A heart-rate monitor eliminates guesswork if you're exercising to improve your cardiac fitness. You can quickly check your heart rate or get a signal when your pulse is outside a predetermined range. The typical monitor consists of a snug-fitting chest strap that contains a sensor and a transmitter that sends heart-rate data to a monitor you wear like a wristwatch. Indeed, most of the monitors serve as a multifunction watch/stopwatch/alarm clock/calendar.

What's available

Brands include Acumen, Cardiosport, Cateye, Freestyle, HEARTalker, Impulse, Mio Polar, and Reebok. In addition to the strap-and-monitor design described above, there are some specialized monitors, including one that "speaks" information through headphones; one that dispenses with the chest strap and picks up your heart rate when you press two fingers on its wristwatch-style monitor, rather like taking your pulse; and one that uses a sensor attached to the earlobe.

The typical monitor costs $80, with prices ranging from about $60 to $130.

Important features

Most heart-rate monitors include several clock functions, such as time, stopwatch, alarm, and date. Other useful features include settable heart-rate target zones, calorie counter, pedometer, and backlight.

How to choose

Performance differences. In our tests accuracy ranged from 89 to 98 percent, which means the least accurate monitor could be off the mark every 10th reading.

Ease of use varies from monitor to monitor, and we found that the more-accurate monitors were also among the easiest to use.

In the strap-and-monitor style design, there was no difference in comfort among any of the chest straps.

The instructions with chest-strap monitors warn that they're susceptible to electrical interference from TV sets or even exercise equipment and other heart-rate monitors. The batteries in some chest straps must be replaced; others cannot be replaced at all.

The monitor that picks up heart rate through fingertip sensors on a watch instead of a chest strap is difficult to use while running. Other problems with the monitors Consumer Reports tested include: instructions that are difficult to understand, difficult setup, monitors that are hard to read while running, and heavy monitors or watches.

Recommendations. Because most heart-rate monitors are in the same price range, look for the functions, weight, and style that suit you best.