Exercise to stay healthy seems a pretty interesting meme of the last 50 years.
You make an assumption that more is always better with doesn't seem to be the case. Recent studies suggest that exercising for 5 hours per week is actually worse than doing 3 hours.
We don't really have a good theory of how exercise provides health benefits.
Ryan Holiday recently wrote:
A winner doesn’t “exercise,” they train in something (martial arts, running, swimming, biking, cross fit, boxing, weights, whatever).
Personally the more I think about the human body the more I get convinced that while the current frame is obviously better than engaging in no physical activity at all, it's still the dark ages of knowledge.
I think it will be very interesting to see how people in 100 years will speak about how people today go jogging on concrete or go to a gym and lift weights in fixed positions and most of the people haven't shown how to do the movement in an ergonomic way.
We don't really have a good theory of how exercise provides health benefits.
That depends on the exercise. The cardiovascular benefits to endurance exercise are very straightforward.
The question is - am I doing enough exercise?
I intend to provide a worked example for you to work alongside with your own calculations and decide if you should increase or decrease your exercise.
The benefits of physical activity are various and this calculation can be done for one or all of them; some of them include: