Use a 40- to 80-lb. sandbag and a standard basketball court for the sandbag shuttle run. Sprint down and back for the length of the court without a sandbag, then pick up the sandbag and repeat another sprint. Run another shuttle without the sandbag and then finish by carrying the sandbag for one more shuttle.
Double under is an exercise done with a jump rope in which the rope makes two passes per jump instead of just one.