Human body stronger?

i heard story's the human body is stronger than we think but are brain stops us from using are full strength so we don't rip our muscles i heard that a person can flip a car if some one is in danger of being crushed there was a story on the news of a police officer lifted a 500 pound piano to save a kid and on Criss Angel he hypnotized 4 kids who then lifted a car but i don't know how real that is