Hello, Bharat, You are a young fellow, active , now doing workout in Gym. I am sure you do weight lifting , tread mill etc. This could certainly affect the abdominal muscles causing strain and may be even sprain. Blood in the stool after a hard bowel movement is due to small piles or Hemorrhoids (Internal or external) or may be a small tear or anal fissure. Continue to drink fluids and use an over the counter stool softener. Your pharmacist in the drug store can give you suggestions about this. Wish you well.