Emslander, H. C., Sinaki, M., Muhs, J. M., Chao, E. Y., Wahner, H. W., Bryant S C., Riggs, B. L., & Eastell, R. (1998). Bone mass and muscle strength in female college athletes (runners and swimmers). Mayo Clinic Proceedings, 73(12), 1151-1160.

Whether female college athletes had increased muscle strength and bone mass in comparison with age-matched nonathletic female Ss was determined. A secondary comparison between weight-bearing versus non-weight-bearing exercise participation was made.

A comparative statistical analysis of the bone mineral density (BMD) of the total body, lumbar spine, and femoral neck, maximal oxygen uptake (VO2max), muscle strength, and level of physical activity in runners (N = 21), swimmers (N = 22), and control Ss (N = 20). Ss were female college students, 18 to 24 years old, who had had more than 8 normal menstrual cycles during the past year.

VO2max was significantly higher in the two athletic groups than in the controls. No significant difference in BMD was noted among the three groups. Total body BMD (r = 0.30) and femoral neck BMD (r = 0.39) were positively correlated with weight-bearing activity but not with non-weight-bearing activity. VO2max (an index of physical fitness) was positively correlated with femoral neck BMD (r = 0.33) and trochanteric BMD (r = 0.29). Shoulder muscle strength (determined by isokinetic dynamometry) was positively correlated with total body BMD (r = 0.34) and lumbar spine BMD (r = 0.28). Swimmers had higher muscle strength in the back and upper extremities than did runners and controls. Hip girdle muscle strength was not significantly different among the three groups. Total body BMD had a positive correlation with percentage of body fat and height. Lumbar spine BMD was higher in Ss who had previously used oral contraceptives. The athletes had a lower percentage of body fat, were less likely to have used oral contraceptives, and had fewer years of normal menses than did the control.

Implications. Total body BMD and femoral neck BMD are higher in weight-bearing exercises than in non-weight-bearing activities. Swimming exercise has no effect on BMD because it is not a weight-bearing activity. Although swimming is not a bone-building exercise, it can significantly improve shoulder, back, and grip muscle strength.

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