This study examines the role of energy availability on menstrual function and bone mass in female adolescent endurance athletes. Specific evaluations include dietary intake, exercise energy expenditure, training schedules, menstrual function and bone density.

The purpose of this project is to examine the relationships among low energy availability, H-P-A axis, menstrual function and bone density and bone turnover in high school female cross country runners. Our objectives are to: 1)determine energy intake, exercise energy expenditure, and fat-free mass to examine energy availability; 2)in a subset of runners, using double labelled water, estimate total energy expenditure and indirect calorimetry to estimate resting metabolic rate; 3)assess the relationship between energy availability, hormones that regulate bone turnover, markers of bone formation and resorption and bone mineral content and density; 4)identify the relationship between energy availability, hormones that regulate menstrual function and current menstrual status; and 5)determine the energy intake and energy expenditure variables exhibiting the strongest associations with energy availability.

Inclusion Criteria:

• high school female cross country runners
• ages 15-17 years
• 1-5 years experience as cross country runner
• 25 miles or more/week training

Exclusion Criteria:

• medications known to affect bone metabolism
• pregnancy

adolescent female cross country runners