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Which is more dangerous, aging or inactivity?By: Carol Cruzan
Morton
Kazmer Laszlo thought he was in pretty good shape. The tall, thin engineer had gained 20 pounds since college, but who hasn't put on a little extra by age 50? He felt active just keeping up with four kids and a dog, and coaching his daughter's soccer team on weekends. Then came the 30-year reunion. The researchers behind a landmark 1968 study into the physiological effects of bed rest and exercise wanted to bring Laszlo and four fellow research subjects back to the lab to see how their bodies had weathered the vicissitudes of aging. And what would happen, the University of Texas Southwestern researchers wondered, if the five men were to repeat, three decades later, an endurance exercise program? The surprising answer is that three weeks of bed rest in these healthy men when they were in college had a more profound impact on their aerobic fitness than did three decades of aging. Equally important, the 50-year-old men were able to reverse 100 percent of their 30-year decline in aerobic power with only six months of endurance training. In other words, these five middle-aged men recaptured a measure of their lost youth - within limits. No one recaptured the cardiovascular fitness they achieved after similar training 30 years ago. And all the training in the world won't offset the lifetime of wear and tear on joints, fatty build-ups inside artery walls or other often irreversible effects of aging and lifestyle. Still, researchers around the country were impressed with the comeback of Laszlo and his fellow human lab rats.
''For people in their 50s, only six months of exercise training can substantially reverse what we think of as aging, but what is really inactivity,'' said physiologist William Haskell, professor of medicine at Stanford University. ''It's an important message, even though it's already reasonably established in the scientific literature.''
''On the other end,'' he said, ''it emphasizes the extremely bad effects on biological function of complete bed rest, especially for older individuals who get bed-rested for any reason from the flu to a bad hip by well-meaning care givers. It's important that patients move about as soon as possible.'' Until the reunion, the five men in the Dallas Bed Rest and Training Study hadn't seen each other for 30 years, but they keenly felt their place in medical history as some of the most extensively studied individuals. In the summer of 1966, they had been probed, poked, and bled as researchers first confined them to bed rest so complete they required a wheelchair to go to the bathroom, and then put them through an intensive endurance-training program. The results documented the extremes of human activity. First came the rapid deterioration caused by complete bed rest. Then came the quick recovery and subsequent surge in cardiovascular health with regular vigorous exercise. The study stimulated cardiologists to prescribe cardiac-rehabilitation programs instead of the traditional bed rest for their heart-attack patients. It also presaged some of the deleterious effects of long manned space flight, because extremely low gravity affects bodies much like bed rest. Thirty years later, no single piece of the follow-up study can be called a breakthrough, but it has a special place among exercise and aging research as one of the longest studies of its type ever conducted. Strangely, very few studies on aging and exercise have followed the same normal people through the years. Some studies have tracked the effect of aging on world-class athletes. Most studies of typical people have examined a cross section of different people of different ages, assuming that the average energetic college students of one generation will gradually degenerate into the average feeble elderly folks of another generation. Dallas physiologist Jere Mitchell, a senior author of both studies, doesn't believe that aging is so predictable in individuals. ''Most people become less active as they age,'' said Mitchell, whose 73-year-old creaky knees have forced him to walk daily instead of run. ''The question has always been: What effects are aging per se and what effects are due to less-physical activity? There's a big difference in the quality of life if you drop dead playing tennis at 90 or if you've been in a nursing home since age 60.'' After the original study, Mitchell assumed the impressive results they achieved from endurance training would turn the five college students into lifelong exercisers. Instead, as the years passed, the five men fell back into typically sedentary American lifestyles, with just enough intermittent weight lifting, running and other activities to fool themselves about their declining physical condition. Although the epidemic of obesity in this country is well-documented, Mitchell said he was shocked by the weight gain of most of the returning men. By the time of the reunion and follow-up testing, they had gained an average of 50 pounds and their body fat had doubled. Remarkably, their average cholesterol levels and blood pressures were only slightly higher. In a small consolation, all of the men remained nonsmokers. ''I don't like to pit one risk factor against another, but lack of aerobic fitness is a stronger predictor of mortality than is smoking, high blood pressure, high cholesterol and obesity,'' said epidemiologist Steven Blair, 62, research director at the Cooper Institute for Aerobic Research in Dallas, and a scientific editor of the Surgeon General's report on physical fitness and cardiovascular health. ''It's not only mortality. People who don't preserve their fitness also are more likely to develop hypertension, type-2 diabetes and certain types of cancer,'' said Blair, who has run nearly daily for the past 30 years. The second time around, the men needed six months of exercise to even approach the same fitness level at 50 as eight weeks of training at age 20. Part of this was caution on the part of the researchers. Extensive baseline testing before beginning the exercise program couldn't completely rule out the risk that one of the men might have a heart attack from trying to tackle too much too soon. In the first week, the men exercised twice for 15 minutes, choosing the exercise they preferred. One person jogged. Two people began with walking, but eventually had to speed up to a run to achieve the training goals of the research training program. Another person pedaled the stationary bicycle. The fifth did a combination of walking and stationary cycling. With some individual variations, they gradually increased their exercise times about 10 to 15 percent a week, until they hit the target level of about five hours a week of moderately intense exercise over about five sessions a week. Darren McGuire, a cardiologist at the University of Texas Southwestern Medical Center and the lead follow-up study author, said that the key was always maintaining their target heart rates, which was defined as 75 percent of maximum heart rate. For those with heart-rate monitors, the simple formula is 220 minus your age multipled by 0.75. For those without, it's a level of exercise where you are breathing hard but still can maintain a conversation. As you exercise more, it takes more exercise to maintain the target heart rate. ''It was just like being 19 again,'' said test subject Gregg Hill, a high school science teacher who has continued to run and has lost 45 pounds since the follow-up testing ended five years ago. ''The smell of wild onions in spring came back to me when I was running along the road.'' ''I felt better than I had in a long time, but I think I only made it back to about 30 or 35 years old,'' said Leo Luebbehusen, now a lawyer. The former college football tackle weighed in at 360 pounds at the time of the follow-up study. He, too, has continued to train on a stationary exercise bicycle and recently dropped 45 pounds with the help of a diet. The major way in which the test subjects ''turned back the clock'' is in their bodies' abilities to distribute and use oxygen, a key fuel of any kind of physical work. Even for nonathletes, a steady supply of oxygen to the muscles spells the difference between a walk upstairs seeming easy or leaving them breathless. ''We measured maximum oxygen uptake, which in many ways is the best objective measure of fitness or aerobic power,'' said co-author and physiologist Benjamin Levine, who founded the Institute for Exercise and Environmental Medicine at Presbyterian Hospital of Dallas, where the testing was done. The five men in the follow-up saw about a 14 percent increase in maximum oxygen uptake. As with the others, such improvements in his physical health inspired Laszlo to make lifestyle changes after the 1996 training. He now plays indoor and outdoor soccer several times a week with other people his age and older. And now he jogs with his children. Like Laszlo, cardiologist McGuire also thought he was in pretty good shape when he started the follow-up study. At 29 years old, he wasn't even born the summer of the original study. McGuire had competed in baseball, football and basketball in school, and had continued to play in intramural leagues and pick-up games. ''I realized I had never done any endurance training in my life, with the exception of soccer,'' McGuire said. ''By the end of the study, I was running quite a bit. I decided if these 50-year-old guys can do it, I can.'' |
