Sit-ups during menstruation are likely to cause significant dysmenorrhea or increased menstrual bleeding, which is essentially caused by the shedding of the uterine lining, and during menstruation the cervical opening will dilate to a certain extent. Sit-ups require intense abdominal force and movement, in the process of abdominal contraction will be obvious will cause the uterus to contract violently, and the end result of the contraction is to cause severe pain in the abdomen, because sit-ups will cause the abdominal pressure increases can easily lead to the backflow of menstrual blood, it is easier to cause uterine infection. The contraction of the uterus after being squeezed will lead to changes in the rate of shedding of the endometrium, which will easily cause changes in the amount of menstrual bleeding, it is not recommended to carry out exercises that significantly stretch the abdomen during menstruation, and pay attention to rest, do not get cold.