Oh for sure! I started walking again a couple months ago when I was still drinking because it helped with anxiety. I would only make it a mile until I was weak and out of breath.
As I racked up more sober days, I noticed I wasn't getting out of breath anymore. Also when I was hungover I would get little heart palpitations when I was exerted, now that does not happen.
After a couple weeks I noticed walking wasn't working me out anymore and I started to shuffle jog, then jog.
A month into sobriety and I jogged a 5K a couple days ago, never in a MILLION years could I have accomplished that hungover. I literally would've passed out.
Quitting was the best thing ever for my fitness!