There is no exact science in this, as in everything else, and besides, each person is unique. Maybe what works for one person won't work for another, but there are certain universal truths. And, certainly, heat can help relieve menstrual cramps.
Temperatures above 140°F activate internal receptors that block pain. When cells in our body die or are injured, we experience pain, and heat seems to "turn off" pain at the molecular level.
Our uterus is still a muscle that contracts during menstruation to remove the remnants of endometrial tissue. By applying heat to the abdominal area, the muscles relax and uterine cramps are less intense.
What is the cause of this?
The contractions in the uterus are necessary for the endometrium to separate, and this is what can cause the discomfort. After all, what is contracting is a muscle, and heat helps that muscle relax. Also, since the endometrial tissue that lines the uterus behaves like honey, the more we "melt" it, the better our body will discharge it.
Also, heat for menstrual pain will relax your muscles while acting on the neural system by increasing the sensitivity threshold of the pain receptors. Why does this happen? Because heat improves blood flow, arterial flow and oxygen supply, the sensation of pain is likely to be reduced.
Not only that, but there is more. Heat also helps relieve edema, which relieves heaviness. So, without a doubt, in the menstrual week, giving heat to the most painful spots is a must.