"40 Yard Dash" is a physics based simulation which uses the principles of power, inertia, and materials science to model the speed of different football players depending on their muscle mass and bone density. You will find details of how this was made in the notes and credits. For super fast, try: Muscle mass: 5454.5454 Bone density: -763.9633
According to the principles of physics, the term "power" refers to the change in kinetic energy (mv^2/2) over time (t). It is widely known that during the duration of very short sprints such as the 40 yards, that the "power" exerted by the sprinter throughout the race is relatively constant. Therefore, we should expect the runner's velocity to suddenly increase in the beginning but then level off their velocity as they reach the end. Additionally, due to the specific tensile strength of the femur bone, exceeding a weight of 6000 kilograms while make it such that the sudden acceleration at the beginning of the race will break your bones instantly.