Background/Purpose:

 More than 50% of peak bone mass (PBM) is gained during adolescence and high impact exercise has been shown to impact bone accrual. We evaluated bone mass in age and gender matched teenagers who were more or less physically active using calcaneal ultrasound.

Methods:

 Forty-six consecutive high school girls (14-18 years) were prospectively recruited between February-April 2018 after obtaining written informed parental consent.  Subjects were divided into two groups, athletes (who reported ≥4 hours of aerobic physical activity/week) and non-athletes with < hour hours. No subject had any orthopedic injuries or metabolic bone disorders. Each study participant self-reported their a) use of calcium (with or without vitamin D) supplementation and b) weekly servings of 8 oz. dairy products.  BMD (bone mineral density) was measured (g/cm2) using a Sahara, Hologic Clinical Bone Sonometer). Continuous variables are reported as mean ± standard deviation and compared using Student’s t-testing, while categorical variables are reported as percentage of total and compared using Chi-square. Linear regression analysis was also performed to test the association between BMD and various predictors. A p-value < 0.05 was considered significant.

Results:

The baseline data are shown in Figure 1a.  Mean BMD was significantly higher in athletes vs. nonathletes (0.58±0.1 vs. 0.49±0.1 g/cm2, p=0.01, Figure 1b). The association between BMD and various potential factors, using linear regression analysis, is shown in Figure 1c. The groups were well matched for age, height, and dairy intake with no significant differences.

Conclusion:

 In high school girls who had heel BMD testing, participants who were physically active had higher BMD vs. those who were not. The findings were independent of age, dietary dairy intake as well as calcium/vitamin D supplementation. This study shows the importance of exercise in adolescent girls for accruing bone and attaining a higher PBM which will have a significant effect on bone mass later in life, potentially resulting in a lower lifetime risk for fracture. These findings need to be validated in a larger sample.