I just got back from the JCC. My Swimming Month (or two) is going well: at the four-week mark, I've swum full miles in two consecutive workouts. Today, I swam a 400m before taking a break to start, and I swam the last 600m (24 laps) without taking a break. That's a significant step up from Monday's mile, which was 8 sets of 200m laps. I'm down around 7 pounds from the start of the experiment, which has to do with the increased aerobic activity and the fact that we're eating out a WHOLE less, AND the fact that I've basically stopped drinking diet sodas and coffee. (Not entirely accurate; I allow myself one thing per day, whether it's a soda or a cup of coffee. Today was a Starbucks half-caf.) I'm proud of that, and I'm at my best shape right now since... probably before Younger Bro was born, if not earlier.
Another thing to know, as we delve into the topic of exercising while taking care of a pediatric cancer patient, is that I'm an intensely emotional guy. I wear my emotions on my sleeve and have a difficult time restraining them from interfering with other aspects of my life. In high school, I was talking to a buddy of mine about dealing with the frustration of normal life and school and music and stuff. He told me that, when he gets frustrated, he would hit the floor and bang out a couple hundred push-ups. The adrenaline spike of the stress gave his muscles the strength to go beyond their normal limits. I tried his advice the next time I got frustrated; I went from being able to do 40 pushups (my normal limit) to doing about 10. This is a pattern that repeats itself still: if I'm intensely emotional about something, I won't even bother to go to the gym. I know my workouts won't last.
So, here's the issue with being a pediatric cancer parent: there's just no way to exercise on a regular basis. It's a matter of schedule: with another infant at home, my schedule was complex. In the morning, be relieved at the hospital by Mommy and Younger Bro, go to work. After work, run home as soon as possible and do any housework that I need to do (pay bills, etc), including errands. Head back to the hospital and send home Mommy and baby. While at the hospital, it's not possible for me to slip away for an hour plus to exercise. The Boy is too young to leave alone, and his care required a lot of time sitting with him while he sleeps and rests, playing with him while he's in bed or on the playmat, and walking back and forth to the playroom.
Normal life activities is getting up, walking back and forth to the kitchen, the bedroom, the bathroom, etc. In-hospital life means far, far less activity. So, instead of burning normal-life calories, you're burning about 1/10 of that. Combine the inactivity with lack of focused exercising, and it's a dangerous combination.
So, what to do? I found something by the Turbulence Training guys called "10 minute workouts." They are workouts that can be done with no equipment, and they will kick your butt. These can be done in a hospital room fairly easily - just don't forget to NOT touch your face with the hands that touch the ground. I also bought a combination push-up / pull-up bar that's supposed to fit in doorways fairly easily. That would help a lot. Bodyweight exercises like push-ups, pull-ups, sit-ups (don't like them at all), and others (just google "bodyweight exercises" and you'll get a nice list) help a lot. Aerobic exercises are more difficult: jumping jacks, running in place, and similar things are no fun at all and are difficult to do in a small hospital room.
I'd love to be able to say that I used these techniques to keep in shape. I didn't. I went about six months (a little longer, actually) with no exercise at all. Finally, after six months of work, I'm just about at the strength and conditioning place that I was at last summer. I know that it's important to keep exercising going during times of great stress; it's supposed to be a stress reducer and a lifestyle improver. It is. I just couldn't bring myself to do it.
I speculate that, with older kids, it's probably more possible. I wouldn't leave The Boy alone in the hospital until he was old and mature enough to take responsibility for his care (...and even then), at least in the sense of being able to check his medicines and dosages for medical errors. But, it wouldn't be a big deal to exercise at home while waiting for / staying with a sibling that's old enough to sit by himself for an hour, after school. Multiple siblings? I'm blank. You got me there. Good luck.