Age at menarche and menstrual periodicity of 21 college swimmers and 17 runners were studied in relation to the age of initiating training. The 18 premenarche-trained athletes had a mean menarcheal age of 15.1±0.5 years, whereas the 20 postmenarche-trained athletes had a mean menarcheal age of 12.8±0.2 years, similar to that of the college control subjects, 12.7±0.4 years. Each year of training before menarche delayed menarche by five months (0.4 years). Of the premenarche-trained athletes, 61% had irregular menstrual cycles and 22% were amenorrheic, whereas 60% of the postmenarche-trained athletes had regular menstrual cycles and none were amenorrheic. Training increased the incidence of oligomenorrhea and amenorrhea among both premenarche- and postmenarche-trained athletes. Metabolic and hormonal changes consequent to an increased lean/fat ratio may explain these findings.
Frisch RE, Gotz-Welbergen AV, McArthur JW, et al. Delayed Menarche and Amenorrhea of College Athletes in Relation to Age of Onset of Training. JAMA. 1981;246(14):1559–1563. doi:10.1001/jama.1981.03320140047029
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