【科普】知道你到底有多健康吗？ Do You Know How Healthy You Really Are? Fat Chance.

Do You Know How Healthy You Really Are? Fat Chance.

By Lenny Bernstein
Tuesday, June 23, 2009
http://www.washingtonpost.com/wp-dyn/content/article/2009/06/18/AR2009061803317.html






I've never paid much attention to the number salad of statistics that experts use to measure fitness. For one thing, I'm convinced that "body mass index" and its ilk were devised by the same people who predict how much money I'll need in retirement: In both cases, it's just too depressing to do the math.

I have a heart rate monitor, but I've never used it. My bathroom scale tells me I'm overweight. I keep track of time and distance in a running log, and I really don't need to know much more.

Nevertheless, when my editor asked me to sort out the confusing array of fitness tests increasingly available to those of us older than 50, I was curious to see what was out there.

Now that I've returned from the University of Maryland's Department of Kinesiology with a thick folder of results and explanations, I will say this: There is a special place in hell for people who suggest that others have their body fat tested.

* * *

The exercise physiology testing lab on Maryland's College Park campus looks much as you would expect. Computers and other equipment share space with a treadmill and stationary bikes in a room of painted cinder block. In a small, curtained area, doctoral student Nathan Jenkins attaches electrodes to my chest, and, later, physician Barbara Albert asks me a battery of questions about my health to make sure it is safe to give me a VO2 max test, which will push me to the brink of exhaustion.

VO2 max measures how well your body takes in oxygen, transports it to your blood, circulates it to tissues and uses it to produce energy. It tests the capacity of your lungs, heart, circulatory system and muscles and is considered the most accurate gauge of aerobic fitness. Seven-time Tour de France champion Lance Armstrong hit 85 milliliters of oxygen per kilogram of body weight per minute, one of the highest scores ever recorded.

After warming up, I stand on a treadmill, wires running out from under my shirt and held to my abdomen by a Velcro strap. They lead to the ECG machine that Albert will use to monitor my heart throughout the test. After fiddling with the equipment and shaving away ever wider swaths of my chest hair so the electrodes stay put, Jenkins and postdoctoral fellow Sarah Witkowski (both of whom look like they would ace this test) fit me with a large plastic piece of headgear. It holds a wide tube that will route my exhalations into plastic bags for analysis.

A clamp is placed over my nose so I can breathe only through my mouth. Jenkins cranks up the treadmill to a 14-degree angle and sets it at 3.8 mph, a brisk walking pace on a sharp incline. Every two minutes, he raises it by two degrees, and when we reach 18 degrees, he increases the speed to 4 mph.

Witkowski has assured me that, as a recreational runner, I should fare well on this test. We would soon find out.

The test begins. Every 30 seconds, the team asks if I can continue. I answer with prearranged hand signals. Witkowski takes periodic blood pressure readings with a cuff attached to my left arm, and Albert monitors my heartbeat and other functions.

After seven minutes and 30 seconds, with the treadmill at 20 degrees, I am a dripping, panting mess, unable to continue another half-minute. My heart rate has reached 164 beats per minute -- almost exactly the average maximum heart rate for my age. Jenkins lowers the treadmill back to zero, and I cool down at a slow walk.

Later Witkowski tells me I have scored 42.2, which qualifies as "very good" for the 51-55 age group on a scale of "poor" (24-27) to "excellent" (greater than 46).

Currently, you can't just call the University of Maryland and ask for a VO2 max test. The time-consuming, labor-intensive exams can cost thousands of dollars. They are mainly sought by elite athletes and conducted by researchers.

But if our overweight society is ever going to get serious about preventing disease associated with sedentary lifestyles and poor diet, people are going to have to stop kidding themselves about how badly out of shape they are. And simple tests are available. Gyms and doctor's offices are full of them. Monitor your pulse and blood pressure. See how fast you can walk a mile. Then do it again, and again, to measure your progress.

"People overestimate how healthy they are," Witkowski says. "What is usually pretty shocking to people when they go through a program like this" is how poorly they fare. "What is equally shocking," she adds, "is how much they improve when they start exercising."

As we all know, cardiovascular fitness declines with age and is influenced by genetics. But it can be improved or maintained with exercise, even into old age. Recently public-health messages have emphasized that exercise sessions need not be long or strenuous to achieve health benefits, and any physical activity, even a series of short workouts, is much better than doing nothing, Jenkins says.

Before the VO2 max test, I met Erik Hanson, another disturbingly fit doctoral student in kinesiology, at a U.S. Department of Agriculture lab about 10 minutes from the College Park campus. There he prepared to measure my body composition with a "dual energy X-ray absorptiometry" (DEXA) scan, the gold standard for determining the ratio of muscle, bone and fat in your body.

He measures my height (71.4 inches) and weight (202.6 pounds, in shorts and a T-shirt), clearly with a thumb on his ridiculously precise scale. I lie on my back on a table, which for three minutes passes back and forth beneath the X-ray machine. There is little danger, Hanson assures me, from the low-energy radiation.

DEXA scans are increasingly used to test women who suffer from, or are at risk of, osteoporosis. By revealing areas of low bone density, they allow doctors to intervene with resistance training, nutrients and drugs, in the hope of preventing fractures, which can be devastating to older people.

Research shows that the body "retains its ability to adapt to the stress" of strength training, even in people as old as 90 to 100, Hanson says. "You can give Grandma a pair of dumbbells," he says. "You can use soup cans."

Predictably, the bone density in my legs is fine, the result of miles of pounding on running trails. In my arms, it is a little low, because I do no strength training. I am reminded yet again that I can't continue this way.

My body fat percentage is another matter. An image of my body appears on Hanson's computer, and he uses a mouse to divide it into six sectors. The shades of gray show not just how much fat I'm carrying, but where it is hiding. Nineteen percent in my left arm, up to 29.3 percent in my right leg. My overall body fat percentage of 26.6 is higher than that of most men my age.

At the end of the morning, I leave with a healthy sense of what I need to work on. But I have to admit that I preferred blissful, self-deceiving ignorance. It's one thing to fight the fitness battle -- and another to take the enemy's measure so thoroughly.

Comments: misfits@washpost.com.