Why is physically exerting yourself to the point of exhaustion at the gym good for you but various jobs involving manual labor seem to cause permanent damage in the long term?

Question

Why is physically exerting yourself to the point of exhaustion at the gym good for you but various jobs involving manual labor seem to cause permanent damage in the long term?

In: Biology

Answer 1

1-3 hrs/week with the option to stop if you get injured (and people still manage to get bad injuries) vs 40-80 hrs/week