As others have said, there's always an adjustment period, and before you know it you'll be doing it without even thinking about it.
When I started at my current workplace five years ago, I was out of shape after spending almost ten years either at uni, or in a succession of office jobs. So going back on my tools as a welder was a massive shock that I wasn't really expecting. But suddenly, six months or so in, I realised that I was finding the work much less physically demanding, which felt really gratifying. I wasn't fit by any means (I never have been), but fit enough to do the work.
Then, 18 months ago I got promoted to a desk job, and I'm fat as shit again. I'd be fucked after a day back on my tools.