Bicycling

If you're at all like me — and I wouldn't wish such a fate on friend nor foe — the prospect of exercise without competition is no more welcome than a visit to the orthodontist. Whenever I pass one of those mega-gyms and see a roomful of panting treadmill fanatics staring into space and going nowhere in a hurry, I feel vastly superior. If I break a sweat, it's generally with a basketball or tennis racket in hand, and a worthy opponent nearby to potentially humble/humiliate with my cunning and skill. En garde!