According to the sex researchers William Masters and Virginia Johnson, both men and women experience physical changes when they are, well, horny. Masters and Johnson came up with something called the "Human Sexual Response Cycle," which is divided into four stages: excitement, plateau, orgasm and resolution. Forget boners, here's what happens to girls' bodies:

Excitement: Pulse rate, blood pressure and breathing rate increase. Increased blood flow causes everything "down there" to swell, such as the labia and clitoris. Next comes vaginal lubrication (which is your body's way of making intercourse a whole lot easier). Nipples may also become erect and more sensitive.

Plateau: Pulse and breathing rates continue to increase. The clitoris withdraws under the clitoral hood, but is still very sensitive. The vaginal entrance tightens, and lubrication continues.

Orgasm: Blood pressure and heart rate reach their highest peak. The muscles in the vaginal walls and the uterus contract rhythmically. Other muscles may contract as well, like in your face, arms and legs. (Note: It's quite common for women go through the first two phases of the cycle without reaching orgasm, which can be elusive at times.)

Resolution: After orgasm, both men and women tend to feel a warm physical "glow" and a sense of well being. Physical arousal slowly subsides and your body returns to normal.

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There are many ways to help ease menstrual cramps. The trick is to find one that works for you. Try:

lying down if possible at the first sign of pain
gently rubbing your abdomen
mild exercise and stretching (see below)
taking pain medication containing ibuprofen

-seventeen.com