That's been the question on my mind since I started this pool running extravaganza, some 10 weeks ago. My progression has been:
a) 7 weeks of nothing save pool-running and the few other things I could do in the aircast (upper body strength-training, modified pilates, front and reverse planks, and hamstring curls/knee extensions using machines).
b) one week of the above plus the arc-trainer, yoga, and walking.
c) 3 weeks of very carefully reintroducing running and leg strength-training.
So, where do I stand, versus where I came in? Well, I'm a numbers/stats person - here's the numbers/stats.
Fact 1: my resting heart rate has remained in the low 40s throughout.
Fact 2: When I first started the arc-trainer after 7 weeks of nothing but pool running, I was able in short order to crank out slightly less than two hours at an equivalent resistance and RPMs to what I had done before, with my heart rate only about 5 beats per minute higher on average.
Fact 3: On my very first yoga class back, I was able to make it through the full class, including holding my warrior 3 and half moon poses on the bad leg (I was shocked). I noted a slight loss of flexibility (especially in hamstrings and hip flexors), but strength and stability were there.
Fact 4: As of 10 weeks out, I am using the single leg press at a higher weight than I did pre-injury (was 130# for the single leg press before; now it's 145#). I haven't reintroduced barbell squats yet, but that's coming shortly.
Fact 5: After about 3 weeks of running in short dribbles with frequent walk breaks, I'm able to hold ~7:30 pace for 10 minutes without too much effort. In fact, that's what I did yesterday morning. It wasn't intentional -- I was just running by feel and focusing on pushing with my glutes, and was shocked by the pace on my Garmin (which was confirmed by timing a few 400m splits on the track I was running on).
I think I could do a tempo run at about 6:50-7:00 pace right now (no worries, I'm not going to try, just yet), which is not too far off of my pre-injury tempo pace of 6:40.
My fitness feels fine; my main limiter seems to be foot and calf muscular strength. And I've GAINED strength in my hip flexors, resulting in improved running form.
So, in a nutshell, the majority of my fitness seems to have endured (pun intended). Oh sure, I've gained a few pounds (less than 5), lost some flexibility, and my feet and calves need a lot of work. But I am NOT starting at zero, and I don't feel all that far behind. Even better yet, running feels natural, and not strange (as I feared it would).
Wow. The pool running worked. You hope and hope, but you're never quite certain.