Dark brown blood in underwear after running

Some people will find dark brown blood stains on their underwear after running. This mainly happens among female friends, especially before menstruation. After it happens, you should pay more attention to rest and stop running. If you run during menstruation, it will affect your menstruation, cause abnormal menstruation, and even lead to irregular menstruation.

Menstruation (called Guishui in ancient times and commonly known as aunt) is a physiological cycle that occurs in some fertile human females, chimpanzees and other animals.

In humans, it refers to the phenomenon that female blood or mucus is regularly discharged from the endometrium through the vagina, which is regulated by the reproductive hormone system. Human female menstruation usually first occurs between the ages of 12 and 15, with an average cycle of about 28 days and ends after menopause (usually 45-55 years old). When menstruation comes, menstrual blood will continue to flow for about 2-7 days.

The main components of menstruation are blood (3/4 arterial blood, 1/4 venous blood), endometrial tissue fragments and various active enzymes and biological factors. Among them, fibrinolytic enzyme makes menstrual blood liquid and prevents it from coagulating, and prostaglandins play a role in contracting the uterus. Medically speaking, only the reproductive cycle experienced by primates (including humans) is called menstruation. In addition, the reproductive cycle of other mammals is called the estrus cycle. Menstruation is regulated by the reproductive hormone system and is necessary for biological reproduction. A woman's first menstruation is called menarche, and the onset of menarche marks the entry of a woman into puberty. The average age of menarche for girls is 12 years old.

Many factors, including genetics, diet, and physical health, can cause menarche to come earlier or later. The cessation of menstruation marks that a woman has entered menopause, also known as menopause. The average age of menopausal women is 51 years old. Of course, just like menarche, many factors such as genetics, disease, surgery and medical treatment can advance or delay menopause. It is normal to enter menopause between the ages of 40 and 58. Menopause occurring before the age of 35 is defined as premature aging.

The female internal reproductive organs consist of the ovaries, uterus, and fallopian tubes. The main function of the ovaries is to produce eggs and synthesize ovarian hormones, while the uterus and fallopian tubes are reproductive organs. The ovaries contain hundreds of thousands of follicles, each of which contains one egg.

Before puberty, the follicles are essentially non-functional. During puberty, under the action of gonadotropin from the anterior pituitary gland, immature follicles gradually develop and synthesize estrogen. When the follicle matures and ovulates, the follicle wall collapses, the cells become larger and yellower, and are called the corpus luteum. It synthesizes estrogen and produces progesterone.