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KMID : 0613820100200040549
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Journal of Life Science
2010 Volume.20 No. 4 p.549 ~ p.554
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Effects of Shoulder Muscle Strength on Terminal Range by Humeral Head Retroversion
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Park Si-Young
Lee Dong-Jun
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Abstract
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Increased external rotation and decreased internal rotation have been noted to occur progressively in the throwing shoulders of baseball pitchers. The purpose of this study was to provide descriptive data for terminal range eccentric antagonist/concentric agonist shoulder muscle strength in collegiate baseball pitchers with humeral head retroversion diagnosed through MRI. The dominant and non-dominant shoulders of 9 asymptomatic baseball pitchers were tested through a range of 20 degrees of external rotation to 90 degrees of internal rotation using the Biodex system 3 isokinetic dynamometer at speeds of 90°/sand 180°/s. Differences between the dominant and non-dominant shoulders were assessed using the paired samples t-test. Total range of motion, measured at 90° of glenohumeral abduction, was 180.1° for dominant shoulders and 183.7° for non-dominant shoulders. Humeral head retroversion measured 47.6±6.1° in dominant and 37.8±5.3° in non-dominant extremities. The mean internal rotator concentric contraction (IR-Con) showed a significant difference compared to 31.5±5.1 (Nm) in dominant and 38.7±5.2 (Nm) in non-dominant shoulders at 180°/s (p＜0.05). The mean external rotator eccentric contraction (ER-Ecc) showed a significant difference compared to 20.3±4.7 (Nm) in dominant and 25.1±3.7 (Nm) in non-dominant shoulders at 90°/s (p＜0.05). There is a pattern of increased external rotation and decreased internal rotation in the dominant extremity that significantly correlates with an increase in humeral retroversion.
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KEYWORD
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Agonist, antagonist, MRI diagnosis, total range of motion
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