NuMetrex sports bra: Electrodes knitted into fabric take pulse

In our health-conscious age, runners like me are advised to monitor our heart rates so we get the most out of our workouts without overdoing it. But I haven't ever felt like strapping on extraneous hardware to keep tabs on my pulse.

The new NuMetrex sports bra has the answer: Woven into its fabric are tiny electrodes that can detect heart rate and display the result on a watch.

The bra, made by Textronics Inc. with components from Polar Electro Inc., is easy to use; just snap a transmitter into a pocket located in the band of the bra, activate a digital watch with a heart-monitor setting, and start sweating.

After about five minutes of running, the transmitter picked up my heart rate. If I didn't want to wait those five minutes, I just moistened the inside of the band with water before I started, the same way you would for the kind of plastic monitor you strap around your chest.

The $75 NuMetrex sports bra and transmitter works similarly to those plastic strap -- on heart monitors, but the benefit of the bra is comfort; no plastic touches your skin, it feels like any other sports bra, and you don't have to worry about the transmitter shifting, chafing or loosening.

The electrode sensors are knitted into a few inches of fabric in the band. These sensors pick up the heart's electrical signal, which is sent to the transmitter snapped into the band. The transmitter, about the size of a matchbook and hidden in the bra's seam, communicates with a watch or the display on a treadmill. All this is designed to help you maximize your fat burning and stamina without wearing out your body.

The American Heart Association pegs your target exercise zone from 50 percent to 75 or 85 percent of your maximum heart rate, which you calculate by subtracting your age from 220. For example, a healthy 23-year-old should be aiming from 99 to 167 beats per minute. (Of course, these are just basic guidelines. You should ask your doctor or trainer for a more thorough exercise plan.)

Product testing

I don't have many complaints about the NuMetrex bra; for the most part, it was great. However, out of the dozen or so times I ran with it, the bra worked spottily on two occasions: once when it was right out of the box and once after its first visit to the laundromat.

The transmitter sometimes lost the signal, apparently because the band wasn't staying sweaty enough. After the second trip through the washer and dryer, I avoided the problem by making sure I wet the band thoroughly before using.

Interestingly, whenever I rinsed the bra out and hung it up to dry, I had no sweat-activation problems the next day.

The company has tested the bra's durability through 100 washings; it's possible it lasts longer than that, but be ready to replace it after a couple of years if you wash it once a week.

The embedded Polar transmitter has an average battery life of 2,500 hours of use (about 20 years if you're exercising a half-hour from four to five days a week). Just don't forget to snap it out of the bra when you do your laundry.

Is it worth buying?

So is the NuMetrex bra worth buying? Yes, if you like running outdoors. Because most treadmills and elliptical machines nowadays have decent hand sensors to monitor your heart rate, it may not be worth it for gym rats.

The product isn't cheap, but it's not a bad deal for a specialty sports bra. The bra itself is $45, and the transmitter (made by Polar) is an extra $30, the same total cost of buying a strap-on transmitter from Polar for $40 and a $35 sports bra.

What does make a big cost difference is the watch you buy. I'd recommend shopping around.

If your needs are basic, go with the simplest Polar watch that is available with the NuMetrex package. It costs an extra $40 (about a $20 savings from the retail price) and worked fine. You can also get another package including a Polar watch with more features, such as a calorie counter, for an extra $70.

Depending on how serious an athlete you are and how much money you're willing to spend, there are fancier watches out there with even more features, better displays and more comfortable wristbands. The embedded transmitter also should work with any brand of sports watch, such as Reebok, Nike and Timex, that offers heart rate functions using an analog platform (as opposed to digital).

The NuMetrex bra comes in small, medium and large. No underwire versions are yet available, but Textronics said it is developing larger bras for women in need of more support, as well as tank tops with shelf bras.

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