introduction
The menstrual cycle occurs only in fertile female humans and other female rodentia, such as rats. Instead of 28 days as the average length in human, the length of rats menstrual cycle is about 4-5 days. Based on vaginal
smears, there are four phases of the menstrual cycle for rats: proestrus (12-14 h), estrus (25-27 h),metestrus (6-8 h),and anestrus (55-57 h) as described previously . The menstrual cycle is mainly regulated by the endocrine system, including the intercoordination of the hypothalamus-pituitary-ovary (HPO) axis in the central nervous system.
Female athlete triad(FAT) is a syndrome consisting of three necessary components: eating disorder, menstrual dysfunction, and loss of bone mass as osteoporosis. Although its epidemiology remains unclear, studies demonstrated that FAT is closely linked to the imbalance between energy intake and exercise -associated energy requirement. One of major symptoms of FAT is exercise-associated menstrual disturbances (EAMD), which involves reduction of energy supply to the reproductive system due to energy redistribution throghout the body as to compromise movement related to energy consumption. As a complementary mechanism, the exercise-induced reduction of energy supply to reproduction system activates neurodocrinologycal pathways, such as the HPO axis, and rebalances the energy intake and energy expenditure to support the reproductive function. Since low energy availability is the primary factor that causes EAMD, in this study, we examined whether carbohydrate supplements can reverse EAMD and protect against exercise-induced impairment in ovary as an important part of HPO axis regulation.