Copyright @ 200 by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited.7 Clinical Investigations Risk Factors for Stress Fracture among Young Female Cross-Country Runners

distance runners.Methods: Participants were 127 competitive female distance runners, aged 18–26, who provided at least some follow-up data in a randomized trial among 150 runners of the effects of oral contraceptives on bone health. After completing a baseline questionnaire and undergoing bone densitometry, they were followed an average of 1.85 yr. Results: Eighteen participants had at least one stress fracture during follow-up. Baseline characteristics associated (P G 0.10) in multivariate analysis with stress fracture occurrence were one or more previous stress fractures (rate ratio [RR] [95 % confidence interval] = 6.42 (1.80–22.87), lower whole-body bone mineral content (RR = 2.70 [1.26–5.88] per 1-SD [293.2 g] decrease), younger chronologic age (RR = 1.42 [1.05–1.92] per 1-yr decrease), lower dietary calcium intake (RR = 1.11 [0.98–1.25] per 100-mg decrease), and younger age at menarche (RR = 1.92 [1.15–3.23] per 1-yr decrease). Although not statistically significant, a history of irregular menstrual periods was also associated wit