My concern with manual labor jobs is not the effect on my body, it's the effect on the mind. Like I said in the previous comment, after a hard day of manual lab

My concern with manual labor jobs is not the effect on my body, it's the effect on the mind. Like I said in the previous comment, after a hard day of manual labor, sure I was tired, but I was mostly bored out of my mind. Moving some heavy object X from position A to position B gets less romantic when you've done it 50 times. Sitting in an office desk for 30 years can't be good for you either, but if it's in a position to keep my brain active (even if my muscles aren't), I'd take that job a thousand times before going back to pure labor. In fact, one of the most memorable parts of those summer jobs was creating a shoulder rest for the 25 lbs bottles to sit on, out of discarded plastic. I honestly can't remember whether it worked at all or not, but I definitely remember being far more interested designing and cutting this piece of plastic than carrying bottles of water.