June 30, 2022

Garmin Forerunner 235 Review


Since the release of the Garmin Forerunner 235, it has made its way to become the market leader in GPS running watches. Specifically, the addition of the optical heart rate monitor allowed Garmin to enter into a new category of watches, adopting for the first time their own technology, moving on from the Mio heart rate monitor used in the Garmin Forerunner 225.

I have had this watch now for a good few months, putting it through its paces in a range of different circumstances. It has been very interesting to see the way in which the technology used by Garmin has performed, and is affected by certain conditions.

To note firstly, the Forerunner 235 succeeded the FR225 which was the first optical heart rate device brought out by Garmin. The Forerunner 235 has a significantly new, smaller form factor, taking on a new circular style which greatly uses the whole screen space available. There were also some other nice software additions to the Forerunner 235, such as the bike mode which had been discarded on many other models, making this not just a running watch. In fact, I use this for gym session by using the ‘Other’ Activity type to help focus on heart rate.

You can purchase the Forerunner 235 from Amazon here.

Running with the Forerunner 235

To start an activity, it is extremely simple. From the lock screen, you press upper right ‘Run’ button to take you to the activities page where you again press select to take you to that activities page.

'Run' Activity Page
‘Run’ Activity Page

Once you start your activity by pressing the ‘Run’ button, you can view any one of 4 different data screens. Two of which are customisable of up to four different data fields, and two are heart rate based. One of the Forerunner 235 specific features is the Heart Rate Gauge page which visually displays which heart rate zone you are currently working in. As with any other of the Forerunner devices, you can set the watch to ‘Auto Lap’ at a specified distance, or press the ‘Lap’ button on the bottom right of the watch.

Heart Rate Gauge Page
Heart Rate Gauge Page

As I am someone who does a mixture of track sessions and long runs, I have a general screen with calmative time, distance, pace and heart rate. I also have a second screen which has the lap time, lap distance and pace which is really useful for when timing recoveries.


The accuracy of the GPS has been of a very high standard, one which we have come to expect with the Garmin GPS watches. I have run many pre planned routes , mapped out on MapMyRun.com and have seen very little deviation in distances run. The same goes for when running on the track, to has always given very accurate, reliable results.

Optical Heart Rate

The biggest talking point for this watch is it’s inbuilt heart rate monitor. This measures your heart rate right on your wrist by a flashing green light which goes through your skins and hits your veins. As previously stated, Garmin opted to implement their own, self designed technology into they watch, rather than using the well known Mio technology. This was a gamble as for their first attempt, there was always going to be problems, not just with the hardware, but also the software.

Heart Rate sensor
Heart Rate sensor

I have subsequently been using this watch on an almost daily basis, getting a grasp of the quality of the readings given by the watch in terms of the heart rate accuracy.

The first key thing to note is that it is on the whole at a good level. For the most part, users will find the accuracy more than adequate to give a good idea of their heart rate level. This is specifically seen on longer runs, where the heart rate level is lower. On these runs, the change in heart rate is not too fast and will increase steadily, something which the watch is able to cope with. For me, the data collected on long, steady runs, or even tempos/ threshold runs has been of a very encouraging level.

Long Runs proved to give best results
Long Runs proved to give best results

This same trend may also been said for over longer intervals, such as mile reps. However, it starts to suffer when the change in heart rate is very sudden, seen when doing faster sessions and sprinting. There is certainly a rise in heart rate shown by the watch, but not to the same level as is noticeable from the level of effort. This is potentially the only down fall, where it struggles to keep up during faster intervals and match recovery rates.

Screen Shot 2016-02-05 at 17.14.59

Heart rate data struggled with faster intervals
Heart rate data struggled with faster intervals

Two other things of note is the performance of heart rate data in the cold and when wearing the watch on the inside of the wrist. It has definitely shown up during sessions when it is very cold that the data is not as accurate. Here, the watch often suffers when charging from running to walking for example, not being able to show this change.

Albeit, the accuracy and response time to changes in heart rate were certainly improved when wearing the watch on the inside of the wrist. Although it may be harder to read the screen, I saw much improved heart rate accuracy as a result.

Different Sport Modes

There are different sport modes which you can use the Forerunner 235 with. These include:

  • Run
  • Run Indoors
  • Other
  • Cycle
  • Cycle Indoors

The Forerunner 235 is not designed specifically for swimming but as you can read in my specific Swimming with the Forerunner 235 post here, it can handle basic swims in the pool.

The watch is also very good at being used indoors due to the addition of the built in accelerometer. This means that running on an indoor track or treadmill will give accurate workout results. More details of running indoors with the Forerunner 235 can be found here.


The watch is far more than just a running watch. With a much decreases size, along with the introduction of Garmin IQ, you can easily get away with using this as an everyday watch, rather than just a sports watch. As well as this, there is the activity tracking features, all of those which appear on the Garmin Vivosmart, making this a perfect all round watch.

There are many, many more features which I haven’t talked about, and I have just touched the surface with the extent of what this watch can do. For example, controlling your music and receiving phone notifications are seamlessly integrated and works great.

A final quick thing to note is on the screen. It has good viewing angles meaning it is easy to see when running. The backlight is not great but under any sweet lighting at night it is easily viewable. However, I have found that it has picked up a few scratches along the way when travelling with the watch in a bag when going to races for example, so would suggest getting a cheap screen protector.

The addition of the optical heart rate sensor is definitely a game changer. It makes this watch stand out from the rest, even above that of the higher end 630 which still lacks this feature. Therefore, it comes across as one of the best GPS watches on the market, catering for all your needs. This is added to also by the fact that many of the high end features of the previous FR620 – such as VO2 Max – have made it onto this watch, making it of an elite level.

I have another blog post on changing the watch strap on the 235 here.

Thanks for reading!

Amazon Links

Amazon link for UK readers here.


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