I actually had to drop to fortnightly updates so that I would have time to do martial arts twice a week so I may not be the best person to ask about balancing these things.
I would definitely agree with you AnnaLandin, taking walks is excellent for keeping yourself moderately active. I also find walks amazing for clearing your head and finding inspiration. Even if you live in a gross city like I do, it's better than nothing.
Although comics are important, and we obviously care about them, I really do think that keeping at least moderately active should be higher in our priorities than getting pages done. Even if it's only slightly higher. If you're doing a daily comic I'd say go for a brisk walk, for about half an hour, maybe around lunch time, so it won't eat too much into your drawing time. (Disclaimer: I'm not an expert in health or fitness, these are just things that have worked for me).