A young man lying prone on a tiled floor with this hands behind his head and his knees bent attempts to perform a sit-up in front of a few friends.  As he brings his elbows towards his knees, a loud crack can be heard as the man laughs, "That hurt my ass. " He attempts a second sit-up and with another cracking sound, exclaims and grabs his buttocks.  The man says, "one more" and attempts another time, after which he says, "that felt horrible. " The man struggles through nine more attempts before giving up to the amusement of his friends.