Blood in urine after male physiological activities, usually refers to blood in urine after sex, may be caused by acute injury, urinary tract infection disease, urinary tract stones and other factors. 1. Acute injury: blood in the urine occurs when the urethra is locally damaged and bleeding due to greater force during sex, which may be accompanied by pain and swelling. 2. Urinary tract infection diseases: for example, urethritis, due to the presence of infection in the urethra, there are symptoms of congestion and edema, during sex, may make the infection aggravated, causing bleeding, may lead to blood in the urine, accompanied by frequent urination, urinary urgency, urinary pain and other symptoms. 3. urinary stones: for example, bladder stones and urethral stones, during sexual intercourse, due to the change of position, the stones move, resulting in bleeding from damage to the urethra or bladder, which may cause hematuria. Men with blood in the urine after physical activity and accompanied by other obvious symptoms of urinary discomfort are advised to seek medical attention for examination and treatment so as not to delay the condition.