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Date of Award


Document Type

Thesis - Pacific Access Restricted

Degree Name

Master of Arts (M.A.)


Physical Education

First Advisor

John G. Boelter

First Committee Member

Doug Meyer

Second Committee Member



The problem of this study was to determine the relative contribution of the strength of shoulder internal rotators among various muscle groups to ball speed in the fastball pitch as exhibited by college pitchers. An objective of the study was to explain at least 40% of the contribution of ball speed. The literature appears to be somewhat inconclusive as to the quantification of component contributors of muscle groups m the upper extremity to ball speed. It appears in the literature that variables other than upper extremity strength account for approximately 50% of ball speed. Some research has indicated that strength of the shoulder internal rotators is a major contributor while most research of this type has either been inconclusive or qualitative m nature. Eighteen college pitchers were tested for upper extremity peak torque production on the Cybex II Isokinetic Dynamometer at speeds of 90 and 240 degrees/second. Fastball speed was measured with a hand held radar gun. Results of regression analyses performed on the data indicate a strong correlation between the internal rotators of the upper extremity and fastball speed. A regression equation using a hierarchical strategy to maximize R2 accounted for 40% of contribution to ball speed using independent variables of shoulder internal rotation at 90° /sec. (X1) and elbow flexion at 240°/sec. (X2); ie, Speed=62.861+245X1 +.39X2. The standardized beta weights for this equation indicate that the greater contributor to ball speed was Sho/Int/Rot-90 when the effects of Elb/Fl-240 are controlled. When elbow extension at 90° /sec. was added to the equation as X3 approximately 59% of ball speed is explained; ie, Speed=68.605 + 268X1 + 807 X2 - .430X3.



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