Review: Polar S625X

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As I've mentioned previously, a heart rate monitor is an essential training tool for endurance athletes. After I lost one HRM in the ocean in Bali and another died on me, I finally decided it was time to buy something new, so I sprung for the Polar S625X.

The S625X is a pretty nice unit with a lot of advanced features including:

  • Five programmable training modes with multiple heart rate limits and interval timers.
  • Polar's new softer and more comfortable wearlink transmitter.
  • Infrared computer interface.
  • Barometric altimeter.
  • Foot-mounted speed sensor.
  • Some automatic fitness detection features that I haven't really tried out yet.

I've had the HRM for a week or so and so far I'm pretty pleased with it. The heart rate feature seems to track better than any unit I've had before (I've seen others that would periodically freak out and read 239 bpm or so and this one hasn't yet). The altimeter is a pretty nice feature. I didn't expect to like it, but it's pretty nice when you're climbing on the bike and want to get an idea how much further it is to the top of the hill.

The big new feature in this unit is the foot pod, which I have mixed feelings about: Either I screwed up calibrating it or I'm running about 5% slower than I thought I was, which is certainly possible but a bit surprising since I've run on timed courses before and generally thought I had a good sense of pace. Even assuming it is accurate, I'm not sure it's really that important to get exact distances, since I generally train by time anyway.

The altimeter makes the watch/receiver pretty thick, but once you have it on you don't really notice it. Same thing with the footpod, which I had originally expected to be annoying but you get used to it fast. You do have to be a little careful how you tie it onto your shoe cause otherwise it can poke into the top of your foot. The other alternative for getting distance measurements is to buy a GPS-based unit like the Garmin 305. I considered the Garmin, but the receiver seems even bigger and clunkier than the Polar (mine weighs 60g versus the 77g reported weight on the Garmin 305) and I worried about having it on my wrist.

The big surprise for me is the UI: traditionally the Polar UIs have been pretty bad, but despite the really large number of features, once you get the general idiom the controls on S625X seem pretty obvious. All-in-all I'm pretty happy with this unit, especially considering I was able to use my 20% off coupon at REI when I bought it (somewhat annoyingly REI doesn't let you use those coupons on GPS units).


I got the Garmin Forerunner 301 for my birthday a couple of weeks ago, not sure the differences with the 305. Previously I had the Timex GPS HRM but it broke.

The Timex had the GPS in a shoulder-mounted unit separate from the watch, which communicated wirelessly with the watch like the heart rate sensor. The Garmin integrates the GPS into the wrist unit. You wouldn't wear the Garmin all day like the usual watch-type HRM, you just strap it on for a run. I keep my regular watch on my left wrist and strap the Garmin on the right wrist.

The negatives on the Garmin are that it is indeed bulky and the velcro strap is not as comfortable as the usual watch strap. However I don't notice it when running. The other thing I don't like, vs the Timex, is that it seems like I can't start it timing and recording until the GPS syncs up, which usually takes about 30 seconds, but sometimes longer on certain courses where I start out in the trees. Plus, it doesn't beep when the GPS syncs (at least, I've never heard it) so I have to keep glancing at it and then start the timer when it does.

However, the HUGE feature of the Garmin is that it uploads all of the run data to the computer. It shows heart rate, pace, elevation, and your course superimposed on a road map. You can scan along with the mouse and it shows you your heart rate or pace at each point, while highlighting your location on the map, so you can see how you were running everywhere along the course. The Timex had no such upload feature so this is a whole new world for me, and I really love it.

The Garmin has some other features, like a map display showing your path while you're running, but it's tiny and has no terrain features so it's not much use. I haven't needed its "create a course back to your starting point" feature, I don't run far enough to get lost. And it has a "virtual running partner" who can pace you; but I run with my dog, which requires a certain amount of flexibility that is unsuited to that kind of clockwork.

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