The changes come gradually, sneaking up on us while we’re busy doing other things. Perhaps walking up a flight of stairs is more tiring than it used to be. Groceries feel like they’ve gotten heavier over the years. Muscle strain and injury occur more often, and a few hours of yard work or home repair requires days of recovery. Our waistlines grow thicker, flesh becomes doughy, posture slackens and energy flags. We chalk up these symptoms to the process of aging, assuming they are inevitable and attempting to endure them with as much grace and good humor as possible.

It doesn’t have to be this way.

In fact, muscle atrophy, weight gain, declining stamina and the increased incidence of cardiovascular conditions and other chronic diseases are not an inevitable effect of aging. More accurately, they are the result of disuse over time. While it’s true that these effects are noticeable as we age, they occur far more slowly in people who are regularly active. Some research indicates that a physically fit 65-year-old will easily out perform a sedentary 20-something. Exercise is that powerful, and that important.

As living organisms, we will undoubtedly age. But the process is slower and brings much less loss of ability in people who exercise. Those who choose to lead sedentary lives can expect a far different outcome.

• Metabolism decreases by 10 percent, increasing weight and dangerous, disease-friendly fat stores in the body.

• Increased weight gain decreases insulin sensitivity, resulting in a greater risk of developing type II diabetes.

• Increased LDL cholesterol forms plaque in the arteries, which narrows the passage and causes the heart to work much harder.

• Hypertension is 35 percent more likely to develop in people who do not exercise.

• Mortality related to cardiovascular disease is 25 percent higher in people who are sedentary.

The deleterious effects of lack of exercise were dramatically illustrated through an experiment in the 1960s. Researchers at the University of Texas Southwestern Medical School recruited healthy 20-year-old men to participate. The subjects simply spent three weeks resting in bed. Following the period of bed rest, the men’s resting heart rates had increased, blood pressure went up, body fat rose, heart pumping capacity dropped and muscle strength was lost. Physiologically, these young men had developed characteristics found in people twice their age.

An intensive eight-week exercise regimen following the experiment not only restored the subjects back to their original physical condition, but improved them considerably.

The same group of men returned for a follow-up study 30 years later. They showed the expected physiological characteristics of middle-aged people who have not been diligent about fitness: weight gain, high fat ratio, high resting heart rate and hypertension. The men began a six-month exercise program. When it concluded, the subjects’ physiology and performance capability had returned to baseline levels recorded when they were in their 20s. Six months of exercise had reversed 30 years of aging.

Loss of ability is not the only downside of taking it easy. Statistics gathered during the last 50 years consistently show that people who remain sedentary suffer a higher incidence of heart disease, hypertension, stroke, diabetes, obesity, osteoporosis and even cancer.

Beyond the Obvious

We know exercise is good for us, but why, exactly, is it so? Harvard University summarized the most relevant research findings on the specific effects of exercise. Among them:

• Exercise improves the cardiovascular system by decreasing resting heart rate, heart stiffness, vascular stiffness, lowering blood pressure and increasing the heart’s maximum pumping capacity. It also decreases thickness of the blood, all of which makes the heart stronger and more efficient, while making its job easier to accomplish. The effects of being sedentary are exactly the opposite.

• Metabolism slows with age, but exercise increases it, while reducing body fat, regulating blood sugar and insulin levels, and lowering dangerous LDL cholesterol while increasing beneficial HDL cholesterol.

• The skeletal and muscular systems benefit from exercise, too. Muscle mass and strength increase over time, which in turn builds stamina and reduces the risk of injury. Bones benefit from increased calcium content and strength, reducing the risk of osteoporosis and decreasing the likelihood of fractures.

• Even our neurological functions are improved through exercise. Physical activity slows the loss of nerve conduction and reflex speed associated with aging, improves quality of sleep, reduces risk of depression, and reduces memory lapses and other cognitive decline.

• Heart health drastically improves with exercise, even for those who have already developed cardiovascular disease. People who are regularly active are 45 percent less likely to experience cardiac-related incidents in their lifetime, and some research suggests that exercise may even improve cardiac event-free survival in coronary patients better than angioplasty.

Reaping the Benefits

Research at Harvard School of Public Health studied 13,000 subjects and found that those who exercise for five hours a week were 76 percent more likely to age free of chronic illnesses, including heart disease and cancer, than those who worked out only 20 minutes a week. Physical activity in this study was also correlated with less mental and physical impairment.

Even if you have been inactive for a long period of time or have never exercised seriously, you can still reap the benefits of getting fit. The New England Journal of Medicine reported that decreased mortality is documented even among those who were sedentary until mid-life or later. It’s never too late.

The National Institutes of Health recommend that all seniors strive for at least 30 minutes of moderate activity most days of the week. Medical conditions such as arthritis, high blood pressure, diabetes and heart disease may all be improved through exercise, so the presence of these diseases should not be considered a reason not to exercise. However, be sure to see your doctor first to learn if there are specific precautions you should take.

Exercise is quite likely the surest buffer against disease and the only known antidote to age-related decline. An investment of a little time and sweat equity will buy you healthier, higher quality, longer life.

For information on how to get started, see the NIH National Institute on Aging website at www.nia.nih.gov.

Dawn Williams is associate publisher of Senior News 50 and Better and a health writer who is pursuing certification as a fitness trainer with a specialty in senior exercise. More of her health articles can be found at www.CSN50andBetter.com.