The main reason for waist pain the day after intercourse, according to Chinese medicine, is kidney deficiency, which is considered by Chinese medicine to be the province of the kidneys. If you have frequent intercourse with a sore lower back, and at the same time have a white face and red cheekbones, five heartburn, short urine and hot hands and feet, it is due to kidney yin deficiency, treatment should nourish kidney yin. If after intercourse there is soreness and pain in the lower back, and at the same time there is coldness in the lower back, fear of wind, cold air, lack of warmth in the limbs, clear and long urine and loose stools, this is due to kidney yang deficiency, and treatment should be based on warming and tonifying kidney yang.