GLOBAL POSITIONING SYSTEM Bodylink keeps you from running in endless circles

A limitation is the system's need for a line of sight.
By ANICK JESDANUN
ASSOCIATED PRESS
NEW YORK -- Along with packets of barely edible energy gels, I carried a training buddy while running this year's New York City Marathon: a satellite-assisted system for tracking my pace and mileage.
Over the past six months, I've logged nearly 600 miles in four states, Washington, D.C., France and the Netherlands, training with a Global Positioning System transceiver strapped around my arm and a companion digital watch around my wrist.
The Bodylink System, from Timex Corp., comes with a 5.3-ounce transceiver made by Garmin Ltd. The GPS unit tracks and calculates where I've been and sends an FM signal to the Timex watch, which displays how far I've gone and how fast -- or slow, as may be the case.
It doesn't give street directions, but it's nonetheless useful for helping me track training miles along new routes.
I crossed the marathon starting line with two main goals: to beat P. Diddy and to break four hours. The latter meant making sure I averaged under 9 minutes, 9 seconds for each of the 26-plus miles.
Because the course was well-marked, I really didn't need Bodylink's distance feature, which didn't work for the first two miles anyhow as I ran along the lower level of the Verrazano-Narrows Bridge. The system needs a clear line of sight to the sky -- not an issue in Dewey Beach, Del., but quite a problem in cities with tall buildings and bridges.
Slowing down
Because the first miles were off, I didn't know how accurate the average-pace display was. But as 9:03 crept to 9:05, 9:13 and eventually 9:39, the system at least confirmed that I was slowing down.
In other races, when I've had more energy, I've been able to use that data to speed up and compensate. But the Bodylink system couldn't help me this time. I finished more than 13 minutes off my four-hour goal (though still faster than Diddy's).
It turns out my actual pace, calculated after the race, was 9:40, so the system was right on.
The watch reported a total distance of 25.1 miles. Excluding the two inaccurate miles under the bridge, it's within 2 percent of the actual total. A traditional pedometer I carried for comparison was 9 percent off and had required complicated calibration beforehand.
Overall, I found the system much more useful in training than in racing.
Visiting Paris on vacation, for instance, I was able to run to the Eiffel Towel and back, logging it as seven miles without needing to estimate distance from a map. (Non-American runners can choose displays in kilometers.)
Even in New York, I got tired of training along the same measured loops within Central Park. I was able to stray with the GPS unit, at one point even detouring around Wollman Rink to watch crews construct the set for a "Survivor" finale.
Limitations
There are limits to my serendipity, however, and it comes back to the system's need for a line of sight. That eliminates the streets surrounding my midtown office or heavily wooded trails elsewhere. And of course, it won't do you any good indoors.
It also takes several minutes longer in cities for the unit to find satellites and to start working.
The watch gives you three lines of display, with choices among distance, current or average pace, current or average speed, and lap or split time. Heart rate can be included with an optional monitor around your chest.
Average pace and speed are more meaningful. With your arms swinging so much, "current" readings can be way off. The system had me running better than two-minute miles at one point during the marathon -- that's almost as fast as a racehorse.
'Hands-free'
The built-in alarm is great for traveling, and the watch has "hands-free" capabilities, adjusting time and pace calculations when you're taking drink breaks or stopping at crosswalks.
Your arm quickly gets use to the GPS transceiver. It can be clipped to your shorts, though I found the unit kept sliding during runs.
With three AAA batteries, you're promised 12 hours of usage. More often, I got less than 9 hours worth, partly because it's easy to forget to turn the unit off right after all that running. I'd invest in a set of rechargables.
The system sells for $250, and for $50 more you get a heart-rate monitor. The heart-rate monitor along with the watch costs $125.
A small data recorder sells separately for $75. It captures your speed, distance and heart information every three or four seconds, allowing you to transfer the data to your computer. That's more information than most runners want.
The recorder, a preproduction test unit, inexplicably failed at times, including the marathon. At other times, it would get speed and distance but not heart rate. The watch, a retail version, occasionally gave me similar trouble. But no matter.
I liked Bodylink best for its GPS capabilities, so I recommend it even if it could better coordinate with the other units.
And best of all, it lets you gloat as you lope freely past runners who, confined to loops they've measured, are literally running around in circles.