sentence: 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. sentence:  As he brings his elbows towards his knees, a loud crack can be heard as the man laughs, "That hurt my ass. sentence: " He attempts a second sit-up and with another cracking sound, exclaims and grabs his buttocks. sentence:  The man says, "one more" and attempts another time, after which he says, "that felt horrible. sentence: " The man struggles through nine more attempts before giving up to the amusement of his friends.