In a cast
A few years ago I broke my ankle joint. To be precise, the fibula broke just above it.
I got a cast and was told to keep my leg high and do nothing for a week. The cast covered my foot and lower leg, but left my toes free.
After that, I got bored and went to work by taxi and train and put my leg on a stool under my desk. Didn't do any exercise at all. Zip. Nada. I figured, the rest of my body won't mind a few weeks of total rest.
By three weeks I got a check up. The bone seemed to be healing slowly and I got a new cast. The doc said that I could now put weight on it, and walk with my cast. And so I did. Must have looked funny, a guy in a cast on a woodland trail. I estimate I did about 25 km every week.
Due to all that walking, by six weeks my cast started to split around my toes, which was good because that way I could roll off my foot a bit better and walk more comfortably. At the check up the doc was satisfied and said I didn't need a cast anymore.
I was very surprised how stiff my ankle joint had become after being immobilized for six weeks! During my walking-in-a-cast-days, it didn't feel stiff at all, but now that it was free, my range of motion was severely limited. There's a very big difference between being in a cast or in a stiff mountain boot!
The day my cast came off, I walked 10 km (on easy pavements). For ankle support I wore light mountain boots with a high shaft. It wasn't painful, but my ankle got rather swollen, so I'm pretty sure I overdid it.
A few days later I had my first PT session. Got massages and exercise instructions to improve the stability and range of motion for my ankle. When I asked about getting back in shape, the therapist advised that I use the rowing machine as much as I wanted, and provided that I didn't overdo it, I could ride a bike and use the elliptical. And so I did.
After reading other rehab stories, I feared that six weeks in a cast would seriously impact my physical shape, but I was pleasantly surprised right from the start. While I had to tone down the elliptical down a notch compared to what I had been doing before, the difference wasn't all that much. I believe that all the walking had had a big impact on keeping my leg muscles from withering away, and my heart and lungs didn't suffer too much from having a rest either.
Forget about gradual. I exercised at very high intensity, doing four or five cardio sessions of 40-45 minutes every week, not counting the warm up and cool down. I also restarted my regular weight training, but for my leg exercises, initially I used only a quarter of the weight I had been using before. On the leg press in particular, I didn't want to put too much weight on my ankle, for fear of breaking it again.
After a few days, I decided to try the stepper, which used to be my favorite machine, and my ankle didn't protest. My therapist was a bit doubtful, but said that as long as I listened to my ankle, it was all right. I pushed hard, and put ice on my ankle after every exercise session to keep the swelling down. But it wasn't painful, so I figured I wasn't overdoing it.
I had an ankle massage twice a week, and I kept on walking regularly.
Over time, I gradually increased the weights for my leg exercises.
A few weeks into rehab, I decided to try the treadmill. No running, just speed walking on a 15% incline. As I wasn't running, there was hardly any impact and my ankle had no reaction to it.
And now for some really good news
After eight weeks of rehab, I was almost back to my former self, except that my ankle was still somewhat stiff. I went off to the mountains, optimistic, but also slightly unsure whether my physical shape would hold up, and if my ankle would give me any trouble. I need not have worried: it would turn out to be one of my best climbing holidays! Mind you, I climbed a whole lot of alpine routes, in heavy mountaineering boots; for climbing in my rock climbing shoes, well, I suppose it would have been possible, but the stiffness in my ankle would have posed a serious limitation.
Still, after six weeks in a cast, eight weeks intensive PT and hard exercising can be enough to get back into alpine climbing.
As for running? Apart from the treadmill, I didn't do that for a long time after. I was afraid that the impact on landing might cause damage to my ankle. That said, I can live without running, as I'm not a hard core runner. It's just one of the things I do to stay in shape so I can enjoy my time in the mountains.
It's three years since the fracture now. My ankle feels the same as the other one, but the range of motion is still slightly less. However, when I'm climbing, be it alpine or rock, I don't feel or notice any difference at all. I don't favor one ankle over the other, in fact, when I'm climbing I'm totally unaware of the difference.
So, good luck on recovery. Keep busy as much as possible while in a cast, and go hard at it during rehab, as long as you don't overdo it. I presume that anything low impact won't be a problem after a stress fracture, but do check with your specialist. Especially with a stress fracture caused by too much running, I fear it's going to take a long time to be able to run without any restraint again, and that part of the rehab will surely have to be slow and gradual. But in the mean time, you can do other types of sports to keep in shape. And you can start rock climbing well before running, because it's low impact - it's just that a stiff foot means you're limited to routes that don't require difficult foot placements. But you can really practice those overhangs now!