I got to thinking about this in the shower today.
When I was helping out on the houses last year and the year before, there was a lot of physical labour. We were joking that we should call it ‘dirt therapy’ and charge people $80 per hour to get fit. And, indeed, it did help my physical condition.
I also go to the gym, paying $30/month to use the facilities.
When I exercise, I feel better, am more alert, etc. This implies that in the regular course of my life as an office worker, I don’t otherwise get enough exercise to be optimally healthy. And I do things like run for the bus, etc, instead of driving everywhere.
On the other hand, I read of people doing hard physical work all day and being injured or unhealthy: slaves chained to oars for example. How much of the slaves’ health problems was due to malnourishment, stress, abuse, etc, rather than just a lot of work?
And couch potatoes and other flabby individuals can increase their strength and endurance through a graduated training regime. At the beginning thery can do much less than, say, after a year of workouts.
Is it possible to get too much exercise? Can we tell from looking at human development what the ideal amount of physical work in each day is?