The symptoms of weak legs after coitus are mainly caused by improper movements during coitus, or too strenuous movements during coitus, or keeping the same position for a long time. If the posture is not correct or keep the same position for too long, coupled with the coital activity is very strenuous, may affect the blood flow of the legs, the blood supply of the legs if insufficient, there will be a distal nutritional deficit, so a large number of lactic acid buildup, there will be the symptoms of leg weakness and acidity. Therefore, when you have intercourse, you should pay attention to the combination of labor and rest, pay attention to the correct posture, and do not keep the same position for too long, which is very big damage to the body. If there is no relief within a short period of time, you must go to the regular hospital in time.