Single-leg sled pushes and pulls involve emphasizing one leg to move the sled on each step, which is especially good if you're trying to focus on a weaker side.
An easy way to implement these single-leg sled push and pull variations is to simply perform half the distance or duration with one leg and do the second half with the other leg.
The Ohio Hellraiser talks Blast & Cruise, Harley Davidsons, the pros of bodybuilding training(!), and what conditioning drills rate high on the awesomeness scale. (Hint: it ain't the treadmill).