Meet the SpeedSpac: an awesome fitness training tool that helps you strengthen your lower body muscles with resistance training. Whether you want to improve your 40-yard dash times or overall speed, the SKLZ SpeedSac Sprint Trainer has you covered. You can adjust its weight to keep your body on its toes. You get 3 durable weight bags that can each be filled with up to 10 lbs of sand. The leash length is also adjustable.
The SpeedSac helps you perform intense lower & upper body workouts. Just bring your own sand, and you are good to go.