An excellent essay or, more precisely, long excerpt from the book Exercised. One quote:
SOMETIMES WHEN I LOOK in the mirror I don’t recognize the grey-haired fellow with a receding hairline who stares back. Happily, I don’t yet feel as old as I look. Aging is inexorable, but senescence, the deterioration of function associated with advancing years, correlates much less strongly with age. Instead, senescence is also influenced strongly by environmental factors like diet, physical activity, or radiation, and thus can be slowed, sometimes prevented, and even partly reversed.
Another:
IN 1966, a team of physiologists in Dallas, Texas, decided to compare the effects of sedentariness versus exercise on health by paying five healthy 20-year-olds to spend three weeks in bed, followed by an intensive eight-week exercise program. The bed rest was ruinous. When they were finally allowed to arise from their beds, the volunteers’ bodies resembled 40-year-olds by many metrics: they were fatter, had higher blood pressure, higher cholesterol levels, less muscle mass, and lower fitness. The eight ensuing weeks of exercise, however, not only reversed the deterioration but in some cases led to net improvements. To the lead researcher, Bengt Saltin, the take-home message was simple: “Humans were meant to move.” Time marches on, however, and to evaluate how aging affects the effects of inactivity, researchers had the bright idea of restudying the same five volunteers 30 years later.
Three decades of typical American lifestyles had not been kind to the original volunteers: they had each gained about 50 pounds, had higher blood pressure and weaker hearts, and were less fit and healthy in numerous ways. But they agreed to be studied once more as they tried to undo the consequences of 30 sedentary years with a six-month program of walking, cycling, and jogging. Fortunately, this second late-in-life exercise intervention helped the volunteers lose about 10 pounds, and, most astoundingly, largely reversed their decline in cardiovascular fitness. After six months of moderate exercise, the average volunteer’s blood pressure, resting heart rate, and cardiac output returned to his 20-year-old level. Many other studies confirm the anti-aging benefits of exercise. But few of them explain why.
