Context. Young females may have decreased bone mineral density (BMD), which puts them at higher risk for stress fractures and osteoporosis.

Objective. To compare site specific BMD among young females and to determine predictor variables of BMD measurements.

Design. Between groups design

Participants. All females ages 20–29 who consistently participated in high impact aerobic exercise (Runners), low impact aerobic exercise (elliptical or cyclers), and sedentary individuals were invited to participate in the study. 30 subjects participated, 10 in each group.

Main outcome measure(s). Each participant was weighed, measured, and questioned about calcium intake and workout history. Using the duel-energy x-ray absorptiometry (DEXA), measurement was taken in the spine and hips. Using analysis of variance, comparison in BMD measurements among the various fitness levels was analyzed. Relationships among variables between BMI and/or calcium intake and any of the three dependent variables were also analyzed.

Results. Out of 30 subjects, 8 out of 30 reported having osteopenia in either the hips or spine. 4 of those 8 subjects were sedentary; the other 4 osteopenic subjects were runners. 1 sedentary female reported having osteoporosis in her spine and osteopenia in her hips, with her calcium intake below RDA at 550mgs. 2 of the 8 osteopenic subjects reported no weight lifting. One subject that was osteopenic in both spine and hips suffered from bulimia. All low impact subjects reported having normal BMD.

Conclusions. The subjects who ran and were sedentary both demonstrated some deficits in site-specific BMD values. The subjects that participated in the low impact aerobic exercise group showed normal BMD. With a possibility of making low impact aerobic exercise just as efficient as high impact aerobic exercise and increasing BMD.