Bone mineral density and menstrual function in adolescent female long-distance runners - A prospective comparative study of bone structure and menstrual function in adolescent female endurance athletes from five secondary schools in Pretoria

Background. In recent years, endurance running as a sport has become very popular. This trend has led to the identification of specific problems during the female athlete's life, especially with regard to reproduction, delayed sexual maturation, menstrual abnormalities and early osteoporosis. Methods. Bone mineral density (BMD) and menstrual function were compared between a group of long-distance female adolescent runners (N=17) from five schools in Pretoria and an age-matched inactive control group of adolescents (N=18). Groups were matched for body height, mass index (BMI 18 to 25) and eating habits. The SAHARA Clinical Sonometer was used to measure BMD on the calcaneus. Menstrual function was denoted by onset of menarche, duration of menstrual periods (days) and number of menstrual periods per year. Results. Baseline BMD was significantly higher in the athletic group: mean = 0,6126 g/cm3 and SD = 0,1217, versus non-athletes: mean = 0,5329 g/cm3 and SD=0,0733 (p = 0,0228). There was a significant delay in the onset of menarche in the athletes: mean = 14,873 and SD = 1,37798, in comparison to the non-athletes: mean = 13,468 and SD = 1,2194 (p = 0,0030). The athletes had a significantly higher incidence of menstrual abnormalities (p = 0,005). Conclusions. BMD at the focus of strain for running (the legs) is higher in endurance adolescent female runners. Endurance runners have a significantly higher incidence of menstrual abnormalities. Key words: . SA Fam Pract 2003;45(10):14-1