He demonstrates that stress corresponds specifically to speed and inversely to time, which is why they must be shot. Races of 55, 100, 110, 300 or 400 meters with obstacles scattered throughout the race, of different stature and in different quantities. Newton's Third Law Physics: For every activity, there is an equivalent and inverse response. If a hurdler enters the obstacle faster, he will fall out of it, quickly due to the power he has applied to the track, pushing him back to clear the obstacle and continue running. This also applies to the reason that a hurdler must clear the obstacle by pushing with the knee, turning forward and pumping his arms. These are normal racing mechanics, so if a hurdler maintains these mechanics through the obstacle, he will fall straight off the obstacle in a sprint. The focus of gravity is the point where most of an object's heaviness seems, by all accounts, to be taught. Hurdlers need a focal point of gravity located simply above the obstacle. This is considered the hurdler's head which barely goes up when he or she