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Excerpt
We investigated relationships between muscle strength and bone mass in athletes involved in unilateral loading activities. Subjects were male collegiate and minor league baseball athletes (BB, n=24) and age-, height-, and weight-matched active controls (C, n=10). Peak force (N) of the hip abductors was assessed by isokinetic dynamometry (KinCom 500H) at 30°/sec. Bone mineral density (BMD, g/cm2) and content (BMC, g) of the right and left proximal femora (Norland XR-26) and right and left proximal radii (p-DEXA, Norland) were assessed by dual energy x-ray absorptiometry(DXA). Physical activity, calcium nutrition, medical history, and baseball participation data were collected via questionnaire and interview. BB and C did not differ regarding age, height, weight or body composition. BB included 54% pitchers and 83% right arm dominant; mean age of initial baseball participation was 7.4±3.0. For all subjects, isokinetic hip abductor strength positively correlated (p <0.05) with ipsilateral trochanteric BMC(right side r=0.37, left side r=0.39). For BB, higher correlations existed between left trochanteric BMC and both ipsilateral (r=0.54 in all BB; r=0.63 pitchers only) and contralateral (r=0.53 in all BB; r=0.61 pitchers only) hip abductor strength. Finally, especially in BB, there were highly significant positive correlations between ipsilateral and contralateral hip abductor strength and right proximal radial BMD (r=0.48 with right hip abduction; r=0.52 with left hip abduction, p<0.01). Results suggest muscular activity at the hip during decelerating force transfer during pitching and batting may positively influence bone density at the hip and proximal radius.
