During menstrual cramps, soaking feet in hot water can promote blood circulation and somewhat relieve the pain. However, applying a hot water bottle to the abdomen is more effective as it raises the local temperature, which enhances local blood circulation and helps alleviate menstrual pain. The principle behind this is that the occurrence of menstrual cramps is due to an increase in prostaglandin levels in the blood during menstruation, leading to muscle contractions and even spasms, causing pain. Applying heat locally through methods like hot compresses can maintain high temperatures and promote blood circulation, facilitating the metabolism of prostaglandins and the relief of muscle spasms, thereby reducing or alleviating pain.