The objective of this study was to investigate the mechanisms by which physical training affects the menstrual cycle.
　510 college students (294 non athletes-group A and 216 athletes group B) were inquired into questionnaires and some of each groups were checked their BBT for 3 or 4 menstrual cycles.
　Blood samples were obtained from some athletes in group B and serum levels of LH, FSH, E₂, P₄, PRL and Testosterone were analysed.
Results
　1) Average menarcheal age of the athletes who had begun sports training before menarche was later than these who had begun sports training after menarche.
　2) Group B had higher incidence of amenorrheaoligomenorrhea and anov. cycle than group A.
　3) The athletes who were amenorrhea or who had anov. cycle in group B had normal levels of LH, FSH and decreased levels of E₂. None had shown the elevated serum levels of PRL and Testosterone.
　4) Most of the athletes who had normal menstrual cycle in group B showed luteal insufficiency.
　It is concluded that hard sports training before menarche delays the onset of menarche and hard sports training disturb the hypothalamus-pituitary function and then often causes the menstrual disorder to athletes.

DESCENTE SPORTS SCIENCE Vol.6/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE