I think you are getting a good work out pulling them in the wagon. Whenever I take my two girls out in their red wagon (they are 4 and 5) I can feel it in my muscles. They are almost two big to fit in the wagon, but I will continue to pull them in it until they are too heavy for me to pull, or until their legs don't fit anymore, lol. When I go for a walk without them, I can feel the difference in my muscles and my breathing, so I know I get a better work out with them.