Muscles are important, but stiff tendons are the secret ingredient for high-speed performance

The fastest sprinter is the world right now is Lamont Marcell Jacobs, who won Olympic gold in the men's 100-meter sprint with a time of 9.80 seconds. You might be surprised to learn that most of the explosive power displayed by Jacobs and other elite athletes doesn't come from their muscles, or even from their minds—it comes from somewhere else.