“Every man,” wrote satirist Jonathan Swift, “desires to live long, but no man would be old.” The clock ticks for all living things, and with each tick, things change. Exercise can’t stop the clock, much less turn back its hands—but it can slow the tick and keep people healthy and vigorous, with the physiological capacities of much younger individuals.
To see how exercise can help keep you youthful, if not young, let’s compare the ways aging and exercise affect the human body.
Exercise should help keep you young for your age. But does it actually work? The Dallas Bed Rest and Training Study, a unique experiment, found the answer by examining the effects of exercise and its polar opposite, bed rest, over a thirty-year period.
In 1966 five healthy men volunteered for a research study at the University of Texas Southwestern Medical Center. It must have sounded like the opportunity of a lifetime; all the men had to do in the name of science was to spend three weeks of their summer vacation resting in bed. But when they got out of bed at the end of the trial, it probably didn’t seem like such a good assignment. The researchers tested the men before and after exercise, finding devastating changes that included faster resting heart rates, higher systolic blood pressures, a drop in the heart’s maximum pumping capacity, a rise in body fat, and a fall in muscle strength. Twentieth-century American actress Helen Hayes got it right when she said, “Resting is rusting.”
In just three weeks of inactivity, these twenty-year-olds developed many physiological characteristics of men twice their age. Fortunately, the scientists didn’t stop there. Instead, they put the men on an eight-week exercise-training program. Exercise did
Aging Versus Exercise
more than reverse the deterioration brought on by bed rest, since some measurements were better than ever after the training. The 1966 Dallas study was a dramatic demonstration of the harmful consequences of bed rest. It’s a lesson that’s been relearned in the era of space travel, and it’s helped change medical practice by encouraging an early return to physical activity after illness or surgery. And by revisiting the question thirty years later, the Texas researchers have been able to also investigate the interaction between exercise and aging.
All of the original subjects agreed to be evaluated again at age fifty. All five remained healthy, and none required long-term medication. Even so, the thirty-year interval had not been kind. Over the years, the men gained an average of fifty pounds, or 30 percent of their weight at age twenty. Their average body fat doubled
from 14 percent to 28 percent of body weight. In addition, their cardiac function suffered, with a rise in resting heart rate and blood pressure and a fall in maximum pumping capacity. In terms of cardiac function, though, the toll of time was not as severe as the toll of inactivity. At fifty, the men were far below their twenty-year-old best, but they were not quite as bad as when they emerged from three weeks of bed rest in 1966.
The researchers did not ask the fifty-year-old volunteers to lie in bed for three weeks, which could have been hazardous. But they did ask them to begin an exercise program, and they had the wisdom to construct a gradual six-month regimen of walking, jogging, and cycling instead of the eight-week crash course that served the twenty-year-olds so well.
Slow but steady endurance training carried the day. At the end of six months, the men each lost only a modest ten pounds of their excess weight, but their resting heart rates, blood pressures, and hearts’ maximum pumping abilities were back to their baseline level at age twenty. All in all, exercise training reversed 100 percent of the thirty-year age-related decline in aerobic power. Even so, exercise did not bring the men back to their peak performance achieved after eight weeks of intense training at age twenty. The clock does tick, after all, but exercise will slow the march of time.
The Dallas study is new, but it confirms the three-hundredyear- old wisdom of poet John Gay: “Exercise thy lasting youth defends.” Or, if you prefer a modern scientific summary, consider the words of Professor J. N. Morris: “Exercise is a natural defense of the body, with a protective effect on the aging heart.” To slow the aging process, as in all areas of health, exercise works best when combined with good nutrition and medical care . Just ask your doctor, or listen to the Roman poet Cicero: “Exercise and temperance will preserve something of our youthful vigor even into old age.
To see how exercise can help keep you youthful, if not young, let’s compare the ways aging and exercise affect the human body.
Exercise should help keep you young for your age. But does it actually work? The Dallas Bed Rest and Training Study, a unique experiment, found the answer by examining the effects of exercise and its polar opposite, bed rest, over a thirty-year period.
In 1966 five healthy men volunteered for a research study at the University of Texas Southwestern Medical Center. It must have sounded like the opportunity of a lifetime; all the men had to do in the name of science was to spend three weeks of their summer vacation resting in bed. But when they got out of bed at the end of the trial, it probably didn’t seem like such a good assignment. The researchers tested the men before and after exercise, finding devastating changes that included faster resting heart rates, higher systolic blood pressures, a drop in the heart’s maximum pumping capacity, a rise in body fat, and a fall in muscle strength. Twentieth-century American actress Helen Hayes got it right when she said, “Resting is rusting.”
In just three weeks of inactivity, these twenty-year-olds developed many physiological characteristics of men twice their age. Fortunately, the scientists didn’t stop there. Instead, they put the men on an eight-week exercise-training program. Exercise did
Aging Versus Exercise
| Effect of Aging | Effect of Exercise | |
| Heart and Circulation | ||
| Resting heart rate | Increase | Decrease |
| Maximum heart rate | Decrease | Slows the decrease |
| Heart muscle stiffness | Increase | Decrease |
| Maximum pumping capacity | Decrease | Increase |
| Blood vessel stiffness | Increase | Decrease |
| Blood pressure | Increase | Decrease |
| Blood | ||
| Number of red blood cells | Decrease | No change |
| Blood viscosity (thickness) | Increase | Decrease |
| Lungs | ||
| Maximum oxygen update | Decrease | No change |
| Intestines | ||
| Speed of emptying | Decrease | Increase |
| Bones | ||
| Calcium content and strength | Decrease | Increase |
| Muscles | ||
| Muscle mass and strength | Decrease | Increase |
| Metabolism | ||
| Metabolic rate | Decrease | |
| Body fat | Increase | Decrease |
| Blood sugar | Increase | Decrease |
| Insulin levels | Increase | Decrease |
| LDL (“bad”) cholesterol | Increase | Decrease |
| HDL (“good”) cholesterol | Decrease | Increase |
| Sex hormone levels | Decrease | Slight decrease |
| Nervous System | ||
| Nerve conduction and reflexes | Slower | Faster |
| Quality of sleep | Decrease | Increase |
| Risk of depression | Increase | Decrease |
| Memory lapses | Increase | Decrease |
All of the original subjects agreed to be evaluated again at age fifty. All five remained healthy, and none required long-term medication. Even so, the thirty-year interval had not been kind. Over the years, the men gained an average of fifty pounds, or 30 percent of their weight at age twenty. Their average body fat doubled
from 14 percent to 28 percent of body weight. In addition, their cardiac function suffered, with a rise in resting heart rate and blood pressure and a fall in maximum pumping capacity. In terms of cardiac function, though, the toll of time was not as severe as the toll of inactivity. At fifty, the men were far below their twenty-year-old best, but they were not quite as bad as when they emerged from three weeks of bed rest in 1966.
The researchers did not ask the fifty-year-old volunteers to lie in bed for three weeks, which could have been hazardous. But they did ask them to begin an exercise program, and they had the wisdom to construct a gradual six-month regimen of walking, jogging, and cycling instead of the eight-week crash course that served the twenty-year-olds so well.
Slow but steady endurance training carried the day. At the end of six months, the men each lost only a modest ten pounds of their excess weight, but their resting heart rates, blood pressures, and hearts’ maximum pumping abilities were back to their baseline level at age twenty. All in all, exercise training reversed 100 percent of the thirty-year age-related decline in aerobic power. Even so, exercise did not bring the men back to their peak performance achieved after eight weeks of intense training at age twenty. The clock does tick, after all, but exercise will slow the march of time.
The Dallas study is new, but it confirms the three-hundredyear- old wisdom of poet John Gay: “Exercise thy lasting youth defends.” Or, if you prefer a modern scientific summary, consider the words of Professor J. N. Morris: “Exercise is a natural defense of the body, with a protective effect on the aging heart.” To slow the aging process, as in all areas of health, exercise works best when combined with good nutrition and medical care . Just ask your doctor, or listen to the Roman poet Cicero: “Exercise and temperance will preserve something of our youthful vigor even into old age.
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