but did not alter maximum racket speed and humerothoracic joint kinematics. However, increased scapular upward rotation was observed in the acceleration (P = 0.02) and early follow-through (P = 0.01) phases. Decreased muscular activity was observed during the early cocking phase for the LT (P = 0.01), during the acceleration phase for the LT (P = 0.01), anterior deltoid (P = 0.03), pectoralis major (P = 0.04), and subscapularis (P = 0.03), and during the early follow-through phase for the anterior deltoid (P = 0.03) and LT (P = 0.04).
The LT weakness altered neither serve velocity nor humerothoracic joint kinematics, but impaired scapulothoracic kinematics and anterior shoulder muscle activation. Such alterations may reduce the subacromial space and jeopardize humeral head stability. These findings shed new light on the consequences of LT weakness, highlighting the importance of monitoring and strengthening this muscle in overhead athletes.
1Univ Lyon, University Claude Bernard Lyon1, Interuniversity Laboratory of Locomotion Biology, Villeurbanne, FRANCE
2Laboratory of Simulation and Movement Modeling (S2M), School of Kinesiology and Science of Physical Activity, Faculty of Medicine, University of Montréal, Montreal, Quebec, CANADA
3Research Center of the CHU SAINTE-JUSTINE Mother and Child University Hospital Center, Montréal, Quebec, CANADA
Address for correspondence: Isabelle Rogowski, Ph.D., UCB Lyon 1-UFRSTAPS, 27-29, bd du 11 novembre 1918, 69622 Villeurbanne Cedex, France; E-mail: firstname.lastname@example.org.
Submitted for publication September 2018.
Accepted for publication June 2019.
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Online date: July 2, 2019