Park, S., Miyakawa, S., Shiraki, H., & Mukai, N. (2008). Upper extremity muscle activity and strength characteristics of overhead throwers during maximal eccentric muscle action. ACSM 55th Annual Meeting Indianapolis, Presentation Number 2492.

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This study determined the patterns of electromyographic responses and torque during maximal, eccentric muscular activities with shoulder flexion, abduction, and diagonal exercises at three velocities on an isokinetic device. Ss (M = 7; F = 4) who participated in overhead sports (javelin throw, badminton, baseball, and tennis) at least three days a week volunteered to participate. The test procedure consisted of at least five maximal-effort repetitions on the three exercises under three velocity conditions -- 60, 120, and 180/s on a dynamometer. Assessments were made of the activation of the anterior deltoid, middle deltoid, posterior deltoid, upper trapezius, middle trapezius, lower trapezius, and biceps brachii muscles by surface electromyography during the flexion, abduction, and diagonal actions at the three isokinetic movement velocities.

The anterior deltoid muscle elicited lower muscle activity during the diagonal activity than with shoulder flexion and abduction. The posterior deltoid and upper trapezius muscles elicited the greatest muscle activity during the three actions. Most muscles elicited greater muscle activity at the faster velocities during each task while the middle trapezius muscle showed greatest muscle activity during the slower velocity tasks. [This indicates that within the shoulder, some muscles function most effectively at high movement velocities while others do so at low movement velocities.]

Implication. There are specific motor controls and strength patterns during eccentric actions with various positions and velocities in overhead throwers. Training for one practice exercise would not carry-over to the performance of other exercises. [The belief that baseball pitchers who train using a variety of shoulder resistance and strengthening exercises produce beneficial transfer effects for the specific action of pitching is not supported by this study. Shoulder-exercise training activities each produce their own unique effects. A routine of performing a variety of resistance exercises at a variety of velocities should not be expected to influence other resistance training activities or complex movements such as pitching.]

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