COMPARATIVE ANALYSIS OF ELITE YOUTH BASEBALL PITCHERS WITH AN AGE MATCHED NON-THROWING GROUP. Michael A. Keirns*1,2; Amanda Kocis1; Mark Kyger1; Cameron Lyons1; Sarah Parker1; Megan Riddle1; Dominic Severino1 1. Physical Therapy, Regis University, Denver, CO; 2. Physiotherapy Associates, Denver, CO PURPOSE: The purpose of this project was to develop a profile of 12-year-old elite male baseball pitchers (EP) by comparing their anthropometric measurements with an active, age-matched, non-throwing control group (NCG). These data are the first of a 5 year longitudinal study. The other purpose of this investigation is to delineate a new measurement of shoulder motion that may be an indicator of internal glenohumeral restrictions. This measurement is internal rotation (IR) at 0 degrees of horizontal adduction (HA) and IR at maximum HA. It was hypothesized that the anthropometric measurements of EP throwing arm would be significantly different from the NCG throwing arm (TA) and that these differences would describe the influences of baseball pitching on the adolescent developing musculoskeletal system. BACKGROUNDS/SIGNIFICANCE: The high incidence of injuries associated with baseball pitching is well documented. It has also been reported that there is an increased risk of injury associated with the developing adolescent musculoskeletal system. The cause of these injuries has not been established, however it has been hypothesized that pitchers are prone to injury due to the extreme magnitude and repetitive nature of the forces involved in the overhand pitching motion. To assist with understanding the influences of baseball pitching on the adolescent, this research project established a profile of EP by comparing the anthropometric measurements of EP with a NCG. These differentces will be tracked for the next five years which will allow a better intrepretation of the developing changes in the baseball pitcher. The establishment of an EP profile will also assist the medical practitioner in establishing expected rehabilitation outcomes post injury. SUBJECTS: Twenty competitive 12 y.o male athletes, 10 pitchers and 10 soccer players, met the pre-established elite inclusion criteria. METHODS AND MATERIALS: Pitching velocity, height, weight, 3 upper extremity girth measurements and 12 passive range of motion (PROM) measurements were evaluated on the dominant (DOM) and nondominant (NDOM) extremities of each athlete. The upper extremity PROM was performed by the same investigator using a hand held dynamometer with 4 lbs of overpressure. ANALYSES: Anthropometric data was analyzed utilizing the SPSS (10.1) system. Data was examined within and between participant groups and within and between DOM/NDOM extremities using single and paired two-tailed t-tests. Results were considered significant at p<0.05. This was a 2x2 experimental design, with sport and arm dominance being the independent variables. RESULTS: Significant differences were found between the EP and NCG with the following variables: pitch velocity; TA IR and external rotation (ER) at 90 degrees of abduction; non-throwing arm (NTA) ER at 90 degrees of abduction; combined IR & ER at 90 degrees of abduction; IR at 0 degrees of HA and IR at maximum HA, and dominant leg hip flexion (Table 2). Significant differences between the TA and NTA in the pitching group was seen in all of the PROM dependent variables except supine shoulder flexion (Table 3). In the control group, a significant difference was only seen between TA and NTA IR and ER at 90 degrees of abduction. CONCLUSIONS: This study found significant differences in shoulder flexibility between the EP and NCG. One important difference between the EP and the NCG was that the EP had significantly more ER and significantly less IR of their TA which may point to alterations in EP shoulder ROM due to the pitching forces. This study also reported that the EP TA had significantly more ER and less IR when compared to their NTA. The EP also demonstrated more total shoulder rotational motion TSR (IR + ER = TSR) on both TA and NTA when compared to the NCG. This may suggest the EP are more flexible than the NCG, however, the EP TA TSR was equal to their NTA. This information suggests a genetic predisposition to enhanced shoulder PROM with the adaptive changes toward increased ER with the throwing motion. This study is the first study to use IR measured with HA to demonstrate that glenohumeral internal rotational differences of a pitcher exist when compared to a control group and when compared to their NDOM arm. The specific tissues that influence these differences of the pitcher TA PROM are unclear but it may be suggestive of either changes in shoulder static constraints or changes in humeral and/or glenoid retrotorsion. Additional research is needed in this area to either support or refute these hypotheses with a possible future research design to use CT of the participants to assess the humeral torsion angle bilaterally. FUNDING SOURCE: None KEYWORDS: Baseball, Pitcher, Anthropometric Measurements, Adolescent Comparison Between Throwing and Non-Throwing Group Comparison of Dominant and Non-dominant Arms in Baseball Group Copyright 2010 by the American Physical Therapy Association. Requests for reprints should be directed to the corresponding author of the article. Educators, students, and other academic customers may receive permission to reprint copyrighted material from Physical Therapy (ISSN 1538-6724) by contacting the Copyright Clearance Center Inc, 222 Rosewood Dr, Danvers, MA 01923. Other types of customers who want permission to reprint should contact the APTA Editorial Office, Attn: Physical Therapy.