I always tell my wife that I am pretty tired because I was thinking too much, she finds that hard to belive because her job involves moving around and so a job where you sit all day is not tiring.
Now I have the science to prove my point :)
Once she's spent a decade behind a desk, the mere thought of doing anything will sound exhausting to her too. It's unnatural and physically deconditioning. The mind being the only "muscle" you exercise makes its unavailability doubly crippling...it's what gives your physical half its marching orders.
She may be dead on her feet at day's end, but if she saw a car coming at her she'd find the adrenaline to respond and move. Myself, I'd struggle to move past "is that really a car driving down the sidewalk? But cars are supposed to drive on the stre--".
In the past I've done a lot of landscaping work on the side, as well as development remotely. My old man has a landscaping company and obviously needs the help at times.
I gotta say also: if you spend your day cutting/pruning a hedge, cleaning the property up - you actually get to look back at all of that and go "Hell yeah, that looks awesome". I never get that feeling of accomplishment with the dev work. In the past, sure - when I've built something big. But it's just not the same. I can't really explain it more than that.
A couple of years ago I wasn't really paying attention where I was and I was on top of a 10m high Macrocarpa hedge that's... about 120 years old. Anyways, I fell off that straight down on to the footpath. Fortunately there was another (much smaller) hedge in the way that was about 100 years old too and that broke my fall except I parted the hedge so to speak. (We fixed it, wired it up and it grew back together). I managed to get up and walk away, I was very very lucky. Damn though I was wired up so much for the rest of the day, I felt like I could've done 50 marathons!
Since then I have stayed away from doing anything like that - because I am a software engineer really, I just have some skills in landscaping with certain tools but at the end of the day for me personally, getting say an injury from a fall or chainsaw would be devastating to my actual career.
If I spend all day programming (8hr)... I'm really buggered and I simply cannot even brain. Cook dinner? Ugh no. If I mow lawns all day and get home (6-7hr), I'm like "oooh what should I cook for dinner, I'll have this cold beer while I do that and ..." it's like COME ON BRAIN.
A day where I can shut that out and focus on a couple things intensely usually leaves me feeling energized and happy and like I actually did something productive.
I think a good manager tries to keep his team mostly in the second camp, but sadly means spending more of their own time in the first.