But I have a hunch there's further explanation of our obsession with exercise. I suspect that what motivates us even more than a fear of death is a fear of dearth .our era is the first to anticipate the eventual depletion of all natural resources. We see wilderness shrinking; rivers losing their capacity to sustain life; the air, even the stratosphere, being loaded with potentially deadly junk. We see the irreplaceable being squandered, and in the depths of our consciousness we are fearful that we creating an uninhabitable world. We feel more or less helpless and yet, at the same time, desirous to protect what resources we can. We recycle soda bottles and restore old buildings and protect our nearest natural resource--our physical health--in the almost superstitious hope that such small gestures will help save an earth that we are blighting. Jogging becomes a sort of penance for our sins of gluttony, greed, and waste. Like a hairshirt or a bed of nails, the more one hates it, the more virtuous it makes one feel.