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Diving with Cardio Monitor

Thread Status: Hello , There was no answer in this thread for more than 60 days.
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Landlocked Jeff

New Member
Dec 26, 2003
I recently recieved a Polar brand heart rate moitor as a gift. I noticed that is was water resistant to 50m so I took it out free diving. It was interesting to see my heart rate gradually slow down as I dove progressivly deeper but at a certain depth (about 40 feet?) the rate went to zero although I could still feel my heart beating.

Has anyone else tried using a heart rate monitor while freediving? If so, what were your observations? Is there a better model perhaps than the one I'm using?
What model are you using... I have A3 but never went diving with it - afraid that it's not so resistant to water...
It could be that loses tha signal - water and suit, or because of the pressure your lungs get squezed and he loses contact with your body
I have used a heart rate monitor (Timex) and my heart rate drops from about 120 just before a static to 60 in a few seconds. I haven't done any depths yet, and I also haven't measured my heart rate during a long static.

Some practicalities on using heart rate monitors at depth:

Ther'e an M series Polar Heart monitor that will register up to 100m. Most will handle 30m and a few 50m. Of course they're not cheap!

Hints on getting recordings: Don't use the elastic strap; instead tape the monitor on with a good adhesive. Reason being, that the chest compression that occurs with depth will result in the loss of contact with the skin.

It's also a good idea to exhale on the surface before attaching it. If you dive deeper than the chest volume at which you attached you'll aslo probably lose contact, unless you exhale on the surface to about RV and attach it properly. Another alternative to placing the electrodes on the chest is to place them on the back since on the back there is less distortion. You'll also need to cover it up to prevent the negative effects of water turbulence "peeling-off" the monitor as you move through the water. A wetsuit works well, as it tends to "pull" it back onto your chest but it make it difficult to readjust or take-off, etc.

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I have the Polar S120 model. It's rated to 50m. The sensor is completly sealed it's the watch/receiver that will probably be the weak link and leak at depth. But, so far all is dry. I hadn'tconsidered the fact that the sensor might loose contact with my skin at depth because I was wearing a wetsuit and had the band set fairly tight. I'll try to press it against my skin at depth to see if I can get a reading. I'm not going to use the tape until the last resort as I'm a bit on the furry side :). Also I'm going to dive in fresh water to see if that makes a difference.

It was amazing to me how quickly my heart rate dropped at depth compared to simply holding my breath. I wonder if the unit has the ability to measure extremely low heart rates? Perhaps I'll send a note to Polar to see if they have any ideas. The instruction manual says that the unit should not be expected to be accurate in an aquatic environment. It's probably just the wrong tool for the job...
what would be amazing would be a dive watch/computer that measures heart-rate from your wrist (no need for chest wrap)
sort of like a Suunto D3 pimped by Star Trek... now that would be DAKINE!
hey guys, since we are on the subject of heart-rate monitors, i was wondering on which of the locations do you attach the monitor. the areas i have used are color coded. i get a small variation (2-5 beats) in diferent areas. which are is the most reliable?


  • chest monitoring locations.jpg
    chest monitoring locations.jpg
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p.s. im not the guy in the pic...

and does chest hair affect reliability?
More diving with the cardio monitor this past weekend. I found that with the moitor strap a bit tighter the electrodes kept contact and gave good readings even at depth. Quite interesting to watch the affects of depth and cold water on the heart rate. I've dove both fresh and salt water, it seems to work equally well in both.

The Polar monitor attaches around the the chest. The sensors are located just below the right and left pectoral muscle.
naiad said:
I have used a heart rate monitor (Timex) and my heart rate drops from about 120 just before a static to 60 in a few seconds. I haven't done any depths yet, and I also haven't measured my heart rate during a long static.


I also have an IRONMAN 50 laps of Timex ; I use it during my warmup before a comp in static ; but up to now I have used it only as a chrono, which is very useful... ; on the other wrist I use a Timex dive watch with big numbers to be read underwater : I use it during the static comp so that I can know where I am...

In future I might try taking my strap in order to assess my bradycardia during static...
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