If you want to dynamically work the muscles involved in sprinting, try to drag heavy loads, walking, which would get the posterior chain. But as far as loading sprinting, that is not a good idea at all, like everyone else said. In general loading any skillfull sport movement is not a good idea, these movements are done at high velocities, usually with your body weight, you cant do anything with high velocity and high force I dont care who you are. Its like practicing with a 30 lb basketball and thinking you'll get better. You'll def get hurt and be a worse sprinter.