Apple Watch Series 2 : Complete analysis and performance in sport and fitness


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Apple introduced its first version of the Apple Watch in September 2014. Two years later, the new Series 2 retains the same essence of the first edition but covers the details that some of us missed in the original model. At least, the more sporty aspects we wanted to see in the Apple model.

These aspects are the GPS receiver and the actual certification of being submersible up to 50m (the first version is only splashproof). Along with the water resistance, the possibility of using it in swimming is also added.

If you are a regular visitor to the site, you will know what the tests I perform are like, but if you arrive for the first time attracted by the new Apple Watch, you should know that I usually cover with the maximum detail everything that concerns the sports use of these devices. I will not forget to talk about its general use, its construction and the daily use of the new S2, including its activity monitor; but if what you are looking for is to go into detail in each of the functions of the watch and its applications, you will not find it in this test.

The reason is simple. There are thousands of sites out there that will do it. Some of them will also do an outstanding job. But by the same token, I'm sure none of those sites will deal with the sports features of the Apple Watch in the same detail that you'll find here. From the performance of your GPS, to the quality of your optical pulse sensor, to how it works when you're swimming in a pool or in open water, to how it can be used for training beyond a race in the park.

Something that the most frequent people on the page also know is that I always like to clarify the origin of the devices I analyze. Some are borrowed (which are always returned to their respective manufacturer, I don't think I have sent any Garmin watch to Suunto yet... but give me time), but in this case the Apple Watch has been purchased by me for the occasion, doing it the same way that any other would do, waiting patiently for the purchase process to open and depositing the 479 euros they ask for the 42mm version.

And once all the details are cleared up, let's get down to business!


Used to square boxes with images of the product inside, the unpacking of the Apple Watch Series 2 is a breath of fresh air. This time the box is elongated and what's inside could well be a good wine.

Apple Watch Series 2

Unfortunately, when you open the box you will notice that there is no wine inside, so you can put away the glasses. Instead you will find a clock and a series of divisions where you can find all its accessories. Think of the divisions as a shopping mall.

  • Ground floor: USB charger and charging cable (wireless charging that is magnetically attached to the watch)
  • First floor: small guide of initial advice
  • Second floor: Apple Watch Series 2
  • Penthouse: Apple Watch box

Apple Watch Series 2


Well, let's take the Apple Watch series 2 out of the wine box and let's have a look at it. Aesthetically you won't be able to tell it apart from the first version, everything remains the same. I'm lying, it's now 1mm thicker, but it's invaluable.

In this case, I bought the "Apple Watch Series 2 with 42 mm gold aluminum case and brown/caramel braided nylon strap". At least that's how Apple is selling it. If you ask me I'd say it's a gold Apple Watch.

Used to the monsters that usually reside on my wrist, the truth is that those 42mm of the Apple Watch become scarce. The feeling on my wrist is that it is a small watch, and in fact I would appreciate it being bigger. Not only for a purely aesthetic reason, but because that increase in size would be accompanied by a larger screen surface and greater autonomy. Although I'm sure that if your wrist is narrower than mine your opinion will be different.

Apple Watch Series 2

At the bottom you can find the optical pulse sensor, which is still the same as its first version, but in the inscription around it we can see the differences of the Series 2: GPS receiver and water resistance up to 50 meters.

Apple Watch Series 2

The watch control is also identical to the first edition, with the touch screen and a button on the right side, along with the selection crown.

Apple Watch Series 2

But the opposite side does change. There is now a second hole next to the microphone hole. Behind it is a barometric altimeter, although it is not software enabled at the moment. It will probably be used later to count the floors climbed or the positive meters accumulated during a training session.

Apple Watch Series 2

The strap change system is identical, easy to remove and can be replaced with any compatible strap to change the look of your watch in a matter of seconds.

Apple Watch Series 2

The quality of the screen and its contrast is simply impressive.

Apple Watch Series 2

The charge is wireless, which means there is no physical contact between the charger and the watch. There are no cables to connect and no connection pins on the bottom. It is therefore the best option for sealing the watch completely against the elements. It is based on the Qi standard, but is not compatible with any charger. Exclusively Apple chargers, as you might otherwise imagine.

The downside of this charging system is that it is somewhat slower than a direct connection and also generates heat, which you will notice if you put your watch on immediately after finishing charging.

Apple Watch Series 2

The base is magnetic, so there is no need to do any kind of test to start charging. A magnet will ensure that everything is in place. However, the union is not very strong, so it is easy to disconnect.

Apple Watch Series 2

What do you say we go over the Apple Watch on a general level before getting into the sportier part of it? Sit down, get comfortable and let's get to it.

Apple Watch Series 2, the smart watch

The new Apple Watch Series 2 is a brilliant watch. Not only because it is a well finished product (both hardware and software), but because it has an impressive display. Very, very brilliant.

The technology used is OLED, so the contrast and vividness of colors it offers is noteworthy, and it continues to have Force Touch technology, capable of interpreting different types of pulses on it.

Apple Watch S2 - Display

But this was already the case in the first edition of the watch. The new feature of the display is its brightness: more than double that of the first model, reaching 100 nits. The new display is easy to read in any situation, even on the sunniest days it is possible to see all the details of the screen with the same graphic quality, as the brightness is regulated automatically.

Apple Watch Series 2 - Sunny display

The main function of the watch remains the same: to display on the watch the notifications you receive on your iPhone. The integration with them is very clean. If a message arrives and you have the phone in your pocket, both devices do not ring, only the watch will alert you.

Also, if you are using the phone when you receive that notification, it will appear on the smartphone screen accompanied by the corresponding sound, but the clock will remain silent.

It is also possible to be away from the phone and continue to receive notifications (and interact with them). Of course, as long as we are on the same WiFi network. This is possible thanks to Apple's Continuity feature. To give an example, with the Apple Watch I can go to "the cave of suffering" to ride my bike while leaving the phone at home (three floors above) and continue to receive the same notifications. Obviously the watch is out of Bluetooth range, but both continue to communicate by being connected on the same network. And this includes not only notifications or messages, but also podrans answering calls from the watch.

Apple Watch S2 - Apps

Of course there are also many productivity applications, but it is an area that I personally find less interesting, except for very specific cases. In the end the functionality of each particular app lies in the work that each developer has done, but there are many that only offer grandiloquent notifications, but as soon as you try to interact with them it sends you back to continue on the phone.


But it is something that is being worked on and will undoubtedly improve over time, especially in voice control. For example as of today it is possible to answer a WhatsApp message with your voice, but it is not possible to start a conversation with "Hey Siri, send a WhatsApp to so-and-so". Siri's response will be for you to continue on the phone.

Apple Watch S2 - Continue on iPhone

In order to have this function available, it is up to the developers of WhatsApp to implement it. The possibility is there, but there has to be an extension of the application installed on the watch (which is not present at the moment). This is just an example of the missed opportunities that are present at the moment in the Apple Watch. And we must not forget that Apple can only provide a platform that allows useful applications to be made, but then it is up to the developers to make it effective.

Obviously all these notifications, even the smallest ones in terms of functionality, are the most complete of all the watches you can connect to iOS. The Apple Watch is not the only device that receives notifications from the iPhone. Polar, Suunto, Garmin, Fitbit... all these manufacturers have that possibility; but none of them will do it intelligently.

Apple Watch Series 2 - Notifications

Not only because of the ability to respond to these notifications, but also because of the dual notification (whatever the circumstance, the clock will notify you and the phone will notify you). And you don't have to see the notification right away. The Apple Watch is smart enough that if you wait a few seconds to lift your wrist, it will show it on the screen. Or leave it for later, and you can delete it as you go. If you delete the notification on the clock, it will disappear on your iPhone, too.

In comparison, for example in Suunto you can already be quick to lift your wrist to check what you have received, because after a (short) time the notification will disappear. Forever. At least on the clock, since it will only be displayed on the phone.

The interaction you can make with each application will also depend on your particular use. No two people are the same, and what may be paramount to you may seem superfluous to me. Personally, I am not very fond of using specific applications, but I do make a lot of use of the notifications that allow me to interact with them, and not only answer emails or messages, but also delete or archive emails.

Activity monitor

As a training device and referring to its sports possibilities, it's the activity monitor that stands out the most, so consequently it's the first thing I want to stop at. I already did it in the first version of the Apple Watch, so in this new version it wasn't going to be less.

Apple Watch Series 2 - Activity Monitor

In the Apple Watch, the activity monitor moves away from the traditional concept, where the important thing is the number of steps we take throughout the day: depending on how many steps we walk, this is how our activity will be.

Apple's approach is somewhat different. Yes, it also counts steps and estimates distances, but it follows your activity in three different concepts: movement, exercise, and standing time.

These are the three target circles that you must meet. The first one, in red, will be completed with a certain number of calories consumed that you select in the initial configuration, but you can modify it to your liking later on. These calories correspond to all your activity, that is, both walks and sports activities.

The second circle corresponds to the time spent standing up, represented in blue. The objective is to stand up every hour, at least 12 hours a day. And if you don't do it, with 10 minutes left you will be warned to do so. It is different from the classic warning to move that other manufacturers use, in which you will have to walk about 200m to remove the warning.

Finally, the yellow circle (or green, you know that men have some problems with colors) is the exercise circle. If the two previous ones are quite clear, this one is a bit more diffuse. And that's because, besides including the minutes of a training session, there are minutes that are added in a non-specific way. I suppose that you will count walks of more than a certain length or at a higher pace. For example, today I've been exercising for 64 minutes, when I've just done a swimming training session of a little more than 30 minutes. However, I've been walking to the gym, so it will be that movement that is counting.

All this is accessible directly on the clock in a rather generic way. At any time you can check how much you have left to get each of the circles closed.

Apple Watch S2 - Activity Monitor

The goal is to get all three rings closed, which means you've had a busy day.

Apple Watch S2 - Full activity circles

It is also possible to review hourly charts, to see when you have been most active throughout the day.

Apple Watch S2 - Activity Monitor

And of course, steps and total distance traveled.

Apple Watch Series 2 - Steps, Distance

But where you'll find the most information is on your smartphone, because that's where all this information is synchronized.

Apple Watch Series 2 - Activity MonitorApple Watch Series 2 - Activity MonitorApple Watch Series 2 - Activity Monitor

That would be the daily view. But you can access a calendar where you can quickly see the circles for each of the days and see when you have been more or less active throughout the week.

Apple Watch Series 2 - Activity Monitor

There are also awards when you achieve certain activity targets.

Apple Watch Series 2 - Activity Monitor

And it is in this same application where you will find all the data of the trainings you do.

Apple Watch Series 2 - Activity Monitor

As you can see, there are other applications that can also provide information (in this screenshot you can see how Garmin Connect and Strava have included trainings). This synchronization is not done with the Activity application (which is the simplest version and the one I've been dealing with so far), but the Health application which provides all that data from other applications, making its function as a bridge between them.

If Activity is focused on simplicity, the Health application is the opposite, becoming a much more complete database where not only the Apple Watch will enter information, but also other applications you have configured on your smartphone.

Health Application - Sources

Here there is information that is repeated, such as all the activity data that can also be consulted from here.

But there are also exclusive data that you can only consult in this application, either the Apple Watch data (such as heart rate data) or data synchronized by other platforms (for example, sleep analysis that comes from synchronization with Garmin).

Application Health - Activity

You may have noticed that for the moment the optical pulse sensor data (which I will talk about later in its corresponding section) has not appeared anywhere, right? Indeed, this is where you will find it, under the "Vital signs" menu.

Apple Health - Heart Rate Apple Health - Heart Rate Apple Health - Heart Rate

As I said, later I will go into more detail on the optical pulse sensor, its operation at rest and in activity, and what makes it different and equal to other models available on the market.

Finally, note that all the information you download from the Apple Watch to your phone lives exclusively on your phone. It cannot be accessed anywhere else, nor is it available in iCloud anywhere. If at any time you need to reset your phone, be sure to back up any data or health data. Because, I repeat, all training, health, and other data resides exclusively on your iPhone, which will be deleted if you don't make the copy.

Fitness applications and other considerations

Apple Watch Series 2

Before I start talking about the use of the Apple Watch in different sports, I must clarify that I am going to focus only and exclusively on the Apple application, the one that comes integrated in the watch, and I will do so for three very specific reasons:

  1. The first and most important is that, as of the day of publication of this test, there is not a single application that benefits from the use of the clock's internal GPS. The developers have had very little time available with the Apple Watch Series 2 (probably, little more than I have) so despite having access to the API available they are still working on it.
    At this time applications like Strava can be used without any problem, but the GPS data will come from the phone (which you will have to carry with you). You have to wait for Strava and other developers to update their applications to support GPS.
  2. If I had to analyze each and every application available for the Apple Watch the best thing I could do is become a hermit and go live away from civilization. It would be a job where you know when you start, but not when you finish. And this article could never be published.
  3. There will be many applications in the future that will support GPS, I have no doubt. Some will install some, others different. But what I am sure of is that all of you will have the Apple application on your watch, and it will be the most used by the average user.

Let's get to work.

Running with the Apple Watch Series 2

Running around with the new version of the Apple Watch is almost the same as with the original model, at least in terms of the software (what you see on the screen). But obviously one of the most important changes in this Series 2 is that the watch now has internal GPS, so you no longer need to run around carrying your phone around.

It is now the watch itself that, thanks to GPS, can calculate rhythms and distances much more accurately than the first model did, which used the internal accelerometer to estimate distances or depended on the connection to the iPhone.

But as I say, the software and what you see on the screen has hardly changed. You start by opening the sport application and selecting the activity you want to do. In this case, running.

Apple Watch Series 2 - Running

We can run with respect to a goal. These include a certain number of calories, duration or distance. Each of these will indicate the maximum record achieved up to that point to motivate you to go a little further. There is a fourth mode, free training, which is simply to go out and run until you feel you have finished or you can no longer, whichever comes first.

There are no other modes present, such as interval training, so you would have to find an application that allows this, although as of today there is none that supports the internal GPS.

Once you have selected the mode, simply click on start and a countdown will begin (which I personally hate). If you want to skip it, simply click on the screen and the activity will begin automatically.

Apple Watch Series 2 - Countdown

It is at this point that the clock starts looking for GPS satellites (not before, as usual).

The screen display options have been given a new possibility. It is possible to view a data at the bottom of the screen and alternate it by turning the crown as before.

Apple Watch S2 - A single piece of information on the screen

The second option is new in Watch OS3.0. You can have a single screen with multiple data, and select which fields are displayed.

Apple Watch S2 - Multiple screen data

This configuration is done from the phone's application, either by choosing which of the two options you want to display or by selecting the order of the options.

Apple Watch S2 - What to Watch During Training

It is possible to mark laps manually by simply tapping twice on the screen and creating a manual lap. On the clock you can see the duration of that lap along with the distance and average pace of the interval. In the training summary you can also see those details.

Apple Watch S2 - Laptop

By default, the clock will warn you every time you complete a kilometre so that you can check your pace.

The analysis you can make of the workout is quite basic, and only on the phone screen. The activity data is not synchronized with any other site, nor is it possible to analyze activities on the computer.

Worst of all, there is no possibility to have an activity file or to synchronize it with any external service (be it Strava, Training Peaks or whatever). That is, the activity will be "hijacked" by Apple without the possibility of taking it anywhere else.

Biking with the Apple Watch Series 2

Using the Apple Watch for cycling training is quite similar to running, but the settings and display possibilities are exactly the same.

Apple Watch Series 2 - Bikes

But there's one small detail to keep in mind: the Apple Watch screen doesn't always stay on.

If one of the positive points of this watch is its magnificent display, with its unquestionable quality, it is also its main problem: if it were always on, the battery would last a sigh.

There are two ways to turn it on. By turning your wrist or touching the screen. The first and most direct way is always to lift your wrist and turn it as if you were going to look at the time. Half a second after this gesture the screen will turn on showing all the details of the workout. It's a pretty natural gesture while standing, walking or even running. But not when you're on the bike.

Apple Watch Series 2 - Wrist Twist Bike

When it comes to turning your wrist while you have your hands on the handlebars, it's not easy for the Apple Watch to understand the turn of the wrist because the starting point is not the same. You don't raise your hand as much and so half the time after you make the gesture the screen doesn't turn on. You'll find yourself looking at a black screen waiting to turn on. Even if you exaggerate the gesture then with a double turn of the wrist.

The next option is to touch the screen, but this is an operation that may include having to remove both hands from the handlebars, so obviously this is ruled out.

If you're going to use the watch for spinning lessons or indoor training, you'll have no problem letting go of the handlebars without worrying. For a quiet ride, forcing your wrist to turn may not be a problem either, but what's really uncomfortable is that you have to do it each and every time you want to check some detail such as the speed you're riding or the distance you've been riding.

In short, to ride a bike regularly I find that there are better options than the Apple Watch, both to wear on your wrist and to put on the handlebars.

Swimming and Apple Watch Series 2

In addition to the GPS receiver, the other major new feature of the second version of the Apple Watch is that it is now waterproof, so the Series 2 includes swimming profiles for swimming pools and open water (using GPS).

The new model not only adds the ability to be submerged up to 50 meters, but also has a system for extracting the water left inside the speaker conduit.

When you use the watch in swimming, the conduit used to emit sound will be flooded. Therefore, when the speaker needs to move air to produce sound, problems arise, as that space will be occupied by water.

When you unlock the screen, the speaker will emit a vibration to explode the water in that cavity. Want to see it in action? You know I take good care of you and I like to show you everything.

Not always all the water comes out, sometimes something is left inside the cabin and the sound stays a little strange for a few hours, but it will end up drying out and returning to normal.

Apple Watch S2. Swimming in the pool

When you select the swimming pool mode, the first thing you have to do is indicate the length of each length. Unlike other clocks where the distance is predetermined to the typical ones (although sometimes you are allowed to select it manually) in the Apple clock you can select the distance manually, meter by meter. Therefore it is ideal if in addition to swimming in the usual gym pool (which is usually 25 or 50 meters) you swim in the pool of your house, hotel, or even in the bathtub, because the distance can be up to one meter.

Apple Watch Series 2 - Pool distance selectionAnd upwards you can add metres and more metres, so you can go for long runs at the San Alfonso del Mar pool without any problem.

But let's get down to business. Just like in the run mode, you can select several goals for your swimming session: calories, duration, distance in meters or free training. It will sound like run training to you.

In swimming mode, the screen remains locked, as the touchscreen no longer works in contact with the water. And it's not just the screen, but both buttons as well. To regain control, simply turn the crown.

Apple Watch Series 2 - Turn the crown to unlock

Again, there is only one data screen, where you can see time, calories, number of lengths and total distance travelled, although remember that you can change these fields from your phone.

Apple Watch S2 - Swimming in the pool

Your only task will be to swim, swim and keep swimming. Once you have finished, you must unlock the screen by turning the crown. In the same procedure, the speaker will expel the water inside the sound pipe as you have seen before. By moving the screen to the right you can pause the training or finish it.

While you are swimming the pulse sensor will be on, recording your heart rate data. It is the first manufacturer to dare to do so with an optical pulse sensor, but it does so because in the analysis of the activity there will be no graph. But it does use the HR data for the calculation of calories consumed, which is a detail to be taken into account.

However, with some application we can access these files and see the recorded data (Health Graph) and check what the sensor records.

Apple Watch series 2 - Swimming CF chart

The results are what I expected. It doesn't always show data accurately, but when it does, it is logical data. You only have to look at how in the first of the series the sample was incorrect. But in the rest of the intervals the graph makes a lot of sense and corresponds to the different exercises I was doing in that session.

When you finish training you will access the end of activity screen where you can review all the generic data of your workout.

Apple Watch S2 - Swimming in the pool

Apple Watch S2 - Swimming in the pool

Apple Watch S2 - Swimming in the pool

In the different pool trainings that I have been doing with the Apple Watch, it has always marked the lengths correctly, without adding lengths that I have not done or trimming in any of them. Even better than other watches that I have been comparing with in the measurements (different models of Garmin and Suunto).

Of course, in this case the Apple Watch was on the left hand while the watches I was comparing with were on the right, which is not my usual place to wear them. Let's not forget that the watches are learning your movements so that change of wrist can affect the measurement of the "control" watches.

At the moment of analysis is when we stumble again over the same stone. And it is impossible to perform a minimally serious analysis. And since the TCX file of the activity is sequestered and cannot be synchronized with any service... we are left "in the dark".

The data presented are the generic ones of the activity, without going into much detail.

Apple Watch Series 2 - Swimming

It is also unable to identify the style of swimming or how the intervals were produced. In other words, on an analytical level, the information it presents is of little use. It only presents times for every 100m. Even if you put the training on pause it will not be taken into account in the final data either.

Apple Watch Series 2 - Swimming

So as soon as you do a rest period all your average pace not only of that fragment of the training, but of the whole activity, will be unplugged from your real data.

In the previous example, in the periods of 500m and 600m I was doing intervals at 1:20/100m, mixed with back-swimming breaks. It is impossible to know at what exact rate I have done these intervals because everything appears to be combined. And there are no rhythm charts that we can consult either.

Apple Watch S2. Open water swimming

Swimming in open water is a totally different animal. Here the GPS is used to record distance (and consequently pace), but more important than GPS reception is the algorithm used.

Unlike when you are on land, you don't constantly receive a GPS signal here. Every time you put your hand in the water the watch loses satellite signals. So the watch only has reception the few moments you are stroking out of the water. At that point the watch will get a location point (if given time) and will lose the signal again when you put your hand back in the water.

So in a training session where you do more than 1,000 strokes, the watch will lose signal and will recover it in 1,000 occasions. As you can imagine, it is not easy to manage. Usually all watches have problems in this type of activity. And if in race we have a possible variation of the real data of a 1%-2%, in open waters a 20% enters within the reasonable.

In the case of the Apple Watch Series 2, despite the fact that right now its GPS has a somewhat regular operation (we'll see it in its corresponding section) the truth is that swimming in open water has a pretty good performance.

Let's look at some example data from a training session. The first thing to note is that I waited more than 5 minutes at the shore before starting to swim, to make sure that the watch had a good GPS signal before entering the water (both the Apple Watch and the other devices that come with me). You know that in the case of the Apple the activity always starts directly, regardless of whether it has a signal or not. In the race the first data shown is obtained through the accelerometer, but in open water as we go out without getting a signal we will hardly get it while swimming.

Next to the Apple Watch I used a Garmin Fenix 3 on the other wrist, plus a Garmin Forerunner 230 which he wore under his swimming cap, always remaining above the water, so he never loses the signal and will be the one to mark us at the end of the series with the most accurate data with which to compare.

At this first stop you can see that there is a small difference in the measurement: 29 meters difference.

Apple Watch S2 - Open water swimming Apple Watch S2 - Open water swimming

The Apple Watch is still a bit less and the gap has been widening, but it is still small.

Apple Watch S2 - Open water swimming Apple Watch S2 - Open water swimming

Last control stop and the difference continues to increase. 102 meters more in the case of the Fenix 3. Also note that the wrist on which the watch is worn affects the measurement, as the time above the water varies slightly due to the difference in strokes and the side you breathe on.

Apple Watch S2 - Open water swimming Apple Watch S2 - Open water swimming

But the best thing is the final confirmation of all the data. And although again I can't extract the route made with the Apple Watch to compare it on the same map with the other two, at least you can check it by comparing both images. First, the route made by the Apple Watch.

Apple Watch S2 - Open water swimming

In this case, the routes of the different Garmin's. In yellow the Fenix 3 on the right wrist and in blue the track marked by the Forerunner 230 he wore under his cap.

Apple Watch S2 - Open water swimming

You can see that the three tracks are very similar. The Fenix 3 has a couple of points where it deviates slightly, while the Apple Watch also has another point where it loses the signal and recovers it (marked by a dotted line).

And what about the distances measured by each of them?

  • Apple Watch Series 2: 2,107m
  • Garmin Fenix 3: 2.223m
  • Garmin Forerunner 230: 2,104m

The new Watch shows that Apple has taken swimming quite seriously, offering very high accuracy both in the pool and in open water. The first case is easier to achieve, but showing good accuracy when recording distance in open water is not easy at all and there are manufacturers who have needed years to get to where they are today. Apple has achieved this on their first attempt, so congratulations are in order. At least for now...

Optical heart rate sensor

The optical pulse sensor has become the new mandatory equipment of any smart watch. Wherever you look at the features of the latest smartwatch proposals on the market, you will find an optical sensor in practically all of them.

Even if they look alike, not all sensors are the same. Some are very accurate, but others are a real mess. So every time a new device comes on the market you have to see where you place it. Even when the sensor is not new (as is the case with the Apple Watch sensor) and redesigns with the model it replaces, even if the physical appearance is identical the algorithms can change widely.

If you don't have much knowledge of these types of sensors and how they work, I recommend that you take a look at the article I published at the timeBut I'll give you the basic details about how they work.

The theory is very simple. The device emits a light (usually green) that illuminates the capillaries. The sensor is then able to check your blood pressure and thus your pulse. This is not a new technology, it has been around for a lot of years. You have never had a finger clip to measure your pulse? Well, the system used is the same.

The difference is that you can now measure your heart rate in motion, not only by walking, but also by performing high-impact activities such as running, and eliminating the noise that is produced in the signal by these actions.

Well, after this basic lesson the first thing I want to point out is that the Apple Watch uses two different methods to measure your pulse. In addition to the traditional green LEDs (which will be used when you are doing some physical activity); Apple has another method to measure your pulse through infrared, so at first glance there will be nothing "active".

Apple Watch Series 2 - IR Sensor

This is the method you use to take the various measurements you make throughout the day, at varying intervals of minutes. This data can be checked in the Health application of your iPhone as you have seen in the section on the activity monitor.

Using infrared has a very simple reason, and that is to save battery power. However, it only works properly when there is not much movement. If you are walking or doing activities without recording them through your application (or any other application that uses the sensor), the watch may not be able to read your pulse and you may find fragments of your daily life without readings being taken.

So when you start an activity the logging method changes, in that case you will log every second (which is usual for sports watches) and use the green LEDs.

Apple Watch Series 2 - LED Sensor

I will go into more detail below, comparing the Apple sensor with other sensors (both optical and traditional chest strap sensors), but first I want to clarify how an optical pulse sensor should be worn for proper operation.

The watch should be placed firmly on the wrist (not loose or appearing to have a boa constrictor on your arm), and always above the wrist bone. Generally, reading problems are due to poor placement of the watch, rather than a problem with skin tone or arm hair.

Optical sensor comparisons

In the weeks I've been testing the Apple Watch S2 I've done a lot of comparisons with different pulse sensors, both chest sensors and optical sensors. In general the results have been good, which doesn't mean they have always been perfect.

My main complaint will always be with the difficulties I have had at all times to extract a quality activity file, not only because it does not support it natively, but also because once extracted the format is not the standard, which has taken me a lot of work when making these comparisons.

Not only that, but it could also be the case that the sensor has taken a few seconds to obtain a heart rate reading. Those first moments without data do not exist in the activity file, which causes the curves, which are already difficult to align, to be separated from each other. It may seem that there is a delay between the different sensors, but this is a standard problem. You will see some of these examples later on,

We'll start with something easy. A gentle training session on a roller. No sudden changes in intensity or other movements other than holding the handlebars of the bike and without much ambient light (the greatest enemy of the optical sensor). The first few minutes should always be discarded, as all sensors, whether optical or pectoral, need a period of "adaptation".

All four give very similar records, except in the case of Garmin that you can see peaks throughout the activity. Probably the tape was a little loose and was moving when playing with Stryd. But you can see how the data read by the Apple Watch is correct.

Apple Watch - Compare Pulse Sensors

We continue with another test not too complicated for an optical pulse sensor. Running at a constant pace. In this case a half marathon without competing, therefore without going too strong. Again we have a good overall result of the Apple Watch with two small objections. In the 40th minute loses the reading, as you can see how the graph makes a completely straight line. And finally we can see two peaks, possibly caused by an increase in cadence as it is the last stretch of the race.

Neither of these two points concern me, a one-off reading failure can happen "in the best of families".

Apple Watch - Compare Pulse Sensors

But we're going to increase the degree of difficulty with rhythm changes and interval training. A smooth trot finishing the training with 3 series of 90m at full throttle. Here we have the first problem of alignment of the graphs.

From the beginning you can see that the Apple Watch is dragging some delay, although not all the difference in the graphics is due to this lack of alignment, because live in the recovery of the intervals you could see perfectly how the Apple Watch was a little late in returning to the data from the other two sensors. But nothing too noticeable, two or three seconds at most.

In the first interval the Apple Watch does not reach the record of the other two sensors, while in the second it goes a little over. That peak is the last second of the sprint so being such a short interval it is easy to get lost.

Apple Watch - Compare Pulse Sensors

The next training again has alignment problems, this time with the Apple Watch clearly ahead, but still allows us to compare the graph of the Apple Watch with the other two.

The peaks reached are the same and there are no noticeable delays in recoveries.

Apple Watch - Compare Pulse Sensors

Another example with intervals in the race, in which there is not much to report either.


These running intervals are not the only thing that nails the record. This example below is cycling intervals, something typically complicated for other optical pulse sensors where for example TomTom and Garmin watches have had numerous problems.

In the case of the Apple Watch, however, the result is entirely positive.


But he doesn't always nail the records. Like all sensors (regardless of the technology he uses), there are days when he doesn't behave as well.

This is another example of cycling intervals. The first four intervals are done correctly, the fifth is lost for the first time and the sixth is not done correctly either, two more where he seems to recover but from then on he is totally lost and does not recover again throughout the training.

Apple Watch S2 - Compare Pulse Sensors

And what about indoor training? No problem. In this example you can see after the first 30 minutes of rolling (with 10 of them stronger) a core session with various exercises.

She suffers a little at first, but the rest of the session she measures correctly.

Apple Watch - Compare Pulse Sensors

It is precisely in this type of scenario where the optical sensors are usually most difficult to use, due to the different movements of the wrist, the changes in the exercises and the lack of intensity.

Finally, it should be noted that the Apple Watch S2 (like the first version) also allows connection to an external pulse sensor.

Apple Watch Series 2 - Stryd

To do this you simply have to pair it as an external Bluetooth accessory, from then on you can deactivate the optical sensor and get all the data from the chest sensor.


The GPS receiver is probably the most important feature that Apple has added to the new version of the Watch. Along with swimming, it occupied an important part of its presentation and the importance that they give to sport is evident with their collaboration with Nike, who are preparing a special edition.

Well, it seems unbelievable that in such a vital part of the new version of his smart watch Apple has screwed up the way it has.

I'll start with the positives. You have them too, and we have to be fair. First of all, the Watch S2's GPS is able to locate you on a map. Positive point.

Apple Watch S2 - Maps

Let's stop joking. Apart from the general good performance in open water swimming, it must be said that the instantaneous pace in running is fast in adapting to the rhythms. In a situation of changing pace (interval training) the watch adapts quickly and shows the real speed in a matter of 2 or 3 seconds.

And... yeah. That's all I can say about the GPS on Apple's new watch. From here, it's party time.

To begin with, someone at Apple has decided that it was a good idea for the clock to start an activity when it has not yet obtained a GPS signal. You start the activity, you start running... and let the GPS find you when it can. Who cares about the first minute of training? Or the first 5 minutes? Besides, why should we do the same thing that the 100% from other manufacturers that have been launching GPS devices on the market do, we are going to turn this around because waiting 10 seconds to obtain a GPS signal is absurd. Woe betide those who start training between tall buildings!

Of course, then you're running with other watches and it turns out that the Apple Watch marks the first automatic lap 300 meters later. But when it becomes surreal it's as you go through the kilometers and not only does it catch up with the other two, but it starts marking the kilometers ahead of them. Compensating for a good final result? Because of course, analyzing the time needed to run each kilometer is totally superfluous, nobody cares about that.

I can continue to talk about the quality of the recorded tracks. Normally when I test a clock I usually compare the GPS tracks in an external application by comparing them to three, four or five different clocks. As you know this is something you can't do with the Apple Watch because it can't export the activity. But don't worry, because it's not going to be necessary.

Softer things than this have set official support forums on fire.

Apple Watch S2 - GPS

I don't need to comment on that, do I? Just confirm that I'm not used to drinking alcohol, especially if I have to train. As for the Apple Watch, I don't know his habits, maybe he does and that's where that route comes from.

And don't think it's a one-day thing or that the location is complicated for satellite reception. Not at all. By the sea I have absolute visibility of the sky, without trees or buildings that make signal reception difficult. And in Marbella we don't usually have cloudy days.

Apple Watch S2 - GPS

That is with a direct view of the sky. As we bring buildings into the equation, it gets even "better".

Apple Watch S2 - GPSApple Watch S2 - GPS

Let's be positive. There are days when he behaves better, usually at higher speeds. A bike track usually looks better and he can pass the same spot twice, although he does choke a little on the turns.

Apple Watch S2 - GPSApple Watch S2 - GPSApple Watch S2 - GPS

Even on race days he seems to want to go along with a good workout and decides not to go out drunk. I think. Such a track achieved with any other device would be considered bad. On the Apple Watch I consider it "a good day".

Apple Watch S2 - GPS

But I think it has a life of its own. Besides being quite vague. For example, you may decide that running a half-marathon is too tiring, and since we're close to the starting point the best option is to stop running, which is Sunday and it's very early. I'll stay here having a beer and you go on your way. But, hey! Don't worry because I'll leave you in the hands of the accelerometer and in the end I'll be able to set a reasonable final distance. It doesn't matter how precise it is; you won't be first, what do you care?

Apple Watch S2 - GPS

Compare that route to the one engraved by a Forerunner 230 on his other wrist.

Apple Watch S2 - Compare GPS with GarminA little longer, right?

And don't think about repeating the same stretch in succession with intervals. At least not without giving him a Dramamine, because he gets dizzy. Three simple short intervals on a straight line with recovery walking. Well, this is what he thinks you've done. Everything but a straight line.

Apple Watch S2 - GPS

It's a good thing I wore a watch that takes training seriously to confirm that I don't go back and forth. This is what I actually did.

Apple Watch S2 - Intervals with the Fenix 3

But let's vary the training, and do a little cycling. We will have to take the mobile, just in case. Feel safe calling it. If you do, and take the watch paired with the iPhone (I think the normal), then you will run out of GPS data.

The GPS will be off and you'll run out of speed and distance data. Why? No idea, maybe at Apple they consider that nobody takes their phone with them when they go to ride their bike.

Apple Watch Series 2 - GPS not active

Even if you disable your Bluetooth before riding (thus losing notifications while you train), it may happen that because you have left on a Sunday morning too early, the GPS has decided that he won't go out that day - in the cold!

You may find that even though you have been recording distance and speed correctly, when you check the activity on your phone... there is no track!

Apple Watch S2 - No map

Well, I think that's all for now.

Really, it's simply incomprehensible how something so theoretically simple can work so badly. And I'm not talking about a mere function that's there as a filler, it's that it's one of the most important factors in the renewal of the model.

Will Apple fix it? Obviously there are many things that are mere software errors, such as disabling the GPS in cycling if the phone is connected or sometimes the track does not appear or is incomplete.

Only Apple knows if it can improve the quality of the tracks. If it is a problem of algorithm adjustment and signal processing there is much room for improvement. If the origin of the lack of precision is in the design of the antenna... little can be done by way of software. But today Apple has MANY work ahead.

Battery life

There are two aspects of autonomy that we must take into account: day-to-day autonomy and autonomy with the use of GPS. Both are extremely important, and I will explain why.

First of all, daily autonomy is the most important thing. The clock must be able to last a whole day with normal use by consulting notifications and making use of applications. And by normal use I mean the usual one, not reading the last 24 hours of your Twitter timeline on the clock screen.

After that normal day-to-day use, the watch should have enough battery power to withstand a moderately long workout. That is, after a hard day's work, there should be something left over for when you go to the gym, go for a run or simply take a walk. Because it wouldn't make any sense if when you go to do your activity, it turns out that you don't have enough battery power and you have to leave the watch charging.

Apple has done its homework well. With the generational change and the arrival of GPS, a new, more powerful chipset has been added, probably with less battery consumption. The latter has also improved its performance, slightly increasing its capacity without changing the thickness of the device.

The result is that the watch can withstand normal use and, when it's time to train, have enough autonomy so that you don't have to fear not being able to record the final part of the workout. Similarly, if you want to train first thing in the morning, you can do it with the Apple Watch without fear of running out of battery at the end of the day. And if you're not going to train that day, in my particular use the battery has easily held out for the day and a half, even reaching the night on the second day. Bear in mind that the particular use of each one can make this battery life vary considerably.

Apple Watch Series 2 - Battery Life

The second case to consider is how long the watch can last if we are training using the GPS and the optical pulse sensor. Apple estimates that duration at 5 hours.

I have not been able to perform a test with the procedure I usually use (leaving the watch recording an activity until it runs out of battery), as the activity is automatically paused when it detects that it has not been moving for a while.

I haven't had the opportunity to do an activity around that length either, because at the height of the season I'm in (end of season and start of rest) there hasn't been any training that has required it. But if you can extrapolate in my usual use, including for example a half marathon, I think that the figure of 5 hours indicated by Apple is not only possible, but maybe it could be squeezed a little further.

If you're planning on taking more than 5 hours to run a marathon or are going to run a mountain marathon, then the battery in the Apple Watch Series 2 is going to be pretty limited.

My opinion

With the Apple Watch S2 and its use in sport, the first thing you have to be very clear about is who it is intended for and who it is not. Apple is very clear about its target audience: the approximately 20 million users of Fitbit. But if you arrived here thinking that you could replace your Garmin or Suunto for your next triathlon or mountain marathon, I'm sorry to give you bad news; the Apple Watch stands out in many ways, but sport is not one of them.

The Apple Watch has many positive points. Starting from an already very good device, the optical pulse sensor has improved from the first version and the data recording is almost at the level of the market leaders (Scosche and Mio) The swimming record, something totally new in this version, is correct, although with data that is too simple.

But the GPS needs work. I don't know if it can be improved in future software updates or if the problem is related to the antenna design, but today the data is not good. And the fact of not being able to have your activity files for a more detailed analysis in a bigger screen or simply share it in Strava or other platforms, is an unbearable failure that would be very easy to solve, but that Apple probably won't do. We will have to wait for third party developers and see if they get a good job or if the API doesn't allow exporting that kind of details.

So you need to be very clear about what you're looking for in the Apple Watch. If you want a good, smart watch - a great one - that lets you do some sport, the Watch Series 2 is for you.

But if you want a watch for running, swimming, or cycling, you have dozens of options for a quarter of the price that triple the functions. Of course, you won't find the Apple Watch's great display, the quality of workmanship, or the wide range of applications available. But that's balanced out by performance for the purpose it's intended: precision, sports features, reliability, and much more range.

Buy Apple Watch 2

At the moment the Apple Watch is only available from the Apple Store, however, the Nike version is now available on its own websiteIt is a special edition with its application, exclusive strap and specific sphere. You can click here to access it.

And remember, by buying through the links I provide you will be helping the web at no cost to you. It's the way you can show your gratitude for the evidence I publish.

And with that... thanks for reading!


Operation - 6.5
Connectivity - 10
Design, finish and comfort - 10
Autonomy - 6.5
Applications - 7.5
Price - 4.5



User Rating: 4.05 ( 5 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. Very good report.
    What I find very strange is the issue of the GPS. Can't you have a faulty version in this regard? Are you going to take it to the technical service to see what they say?

    A salute.

    1. Unfortunately, it's common to several watches, not just my unit. And if it were a unit problem, it would fail every time, not sometimes.

      1. I have the apple watch series 2 and I don't get that kind of drawing on the GPS. It's a straight line. I think your watch must be wrong. But I had a Phoenix 3 and this one made some exaggerated peaks.

  2. Very good analysis, and very complete.
    I have to congratulate you on your great work.

    Just one question.
    How would the clock behave when paired with an Android phone?

    Not everyone has an iPhone.

    Greetings and thanks for your work

      1. For Android there is the possibility of acquiring the samsung gear fit 2. I had it and was very happy but as I have iphone, I sold it and bought the apple watch series 2 nike+

  3. You can only give applause ???????????.
    Piece of analysis. I thought I had it down for a price. And even though I'm a fitbit user, I think I'll go with a simple garmin with GPS.
    And by your count, it'll get even better.

  4. I bought a Suunto Ambit3 Peak Sapphire and I think it's a great watch, but I'm under using it. I just go out for a run, and occasionally with the bike. As an Apple user, I'm thinking of selling the Suunto (it's 3 months old) and getting the Nike+ or keeping the Suunto for sport, and getting a Series 1 for everyday use.

    Actually, I'd go for the Nike+... what a mess.

    Congratulations on the analysis.

    1. Hi, I also had the Ambit3 Peak and I sold it to buy the Series 2. The thing is that I'm an INEF student and I have to use heart rate graphs to do some work and I think I screwed up. With the review I realized...

  5. Thank you very much for the analysis, I am about to buy it and all this information is appreciated.
    From ignorance I would like to ask you if it is possible to follow a route that you have previously uploaded to the Apple Watch and be able to follow it without having to carry your mobile.

    Thank you and a greeting

    1. I don't think so. Or at least not from the native applications (that's for sure). And from third parties I don't think so either. Runtastic can load a route (at least in the phone's app) but I don't think it gives you concrete indications. It rather warns you if you go out.

      You'll have to confirm with another partner.

    2. As Emilio tells you, no native application allows this at the moment. We will have to wait for some developer to think about it, but it will be more complicated if it is not a simple navigation application but is used to follow a route through a mountain (i.e. not associated with a map) and also records exercise data.

      It's possible, but I don't know if there are many developers who would be compensated for doing all that work.

  6. Great analysis, I just discovered your blog and it's very interesting.
    I have just received the apple watch series 2 nike+ and I am trying it out little by little, to see how it behaves.
    is there a way to see the tour directly on the watch?

    Thank you and greetings.

  7. Congratulations!! Brutal work and's impossible to find better studies.
    After analyzing practically all the watches, will you do fitbit blaze?
    Thank you!

    1. From Fitbit I'm currently testing Charge 2. Blaze is on my "to do" list, but it's pretty low on it at the moment....

  8. Very good review and very complete...

    A couple of questions:

    In my case, when I would limit the battery issue is in the bike tours, but I understand that there pulls the GPS of the iphone (for me essential to take it on a mountain trip in case the flies) so my doubt is how long the battery can last in that case ... (extrapolating what you may have consumed in any output you have done)

    And my other question is how do you know it has a barometer? and if you think that apple will enable it in the future...

    Thank you very much for your attention.

    1. You can select which device to use for GPS, so you could use the one on the iPhone, in which case the autonomy that would be compromised is that of the phone (which I think is more important to maintain). But honestly, I can't tell you how much longer it will last.

      You can see it on the iFixIt exploded view:

      It will probably be used in the future to count the number of floors climbed, to match the features offered by Garmin or Fitbit, but I don't see them adding altimetry data information in the middle of an activity.

  9. One thing I can't understand is that you can't export the track to Wikiloc, for example, or the workout to Strava. I also don't understand how Strava has not yet become "independent". As for the elevation calculation (I run trail), I also don't understand why the barometer is not being taken advantage of. In any case, if we exported the track with the course, even if it was to the Apple Maps App, it should poder calculate that elevation gain. I really like the watch and I think it works great, but, as you say, it is unacceptable that Apple does not let you share and analyze the training in depth. I also don't understand that you can't train by zones or that you can't program workouts, e.g. 300 meters z2-700 meters z4, and be warned as you train. Hopefully the software will be able to solve all this.

  10. Hello. Good morning, Eduardo.
    Excellent review on this Apple Watch 2.
    Currently I'm hesitating between the Apple Watch 2 and the Garmin Forerunner 735XT, let's say that my sports are limited to athletics (speed and middle distance (maximum series of 1500 meters) and weights / cardiovascular exercise.
    Obviously I am very interested in the daily activity log, but also in the stopwatch and interval functions.
    Which one do you think would best suit my needs?
    Greetings and thanks in advance for your attention.

    1. They are two very different devices... the Garmin is a watch for training and competition and has some functionality as a smart watch. The Apple Watch is the opposite. It already depends on which facet you give more importance to.

  11. Hi Eduardo, first of all CONGRATULATE YOU on ALL your work crack ... VERY BIG ...
    You could tell me how you get the heart charts from the workouts, in your case you make comparisons between three or two heart rate monitors, but, how can I get that chart from the apple whatch 2 ... ????

    Thousands of THANKS

    1. To be able to extract the file with heart rate you can use the app Heart Graph. The comparisons with Sports Tracks

  12. Hello!
    Congratulations for the analysis, very clear and objective, the best I found. I have a question: I swim in the pool. I was using Garmin swiming very satisfied but, the quality of the mesh and the battery life is not very good and I'm tired of replacing the same. The doubts I have are:
    1)The data you used is practically the same as what you show in your report, I only need a few strokes Apple Watch 2 records them?
    2) in my training I do a series of 200 and pause without doing any movement for 1 minute, this pause is counted in the time of a series if you are not doing anything ? I'm just resting.
    3 after syncing on the iPhone the data, from the iPhone there is a way to sync somewhere else, (you can visuslixsr some other way like garmin connect from a notebook)

    1. There are no series, the whole exercise is counted together. Therefore those minutes of rest will not appear in the summary and will alter the whole result of the training. The trainings cannot be exported.

  13. Congratulations, complete review.
    The truth is that I sold the Suunto Ambit3 Peak recently to buy the series 2 (the day before yesterday). I do a lot of running (half marathons and marathons). I also study INEF and I have to do some work with heart rate graphs. Do you think I screwed up? Do you know if any app makes graphs where you can see the frequency evolution?

    I'm on time to return the Apple Watch so it'll be a big help if you tell me... thank you.

    1. The Apple Watch is a basic user-level watch. If you still have time, return it and go back to a more complete solution, because obviously for your studies you're going to need it.

  14. Good evening Eduardo, I'm thinking about buying the apple watch series 2. I have doubts about the basic information that the watch gives about the physical exercise sessions. Right now I have a Garmin and after my workouts I like to see the heart rate graphs and so on. From what I see in your photos, in the apple watch series 2 in the intervals you can't see the heart rate of each interval? If so, some application like strava doesn't allow that option?

    1. Strava has just launched an update of its application, allowing it to be used on a standalone basis. I haven't tested the application, but it will offer more possibilities and above all the possibility of exporting the file.

      However, if you're interested in having a lot of data about your activities, I don't think the Apple Watch is interesting. It's more intended for simpler use.

      1. Hi, Eduardo. Good morning.

        I don't know if you've had time to try out the native strava application in Series 2. I'd like to know if it records all the necessary data to be able to analyze an output. Once in Strava the data is synchronized with Salid, currently what I do is run with suunto, it automatically uploads to strava and so passes the exercise to Salud.

        I have put the ambit 3 peak on sale and I think I will wait for the series 3 to be announced in September.

        1. No, I haven't tried the Strava application. I don't have much hope for the new version... it will still be focused on an occasional audience, so if there are changes it will probably be more socially focused, but not on pure benefits

  15. Hi, i am a fitbit charge 2 far so good. i train alternating routines daily kickboxing, tabata and other indoor workouts with weights. i want to change my fitbit ...will this device work for me to monitor my workouts?

  16. Thanks for the analysis, you missed the track comparison on a running track 😀.
    I'll wait for better versions.

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