Harnesses are required to do this conditioning since the dogs do pull. The "Springer" with a harness attached is used for mushing dog conditioning. Bailey can pull me right along on flat ground without a problem.
With the "Springer" there is no way for him to get in front of the tire, and the spring takes the majority of the pulling in any direction.
Stay tuned, but I think it will work well. Now off for 5 miles in the hills without leashes. YEAH!