[Purpose] This study examined the inter-rater and intra-rater reliability of measurement of isometric shoulder internal and external rotation strength using a hand-held dynamometer (HDD).[Subjects] For intra-rater reliability, the subjects were 21 healthy persons (8 men and 13 women), and for inter-rater reliability, the subjects were 17 healthy persons (9 men and 8 women).[Method] For intra-rater reliability, an examiner performed measurements of isometric shoulder internal and external rotation strength twice with an interval of two days. For inter-rater reliability, two examiners measured isometric shoulder internal and external rotation strength. Making allowance for fatigue, measurements by different examiners took place after an interval of at least 30 min, and at random on the same day.[Results] The inter-rater and intra-rater reliability were analyzed using Student's t test, which showed no significant differences, and intra-class correlation coefficients, which gave good results.[Conclusion] Measurements of isometric shoulder internal and external rotation strength using a HDD fixed to the upper limbs and trunk by a belt gave good results for both inter-rater and intra-rater reproducibility.

We investigated the change in shoulder function of junior-high school baseball players after 70 pitches, a limit proposed for preventing juvenile baseball injuries. [Subjects] The subjects were 10 junior-high school baseball club pitchers. [Method] Before and after pitching we measured shoulder internal range of motion (ROM), shoulder internal and external rotation strength, and fatigue on the throwing side, and ball speed. Seventy pitches, straight and curve balls, were thrown as if in normal practice. Shoulder ROM and strengths, and fatigue before and after practice were examined with the t test, and ball speed with one-way analysis of variance. [Results] Shoulder ROM was significantly reduced after pitching practice; however, no differences in internal or external rotation strength were found. Fatigue significantly increased after pitching practice, but no difference in ball speed was found. [Conclusion] Similar to a report on high school baseball players, shoulder ROM declined after pitching practice without any difference being found in internal or external rotation strength. Therefore, we consider it necessary to perform shoulder external rotation stretching after pitching practice.