I wonder if this is a case of building endurance. If your work level doesn't increase dramatically (IE you have to carry say 5 bags of flour, 3 bags of sugar, e

I wonder if this is a case of building endurance. If your work level doesn't increase dramatically (IE you have to carry say 5 bags of flour, 3 bags of sugar, etc. several times a day every day from day 1 to day 3651) you're eventually going to build the right combination of muscle to minimize the expenditure of energy. I know there's a term in exercise for this, but I work in construction so I get about 8 hours of vigorous exercise a day, so I've never been interested in going to a gym and doing more repetitive tasks than my day job and actually cost me money.