If it feels like a strenuous workout, is it?


ANYONE WHO has known the pleasures of a treadmill test -- electrodes on the chest, tubes in mouth, the machine's belt growing faster and steeper -- has seen the Borg scale. Scrawled on a piece of cardboard, perhaps, and held up by a bored lab assistant, it's your lifeline, the only way to tell the people in the white coats how you feel.

Granted, they're counting your heartbeats and collecting your exhalations and maybe even sticking you for blood, so in some important respects they know exactly what you're going through. Still, they use the board to ask on occasion, "How you doing there?" You peer at the scale, numbered six through 20, and you raise a hand to point (remember, your mouth is full): Eighteen, working hard, very hard. Eight, hardly working.

"Ratings of perceived exertion," they are called, following steps laid out in 1962 by Swedish physiologist Gunnar Borg. His reasoning: As your heart rate rises, so does your gut feeling that you're exerting yourself.

Now, 30 years later, in this new age of exercise as life insurance, health mavens have resuscitated Borg: If you feel like you're working hard, you are working hard. And your heart's getting the benefit.

Borg, unfortunately, was wrong. Not for every circumstance, but wrong all the same. Perception, it turns out, is as malleable as modeling clay. Even prisoners of the treadmill can be experiencing one thing and feeling quite another.

In fact, the treadmill trials have shown that perceived exertion is most likely to be at odds with heart rate and other vital signs

in people who are exercising at workaday levels -- as when jogging to stay in shape, for example, as opposed to running a race.

Take, for instance, a test run by Borg's colleague Kent Pandolf, now at the U.S. Army Research Institute of Environmental Medicine. He put volunteers onto exercise bicycles, then turned up the temperature around them. In separate sessions, each man exercised at the same intensity in a chamber heated to 75 degrees Fahrenheit, then 110 degrees, then 130 degrees. It's a known fact: Under heat stress, any human's heart rate rises, and sure enough, the volunteers' did. Yet no matter how hot it got, each volunteer pointed to the same middling number. Though their bodies were working harder, the men didn't feel it.

Look again at the Borg scale. There are 15 points, starting at six. Why not at one? Add a zero to each number -- make the six a 60, the seven a 70 -- and it begins to make sense. Borg saw a direct correlation between heart rate and perceived exertion. A heart rate of 150 prompts a rating of 15. It's a tidy premise, but Borg neglected to account for one thing -- that powerful and impalpable human organ, the mind.

In 1985, sports psychologist William Morgan published a review of researchers' success at influencing metabolism via the mind. In several studies, subjects sitting in chairs were hypnotized into sensing they were exercising at various levels of intensity. Metabolic responses -- heart rate and breathing, in particular -- rose and fell accordingly.

In one study such "suggested exercise" produced an average jump in heart rate of 25 beats a minute. When some of the same subjects then got up and actually exercised at the "suggested" level, their heart rates rose by 42 beats a minute. "In other words," Morgan says, "imagined exercise produced an increase in heart rate that was 57 percent of that following actual exercise."

In another study, Morgan himself gave hypnotic suggestions of light, moderate and heavy exercise to people gently pedaling exercise bicycles. When told the pedaling was becoming more difficult (it wasn't), the subjects rated their effort as harder, and their heart rates and respiration increased.

But hypnotism is hardly the only way to distort perception. People readily fool themselves. In a 1988 study, men classified as "high self-constructors" (they thought highly of themselves) reported significantly lower levels of exertion than did "low self-constructors" -- at equal levels of effort. Macho minds make light work, you could say. In a telling extension of this test, men reported having an easier time when the white-coated observer standing by with a clipboard was not a man but a woman.

In the right company, even fairly strenuous workouts can be made to seem easier. In a 1986 test, subjects rode exercise bicycles -- first alone, then face to face with "co-actors" in cahoots with the researchers. As both pedaled, ostensibly under identical loads, the co-actors put out "low-intensity social information": They took their hands off the handlebars, looked around and smiled comfortably. The real subjects reported exerting themselves less in this case than when they rode alone.

The implications are obvious. If you embrace the new credo and simply "listen to your body," you're bound to hear some tall tales. Even when it seems like you're pushing hard enough to give your heart a decent workout, you could well be falling short. You may feel you're at a vigorous 15 when your heart's actually at a moderate 12.

That said, Gunnar Borg deserves this credit: Neither hypnosis nor personality nor social setting nor anything else, apparently, can lower perceived exertion when exercise becomes truly difficult. When your straining muscles have peppered your blood with lactic acid and your pulse has soared to 170 beats a minute, nothing will come between you and the realization that you're having a rough time. Treadmill tests run over the years by Borg and countless other researchers have proved it.

But what's your pulse doing up there anyway? The exercise JTC heart rate recommended for people in their 40s is down around 120 or so. Take yourself there for 20 minutes three times a week, and you're entitled to call yourself fit.

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