Just because dragons can get too fat to move doesn't mean they can't work out to keep in shape. (As explained here [link]
) This dragon runs to keep the parts of her body unaffected by her weight gain very trim, that doesn't stop her from swelling up during the workout [link]
. She has sensors attached to her that tell her how fast she'd be going without that big sloshy tummy. Sometimes in a dragon gym your belly can get pumped full of food while you're working out.