Garmin HRM-Tri and HRM-Swim Sensors | Full Analysis and Testing


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After a few months in the market, it was time to take a look at the new Garmin HRM-Swim and Garmin HRM-Tri sensors. Garmin was the latest among the major manufacturers to offer heart rate data recording in swimming, so it had the advantage of knowing what the competition was offering, to give it a twist and try to improve it.

In recording heart rate data the first was Polar with the V800 which, together with the Polar H7 sensor (which in addition to sending data via Bluetooth also has a 5Khz analog band capable of transmitting data underwater), already offered not only recording but also being able to view live heart rate data while you were swimming. Then came Suunto and its Smart Sensor which uses a memory recording system similar to what Garmin is now using in its HRM-Swim and HRM-Tri. But unlike Garmin, Suunto includes the Smart Sensor in all Ambit3s that are purchased as a pack with the heart rate sensor.

This time I'm analyzing the sensors that came along with the Garmin Forerunner 735XT that Garmin sent me to do the analysis. As always, after finishing both tests everything will be sent back to them. You know that if you like the work I do and want to help the site, you can buy your HRM-Swim or HRM-Tri via AmazonThere is no extra cost for you, you will benefit from an optimal price and quality of service and you will be doing your bit to pay for the website.

After a lot of training with both sensors underwater I know them perfectly, so I can get wet in the opinion (easy joke). Ready to go then with all the details of both sensors.

How HRM-Tri and HRM-Swim work

The HRM-Tri and HRM-Swim are both traditional pulse sensors. There is only one thing that makes them special, and that is that they have a memory where they record the heart rate data so that, once the activity is finished, they send the data to the watch when transmission is possible. At that time the watch will take care of joining the activity data with the heart rate data and then synchronize a single activity file containing all the data.

This is similar to the operation of the Suunto Smart Sensor, but Garmin did not invent the wheel, but they did innovate in materials, as you will see in the next section.

Both sensors continue to be ANT+ compatible and can be used in the same way as the rest of the Garmin range, so if you want to take the HRM-Swim with you for a running session, that's no problem, except that it won't be very comfortable.

Going back to memory, when you use the sensor it will record the pulse data of the workout and assign a time code to it, as the sensor has an internal clock that synchronizes its time with the clock when you connect and pair it. Therefore the clock and the sensor will record the data separately and, after finishing the workout and before recording the data, the clock will ask the sensor if it has anything for it. In case there is a file available with heart rate data in a time code identical to the activity you just recorded, it downloads it wirelessly and links it to the stored activity.

Not all watches are compatible with these sensors. Although they have swimming mode and ANT+ connectivity, only the latest models of multi-sport watches support it.

  • Supported models (at time of writing): Garmin Fenix 3, Garmin Epix, Garmin Forerunner 920XT, Garmin Forerunner 735XT
  • Models not supported: Although they have ANT+ connectivity, Garmin Vivoactive and Garmin Vivoactive HR do not allow synchronization of swimming sensor data.

Garmin HRM Tri HRM Swim - Preparing watches


Therefore, to make sure you record heart rate data in your swimming training you should follow the procedure you can see below:

  1. Without entering the water, select the activity to be performed (swimming in a pool or in open water) and wait for the watch to find the sensor. You will be able to tell because the heart rate icon stops blinking and remains fixed and, in case you have a heart rate data field, you will see your HR at that moment. If you are already in the water you can put the watch next to the sensor, because at a distance of less than 3 centimeters it is able to receive the signal. But it is important that before starting the activity both devices have greeted each other.
  2. At this point you can start swimming normally, completely forgetting about your heart rate, since you won't see it on the screen. It doesn't matter what you do: pool exercises, series, thousands of meters in open water... All of this is independent of the recording of the data.
  3. When you finish the activity, press the button to pause. You will be on the screen that indicates you can save the activity or discard it. At this point it is important that you are out of the water so that the watch can reconnect to the sensor.
    Garmin HRM Tri HRM Swim - synchronizing
  4. Select save and the watch will search for heart rate data, because having been paired with a sensor with memory before you started swimming you know you now have something to look for. After finding the HRM-Tri or HRM-Swim the download process takes only a few seconds.
    Garmin HRM Tri - Downloading Data

And after synchronizing the activity you will have new data that you didn't have before, the heart rate, and you can combine it with other graphs with which you can compare other variables.

Garmin HRM Tri HRM Swim - synchronized data

Garmin HRM Swim - FC

Garmin HRM Swim - FC

Or the average heart rate at the end of the exercise, as well as a much more accurate calculation of calories burned that in case of not incorporating FC data.

Garmin HRM Tri HRM Swim - Activity Summary

However, there is one thing you should be aware of: If you use external platforms to synchronise your activities (Strava, TrainingPeaks, WKO4, etc.) they are not yet ready to display heart rate data correctly. Garmin is using a slightly different FIT file format, with a more modern version of the ANT+ standard. The other platforms have yet to adapt to this new format, so for the time being you will be limited to Garmin Connect in your analyses.

It is common for you to find that your heart rate is lower than the perceived exertion, especially when compared to other exercises, such as running. Keep in mind that when swimming the position is horizontal, which favors blood flow and allows the heart to pump more blood with each contraction. In addition, the temperature of the water also helps to keep the heart rate at bay, since the body should not act as a thermoregulator.

Typically, the heart rate when swimming will be 15 to 20 pulses lower compared to running, at a similar effort. So swimming at 155 pulses per minute may be equivalent to running at 170-175 pulses. But let's drop the concepts and look in detail at what each of the pulse sensors offer.

Differences between pulse sensors

In the water, the two sensors have the same function. They store the heart rate data in their memory; to transmit it to the watch so that it combines the data to synchronize a complete activity, but there are important differences between them.

To start with, the HRM-Swim is wider. The sensor itself is the same size (and is fixed, cannot be separated from the sensor strap), but the strap of the pool version is wider so that more adhesive material is available.

Garmin HRM Swim - Garmin HRM Tri

The HRM-Swim is coated with a "sticky" material that adheres to the skin, keeping the strap in place even if you push hard on the wall. The HRM-Tri also has some of that material around the electrodes, but a smaller amount. That makes it more comfortable while running or cycling, since the strap is also elastic like the HRM Premium band and doesn't dig into the body.

Garmin HRM Swim - Garmin HRM Tri

Precisely because of this lack of elasticity, HRM-Swim includes three extenders of different lengths, so that you can find the most appropriate one for your thoracic diameter. You must choose one of the three options to place it, and then adjust it accordingly. Only the extender is slightly elastic, as the band is totally fixed.

Garmin HRM Swim - extenders

The HRM-Tri band is standard and can be used without extension, with minimal adjustment until a firm but comfortable point is found, as it is totally elastic. However, it also includes an extender for those with a larger diameter chest profile.

Garmin HRM Tri - Extender

Apart from this, out of the water they are used for very different things, so let's go into detail on each of the sensors so you can get to know them better.

Garmin HRM-Swim

Garmin HRM Swim

First of all, I will talk about HRM-Swim, which is the more specific of the two. The sensor is designed to be used exclusively in swimming pools or open water. Therefore, you cannot use this sensor for any other activity than swimming. Not because it does not work, but because it is not comfortable out of the water.

Unlike any other swimmer's band, the one used by the Garmin HRM-Swim is not elastic. It is made of a sticky material to prevent any movement while swimming in the pool. The sensor will not move out of place no matter what you do in the pool. You can do cartwheels, push yourself hard against the wall, or any other movement you can think of; it will not move out of place. Because the material it is made of is not elastic, it takes a little more effort to find a proper fit. The extender is slightly elastic, which allows for some freedom of movement so you don't feel uncomfortable when you breathe. But once you put it on, you can't turn it around to put the electrodes in a better place. Just the band and you are all one.

In the pool it's a very comfortable sensor, precisely because you know that it won't slip when you make any movement. Even when doing fast series at 1:10/100m with fins and pushing me hard on the wall I managed to move the sensor, and I was trying to do it by all means.

After a few lengths you forget it's there, unlike other sensors such as those from Polar or Suunto (or the Garmin HRM-Tri itself as you'll see below), which are uncomfortable in the pool because you have to keep an eye on it at all times, not because it rubs or is uncomfortable, but because you have to be careful when making the turn or increasing the pace too quickly.

The only thing you have to take into account is that, precisely because of this lack of elasticity, it is possible that after a long training session (more than 1,500m) it will loosen a little and you will have to stop for a moment to get back to your correct size.

As I say, it is designed to be used exclusively when swimming both in the pool and in open water. You could use it in any other activity, but the features that make it comfortable inside the pool can become a real torture running or cycling.

Garmin HRM-Tri

Garmin HRM Tri

The Garmin HRM-Tri combines, in one sensor, the advanced running metrics functions of the HRM-Run sensors along with the heart rate recording function in its internal memory. It is designed for swimming, but unlike the HRM-Swim version it is not intended for use in the pool. Yes, the electrodes are surrounded by some of that sticky material that is present throughout the HRM-Swim band, but it is insufficient to withstand a turn where you are pushing hard from the wall.

Although it depends on how your swimming is in the pool. If when you get to the end of the street you make a simple turn without much impulse you won't have much problem because you won't be generating much force. Swimming this way I have been able to use the sensor in the pool without any movement or sliding problems, that is to say, that the sensor doesn't slip from my chest area and fall down.

But as soon as I try to push myself with a little more force, it doesn't take long to lose the sensor. And of course if I try a turn with a flip and a quick exit (and I'm bad at it) it's very easy to lose it.

There's another factor in the equation, and that's the chlorine and other products that are put in pools. Garmin recommends that if you're going to swim in a pool, you use the HRM-Swim sensor that is properly treated to withstand it, whereas the HRM-Tri would suffer much more. I've swum without any problems, but it's true that I haven't done a long-term test to see how long it continues to work properly. And with a price tag of over $100, I don't think you'll be comfortable using the sensor in a way that isn't recommended by the manufacturer itself.

The Garmin HRM-Tri does its best work in open water swimming, and during a triathlon. Swimming in open water there is no problem with sliding, because with the normal impulse of your strokes and kicks you won't be able to move the sensor. And of course if you wear it under your wetsuit you can forget that any kind of movement, no matter how strong, will affect it.

Garmin HRM-Tri

You can use it in a triathlon, aquathlon or combined training. The sensor will record the heart rate data and when you are out of the water it will work in the usual way. When you finish the race, then yes, it will download the heart rate data from the swimming part.

In addition to the memory, the Garmin HRM-Tri has the same accelerometers as the HRM-Run, so you get advanced racing dynamics in the watches that support it, which today are all the models that HRM-Tri supports.

Garmin HRM Swim - Advanced Career Dynamics


The Garmin HRM-Swim sensor is, without a doubt, the best sensor available for swimming right now. Because in addition to doing what is expected of it (recording heart rate data), it is extremely comfortable. You put it in the pool and forget you're wearing it. You can make all the turns you want with the force you want, and the sensor won't move from its place. Among the different options that exist between the brands (not only the two Garmin options, but what Polar and Suunto offer) it is the best of all and the one you would undoubtedly choose for serious training in the pool.

The Garmin HRM-Tri doesn't have as much magic as the HRM-Swim. It's a more traditional sensor, since it can't use the sticky material all over its surface. But in return it offers all the advanced racing dynamics features you can find in the HRM-Run and HRM-Run 2 sensors. It has some of that sticky material, but it's insufficient to keep the sensor attached to the body in the most aggressive turns. If you make open turns or don't push yourself hard on the wall, it may also be useful for swimming in the pool. And of course, for girls who swim in full bathing suits, you won't have any problems with holding the sensor quite tightly. But always keep in mind that Garmin doesn't recommend this sensor in environments with chemicals.

The question you may have left is about the need for heart rate data from your swimming sessions. It all depends on how seriously you take the swimming segment (if you're a triathlete). If you're the type of person who does it without worrying too much about getting out of the water early and being competitive, I don't think you'll take much advantage of what it has to offer.

However, if you are one of those who like to scratch seconds from any possibility, it can be a good addition to your equipment, especially when it comes to seeing the progression in rhythms for the same heart rate or working on the technique to know if you are sliding better with less effort. This is data that you will not be able to use in the pool while you train, as you will not see it in real time (although if you stop for a moment and put the watch next to the sensor you will be able to consult the data), but when analysing the data with your trainer it can help you to identify when you are sliding better and swimming more economically and, consequently, with the possibility of being faster or saving more energy for cycling and running.

Buy Garmin HRM-Swim and Garmin HRM-Tri

You can buy the sensors separately, depending on which one you're interested in. The Garmin HRM-Swim is less expensive and is actually the more interesting option for training. And if you're serious about swimming training, it's an ideal complement for further analysis and to help you find the right running pace, beyond just being guided by pure sensations.

If you want to analyse your races and see how you performed, or if you want to analyse your open water training and use the sensor for something else, the Garmin HRM-Tri is also a good option. Or if your HRM-Run sensor has broken down, it is obviously better to switch directly to the HRM-Tri. There will hardly be any difference in price and you will have more data in swimming.

Finally, you have the option to buy the complete package, but you may find that it is cheaper to buy both sensors separately than as a pack, because with the lower price that the HRM-Swim usually has individually, it probably compensates more than doing it together.

Thank you for reading and supporting the page!


Operation - 10
Design, finish and comfort - 9
Price - 7



User Rating: 4.32 ( 3 votes)

Eduardo Mateos

I've been surrounded by electronic devices of all kinds for more than 25 years. Using them, testing them, taking them apart and dissecting them. Long distance triathlete: I swim, run and cycle for a long time. Maybe too much.

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  1. Hello.

    I have seen that you can connect Mine to the Forerunner or the Phoenix so that you can see the pulses while you are swimming.

    Doesn't it seem a much better way than the one garmin is taking with the HRM Swim? Firstly because of the great advantage that this way there is data transmission inside the water. You can consult ,you can program trainings according to pulses (similar to how it is done in athletics) ,etc... Secondly, because it always seems more comfortable and less cumbersome to wear a tape on the arm than on the chest.

    1. The optical sensors, at the moment, are not prepared to work under water. I have carried out tests with various types of sensors (Mio, Scosche, Garmin Elevate...) and the data recorded is not precise, very variable.

  2. Hi Eduardo, during all your magnificent post I understand that in the water and with the hrm swim sensor, it is not possible to see the pulses until you finish the session, but at the end of the post you say that if you bring it closer to the pulse meter it could be seen and my question is, if you stop at the end of the pool you can see the reading of the pulses in real time without having to stop the recording of the workout? Thanks

    1. Yes, if you put the watch next to the sensor (or you are out of the water at the height of the sensor) it can receive the signal and display the pulse, or if you have some field as a last lap HR average, display it as well.

  3. Hi, My question is more focused on the duration of the HRM-Tri band. Once you have finished training, if you still have the band on, does it still send data? Do you have to disconnect it from the clock or once the training is over it automatically disconnects? Thank you,

    1. It is the watch that asks the sensor for data, so if it is not recording an activity, that data will not be recorded, even if it has memory.

  4. Hi Eduardo, thanks for the post. When I do a triathlon, in the bike sector I like to look at the screen of my Garmin edge 705. The thing is that I am evaluating the purchase of a Fenix 3 watch with the HRM-Tri heart rate band and I would like to know if it is possible to send the heart rate data simultaneously to the two devices.

  5. I can't find anything anywhere. Does anyone know if it's possible to use two sensors during the same triathlon? I mean, use the HRM-Swim for the swimming section, and then remove it and put the HRM-Run for the bike and run. Having the HRM-Tri there's no longer that problem, but I just have the other two...

    1. Yes, what you have to keep in mind is that you cannot save the activity until you are next to the HRM-Swim, because it will look for the data in the memory of the HRM-Swim.

  6. Hi! Fantastic explanation. My question is if I can have two baths associated with the watch, that is, the one I usually use for Gym and Bike and then the swim version for swimming. It would be with a Fenix 3

  7. Hi, I have the garmin forerunner 910xt, my heart rate monitor band is broken. I'm looking for a new one, and I saw that this brand swims. I'm very interested. Is it compatible with this device?

    1. No, the 910XT cannot download the data stored in memory.
      If you will read out-of-water pulse data because it is ANT+, but not shared for swimming

  8. Hi, I have the Vivo Active 3 and it has the swimming option, it is compatible with the HRM-Tri? Thank you

  9. Hi, Eduardo,
    In your article you talk about how in swimming, the CF zones, with respect to running, are about 15-20 ppm less per minute, but do you know of any test to calculate these zones more accurately than by subtracting 15-20 ppm from the running zones?

    I have searched for the Garmin apps for the clock (Fenix 5) and I haven't seen anything for it. On the other hand, do you know if using the MySwimPro app you can do some test? I have the app and I don't see anything for it.

    Thank you for everything,

  10. Morning!

    I have a question, I have the Forerunner 735XT and I'm happy with it, but I referee basketball (indoors) and I would like to record my activity while I referee, but of course, I can't wear the watch. With some band, could I monitor my heart rate, as well as the distances I travel without wearing the watch (I could carry it in my pocket)?
    Because I imagine that the watch in the pocket doesn't mark very correct distances.

    Thank you very much,

    A salute.

    1. You're just gonna be able to register keystrokes, that's all.

      With an HRM-Tri sensor you can synchronize the pulse data afterwards.

  11. Hi, I have a 935 that until now worked with a Polar H10. Now I have bought a HRM Tri and the heart rate is slightly higher than the H10. Do you have any reference for comparison between chest bands?

    1. I often use both the HRM-Tri and the H10 and the data I get with both sensors is the same, and so it should be...

  12. Hello Eduardo, thank you very much, as always for your detailed review.
    I've been to Garmin for a while now, and I still use Stryd to measure power and other data in my races. Here's my question: I want to start triathlon. Do you recommend that I buy the HRM-Tri and leave the Polar H10 aside? The Stryd gives me the stride data and other data so far. What happens if I buy the HRM-TRI and Stryd cross data and it will be a mess, right? (I wouldn't like to stop using the Stryd because of the power issue). Would you make the change? Thank you very much.

    1. With the HRM-Tri you will have heart rate data during swimming. As for the running metrics you will have both separately, it will simply be a matter of seeing which one you listen to more and have no problem keeping Stryd.

      If you are interested in the FC data in swimming you will have to get the HRM-Tri, if that does not matter to you stay as you are.

  13. Thanks once again for the article. My HRM Run (old black model that came with the Fenix 3) has broken and I was hesitating between HRM Run or Tri. I don't do triathlon as I don't like swimming very much. And therefore I only swim when I can't run or bike either due to heat, lack of time or injury.

    The idea was that for 15 € more I had the same metrics of the HRM Run and podía measure heart rate while swimming. But I almost always swim in the pool and the information you have given that the sensor is not recommended for pool use has been definitive.

    Thank you very much once again!

  14. Hi Eduardo, a very similar question to one from September 8, 2017:
    With the 735xt 1TP10I could swim with the HRM-Swim for the swimming section, and then remove it on the T1 and continue with the optical reader of the watch? Thank you very much!

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