I feel moved to comment on parts of R. J. Stove's statement. Maybe later. But at the moment I am more strongly drawn to the pleasures of the mountain bike. There is nothing quite like cranking a mountain bike through the foothills of a beautiful mountain range at sunrise. And the high I get after 1-2 hours of this is qualitatively different from the types of euphoria induced by hiking and running, though these are exquisite as well.
The strenuous life is best by test.