Measuring progress

So, you went to the gym, hopped on a stair-climbing machine and worked to near exhaustion. And, the machine's monitor rewarded you with news you had burned off 400 calories. It can't hurt, you think, to treat yourself to that tempting, 282-calorie piece of apple pie. Don't be so sure, say some exercise physiologists and equipment manufacturers. In reality, the 400 calories may have been only 250. Or 300. Or 500.

The electronic monitors--feedback devices that tell exercisers such things as heart rate, miles pedaled or calories burned--are often imprecise or inaccurate, experts say. "There are no standards set for machines. There are ones that are really accurate and ones that aren't," says Jim Erwin, an exercise physiologist at the Centinela Hospital Fitness Institute in Inglewood, California. Moreover, some monitors are intended only to give approximate readouts.

Americans have responded to the new generation of sophisticated exercise equipment in a big way. Stair-dimbing has increased by more than 500% since 1987 with about 1.8 million regular participants in 1990, according to a recent poll by the Sporting Goods Manufacturers Association. Treadmill use has increased by 300% over three years with about 2 million regular participants in 1990. Cycling and walking are also high on the list of favorite recreational pursuits.

But without industry standards to ensure equipment monitors provide accurate readings, how do exercisers know if the feedback they are getting is right?

"I don't know how the consumer would know," says Jeff Zwiefel, an exercise physiologist with the Exercise for Life Institute, an information bureau sponsored by NordicTrack. "I would base it on the quality and brand name of the product."

Says Michael Hoffman, of Life Fitness Inc., the Irvine-based maker of the Lifecycle Aerobic Trainer and other machines: "There is no 'Federal Trade Commission' for exercise products. It's a self-policing industry at this point. The standards are a result of the integrity of the manufacturers and the increasing sophistication of the buyers of the product."

Exercise experts, however, offer several tips to guide consumers. Feedback devices that give distance, speed, repetitions or time are usually technically uncomplicated and accurate, Zwiefel says. But some devices that give heart rate and calories burned have a larger margin for error.

According to Zwiefel, consumers should ask themselves, does the equipment require you to enter weight, height, age and sex before exercising? If not--or if it only demands one parameter, such as weight--you could be getting a very inaccurate reading. If the machine doesn't allow the user to input any parameters, it is probably pre-set to calculate calories lost by an average-sized person of about 150 pounds. If you weigh 110 or 220, you will get a very rough estimate. But even if you can input height, weight, sex and age, the readout will be approximate. The machines do not compute muscle mass or individual metabolism, both of which affect calorie expenditure.

"It's a plus-or-minus 20% accuracy range for calorie expenditure," says John Bergeron, chairman of Precise International, a manufacturer of exercise feedback devices. "That's a pretty wide range. So it's more of an indication.

People burn calories so differently. You burn more calories if you .have more muscle than someone else, but you can be the exact same height and weight,"

Heart rate readings can also vary tremendously depending on the equipment, studies show. While some machines use heart rate monitors, others have pulse meters. The most expensive type of heart monitor is an electronic device that straps to the chest with electrodes. This device, used by cardiac rehab patients, measures the heart's electrical impulses and is highly accurate, says Bergeron.

Pulse monitors--which include devices that clip to the earlobe or are strapped around a fingertip-rely on optical technology. "This device uses an infrared monitor that senses changes in coloration of the skin," says Bergeron. "When the heart beats, it pushes a flow of blood. The device measures the change in color, The problem is it can move around and give false readings."

While pulse devices may be fairly accurate for light to moderate workouts, they are particularly inaccurate for heavy exercise--such as those raising the heart rate to more than 140 bpm, says physiologist Erwin.

Product reputation and cost may not be good indicators of accuracy. A recent U.S. News & World Report study of 16 heart rate monitors showed price and accuracy were not necessarily related. The findings ranged from one completely accurate device to another off by 11 bpm.

Hoffman, of Life Fitness Inc., says the exercise machine industry has become increasingly concerned about the accuracy of monitoring devices. "People have less and less time to exercise these days. When they go into a club they want to get maximum results in the least amount of time. They need ways to verify what they've accomplished other than just how they feel," he says.