I know that when the sprinter takes off, the friction acts on you that causes his acceleration, same but opposite force that you put on the ground. But why does he start in a crouched position? Is it because to increase Fn? How would crouching increase the Fn? If one's crouched, the Fn would be cos(theta)Fn because we want the force normal to the surface? Wouldn't his Fn be less than if he was just standing straight up because of cos(theta)? And why do they use starter blocks? Can somebody elaborate on this so i can understand this concept?