Heart-rate monitors.(Product/Service Evaluation)

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 costs $80 or so. It 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.

Six of the nine monitors we tested use the strap-and-monitor design. Three are specialized. The HEARTalker Advanced Fitness "speaks" information through headphones. The Mio Shape dispenses with the chest strap; it picks up your heart rate when you press two fingers on its wristwatch-style monitor, rather like taking your pulse. And the Cateye Heartbeat Counter PL-6000 uses a sensor attached to the earlobe.

HOW THEY PERFORMED

Accuracy. We asked five men and four women on our staff to test each monitor as they worked out in our fitness center. We connected each tester to a portable electrocardiograph and a heart-rate monitor for a 15-minute workout. We took heart-rate readings about once a minute. The testers tried each monitor at least once. Our aim was to gauge how often the monitor came within five beats per minute of the EKG. That difference means the monitor is more accurate than manually counting pulse beats for 10 seconds, then multiplying by six.

The Acumen Cardio Trainer and the Polar a3 came within five beats per minute 98 percent of the time. The Reebok Studio Trainer reached our five-beat benchmark only 89 percent of the time. According to our tests, that means a monitor like the Reebok could be off the mark in every 10th reading.

Ease of use. Staffers used the monitors in their own workout routines. Overall, the more-accurate monitors were also among the easiest to use. There were no differences in comfort among any of the chest straps.