Some training aids used here are:
Tractor Tires: Pull them, push them, flip them and beat them with a sledge hammer. They never quit.
Training Ropes: Zero-impact conditioning tools. These ropes will get your heart pumping while developing core stabilization and increasing authentic strength.
Sleds: Weighted. Pushing and pulling these sleds in different configurations increases acceleration and develops core stabilization. You will feel the burn.