Peak bone mass is achieved during the first twenty years of life, and dietary and activity patterns that contribute to the formation of peak bone mass are developed during childhood. The IMPACT intervention was designed to increase bone density and ultimately prevent osteoporosis during adulthood. IMPACT included physical education, food service, and classroom environmental and behavioral components and was delivered by physical education (PE) specialists, food service personnel, and classroom teachers.

A group of 718 sixth grade girls (mean age 11.1) from twelve middle schools in central Texas participated in the study. The group was 72% non-Hispanic white, 12% Hispanic, 5% African American, and 11% other ethnicity. After baseline measurements were completed in the fall of 2000, the twelve middle schools were pair-matched based on school characteristics (ethnicity, % economically disadvantaged, % girls in athletics) to a control (usual health education program) or the IMPACT program. The intervention was implemented for 18 months and consisted of three major components: a PE component, which emphasized daily weight-bearing activities (WBA); a health lessons component consisting of sixteen behaviorally-based lessons which emphasized WBA, calcium-rich foods, and osteoporosis prevention; and a food service component.

Outcome measures included physical properties of the students' heel bones, calcium consumption, physical activity, and psychosocial factors believed to be precursors to these behaviors. Changes at the school environmental level, such as the number of calcium rich foods offered in the cafeteria and the number of opportunities offered for weight-bearing and aerobic activity, were also assessed.

Inclusion Criteria:

• Girls enrolled in 6th grade of selected schools
• Student assent
• Parental consent
• No fractures or medications that compromise bone health or strength
• Enrolled in 2 semesters of physical education