I can attest to the workout from changing tires. A little while ago (in the 50"s) I changed out 4 tires one day in the living room (in the winter in Montana) using screw drivers and a hammer. Then pumped them up with a hand pump. That was a workout even for a young man.
Another reason is to solve a problem that the tire shop couldn't solve. My back hoe's rear tire kept loosing air so we got a new tube installed by the shop. It kept loosing air slowly needing refilled every month or two. I kept taking it back to them to fix but they couldn't find anything wrong with the tube and began blaming the tire since it's worn. I kept telling them that the tube is what holds the air, not the tire which protects the tube. A long story short, I broke down the tire myself and took in the tube to have it rechecked again. No leak found but I bought a new tube anyway. The rim is 28" and the tube is rated for 18" to 28" because the rubber will stretch that much. That's when I discovered that the tube was almost impossible to slide to the center of the wheel. I managed to move it there using a bicycle tire spoon. That's when I realized what the tire shop had done. They had left the tube by the side and pinched it while putting the tire back on. Just enough to make a high pressure leak because the tube was stretched so much. Now it doesn't leak at all.
I now have a snow tube. No it doesn't leak at all when inflated normally.
Now, breaking down and changing a backhoe tire is a workout.
To keep up the workout, start inviting your neighbors over. They watch, you work.

eace: