Physical fitness effect on bone mass in postmenopausal women.

This study was conducted to determine if bone mineral mass is influenced by the level of physical fitness in active, healthy, postmenopausal women from 50 through 59 years of age. In vivo neutron activation analysis (NAA) was used to measure calcium or bone mineral in the trunk and proximal femurs. The NAA measurement is expressed as calcium bone index (CaBI), which relates the subject's Ca value to the estimated mean value for normal subjects of the same size based on height and arm span. The normal CaBI is 1.00 +/- 0.12 (ISD). The level of physical fitness was determined by calculating the maximum oxygen uptake (VO2max), attained by a graded exercise test on the treadmill, and evaluating the muscle strength in performing one repetition maximum in the bench press and leg press. The "above-average fit" group (VO2max greater than 29 ml/kg/min) when compared to the "average fit" group (VO2max 21-29 ml/kg/min) had significantly higher CaBI (p less than 0.001) and leg press (p less than 0.01). There was significant correlation between VO2max and CaBI (p less than 0.01). The findings suggest that level of physical activity may modify the amount of bone loss in postmenopausal women.