Hi there I too was a workout a holic - well I'd work out for an hour a day up until diagnosis - I did the elliptical a few times after surgery and during radiation up until it became too much for me - regardless for all except a week when things were the worst - I walked my dog for 30 minutes every day! And did some yoga! do what you can but as it becomes harder to eat your energy level may drop - at that point stick to things like walking for a bit and yoga and deep breathing if you're into that kind of thing - mucositis will hit you when it hits you breathing through your nose isn't a bad idea as - despite the fact that you are not getting chemo - you may have issues with immunity as radiation does a number on your system. Mostly though rads will make you tired. However if you arent taking in enough calories lay off the gym. bulk up now!! Good luck! It's not fun but it is doable... take care