Haha! Okay yes exercise in that sense does make more sense. Vet just had mentioned about getting him "out and about" more because he seems to be more sedentary than the average chameleon.I think he does not mean "exercise" as we think of it (i.e., abwork, running around LOL) as much as being without the "exercise" of pooping for a while and therefore his muscles became too weak to do it effectively-such as from a very long bout of constipation. So yes if you can help him express his droppings he can hopefully regain this strength. Of course you won't do this without having the vet show you how as you mentioned, and I would also ask him about the possibility of an internal cloacal obstruction such as a swelling or growth.
Since "poop" includes urates and both are toxins, he should feel much better from having this regularly relieved before he gets to the lethargy stage.
I will be heading to the vet this evening. Will post any other updates that come from the visit.