Can a heart rate monitor get to you to exercise smarter, or more, or both?

Two physical education teachers at Loudoun Valley High School in Purcellville think so, prompting them to acquire 80 high-end heart rate monitors (also known as HRMs) for 10th graders at the school.

"If we just tell kids to go out and run a mile in less than 10 minutes, that can be dangerous," due to differing fitness levels among students, said Kristen Griswold, who created the program with colleague Kevin Barr. "But if we tell them to keep their heart rates in the 150-to-160-beats-per-minute zone when running, that's a lot safer."

The teachers hope the devices will motivate students to exercise regularly, as well as raise their awareness about cardiovascular fitness. Health care provider Loudoun Healthcare donated the devices, citing a desire to lower future health care costs in the community.

Most HRMs consist of a thin elastic chest strap worn against the skin and a wristwatch-like unit that displays data. Loudoun Healthcare spent $20,671 on the high-end monitors, or about $258 each.

Students tested the devices on a running track but will not begin using them regularly until their PE classes resume after the holidays.

"I think they'll help if we decide to train," said Erin Cotter, a 15-year-old gymnast and soccer player. "Most of the kids were really interested." Charlie Schweiger, also 15, agreed that the monitors are nifty, but added, "Some kids aren't into the running part."

A basic monitor tells you how fast your heart is beating, the time of day and not much else. The more advanced the model, the more information conveyed, such as your maximum heart rate (imprecisely but frequently estimated at 220 minus your age in years), your average heart rate for the session, the time you stayed in a certain heart rate range, calories burned, exercise session comparisons and even altitude gained and lost (for example, during a run or bike ride).

In many models -- including the Polar E600, the one used at Loudoun Valley -- details can be downloaded to a computer and converted to graphs to help track long-term progress.

People wear monitors during many kinds of exercise, from running and cycling to weight training, soccer, cross-country skiing and other activities where they want to track their cardiovascular exertion.

For exercisers with modest fitness goals, many of the features of the tricked-out monitors are extraneous. But the basic data -- tracking your current heart rate and average rate throughout a workout -- can help people optimize exercise time by keeping their heartbeat within desired ranges, whether to boost cardio capacity, burn fat or exercise safely with heart disease.

HRMs can also help monitor interval training, in which high- and lower-intensity periods of work are alternated.

You can measure heart rate by taking your pulse, but this may disrupt your exercise and yield less accurate results.

Numerous Web sites that sell monitors advise exercisers about target heart rates. Beginners should exercise at 50 to 60 percent of their maximum heart rate, makers say; regular exercisers should strive for 60 to 70 percent of maximum; those seeking to boost cardio capacity and athletic performance should target the 70 to 80 percent range. More details -- including comparisons of various monitors, prices and direct sales -- can be found at

We'll be online, working at an only slightly elevated heart rate, this Thursday from 11 a.m. to noon at Share your adventures with heart rate monitors, or ask any fitness-related question.

-- John Briley

Loudoun Valley High School students try out heart rate monitors.