Medical Division

IN STRENGTH LIES BEAUTY. FOR BONES, BOTH CAN BE ACHIEVED WITH WEIGHT-BEARING EXERCISE – WALKING, DANCING, RUNNING.

Two decades into the fitness revolution, we take for granted that exercise makes the human machine look, feel and function better. But now, as the baby-boom generation moves into mid-life, another advantage is emerging. A growing body of research is challenging assumption about what happens to bodies as they age. The evidence suggests that an active lifestyle can have a dramatic impact on much of the physical decline – in strength, vitality, disease risk and many other areas – traditionally associated with getting older. That comes as no surprise to some experts. “Exercise is our normal state, the state we’re geared for genetically,” says Dr. John Holloszy, professor of medicine at Washington University in St. Louis. Bodies are designed to be used, and the modern tendency to become less active as we grow older has created a vicious circle: As we move less, our bodies lose function; that makes exercise harder, more challenging, and leads to even less activity.

Of course, exercise doesn’t have the power to prevent all age-related deterioration – it can’t head off failing eyesight or hearing loss, for example. But it can help make the difference between a vigorous old age and a frail one. “There’s no question that a general decline in virtually every biological system occurs as a person ages,” says cardiologist James Rippe, director of the exercise physiology and nutrition laboratory at the University of Massachusetts Medical School in Worexter, “but the speed of that decline can be dramatically showed by staying active throughout life.”

The message seems to be getting through – at least to the ranks of those who exercise the most: Forty-two percent of entrants in last year’s New York City Marathon were 40 or older, up from 22 percent than previous years. But benefits extend to non-competitors as well: Studies show that people of all ages and fitness levels can improve in endurance, strength and flexibility with moderate, regular exercise.

It’s too early to call the research conclusive: Many studies are cross-sectional, meaning they compare groups of people, usually older with younger or active with sedentary. That can highlight differences but does not prove a cause-effect relationship, nor can it show change in one person over time. Longitudinal studies may reveal more – they follow a group for days, months, even years – but controlling for all variables is nearly impossible. Another limitation: The bulk of research has been on men only.

Even so, the evidence is compelling that exercise has a beneficial effect on changes in all parameters of fitness – heart and lung function, muscle versus fat percentage, strength and flexibility, bone health, blood chemistry and psychomotor skills. Here’s what the scientists report:

Keeping the Motor Humming

One of the most heavily studied areas is heart and lung health. Maximum oxygen uptake or VO2 max – the greatest amount of oxygen you can consume when working your hardest – has been shown to decline by about 9 percent per decade in inactive men and women beginning in their mid-20s. Active people have an edge, however: Their VO2 max is greater than that of age-matched sedentary people. Although VO2 max declines with age even among athletes, a number of studies have shown that in active folks it is comparable to that of inactive people 20 years younger. That mean if you work out regularly you’ll probably be able to climb stairs or walk with as much vigor as an inactive person 20 years your junior.

What’s it take? At American College of Sports Medicine (ACSM) meeting, Michael L. Pollock, director of the Center for Exercise Studies at the University of Florida at Gainesville, recommended 20 to 60 minutes of continuous aerobic activity, three to five days a week. While working out, aim for a heart rate at 60 to 90 percent of its age-adjusted maximum (220 minus your age).

Flab and Other Factors

“If you weigh the same at 50 as you did at 25, you may think you have the same body. You don’t,” says Margaret Flynn, professor of family and community medicine at the University of Missouri at Columbia. The percentage of the body that’s made up of fat tends to increase slightly with age – a change that is strongly related to inactivity. In addition, lean body mass (everything that isn’t fat, including muscle, bone and water) is lost as you get older. In Flynn’s 18-year study of 500 men and women, men began to lose lean body mass after age 40, women after menopause.

Loss of lean body mass affects many functions, muscle strength being one of the most significant. Strength is a quality often taken for granted; people don’t realize how much it affects the ability to carry packages, climb stairs, open doors and accomplish a host of other daily tasks. It also permits vigorous exercise with less risk of injury. The evidence suggests that use retards loss of strength. People in physically demanding jobs may remain strong for many years: Researchers at Pennsylvania State University found that coal miners in their 50s and 60s tended to be stronger than their sedentary peers.

Strength losses are partly attributed to the decreasing power of fast-twitch muscle fibers involved in strong, sudden contractions such as those used in sprinting and hoisting heavy objects. The actual number of fast-twitch fiber also decreases with age. For reason not understood, slow-twitch fibers, which play a part in muscle endurance, seem to fare better over time. Muscle endurance declines very little until a person’s 70 or 80s.

Everyday activities are also highly dependent on the flexibility that allows your joints their full range of motion, whether you’re walking the dog or retrieving a book from a high shelf. With age, chemical changes stiffen the connective tissue – the ligaments, tendons and other structures that connect bones and muscles. Inactivity magnifies that tightening by allowing the tissues to become weaker and shorter. Exercise that coaxes joints through their full range of motion – such as regular stretching, dance, gymnastics and yoga – has been shown to improve flexibility in young and old.

Help for “Old” Blood

Blood levels of triglycerides, low-density lipoproteins (LDLs) and total cholesterol – all of which have been shown to increase the risk of heart disease – rise substantially with age. High-density lipoproteins (HDLs) – the so-called good cholesterol because a high ratio of HDL to total cholesterol lowers heart-disease risk – increase only slightly. Exercise appears to raise HDL levels among adults of all ages. Researchers at Washington University School of Medicine found that the ratio of total to HDL cholesterol in 14 male endurance athletes (whose average age was 60) was as low as that for trained runners in their 20s, and 25 to 46 percent lower than that of sedentary men their own age.

Mending the Mind Behind Motion

The complex neural processes that control movement are affected by age, as brain cells shrink and the working of neurotransmitter systems declines. One of the most obvious results is a reduction in speed of response, which affects not only the ability to return a tennis volley but also to drive a car or prevent a fall. It involves both reaction time (how quickly a runner leaves the block or a driver takes her foot off the gas in an emergency) and movement time (how fast the runner covers 100 meters or the driver gets her foot to the brake). Cross-sectional studies suggest that response speed is faster in active than in sedentary older adults. Roberta Rikli, professor of physical education, tested women whose average age was 70 and who had been exercising three times a week for 15 years or longer and found their response times to be almost identical to those of inactive college women.

Balance, which is important in moving efficiently and preventing falls, is associated with both motor skills and muscle strength. In Rikli’s study, the long-active older women scored nearly as well on balance tests as the sedentary college students did.

Latecomers to fitness benefit too: Priscilla MacRae, associate professor of sports medicine at Pepperdine University in Malibu, California, studies a group of 65-year-old women runners and found that even those who hadn’t started exercising until age 50 or 60 showed psychomotor reactions similar to those of inactive 25-year-olds. Exercise may affect an even broader range of intellectual skills: Louise Clarkson-Smith and Alan Hartley of Scripps College in Claremont, California, found that the more active 55- to 91-year-olds were, the better they performed on tests of reasoning, memory and reaction time.

Aerobic exercise seems to be the most effective in keeping psychomotor skills sharp. Robert Dustman of the Veterans Administration Medical Center in Salt Lake City studied previously sedentary adults ages 55 to 70; the group that went through four months of aerobic training improved on a variety of perceptual and motor tasks, while the group that trained for strength and flexibility showed little improvement. The difference could lie in the greater efficiency of an aerobically fit body in transporting oxygen to the brain; that may explain why you feel alert and clear-headed when you work out regularly.

What about Bones?

Few aspects of aging have received as much attention these days as bone loss, or osteoporosis. Rightly so, with the annual 10 to 15 percent who die from complications of hip fracture almost equal to the number of women who die from breast cancer.

Bone loss seems to occur naturally with age: After 35, the average woman loses three fourths of a percent of her spine and arm-bone mineral per year. Following menopause, when the amount of bone-preserving estrogen circulating in the body drops sharply, that rate increases to as much as 2.5 percent a year until about age 65, when it seems to level off at 0.5 to 1 percent. Although there are usually no noticeable effects before menopause, mineral loss makes bones weak, brittle and more susceptible to breaking later.

You’ve probably heard about the suspected link between lifelong exercise and dense bones. Studies by Dr. Peter Wood of the Stanford University School of Medicine indicate that men and women over 50 who have been running for many years have spines that are 40 percent denser than those of a comparable sedentary group. Weight-bearing exercises – such as running, walking and similar activities that put stress on the legs and spine – probably offer better protection against bone loss than activities such as cycling or swimming, which are not performed standing up. But any exercise is better than none, says Everett Smith, director of the biogerontology laboratory and department of preventive medicine at the University of Wisconsin in Madison. Swimming, for example, has been shown to increase bone density in arms and legs. Says Smith, “If a person can’t jog but can swim or ride a bike, then by all means she should swim or bike.”

The Life-Extension Question

It’s possible that exercise not only shows the aging process but also adds years to life. Consider the results of a longitudinal study of women reported by Steven Blair, director of epidemiology at the Institute for Aerobics Research in Dallas, at a meeting of the ACSM: A group of 3,216 healthy visitors to the clinic was followed for eight years; those who were less physically fit had mortality rates four and a half times that of the fitter women. Probably the best-known study linking exercise to longevity was done by Dr. Ralph Paffenbarger Jr. of Stanford University School of Medicine. He tracked 17,000 Harvard University alumni and found that over a 12- to 16-year period, those who had expended 2,000 or more calories a week in physical activity, such as walking, stair climbing and recreational sports, had a 28 percent lower death rate than their less active counterparts did. The gain translated into a welcome 2.15 years of added life.

A caveat: The data also showed that college athletes who quit exercising lived no longer than their sedentary classmates who never worked out. “There’s no lasting benefit to being fit in young adulthood if a person doesn’t stay active,” says Paffenbarger. The good news: College couch potatoes who switch to an active lifestyle reap the same benefit as those who’ve always been active.

A variety of fitness studies support this observation. Not only does regular exercise preserve body function in the young and middle-aged, but also the elderly benefit, even if it’s their first exposure to moving around. “A sedentary person who goes into training can produce a response that may be the equivalent of a 10-year or even a 20-year rejuvenation,” says Dr. Roy J. Shephard, director of the School of Physical and Health Education at the University of Toronto. “I don’t think there’s any form of medication that can match that.”

START YOUR EXERCISE (RUN OR WALK) TODAY IF YOU DON’T AND CONTINUE TILL YOU TAKE YOUR LAST TURN OF LIFE!