Rasu has to laugh a bit at the description.

"I think it's fun. It'll come back quick. You ever do anything like that? I mean not martial arts, obviously, but running, weights, stuff like that?"

Mizuki clearly keeps a trim form, but that's possibly just from a lean diet. He does have a rather tight schedule, so Rasu doesn't imagine there's much physical activity going on for the sake of leisure-- and perhaps not even much for the sake of exercise.