Impact of a school-based physical activity intervention on fitness and bone in adolescent females.

BACKGROUND Many female adolescents participate in insufficient physical activity to maintain cardiovascular fitness and promote optimal bone growth. This study evaluates the impact of a school-based intervention on fitness, activity, and bone among adolescent females. METHODS Subjects were assigned to an intervention (n = 63) or comparison (n = 59) group, and underwent assessments of cardiovascular fitness (VO2peak), physical activity, body composition, bone mineral density (BMD), bone mineral content (BMC), and serum markers of bone turnover at baseline and at the end of each of two school semesters. RESULTS The intervention increased physical activity, VO2peak, and BMC for the thoracic spine (P values < 0.05). Bone turnover markers were not affected. In longitudinal analyses of the combined groups, improvements in cardiovascular fitness predicted increased bone formation (P < 0.01) and bone resorption (P < 0.05). CONCLUSION A school-based intervention for adolescent females effectively increased physical activity, cardiovascular fitness, and thoracic spine BMC.