Heart Rate Monitor
GPS Speed-Distance System
This article describes an interesting and
useful device that I use while running -- the
Timex Bodylink® System --
Digital Heart Rate Monitor, GPS
Speed + Distance Sensor, Data Recorder, and Ironman
Data Recorder Watch. (NOTE: "Bodylink"
and "Ironman" are registered trademarks of the
Timex Company; I will use these trademarked names
several times in this article.)
This system consists of several devices that
can be used in various combinations. You
wear these devices while exercising and the system
measures some or all of: time (total, lap,
split); heart rate (max, average, heart rate in or
out of specified zones); speed (pace, fastest
pace, average pace); and distance (set to miles or
km). First, let's establish some guidelines
for this article.
- I am not a fitness expert nor am I an
expert in the topic of training, heart
rate, VOmax (or whatever it is), training
heart rate, and the like. I do know that
one goal of aerobic exercise is to get your
heartbeat up to a "training rate" and hold it
there for a period of time.
- I am a recreational runner and am not
an expert on running. At age 60, my
average pace is 8 min 45 sec per mile -- not
exactly world class. I run five days a
week, 3 - 6 miles per day. For many
years I ran 40 - 70 miles per week and
completed three marathons in 3 hr 35 min - 3
hr 45 min (1988 and 1989 Marine Corps
Marathon, 1990 Honolulu Marathon).
- I am writing this article to describe
my experiences with the system and -- I
hope -- to provide an introduction to the
system for someone who may be planning to
purchase the system. This article is NOT
intended to be a learned treatise on training
heart rate, endurance training, or the Timex
Why the concern about heart rate while
One purpose of athletic training -- running,
biking, kayaking, walking, and anything else that
makes you breathe hard and makes your heart beat
faster -- is to improve your endurance by putting
stress on your heart and lungs -- your
cardiovascular system. Just as muscles grow
stronger if you lift weights or otherwise use the
muscles, your heart and lung
become stronger if you make them work.
One measure of how hard you are making your
heart work is heart rate -- how
fast is your heart beating. To improve
cardiovascular conditioning, you want to get your
heart rate up into the "training zone" and hold it
there for a period of time. There is a formula
that you use to determine your maximum heart rate;
with that number, you then determine "training
zones" -- as you elevate your heart rate, you got
more and more training effect. For detailed
discussion of heart rates and training zones, check out
these websites -- they will tell you more than I
can. There are likely other sites just as
good -- these are some that I found.
Understanding Your Training Heart Rate.
Good basic article, short.
Heart Rate Training. This site is
sponsored by Polar, manufacturer of heart rate
monitor systems for athletes.
Heart Rate Monitors. While this
article discusses heart rate monitors, it also
has an good discussion on training heart rate
and heart rate zones.
- For more articles, use your favorite
search engine and search for "training heart
rate" or a similar phrase.
So -- one point of training is to get your
heart rate up into the training zone -- into the
area where you are improving your cardio-vascular
well-being. And the best way to monitor your
heart rate is by using a heart rate monitor.
This is where the Timex Bodylink® System comes in.
For several months I had read about training heart
rate and heart rate monitors so, in mid-2004, I
took the plunge and purchased the entire Timex
The Timex Bodylink®
Link to Timex Bodylink®
Here is a link to the Timex website section on
Read their information -- it's complete and the
photos are better than mine.
(NOTE: I will not put
mark next to the term "Bodylink" through the rest
of this article -- just remember that "Bodylink"
is a registered trademark.)
The whole thing
The entire Bodylink system consists of four
devices and supporting software. You do not
need all four devices -- I'll address this point
later. Here is a photo of the entire Timex
- Heart Rate Sensor (HRM)
(Timex calls this the "Digital Heart Rate
- Speed + Distance Sensor (GPS)
- Watch/data recorder (watch)
(Timex calls this the "Ironman
Triathlon® Bodylink™ Performance Monitor.")
- Date recorder
How it works -- briefly
The watch is similar to other Timex
watches such as their classic Ironman watch.
It tells time and has other functions -- time,
countdown timer, alarm, and the like. More
important, though, the watch has built into it a tiny radio receiver that
receives data from the HRM and the GPS; it
displays and records this data to measure your
heart rate, distance, speed, and time in various
combinations. The watch has a Summary
Mode that stores the data from your workout.
After you stop your workout, you can put the watch
in the Summary Mode and see your workout data.
The Heart Rate Monitor (more correctly,
a heart rate sensor) straps around your chest just
below your breasts. Your heart beats because
your brain sends
electrical impulses through your nerves to your heart
-- one impulse, one beat. The HR sensor detects these tiny
electrical impulses, thereby counting your
heartbeats. The HR sensor has a built-in radio
transmitter that sends heart rate data to the
watch and the data recorder.
The strap cinches around your chest and is
adjustable in length. On the back of the
sensor are two elliptically-shaped areas with
grooves -- these need to be moistened before you
strap on the sensor. The moisture
causes the sensor to pick up the electrical
impulses that cause your heart to beat -- some
people moisten these sensors with water; I just
lick them with my tongue. The HR sensor
stays turned on all the time, it does not have an
The GPS Speed-Distance Sensor straps
onto your biceps by means of the elastic strap you
see in the photo. The GPS sensor proper is
in a small plastic case. In this photo you
see the case -- the part with the labels -- inside
its rubber outer shell. You can remove the
GPS sensor from the outer rubber shell -- this
removes the rubber shell and the strap -- slide on
the belt clip, and clip it to your waist band.
Note the elliptical object below the word "GPS" --
that's the on-off switch; between the switch and
the word "GPS" is a tiny LED that tells you when
the sensor is turned on and when it is locked onto
the GPS satellites. The
sensor receives signals from the GPS satellites,
thereby constantly monitoring your speed and
distance traveled. Not familiar with GPS --
Global Positioning System?
about it here.
The Data Recorder. This little
device clips onto your waistband and receives the
data being transmitted by the HR sensor and the
GPS sensor. It records that data into a
format that can be downloaded to your computer and
displayed on the software that accompanies the
data recorder. Both devices record
data from the HRM and GPS. The watch
displays the data on the face of the watch.
The data recorder does not have a display -- it
records the data and dumps it to your computer via
a USB cable. You can use both the watch and
the data recorder, or the watch or the data
recorder alone. If you use
the watch alone, you can read your workout data
from the watch in the Summary Mode and enter the
data into your workout log.
Not very good photos -- but --
notice: on the front, a round button above the
words "DATA RECORDER" -- that's the on-off switch.
There is a small LED above the switch to let
you know the recorder is operating -- it flashes
in a unique sequence when it's receiving data from
only the HRM, or only the GPS, or both HRM and
GPS. On the rear view
you see a row of four brass dots
-- this is the connector to which you connect a
USB cable to download data from the recorder
to your computer.
Data recorder with USB cable
Do I need it all?
You do not need all these devices at once.
At a minimum, you need the watch -- after all,
you do want to time your workout, right?
With the watch, you need either or both Heart
Rate Monitor (sensor) and GPS Speed-Distance
Sensor. You can use the HRM by itself, the
GPS by itself, or the two together. The
watch has a Configure Mode and a Display button
that lets you change the data shown on the face of
the watch while you work out. Here is a
photo of the watch during a workout -- note there
are three lines of data displayed with the center
line using larger digits than the other two.
By pressing the Display button, you can move the
data around from line to line -- the charts below
show what data will be displayed with each sensor,
or with both sensors, and the charts show how you
can change the way the data is displayed.
In this view, the top line shows
the heart rate (158 beats per minute), the current
pace (10 min 53 sec per mile), and the distance
covered (1.104 miles)
So, how to use it?
I have the full system -- watch, data recorder,
heart rate sensor, and GPS time-distance sensor.
Here are some important points:
- The watch records data from the sensors
ONLY when it is in the CHRONO mode.
- The watch and the data recorder record
data from the GPS time-distance sensor only
when you are moving.
- The data recorder records data only when
it's turned on.
- This is important: Do not put the
watch in the CHRONO mode until you have turned
on the sensors and the sensors have had a
couple of minutes to start sending data to the
This is what I do to get ready.
- Put on my shorts, socks, and shoes.
- Moisten the sensor elements on the
back of the HR sensor and strap it around
- Put on my shirt.
- Pull the GPS time-distance sensor up
on my left biceps. Do not turn it on
- Put the watch on my left wrist.
- Clip the data recorder into the
waistband of my shorts, in front of my
left hip. Do not turn on the data
Then, I go outside and do my warm-up
stretches. Before I start warming up
I do this:
- Turn on the GPS time-distance
sensor -- it needs a couple of minutes
to get a fix on the GPS satellites.
- Warm up, stretch, walk up to where
I start running.
- Put the watch in the CHRONO mode
and reset it to zero out previous
settings. The watch will start
to search for signals from the sensors
and almost immediately will start to
display your heart rate. DO NOT
START THE STOPWATCH.
As I start to run, I do this:
- Push the on-off switch on the
data recorder and watch to see
that the pilot light comes on.
- Push the start button on the
watch to start the stopwatch
- Immediately start running.
- The watch and data recorder
start recording data from the
Now, this is important.
Remember back up the page where I
showed the various ways that the
data can be displayed? You
can switch the data display and
you can swap the data in the top
line and the middle line (the one
with the big digits) but you can
do this only when the watch is in
the CHRONO mode. So, let's
suppose you have the watch set up
But you want the heart rate to
show in the big digits in the
middle of the display. Just
push the "Display" button to
switch the top and center lines.
Now the watch shows:
When I am finished
running, this is what I do:
As I reach the
point where I stop running, I
reach down and turn off the
data recorder, watching to see
that the pilot light goes off.
This is important -- if you
don't turn off the data
recorder and stop running, it
continues to record data and
you will get corrupt data.
Hit the stop
button on the watch.
After I cool
down and go back inside, I sit
at the computer, start the
Timex software and connect the
data recorder. The
downloads the data from the
if you purchase
the data recorder, it comes
packaged with a mini-CD that
contains the Timex
Trainer® software. This
software stores your workout by
date and displays it in various
graphs and titles. Here is a
screen shot of one view of the
graph shows data collected during
a run. The numbers along the
top are MILES -- 1.1 mile, 2.5
miles, 3.9 miles. Along the
bottom are HRS:MINS -- 00:05,
00:35. Note that I ran 3.9
miles in just over 35 minutes.
The numbers along the right side
of the graph show my heart rate
and the red line charts the heart
rate throughout the run -- note
that at 2.5 miles, approximately
00:22:30, my heart rate was
slightly over 140. The
numbers along the left edge and
the black wavy line plot my speed
in MPH -- note that at the 15
minute mark I was running a little
faster than 6 MPH. I would
like to see the software smooth
out the pace line instead of
showing a jiggly line for pace --
and I wish it would show the pace
in MIN:SEC, not in MPH.
change the data you see on the
screen. Here is a screen
shot of the various choices of
data to display:
Read the instruction manual
The watch comes with a
and detailed instruction manual.
This article has only touched on
the Timex Bodylink system -- you
can find a lot more on the Timex
site. Here are a few random,
How much does it cost?
The system is not inexpensive.
I have right at $300.00 invested
in the system -- shop around for
the best price.
Setting the watch
Here's a neat feature.
The GPS satellites transmit
precise timing data synchronized
to the atomic clocks at the U. S.
Naval Observatory. Every
time you start the GPS
speed-distance sensor and start
the watch in CHRONO mode, the GPS
sensor automatically sets the
watch to this precise time.
Now, is that slick or what?
Who needs it?
For me -- a recreational runner
and a gadget freak -- the system
is a neat gadget and that's about
it. For the serious
competitor -- amateur or
professional -- or for the serious
athlete who wants to sharpen
his/her workouts, this system is
Am I happy with the Timex
Lessons learned while using my Timex Bodylink®
Here are some important lessons learned about
using the Timex Bodylink®
The sequence in which you turn on the
sensors and the watch is important -- but not
fatal if you do it wrong. Let me
When you put the watch into the CHRONO mode, it
searches for a signal from the sensors for one
minute. If you do not have one or both of
the sensors turned on, the watch will not receive
a signal and will stop searching. If one or
both sensors were not sending data, the watch will
not display the missing data because it did not
find the sensor during its one minute search.
If you know the sensor is turned on and want to
make the watch search again, press and hold the
DISPLAY button for more than two seconds, with the
watch in the CHRONO mode, it will start searching
Here's why this is important.
- The heart rate sensor does not have an
on-off switch -- it turns itself on when it
starts seeing heart beat impulses.
- The GPS sensor has an on-off switch.
You must turn it on then it must get a fix on
the GPS satellites before is starts sending
- Remember earlier in this article where
there are three tables showing the information
that the watch will display for the various
combinations of sensors? The watch
must be receiving signals from the sensors to
show the data associated with that sensor.
A couple of days ago, I strapped on the HR
sensor, GPS sensor, and watch. I have my
watch set to show: heart rate, pace,
split time. I put the watch in the
CHRONO mode; I warmed up and walked up to the
point where I start running. As I was
walking to my start point, I turned on the GPS
sensor. When I started to run, I switched on
the data recorder and pushed the START button to
start the watch -- the watch would not display
data from the GPS sensor -- no distance, no pace
-- I thought something was wrong with the watch --
it would display only split time and heart rate
because, during the first minute of searching
(back when I was warming up), I did not have the
GPS turned on, the watch did not find it, so, it
would not display GPS data (speed, distance,
When I got back home and downloaded data from
the data recorder, all my data was there --
because I turned on the GPS sensor before turning
on the data recorder, it picked up all data.
However, because I put the watch into the CHRONO
mode several minutes before turning on the GPS
sensor, the watch had already searched, found only
the HRM signal, and it never did pick up the GPS
After I got back home, I re-read the
instructions and learned that all I needed to do
was hold down the DISPLAY button for more than two
seconds with the watch in the CHRONO mode and it
would have searched again.
So, remember to have your sensors turned on,
make certain the GPS sensor has locked onto the
satellites, THEN put the watch into the CHRONO
The watch must be in the CHRONO mode and
must be receiving data for you to set the data
Recall the place back up on this page where I
show three charts -- each of them shows what data
the watch will display with the HRM only, GPS
only, and with both sensors. You cannot sit
in your recliner and configure the watch to show
the data. To set the data that the watch
- Go outside so the GPS gets a clear shot at
- Put on the HRM, the GPS, and the watch (or
put on whichever sensor you have and the
- Turn on the GPS sensor and wait until the
LED above the on-off switch starts blinking
green, indicating it has a satellite fix.
- Put the watch in the CHRONO mode.
The antenna icon will display, the watch will
search for the sensor signal(s), and when it
has locked onto the signal(s) from the
sensor(s), it will show the data.
- Press and release the DISPLAY button to
cycle through the various display formats,
stopping at the one you want. Once you
have the format in which you want to display
the data, you can press the SET/FORMAT button
to swap the upper line of data and the center
line of data back and forth.
- Now, the data display is set. You
can turn everything off and it will remain
where you set it -- or you can now start using
Changing the battery in the watch takes some special attention
Two points to remember when changing the battery in the watch.
- You must remove at least one of the straps to change the watch
battery. Look at the back of the watch and you'll see how each
strap has a lip that fits down over the metal back of the watch. The
straps are held in by the typical spring-loaded pins that must be removed to
remove the strap. I take off only one strap to replace the battery in
my watch. You need a very fine bladed flat-blade screwdriver to
depress the spring-loaded pin to remove and to replace the strap. It
takes a bit of patience.
- When you remove the metal back of the watch -- look carefully at how the
plate is oriented. Make a sketch if need be. You must put
this metal back plate back onto the watch in the same orientation as it was
when you removed it -- otherwise -- the BEEP function on the watch will
not work -- the watch will be silent -- no hourly chime, no alarm, no button
beep, not a sound.
When you open the back of the watch to replace the battery, take a minute to
study how the battery fits into the watch. There's a thin metal strap over
the battery that you must pry out with a thin knife blade or a very thin
flat-blade screwdriver. The watch takes a CR2025 battery.