Checking up on heart rate monitors

Hop on any cardiovascular machine these days and, in addition to the display panel, you’re likely to find metal plates on the handlebars; grip them and your heart rate will pop up on the digital readout.

Those metal plates are sensors for an internal heart rate monitor, increasingly popular in recent years, that’s been showing up on stair climbers, treadmills, elliptical trainers and stationary bikes from companies such as Precor Inc., Life Fitness Inc. and StairMaster Inc. Calculating heart rate during exercise and comparing it with a standard target-heart-rate chart is a popular way to determine whether someone is working at an appropriate level, and these touch-sensitive monitors are a step up from the old-school method of manually taking a pulse. The monitors are also available as chest-strap devices.

But not all experts are convinced of the tools’ usefulness. Though some say the monitors can help people exercise at an optimum level, others dismiss them as unnecessary bells and whistles.

At Gold’s Gym in Venice, many members use the cardio machine monitors, says area manager Matteo Baker. “The better the technology has gotten, the easier it’s become for members to figure it out,” he says. “Consumers nowadays are aware of heart rate, especially when it comes to burning calories, and that’s why they’re demanding it from manufacturers.”

Most machines in commercial facilities have monitors, and higher-end home equipment incorporates them as well. Some newer models are able to pick up signals from chest-strap devices; among those, some machines can adjust the workout intensity to keep the user in the ideal zone.

The monitors integrated into the machines work like an electrocardiogram, which uses sensing devices placed on different parts of the body to measure the heart’s electrical activity. Gripping the metal sensors sends an electrical impulse from the heart into the machine, which then gives a readout.

Exercise physiologists interviewed say the results are generally accurate, even if the machines are used constantly and with different grip strengths. A few things can skew the results, such as dry hands (slightly sweaty hands are actually better conductors), a buildup of dirt and sweat on the sensors, and a low-flying plane overhead. The accuracy can also decrease if the upper body is moving while the sensors are gripped, such as when using an elliptical trainer with movable arms. When upper body muscles are engaged, the movement can distort the signal.

Not everyone agrees that the devices are essential for keeping tabs on a workout. “Perceived exertion is enough for the typical person to know if they’re exercising at a proper intensity,” says Cedric X. Bryant, chief exercise physiologist for the American Council on Exercise. “The ones who need it most are people in cardiac rehab, but they’re going to be in environments where they’ll have monitoring tools anyway.”

Perceived exertion is just that -- how hard you think you’re working based on breathing, and levels of pain or discomfort. Some scientists use a zero to 10 scale, zero being sedentary and 10 being working at a maximal level. Bryant also advises using the “talk test.” If you can carry on a conversation while exercising without gasping for air, then you’re working out at an acceptable pace.

Relying on a numerical heart rate, he adds, may cause people to check only against the target-heart-rate-zone chart on the machine, which most exercise scientists agree is inaccurate. Those numbers are based on averages and don’t account for variations among individuals who may have higher or lower maximum heart rates, risk factors such as heart disease, or are on medication that may affect heart rate. A stress test, given by a physician, can calculate one’s maximum heart rate.

Bryant acknowledges, however, that the heart rate monitors can be useful to hard-core athletes, people training for an event such as a marathon, or to “number-oriented individuals” who like to keep tabs on their workout figures.

Fitness equipment manufacturers and some fitness trainers go even further. They say heart rate monitors are especially useful for those who are new to exercise and need guidelines to keep them from injuring themselves.

And the notion of perceived exertion has its flaws, says Scott Eyler, vice president of sales and marketing for True Fitness Technology Inc., which manufactures cardio equipment with heart rate monitors.

“Most people perceive they’re working hard enough, and say, ‘I’m walking every night.’ But are they walking hard enough to get into their target zone? And as they get in better shape, they’re usually not changing the course or adding weight by wearing a weight vest. They don’t continually push the envelope, where with the heart rate monitor, it teaches you where you need to be.”

People could be undertraining or overtraining and not know it, says Jim Birrell, chief innovation officer of Precor. “If you’re doing an exercise, the minute you throw your upper body into it, your perceived exertion goes through the roof,” he says, even though the body might not be working that much harder.

So if exercise physiologists aren’t completely sold on heart rate monitors for the general population, why do they continue to be popular? “The average exerciser is more sophisticated about what heart rate is, compared to 10 years ago,” says Birrell, “and a larger percentage of users are interested in that information and have a better understanding of what it means.”

People like specific advice, says Carl Foster, a professor in the department of exercise and sport science at the University of Wisconsin-La Crosse. “People like to be told, ‘OK, this is how you do it,’ ” he says. “These are important tools, but you have to know how to use them. For heart rate, you have to calibrate it against your own maximum heart rate.”

Bryant says the monitors have become “a marketing requirement” in an increasingly competitive field. “Customers think the more bells and whistles, the better,” he says. “Companies are going to look for ways to provide other types of biofeedback that people are interested in.” Driving that, he says, are the methods athletes use to chart their progress, such as examining metabolic rates and testing lactic acid levels.

“I wouldn’t be surprised if the manufacturers come up with affordable ways to offer those kinds of feedback on their equipment,” Bryant says.