The main reason for not exercising vigorously during menstruation is that if you exercise vigorously during menstruation, it may cause uncoordinated contractions of the uterus and the menstrual blood in the uterine cavity may flow backwards into the pelvic cavity, which will not only cause pain in the lower abdomen, but also endometrium in the menstrual blood, and active endometrial cells planted in the pelvic cavity will This can lead to endometriosis, such as chocolate cysts in the ovaries, or other foci of endometriosis, which can lead to severe menstrual pain and infertility. It is recommended not to exercise strenuously during menstruation, but to rest properly, and it is also recommended to keep warm during menstruation to avoid catching cold and affecting menstruation.