Myth or Fact: Human Body Humans only use 10% of their brains. Myth Fact None Hair and fingernails continue to grow after death. Myth Fact None Your stomach lining replaces itself every few days to avoid digesting itself. Fact Myth None You can swallow and breathe at the same time. Myth Fact None Cracking your knuckles causes arthritis later in life. Myth Fact None Time's up Most Popular Most Popular