For a similar workout or that isometric hold you are looking for I use a bungee lead. Overtyme sells a nice cheap one. My bulldog is a natural puller so when we're either walking or running his body is always flexing different directions when he's moving and pulling. It seems to wear him out faster when we're out. A plus is I don't get that jerking in my shoulders when he makes a swift change in direction and bottoms out on the lead.