The ulnar collateral ligament (UCL) is the primary restraint against valgus forces at the elbow. This structure cannot support the entire load placed upon the medial elbow during overhand throwing motions such as pitching a baseball. In this study we measured the contributions that different muscle groups make to the stability of the medial elbow, under conditions intended to reproduce the loads during pitching by varying the forearm position and loading conditions. We also evaluated the strength of the elbow musculature for the possibility of a training effect in the dominant arm of 11 male high school baseball pitchers. We collected surface EMG data in the two forearm positions to determine if the different positions used in various pitches have an effect on muscular action. We also tested an isometric and dissipative loading condition to determine if the muscles activity was load reactive. The four muscle groups tested were the flexor-pronator group (FP), the extensor-supinator group (ES), the tricep brachii (TB), and the pectoralis major (PM). We found significantly (p-value=0.001) higher peak activity levels of the flexor-pronator group in the neutral forearm position (79.4% MVIC �� 27.0% MVIC full trial peak, 30.8% MVIC �� 20.8% MVIC initial l50ms peak following activation) when compared to the supinated position (55.5% MVIC �� 29.6% MVIC full trial peak, 16.9% MVIC �� 14.8% MVIC initial l50ms peak following activation), which may explain the link between breaking pitches and medial elbow injury. We found an increase (p-value=0.001) in force output of the dominant arm (49.3 N/kg �� 12.5 N/kg) over the non-dominant arm (38.1 N/kg �� 11.0 N/kg). This finding is attributed to a training effect, which assists in protecting the elbow. These findings help provide baseline muscle activity information on protection of the medial soft tissue structures of the elbow. / Graduation date: 2004

This study analyzed the relationships present between grip strength, wrist flexion, arm length, partial and total, and throwing velocity. Thirty-one subjects were tested to obtain the data on these variables. A multiple linear regression equation produced a significant F ratio for the relationship between grip strength and throwing velocity. Neither wrist flexion nor arm length obtained a significant F ratio to throwing velocity. A stepwise multiple regression equation again displayed a significant F ratio for grip strength and throwing velocity. Wrist flexion and arm length did not produce a significant F ratio for their relationships to throwing velocity. This study concludes that of the variables tested, only grip strength displayed a significant relationship to throwing velocity. This study indicates that throwing velocity can be predicted at a moderate level from the measurement of grip strength.

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.