Harvard Men's Health Watch

Moderate exercise: No pain, big gains

America is in the grip of an energy crisis. The rising costs and dwindling supplies of fossil fuels get all the press, but from a medical view the real crisis involves human energy — or the lack thereof. In the United States and throughout the industrial world, insufficient exercise is a major cause of disability and death. In America, it is an important contributor to four of the six leading causes of death: heart disease, cancer, stroke, and diabetes. In all, sedentary living accounts for some 250,000 premature deaths annually. That means about 10% of all the deaths in America are caused by sloth, as are about 23% of our chronic illnesses. It's a staggering burden of illness, death, and expense, and it's all the more tragic because it's unnecessary.

Scientific studies have been documenting the health benefits of exercise for decades, but fewer than 25% of Americans get the exercise they need. What accounts for the gap between theory and practice?

In part, we are victims of our own success. Before the industrial revolution, about a third of all the energy used in American agriculture and manufacturing was provided by human muscles; now, that contribution is minuscule. We don't exercise because we no longer have to.

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