All I would say is that don’t “overdo it” and moderation is the key. Your topic is about “working out hard”…and that means using as much energy as possible (my interpretation). If you overdo it, it could set you back some, but if you start out slow…it’d be best. I’m happy you are starting to feel better; for me I noticed I was really “gassed” for the first month or so. Don’t go on any 30 mile runs or anything!