Intro
The Polar S625X is Polar's entry into the increasingly competitive pace and distance
monitor market. Polar, which has long deserved its command of the Heart Rate Monitor
business, has not had a pace and distance monitor till now. With this device, Polar
steps into this market with a top notch, although somewhat expensive, tool.
This is a long review, so if you want you can go straight to
How well does it work or to
the summary. [top]
What is it?
The Polar S625X is a top of the line Heart Rate Monitor (HRM). Let's get that out of
the way. You won't find a better HRM anywhere. It is, after all, a Polar. But in
addition to the HRM, you also get a foot pod that you lace into your shoe. This pod
contains an accelerometer, which estimates the distance of each step. This differs
from a pedometer, which simply counts your steps. Because the foot pod actually
estimates the distance of each step, it is pretty accurate even without calibration.
Our tests show that the Polar S625X's accuracy was within 90-95% before calibration
at a variety of paces, on a variety of shoes, over a variety of terrain. (The more
varied the terrain or pace the less accurate the S625X was.) With calibration, accuracy
was generally within 98%, but again, diverse terrain and pacing will throw that off.
A description of the S625X would not be complete without a description of the
Wearlink® chest strap, or heart rate transmitter. The Wearlink® is without a
doubt, the lightest, most comfortable, most flexible, heart rate monitor transmitter on
the market. The electrodes are not embedded in plastic or rubber as with most transmitters,
but are part of a flexible mesh cloth. Anybody who owns a Polar HRM will want to consider
upgrading their transmitter to Wearlink®.
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What do you get?
The Polar S625X box contains the following items:
- Receiver watch (weight = 53 g)
- Wearlink® transmitter chest strap (weight = 64 g)
- S625X foot pod (weight = 74 g with battery)
- AAA battery
- Polar Precision Performance Software CD
- S625X Manual
- Software Manual
- Various warranty and registration cards.
The receiver watch is quite a bit heavier than a normal watch, but only slightly heavier
than other HRM receivers.
You do not get an infrared device for your PC with your S625X, so if your PC doesn't
already have one and you want to use the Polar software, you will need to spend and
about $40 to buy one.
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How do you use it?
If you have used a Polar HRM before, you will have no trouble figuring out
how to use your Polar S625X. If you want, you can take the thing right out
of the box, moisten the Wearlink transmitter and strap it on, put the battery
in the foot pod and the foot pod on your shoe, turn on the foot pod, push
the big red button twice (once to get an initial HR reading and a second
time to start the stopwatch) and start running.
But to get the most out of your investment, you will want to configure your
S625X first. This includes entering basic user information (weight, height,
date of birth, gender, activity level, max HR, and VO2 max), exercise settings
(HR limits, a variety of interval exercise sets, recording rates, and autolap
functions), monitor settings (sound and measurement units), and watch settings
(time of day and date). You need not set all these variables at once. Start
with the basic user information and set the interval and other settings at a
later date.
Calibration
The automatic calibration process is fairly straightforward. Visit Polar's
calibration manual if you wish to see the instructions. Try to run a least
1km during calibration, since the farther you run during calibration, the more
accurate the calibration will be. After you calibrate your S625X, write down
the calibration factor for future reference.
The calibration factor is defined as the ratio of the actual distance traveled
to the uncalibrated distance measured multiplied by 1000. For example, if you actually
ran 1.0 K but the uncalibrated S625X thinks you ran 0.950 K then the calibration
factor equals ((1.000/0.950) x 1000) or 1052. You should also mark on your shoe
exactly where the food pod was located when you calibrated the S625X. If you
wear the foot pod low down my your toe one day, move it high up on the shoe the
next day, you will get different mileage readings, even if you ran the exact
same course on both days.
You can also calibrate the S625X manually, and this is a good idea if you are
not getting the results you want using the automatic calibration method. This is
best done on the surface on which you normally run. Find a stretch of road, if
you train on the road, that is accurately measured. Don't rely on your car
odometer or a treadmill; neither is usually all that accurate. Certified race
courses can be used, but remember the distance you run will probably be greater
than the measured distance. That is because the path used to measure a certified
course cuts all corners, whereas that is not always possible for the people
actually running in the race. Even certified courses that are precisely measured
may have imprecisely placed mile markers. If you have a bicycle with well
calibrated cyclocomputer, then you can use the distance measured by it to
calibrate your foot pod. Once you have an accurately measured place to calibrate
your S625X, run that distance and make note of the distance recorded by the S625X.
Your calibration factor would be
((Actual distance)/(Measured distance)) x 1000 = Calibration factor
or if you have previously calibrated your S625X, the your calibration factor would be
((Actual distance)/(Measured distance)) x (Prior calibration factor) = Calibration factor
A note to those requiring near perfect precision: the calibration factor will vary
between running surfaces, so if you run on concrete some days and on a dirt or gravel
road other days, even if it isn't loose, you may want to record calibration factors
for both surfaces. If you alter your stride at different speeds, your calibration
factor may also vary depending on how fast you are running, so if you insist on
minimizing error, record calibration factors for faster paced and slower paced runs.
A note to vast majority not requiring perfection: calibrate your S625X on the surface
and at the speed you run most of your miles.
If you train in more than one pair of shoes, you may need to calibrate the S625X for
each pair of shoes. Make note of the calibration factor and manually reset the calibration
each time you change shoes. Manually entering a calibration factor into the Polar S625X
takes 15-20 seconds, so this is easily done as long as you have made a mark on your shoe,
positioned the foot pod appropriately, and have written down the calibration factor.
Your calibration factor may also be different from one foot to another. This can be
both frustrating and useful. It is frustrating because now you have one more thing
you need to adjust if you want to wear the foot pod on different feet on different days.
Why would you want to switch the foot pod from foot to foot? You would because the foot
pod weighs 74 grams. That isn't a lot, but it happens to be about the difference between
a pair of light weight trainers and medium weight trainers.
By comparing the calibration factor when you have the foot pod on one foot to that of
having the foot pod on the other foot, you will see if there is an imbalance in leg
strength. Such an imbalance is not uncommon. If one leg is much stronger than the
other, you could be prone to injuries. The difference in the calibration factor from
one foot to the other could also be due to a difference in your stride pattern and not
necessarily due to differences in the length of your stride. If you run with your left
foot facing forward, but the right turns out, then the S625X will think you
are running faster and farther when you have the foot pod on the left foot than it will
when you have the foot pod on the right foot.
Controls
The Polar S625X has four buttons on the side (two on the left and two on the right). Of
course there is also the big red button in the face of the receiver below the display that
Polar users have come to know and love. This red button is well situated and easy to press,
even when you are wearing mittens. Push this button once to get a HR reading and a second
time when you start running. Pushing it again will record a split. You push the stop button,
on the lower left side of the receiver, when you stop your run.
The S625X does have an auto lap feature, so you can get it to automatically record a lap at
an interval you define. Unfortunately, the auto lap and manual lap functions do not work
together. If you set the S625X to trigger a lap every mile, and go for a 1.25 mile warm up,
at the end of which you manually trigger a lap, the S625X will continue to record laps at mile
intervals from when you started your run, not from when you last pushed the lap button. Polar
should rewrite the firmware so the the autolap and manual lap triggers work together.
The S625X does not have an auto-pause feature. It would be nice if the user could set an
option that would cause the S625X to pause when going below a certain speed or when stopping
altogether. The Garmin GPS units have this feature and generally it works well.
The upper left button turns on the back light. This back light never seemed sufficient when
running in the dark. If you have eyes like a cat, you will probably not have a problem.
The two right buttons control what is displayed while running. They act as forward and
back buttons when setting options or reviewing the running history.
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