Español Currently all GPS watches (and I would say almost 100% of activity wristbands) incorporate an optical heart rate monitor. But many of you have suspicions on how they work and their reliability; some are true but some are totally unfounded.
The leading manufacturers equip their watches with optical heart rate monitors, sensors that with every new model the brand cares to improve. Those same manufacturers also design and sell chest straps. It's not that they keep selling the old monitors they already offered before OHR became popular, it's that they are making and releasing new versions of those same sensors.
These chest straps can be very reliable during training, but it is not possible to wear them 24/7. Keeping a daily record of our heart rate and knowing our rest heart rate is a key factor in determining the health level not only of those who are athletes, but also of those who aren't.
Monitoring heart rate changes throughout the day can provide valuable information that will help you lead a healthier life and recognize when it's a good time to train and at what intensity.
Optical heart rate monitors and chest straps are the two most common measurement types used in devices today. However, there are differences in the way they are designed and in how they work, and you need to know them to know which one to use depending on what training you are going to do.
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Chest straps
Chest straps have been the most common way to measure heart rate for a long time. However, they have not been without problems.
The common critics they have received has been regarding their comfort. The cheaper models were often made of thick and rigid rubber on which the electrodes were placed. That rubber strap could cause rubbing and burning when running. The more expensive models were somewhat more comfortable, being an elastic textile band with more comfortable electrodes. But despite their better design they could also produce abrasions and burns with use.
The way heart rate chest straps work has nothing to do with their optical homonyms (which we usually carry on the wrist because they are integrated into the watch). The measurement is carried out through a technique called electrocardiography. Basically it's a constant electrocardiogram.
It's a direct method of measurement of what happens in the heart, as it amplifies its electrical impulses. The electrodes (which are those gummy touch areas that you find on your chest strap) are responsible for recording those electrical impulses.
The electrodes must be moistened in order to capture the electrical signal. When we are practicing sports and sweating, we don't need to do anything special to capture the data correctly; but it is for the same reason that it is advisable to wet them when we are going to start training, or we may have problems on cold and dry days.
Therefore, the electrodes pick up the electrical signals, but how do they reach our device? Through the transmitter, which is that "tablet" that we place in the band.
Inside that pill are the electronic components that transmit the signal to the watch, bike computer or mobile phone (usually via ANT+ or Bluetooth). But also the chip that processes the signal it receives from the electrodes and turns it into information that we can understand.
The transmitter simply emits a heart rate figure after analyzing and processing the data it has received from the electrodes. It does this at a rate of 60Hz (that is, once every second).
Powering all this we also find a battery, usually a 2016 or 2032, with a duration of about 8-12 months.
Getting good results from this type of monitors is very simple because there are really not many aspects were we can go wrong. But don't doubt that there might be issues. These are the most common ones:
- The electrodes are dry. If this happens because you are not sweating the electrical conductivity will not be good, so no heart rate recording is done. You can moisten the electrode zone with water or just spit on it.
- Sensor battery is low. Obviously this can affect data transmission due to lack of emission power. Depending on the monitor and its communication, it will usually notify the connected device that the battery is low, no matter if it's connected by ANT+ or Bluetooth.
- Wear down electrodes. Yes, they can also be spoiled and are not eternal. The rubber cracked, or you bent the strap too much damaging the internal wiring.
- Transmission failure because the transmitter broke. Just as the electrodes may get damaged, the transmitter can also do it. It still is a board with electronic components that, like any other electronic board, is subject to breakdowns. Beyond falls or temperature changes, what can usually cause the transmitter to die is a bad seal (from the factory or when changing the battery) that lets sweat inside. That'll kill it almost instantly.
- Interferences. It is no longer common because now communication is digital, but when most of the sensors were analog the simple fact of passing near high-voltage wiring or any signal transmission equipment (telephone antennas, etc.) could disrupt operation.
Bottomline, if you keep the strap electrodes moist and worry about changing the battery every 6-8 months, you'll be doing everything in your power to get good heart rate monitor performance.
Optical heart rate monitor
Currently the optical heart rate monitor is the one we see in 99% of GPS watches or any other wearable. But before we go into specifics let's go to the technical aspects of this matter.
An optical heart rate monitor, whether a watch or external heart rate monitor, uses "photoplethysmography" (or PPG) to obtain heart rate data. To put it very simply and in language that any human being is capable of understanding, optical pulse measurement uses light to measure changes in the tissues where the sensor is placed. These changes occur as blood circulates in the body.
Depending on the number of beats the volume of blood in circulation increases. Everything will depend on how much light is absorbed or how much is reflected. Blood reflects less light, so when there is greater volume of blood in circulation, less light will be returned to the sensor.
That's why optical monitors are built surrounded by LEDs, usually green.
Then there are more complex designs such as the Polar Precision Prime heart rate monitor, which features four optical sensors and four electrodes that confirm that the watch has good skin contact, as well as using more colored LEDs to vary the wavelength.
Different manufacturers have been working the sensors in different ways. Another special case is Apple, which uses green lighting for workouts but has an infrared sensor to record heart rate throughout the day.
It's also possible to estimate oxygen saturation in the blood, but that is a completely different topic that may be interesting for another day.
This technique (photoplethysmography), although we have begun to see it in watches recently, is not new at all. Indeed, on more than one occasion, when you went to the doctor, they put a fingertip pulse monitor to measure your heart rate. The technique used is exactly the same.
Then why hadn't it been adapted to the sport yet? Because until recently this technology worked correctly while at rest and static, but as soon as movements were introduced, the accuracy dropped tremendously.
To alleviate this issue, the devices now use accelerometers to measure the type of movement and intensity as well as other elements (for example, in the case of Polar, electrodes to ensure contact with the skin). Accelerometers identify the movements we perform in space to try to discern whether volume changes occur by your heart pumping blood or caused by movements of your arms.
This is what has changed recently. Now all such data can be processed by the device to estimate your heart rate.
You will see that I have emphasized the word "estimate". That's what I want to make clear to you, unlike the sensor on the chest it is not making a direct measurement, but a series of algorithms try to eliminate "noise" and focus on what it really has to measure: heart rate.
To understand this, it can be said that the sensor on the chest measures the heart rate "live", while the optical heart rate monitor does it "delayed", because it is necessary to work all this data to arrive at a final record.
This is where we find the first issue, since it is necessary to process a quantity of data that is being recorded constantly it is necessary that the device has sufficient processing power to do so and not delay the response of the data. This is why we usually see that optical heart rate monitors take longer to identify changes in intensity during our workouts, for example running intervals.
This is the same reason why they do not usually present problems when recording sports at constant intensity, because what is happening "right now" is the same as what was happening "five seconds ago".
Measurement also depends on which part of the body the sensor is placed. No matter where the device is located, the PPG process is exactly the same. What changes is the movements that occur and also that some areas are better than others for measuring.
Polar conducted a study among the different sensors they have on sale. Considering the Polar H10 chest monitor as their golden standard, the Polar OH1+ optical heart rate monitor could have an error of less than 1% in all activities. On the other hand, the sensor we find on watches ranged from 1% error at rest to up to 13% practicing floorball.
Tips on how to use your optical heart rate monitor
Historically, optical heart rate monitors have had bad press. Those bad opinions have not been without motive, but technology continues to advance and improve. The improvement is slow and progressive, but it's there.
One of the reasons we see improvement is because of the increased data processing capacity we have now. There's nothing in common between the processor we found on a TomTom Runner Cardio to the one used on a Garmin Fenix 6X Pro.
But some tips remind to be told regarding the correct use of optical heart rate monitors:
- Wear the strap tightly
- One finger above the wrist bone
- Centered on the arm, neither higher nor lower
Carrying the device correctly positioned and tight on the wrist, the movement should not be an issue. Here the adjustment is tremendously important.
If you put the strap too hard, it is clear that it will not move out of place, but you can interfere with blood flow and have false data, because blood does not flow naturally into your wrist. And if he's too loose it'll move out of its place.
Basically, firm but without becoming annoying. I personally can put a finger under the sensor by pulling the watch up, and when it comes to workouts I tighten the strap by one hole, and then I'm no longer able to fit that same finger under the sensor.
Finally, it should not be forgotten that there are other factors that can make the measurement more or less accurate. Every person is different and what it works for me may not for you. Body hair, skin tone, tattoos... everything can affect heart rate measurements.
Which one should you use?
It all depends on the type of training and the data you want to get. If you want to have all the data possible and in the most precise way, the chest strap is the option you should choose, especially in workouts with changes in intensity such as HIIT or running intervals.
But the fact is that some people won't find comfortable with straps on the chest, especially women because of sports bras. In that case we can sacrifice some precision at certain times in exchange for greater comfort.
For constant pace long runs you can perfectly rely on the optical heart rate monitor. Usually you will do it at a fairly stable pace so there are no changes in intensity or movements, and in these conditions the optical heart rate monitor is usually just as reliable as the one on your chest.
However, if you go cycling, you have no choice but to opt for the chest strap. The movements and vibrations that occur are totally different from those we find in running or any other sports, so it is common for the algorithm to be confused. Road vibrations or road bumps have nothing to do with typical sports movements, so in most cases an optical heart rate monitor is not the best solution.
In the same way, for strength exercises in the gym the chest strap is a better option because by exerting strength with the arms we can alter the way blood flows. However, in this type of exercise, heart rate data is less important.
It can be important while doing Crossfit workouts, in which case it is better to use the chest strap.
The best heart rate monitors
Well, after all this information and what you have learnt, what do you need? You have quite a few options from different manufacturers.
Best chest straps
As for reliability, they are all very even. In fact I have never noticed differences between different manufacturers, as long as they are reliable. I have had problems with Chinese straps purchased on Aliexpress, even if I use a transmitter of a well known brand.
It's what has happened to me with a 4iiii HR monitor that I used occasionally on the bike trainer with a strap I bought on that site, when it works well everything is fine, but when it goes wrong it blows all the training data.
As for things you need to look at in a chest strap, it will depend primarily on which watch you use.
Connectivity
It's the first thing you need to keep in mind. There are currently two transmission methods: ANT+ and Bluetooth. Depending on the manufacturer of your watch you will have to use one or the other, although it is less and less important because the most modern monitors all incorporate dual ANT+/Bluetooth connectivity.
In fact, my recommendation is to opt for such sensors to ensure compatibility in the future (in the hypothetical change of watch brand), unless you are looking for other types of functions.
Additional features
Heart rate monitors in the chest are not only used to measure heart rate. Its usefulness has been growing over time and it is now common to find HR monitors that provide additional running metrics (Garmin HRM-Run and HRM-Tri) or memory to store heart rate data and transmit it afterwards (Polar H10, Garmin HRM-SIM and HRM-Tri).
We can also take into account the number of simultaneous connections that we want to have via Bluetooth, in case we want to connect to more than one device at a time, for example with the phone and the bike computer.
The best chest straps
Wahoo TICKR X
Revamped for 2020, the Wahoo TICKR X is one of the most complete options you can find on the market for the amount of things it offers: Bluetooth and ANT+ simultaneous transmission (and three Bluetooth connections at once), accelerometer for running metrics in Garmin and a new slimmer design.
The Wahoo TICKR X 2020 is certainly one of the best options to consider.
Polar H10
Right now my favorite heart rate monitor (the one I almost always rely on), as long as you don't need special functions, is the Polar H10. Reasons? A very comfortable strap with a handy clip, dual ANT+ and Bluetooth HR monitor, two Bluetooth channels for transmission to two devices, 5kHz analog band and internal memory for use independently without any other device.
Polar H9
If you want to save a little money and do not need so many features, within the same brand you have the Polar H9. The strap and hook are simpler, it has no internal memory and although it is compatible with ANT+ and Bluetooth simultaneously, it does not have dual Bluetooth band.
But it is true that it will cover the use of the vast majority of users, and if it does so by spending less... then that's a win-win.
Wahoo TICKR
As with the Polar H9, if you don't need so many features (because you basically won't use them), instead of opting for the Wahoo TICKR X you can go for the regular model.
It still offers simultaneous ANT+ and Bluetooth connection (unlimited connections on ANT+ and up to 3 on Bluetooth), but lacks the ability to record to memory nor does it offer running metrics.
The other HR monitor I use regularly, alternating it with the Polar H10. And it's the one that I bring with me in triathlon races.
The main issue with the Garmin HRM-Tri is that it doesn't have Bluetooth connectivity. It broadcasts only via ANT+. Then why is it here? Because if you do triathlon, it's THE HEART RATE STRAP.
And it is because if you look at the starting line of a triathlon (especially medium or long distance) the vast majority of participants will have a Garmin on their wrist. With Garmin's high-end multisport watches, we have access to two important functions:
- Advanced running metrics
- Internal memory on the sensor that synchronizes at the end of the workout (useful for the swimming leg)
Plus, with advanced race metrics, you can access the Garmin Running Power thanks to a Connect IQ app. I'm looking forward to the dual-connectivity version arriving very soon.
The HRM-Dual lacks all the advanced features of the HRM-Tri or HRM-Run, but in return it can boast dual connectivity. It is very similar to the Polar H9 we have seen earlier and, in fact, they sit at very similar prices.
Basically Garmin launched this chest strap for those who want to train using Zwift (syncing via Bluetooth) and also want to record or view training data on their bike computer or watch (via ANT+).
Optical heart rate monitors
Talking about optical heart rate monitors is primarily limited to what you have on your own watch and depends on the manufacturer of the watch. There are external monitors that also use this type of measurement, although this is not something as common as chest straps.
Grading an optical heart rate monitor integrated in the watch as reliable or unreliable is not as easy as saying that one brand's is better than another, for the simple fact that there are other factors that should also be taken into account.
The main one is the weight of the watch. The higher the weight of the watch, the more difficult the heart rate measurement will be, because due to the larger mass it will be easier to move on the wrist. So in that case it's more a question of looking at per watch performance, rather than determining that those of one brand are always superior to those of another.
Of the last watches I've reviewed there have been two with which I have had very good results in while running: Suunto 7 and Apple Watch Series 5. If you notice there is one common denominator in both cases, and it's that they are both smart watches.
Why have they worked so well in these two cases, especially in terms of interval running? Because both have much more powerful processors than what we can find in traditional GPS watches (at the cost of the battery life of the watch), which makes them able to process more data and at higher speed. This means that when comparing the delay in the increase or decrease of heart rate with the chest strap, it is shorter than usual in this type of sensor.
As I was saying, there are external optical heart rate monitors, with several manufacturers offering them: Wahoo, Polar or Scosche, for example. All of them are compatible with ANT+ and Bluetooth, but as special functions they only offer the memory to record workouts autonomously.
The best optical heart rate monitors
Polar OH1+
Another of my favorite monitors that accompanies me in many of my reviews is the Polar OH1+. It's a very reliable sensor (almost par with the Polar H10) that stands out for its lightness and comfort, but also because it allows you to record an activity autonomously very easily. Simply by double-clicking the button it has it will start recording, and then you can download it to your phone. If you only want the heart rate data of your workout it's the perfect choice.
It can be placed in various places (it even incorporates an adapter to place it on your swimming goggles and measure your heart rate on the forehead), but where it will be most common to see it is on the forearm.
Here it is barely subject to movement or vibration and offers very high performance regardless of the kind of workout, including use in gym or cycling.
Wahoo TICKR Fit
It's very similar to the Polar OH1+, except that it does not have a memory to store a workout. In return what it offers is a much greater battery life, reaching up to 24 hours of use.
I would only opt for Wahoo's sensor if that level of battery life is really necessary for your use case (OH1+ has 12 hours).
I hope you've learnt everything about the operation of heart rate monitors and the difference in direct ECG and indirect measurement made by PPG sensors. However, if you still have any doubt, here are the comments so you can shoot me your question and I'll answer right away.
And with that, thanks for reading!
Good morning, Eduardo.
Very interesting article, thank you very much.
Could you recommend a watch in which I can combine running (including changes of pace) and golf; and that has a large screen to see numbers, etc.?
Thank you very much and best regards.
Alfonso.
Thank you Alfonso,
The option would be the Garmin Fenix 6. It has a Golf profile for poder to note the strokes and details and, above all, the maps of the courses to know distances to green and location of obstacles. The screen is larger than in the 5 Plus and that little bit more is noticed.
If you want it to be even bigger, the other option would be the Fenix 6X. But it will depend on the size of your wrist....
I always learn from reading your articles Eduardo! I currently have a F6 and I always do my workouts with a chest strap, I come from a Forerunner 645M and I bought a chest strap (the cheap one from decathlon) and the changes in HR for my series and crossfit workouts were remarkable. Now I'm thinking of buying a higher quality band (Garmin or Polar), will I notice the change with some of these bands compared to the decathlon one? I am talking about HR without advanced metrics. Thanks. Regards
Thank you, Andres.
If you notice any strange peaks that should not be present in the graphs, you will notice a difference. Otherwise, if you do not need any of the extra functions, you will not notice anything different.
Hi! Thanks for the article, I am precisely struggling with my Garmin 6s because I feel that it does not measure correctly: When I use a treadmill from the gym, the values are absurdly different. I would like to buy the Garmin triathlon band, but what I don't quite understand is if there is a special one for swimming and another one for both sports...I would be very grateful if you could help me if you could give me some advice. I would be very grateful if you could explain this to me so that I don't make a mistake when making the purchase.
Diana, here you can find the information about the two sensors, HRM-Tri and HRM-Swim: https://www.correrunamaraton.com/garmin-hrm-tri-hrm-swim-2/
If you want to use it for running, the HRM-Tri is the one to buy.
Good afternoon Alfonso, I have recently been given a Huawei Watch GT-DF4 model FTN-B19. My normal sport practice is Trail - Running, but I only had time to use it one day. That measurement in principle seemed to me correct in everything. Since the confinement, the sport that I practice is static cycling. I don't know why, but most days, practically at the beginning of the exercise, my heart rate goes above 190 beats and until 20 to 30 minutes later, it doesn't go down to normal heart rate, unless I stop for 5 minutes and in that time it goes down below 100 and then I continue with the exercise. I would like you to tell me if, for my type of exercise I normally practice, it is a good heart rate monitor and also if it could be due to the rise in heart rate at the beginning of the exercise on the exercise bike. Thank you very much in advance.
In general, generalist smartwatches do not have reliable pulse sensors, they are more intended for activity tracking than for an intensive sport such as trail running.
Thanks for your article Eduardo! It was just what I was waiting for. Keep up the good work!
Thank you, Nacho.
Hi, Eduardo.
Very interesting article.
I recently bought the SUUNTO 9 BARO
I find it a good watch, many functions that I am still studying. I miss that it has more home screens, the one for the time. Otherwise fine.
What do you think about the model?
Thank you
Here you can find the Suunto 9 test: https://www.correrunamaraton.com/suunto-9/
Very good article, congratulations.
Thank you very much, very interesting and very complete
I don't train with a band because I'm just starting. I'm from Argentina and everything is very expensive. But I want to take my training to another level!
For now I just run but my goal for this year is to do an Ironman.
I have heard that there is an app that you can compete from home, individually. I have a Garmin 245 music, which band do you recommend to buy?
Any of the sensors I have put in the article will work perfectly with the FR245, both via Bluetooth and ANT+. If you want something economical, you can opt for the HRM-Dual or the Polar H9.
Hello, Eduardo.
This analysis has come in handy.
I have a Fenix 3 from April 2016, stopping working HRM-Run sensor in June 2019 (it held up pretty well). That same month I changed it for a HRM-Tri and yesterday it stopped working. After much testing, I understand it is unrecoverable, although I don't know what happened to it.
I train for triathlon incorporating strength exercises. The data in the water, although with neoprene and the HRM-Tri were interesting, I do not consider them critical. Hence, along with the bad experience with this sensor, I discarded buying it again.
Considering that I will probably replace the Fenix 3 at the end of the year, I do not want to spend a lot, so I discard the HRM-Run or other Polar.
I'm in doubt about whether to go with the HRM-Dual, the Wahoo Tickr or the optical Polar OH1+ (even though I can't link swim data with Garmin Connect).
The first two are somewhat cheaper and it seems that in terms of reliability the OH1+ is on par (hairs clear). Please, 1TP10Could you give me some advice? Thanks for your help.
The first thing you should do is change the battery, although I'm guessing you've already tried that. If your HRM-Tri sensor is from June 2019 and you keep the purchase invoice, it is still under warranty. I recommend you to contact Garmin to to make the warranty claim and replace the faulty sensor.
As for the other question, if you are going to change to a model with an optical sensor soon. You would already have the comfort that the OH1 can offer you, so perhaps for variety of possibilities, opting for the HRM-Dual or the Wahoo would be a good idea.
In any case, try the warranty procedure first.
Hello, Eduardo.
Indeed, I already checked the battery. Also the same sensor on another Fenix, not working. On the other hand, another sensor on my Fenix 3 was working, so I would conclude that it is broken.
As for the warranty, I wrote to Garmin today. We will see their response. If it is satisfactory, the solution may be delayed, so I was thinking of buying one.
The doubt becomes double, because I would follow your indications for the reasons you indicate. But if they finally repair it or send a new one, I would have to have two bands?
In any case, thank you very much for your time.
Under normal conditions the replacement time is one week. But of course, we are not in normal conditions so it may take a little longer.
In case of sending it logically the OH1+ option takes all the interest.
Hello, Eduardo.
After dealing with Garmin and completing the paperwork, I had a new HRM-Tri sensor in a little over a week. A 10 for Garmin.
Thank you.
I'm glad you got it podido solved without spending a dime.
Hi, Eduardo:
Excellent article, first of all!
I have a Polar Vantage M and I usually run in and around the city (basically asphalt and trails). Despite following the directions for use and having good conditions for use (runs tight but not cutting off circulation, separated to a finger from the ulna and radius styloid process, I have no tattoos in the area, I have little hair and fair skin, etc), it does not give me real readings (for example trying very slowly where I can talk and I'm very comfortable, 165 bpm). That said, I'd like to make the leap to a chest heart rate monitor. Specifically, I'm between two heavyweights: the Polar H10 and the Garmin HRM Run. Apparently, please correct me if I'm wrong, the Garmin has more features and the Polar is more accurate. Logic tells me that compatibility will be better with the Polar, since I have that brand. Please, 1TP10Could you shed some light on this purchasing dilemma?
Thank you very much for your time and best regards,
Tincho.
You can't use the HRM-Run, because it doesn't have Bluetooth and the Polar can't sync with ANT+ sensors. Also, the running metrics functions would be exclusive to Garmin, so they wouldn't bring you anything either.
The choice is therefore the H10, or the H9 if you want to save some money.
Ah, ok. I overlooked those important details hehe Thank you very much for answering me and clearing my doubt.
A hug.
hello everyone, I have a polar m200, and the pulse I see it strange, I get averages of 170-175 bpm in 30-40 min, and peaks of 184-185, I look forced but podria carry a conversation, I have 25 years, is reliable, or like everything the more money the better performance, I'm looking at a garmin fenix 5, to replace it if the clock, thanks this has me food the head
The pulse of each one is something totally personal. These data can be perfectly valid.
With the Wahoo Tickr and a Garmin edge 1030 plus and Farero Assioma potentiometer, is the VO2Max estimation still effective or do I have to use a Garmin heart rate monitor?
Yeah, no problem.
Hi, Eduardo;
I have been using a Vantage M for a couple of months. The pulse readings so far have always been correct except in specific cases, but in recent days and with the rise in temperatures (I live in Cordoba) I have seen that the pulse is triggered giving erroneous readings. These readings occur once the training is advanced. I have changed several times the tightening of the watch as you indicate but it is not corrected, so I thought that perhaps it is the sweat that causes these errors.
Could this be the reason for these anomalous readings?
Thank you.
Sweat should not be the source of problems with the optical sensor. Perhaps it is the combination of heart rate with cadence, being based on an algorithm sometimes when running with a certain cadence confuses it. When you see that this is happening to you, try varying the cadence and check how it behaves.
I keep it in mind, thank you.
Hello Eduardo, very good your article and very impartial as always, I follow you for a long time and thanks to your advice I bought first a mio link sensor and then a polar oh1, both have always been quite accurate and especially the polar that I use it on the upper arm and it is better for strength exercises and hitt. I have tried using other watches to have it all in one device such as the Huawei gt 2, Garmin vivoactive 3 and finally the Coros Apex, but I have not found any of them accurate when training, currently along with the oh1 I use the bracelet Polar A370 with which I more or less reliably records the data of sleep and activity during the day and allows me to connect it with the oh1 for training by recording and viewing the data on screen. The big problem of the Polar A370 is the battery life that does not reach two days, which is why I wanted to ask for advice to buy a bracelet or watch that can record and do the same as with the Polar A370 during the day and above all connect it to the oh1 sensor for training but has a battery that can last me at least 5 days, I would appreciate your comments.
Thank you Sergio.
If you want to follow in Polar, you can have a look at the Ignite or Ignite 2. They are very similar to the A370 in concept, but far more advanced and with many more metrics.
Thank you very much Eduardo, I was thinking about the new Ignite 2 as you well recommend me, but I do not trust the duration that promises polar 5 days, in the case of the A370 I have promised 4 days of battery life and when it comes to the truth with the pulse all day, mobile notifications and a workout of 2.30 hours never reaches two days with two workouts.....I think that those that can really last about 5 days are those in which the manufacturer specifies 7 or more days of duration, which is why I'm still pretty annoyed because I think there is no real reliable device with pulse more or less decent that can be connected to the oh1 sensor and the battery lasts at least 5 days ... anyway thank you very much for your answer.
If you want more autonomy you have to do without the LCD screen. A Polar Vantage M or M2 gives you more battery life.