The bicycle is a masterpiece of physics. It harnesses human muscle power directly to that old-time marvel-the wheel-and yields a vehicle more energy efficient than any other devised, ever, by anyone. A human on a bicycle is more efficient (in calo- ries expended per pound and per mile) than a train, truck, airplane, boat, automobile, motorcycle, skateboard, canoe, or jet pack. Cycling is more efficient than walking, which takes three times as many calories per mile. Pound for pound, a person riding a bike can go farther on a calorie of food than a gazelle can running, a salmon swimming, or an eagle flying.
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