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Tennis| Muscles| Actions

Posted Sep 18 2008 10:09am
Shoulder injuries in tennis players are common because of the repetitive, high-magnitude forces generated around the shoulder during the various tennis strokes. An understanding of the complex sequences of muscle activity in this area may help reduce injury, enhance performance, and assist the rapid rehabilitation of the injured athlete.  

The supraspinatus, infraspinatus, subscapularis, middle deltoid, pectoralis major, latissimusdorsi, biceps brachii, and serratus anterior muscles were studied in six uninjured male Division II collegiate tennis players using dynamic electromyography (EMG) and synchronized high-speed photography. The tennis serve contains four stages. Three stages characterize the forehand and backhand groundstrokes.

The results indicate that the subscapularis, pectoralis major, and serratus anterior display the greatest activity during the serve and forehand. The middle deltoid, supraspinatus, and infraspinatus are most active in the acceleration and follow-through stages of the backhand. The biceps brachii increases its activity during cocking and follow-through in the serve with a similar pattern noted in the acceleration and follow-through stages of the forehand and backhand. The serratus anterior demonstrates intense activity in the serve and forehand, thus providing a stable platform for the humeral head and assisting in gleno-humeral-scapulothoracic synchrony.

The tennis serve and forehand and backhand groundstrokes are accomplished by complex sequences of muscle activity that incorporate contributions from the lower extremities and trunk into smooth, coordinated patterns. (Ryu RK. McCormick J. Jobe FW. Moynes DR. Antonelli DJ. An electromyographic analysis of shoulder function intennisplayers.American Journal of Sports Medicine. 16(5):481-5, 1988 Sep-Oct.  

Rehabilitation and conditioning programs for tennis players should be structured to restore and optimize the activation sequences (scapular stabilisers before rotator cuff), task specific functions (serratus anterior as a retractor of the scapula, lower trapezius as a scapular stabilizer in the elevated rotating arm) and duration of activation of these muscles. (Kibler WB. Chandler TJ. Shapiro R. Conuel M. Muscle activation in coupled scapulohumeral motions in the high performancetennisserve.British Journal of Sports Medicine. 41(11):745-9, 2007 Nov).

Investigators have suggested that the greater prevalence of lateral humeral epicondylitis ( tennis elbow) in novice tennis players compared to expert players may reflect the novice players' use of faulty mechanics for the backhand stroke.

Experts performed the backhand stroke with the wrist extended (re: neutral alignment of the forearm and hand dorsum), moreover, their wrists moved further into extension at impact. In contrast, novice subjects struck the ball with the wrist flexed while moving their wrists further into flexion.

The wrist motion analysis and EMG data together showed that the novice subjects eccentrically contracted their wrist extensor muscles throughout the stroke. The resulting eccentric (lengthening) contraction of wrist extensor muscles may contribute to lateral TE in novice players. Research evidence indicates that eccentric muscle contraction facilitates muscle fiber injury. (Blackwell JR. Cole KJ. Wrist kinematics differ in expert and novicetennisplayers performing the backhand stroke: implications fortenniselbow.Journal of Biomechanics. 27(5):509-16, 1994 May).

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