Review: Garmin Forerunner 235

I recently purchased the Garmin Forerunner 235. When I make an expensive purchase like this (It was expensive to me anyway!), I try to be careful and do my research –  so I know I get what I want AND need.

After having my Forerunner 220 for over 3 years, I figured I was due an upgrade. Running watches are expensive, but if you think that I’ve used mine 5 times a week for 3 years, that’s 750 outings. For a watch priced at £250, that equates to about £0.33 per run. That’s significantly cheaper than a coach and represents good value in my eyes.

Which Watch?

I did a bit of looking around and had a think about what I really wanted in my new watch. Optical heart rate was on the list (one less device to worry about and reduced aggravation on my chest from the strap). Activity tracking was another feature I was keen on, as was a device with some better GPS accuracy.

These features were all “nice to haves” along with what I consider my absolute essentials.

1. Must have heart rate monitoring
2. Footpod/cadence capability
3. Programmable workouts
4. Strava integration
5. Customisable data screens so I can have timer, lap pace and distance on the same screen

When it boiled down to it, there were a lot of devices that fit the bill, many offering a feature set far in excess of what I actually needed and would have found useful on a practical level.

For example, it may be nice to know what my Vertical Oscillation is, along with my ground contact time – but I can’t say that’s really going to help me run faster, not at my standard.

Equally there are a number of devices on the market now which will let you play music through them – but I don’t listen to music, so wouldn’t want a watch with that feature on it.

What I think I am saying is, “Only pay for what you need or are likely to find helpful”. When I compared all the facts against my requirements, the Garmin Forerunner 235 hit all the right notes.

Garmin Forerunner 235

The device itself comes in 3 different colour options, but the one I went for was black and grey as it looked most like a “day-to-day” watch. I personally wear my Garmin all the time anyway, but as this devices doubles up as an activity tracker, people who wouldn’t usually wear a Garmin all day would probably want something that blends in with their non-running wear!

Garmin Forerunner 235 - Top

Garmin Forerunner 235 - Side Speaking of day-to-day use, the watch face itself is pretty clear. It comes with a highly programmable alarm, and you can set multiple different alarms for different days of the week – which crucially you can set to repeat. This is a brilliant feature as far as I’m concerned, as on my 220 I used to have to turn it back on every day and adjust the time at the weekends.

The charge cable for the Garmin Forerunner 235 is different to the 220, and features a side clip instead of the “right around the back” method. This makes the cable much smaller, but less easy to identify in a laptop bag filled with cables like mine is!

Size wise it is on a par with the 220 and weighs slightly less – I barely feel like I am wearing it most of the time.

Some reviews I have read have complained about the backlight being too dim – I’ve run plenty of times in the dark and it is more than bright enough to read the screen.

Unfortunately, I also read that the alert sounds on the device are a bit quiet – and I have to say I agree. Even when I am running on my own with no traffic around, I struggle to hear the alerts over the sound of my own breathing. There doesn’t seem to be a volume control either – thankfully the vibrate is just about strong enough so I don’t miss my laps.

I’ve also heard some negative feedback on the user interface when using the watch. In my humble opinion, this is the simplest user interface I’ve found on a running watch. It’s very easy to navigate around, make selections, and you can clearly see whats turned on and off using easy to understand logos and symbols… to me it just seems very well designed.


With all the above in mind, lets dig into some of the highlighted features the Garmin Forerunner 235 offers.

Optical Heart Rate

One of the big selling points for me (and probably others) is the Optical Heart Rate sensor that’s built into the watch. I don’t want to worry about using an HR strap as well as a watch so this should be the right solution.

I’d heard mixed reviews on the implementation of the sensor into the Garmin Forerunner 235, with negative comments around the reliability of “locking onto” the heart beat, through to it missing the mark completely and over or understating stating the heart rate readings.

Personally, I’ve had a mixed bag of results but ultimate agree with other people’s comments and views.

Shown below is the data captured from a basic recovery run – the first I did with the watch. Despite running at a very relaxed comfortable conversational pace, it massively overstated my heart rate throughout the workout. Using my personal knowledge of my effort during the run, I know the data should have mostly been in Zone 2, with a bit in Zone 3.

Garmin Forerunner 235 - HR Woes

The next diagram is taken from a long run (20 miles) the day after the previous diagram, and the data here is much more in line with what I would expect to have seen, given the type of run and the effort I put in.

Garmin Forerunner 235 - HR Woes 2

The next chart comes from an easy run. With this data set it’s difficult for me to work out of the chart is right, as it did feel tough – but given the previous two runs I naturally had limited confidence in the watch.  So during the “cool down” phase of this run (Which I had on a programmable workout for the last 10 minutes), I took deliberately the watch off completely, and the watch continued to record a heart rate of 160+! This is obviously not a good result.

Garmin Forerunner 235 - HR Woes 3

The last diagram is from an Interval workout I performed yesterday. If you look at the data you can see the HR for the first part of the workout (and the first 3 interval reps) reps was woefully shoddy, before picking up again and seemingly being right for the rest of the run.

Garmin Forerunner 235 - HR Woes 4


I tweeted Garmin about it who gave me some advice on improving the accuracy (Which is what resulted in a good set of data for my long run), but despite carefully wearing the watch following that guidance I’m still experiencing issues.

Rumour on the Garmin forums is that an update is due to help with this, so i’ll wait and see if this helps (if and when it arrives).

So basically, at the moment it’s not good. It’s just not reliable enough for the data it produces to have any meaning.

A plus point is that I can override the Optical Heart Rate Sensor by pairing the watch with my old strap, but that defeats the object of having the Garmin Forerunner 235 over the 230 (And paying more for it).

EDIT: Following some further research, It seems I may not be wearing the watch tight enough. I’ll retry it and report back with my results next week.


There’s a great feature in this watch which they call “GPS and GLONASS”. GLONASS is the Russian set of satellites that they use for GPS, which means by using GPS AND GLONASS you get double the amount of satellites to your Garmin Forerunner 235 uses to track your activity.

In addition to this, the 235 now offers “1 second recording” for your activities. This means it will record your GPS location every second. The other option – “Smart” recording – which the 220 used instead, detecting when you were running in a straight line and then record fewer data points as it was “smart” enough to know when you were not weaving around too much. This saved battery but if you made a sharp turn it would often not quite “get it” and result in your run recording as a shorter distance than you actually completed.

Additionally, the watch downloads GPS satellite coordinates whenever its synced with Garmin Connect/Mobile. This results in a super-fast satellite lock-on. I was indoors when I first tried it out, and it acquired a GPS fix in seconds!

Essentially, by using GPS, GLONASS and 1 second recording, your Garmin Forerunner 235 should be faster than ever locking on to satellites, and also show an increase in GPS accuracy.

The downside to this is that it results in increased battery consumption. That’s a downside I’m willing to take – it’s not an inconvenience to charge the battery twice a week (See below), especially as using the combination of GPS, GLONASS and 1 second recording produced such accurate results.

From an accuracy point of view, it really is excellent. Of course, its difficult to contextualize this because often implementation of route overlays on a map don’t correlate, but when I’ve made sharp turns or crossed roads, the Garmin Forerunner 235 records them much better than the 220 did.

Garmin Forerunner 235 - Good GPS Accuracy

Garmin Forerunner 235 - Good GPS Accuracy 2

Now, this is all fine when it comes to reviewing the activity in Garmin Connect afterwards, but unfortunately there seems to be a bit of lag when its displaying things on the device. For example, I found that my Lap pace on the watch was a bit “laggy” and struggled to keep up. Early in the lap it would show a much slower pace and then gradually re-adjust until it was correct at the end of the lap. I had a similar issue when I first got my 220 though and this was fixed over time with subsequent software updates.

Customized Data Screens

The main improvement with the Garmin Forerunner 235 over the 220 is around data screens. Not only can you now display 4 metrics instead of 3, there is a wealth of new fields you can display.

This includes temperature fields (Current, and Min/Max in the last 24 hours), lap counter and your navigational heading, as well as some other (To me) non-essential features. But more importantly, your key metrics like distance, speed, cadence and heart rate are all now displayable as “Current”, “Lap Average”, “Average” and “Last Lap” – much better than the 220.

Additionally you can have graphs and charts for your Heart Rate zones as a data screen, and add custom data fields and screens using Connect IQ – but more on that later.

I am very happy with this level of configuration.

Activity Tracking

The device also acts as an activity tracker. It records your heart rate all day, counts your steps, and records your sleep.

Having watched the step counter tick up as I walk, its pretty accurate. I can also vouch for the all day HR being pretty accurate, having done some spot checks while manually checking my pulse.

It does some clever things on the display which shows how its gone up and down in the last 4 hours, and then also calculates what your resting heart rate is. It seems to be pretty accurate there too.

One of the things I also like on the Garmin Forerunner 235 is the sleep tracking. What it seems to do is track your movement along with your heart rate in order to determine your level of sleep. I have no idea if this is right, nor how accurate it is, but when looking at my sleep charts it at least detects the right time I am going to sleep and waking up. I am relying on good faith as to how much of my sleep is “deep” and how much is “light” though!

Garmin Forerunner 235 - Sleep Tracking

The implementation on the watch for activity tracking is good too. All I need to do to see it is scroll through the watch faces and it shows me all I need to. I can turn these on and off using Connect IQ.

Programmable Workouts

One of my key use cases for my watch is using Garmin’s programmable workouts. it keeps me focused in the right pace zones at the right times and keeps me honest. I use a custom workout 95% of the time I am running.

It’s easy to push them to the watch (Either manually or by syncing my whole calendar) and selecting them to use on the Garmin Forerunner 235 is very easy.

Unfortunately, the device has had some issues in implementing them. Specifically, at the end of a “workout step” it sometimes seems to insert a random lap.

This is a workout I programmed and selected on the watch. A simple 8 mile run at a certain pace zone.


When I actually did the workout, it inserted these random laps for no apparent reason. I originally thought that it was a watch glitch, but it is displaying them in the recorded data too.

Garmin Forerunner 235 - Workout Split Issues

These can’t have been added manually (via lap button press) as when you are mid workout, pressing lap would skip you to the next step. The total number of legitimate laps still equates to 8, so I have no idea where these came from!

The main problem for me though is that I want the watch to beep at me when I’m running too quickly or too slowly. At the moment this doesn’t work either.

It’s a minor gripe, but an annoyance that needs to be fixed. According to the Garmin forum these are confirmed bugs though, so I hope to see them resolved in the next update.

Connect IQ

Connect IQ is a bit like an App store for your watch. You can use it to install custom watch faces, custom data fields, and even rudimentary “apps” to your watch.

The “watch faces” customisation is quite a nice feature – If you don’t want to use the default display, you can install an “analogue style” watch face instead for example. There are dozens to choose from in the Connect IQ “Store”.

Similarly, I really like the customisable data fields. One feature I wanted was a “Virtual pacer”, which is available on the higher end watches. It’s not available natively on the Garmin Forerunner 235, but someone has developed it in Connect IQ, so if I wanted to use it for a race, I can now add it to my watch screen.

“Apps” can also be installed to the watch for a variety of reasons, like showing the weather, installing basic games etc – but I have to say I haven’t found one that’s really useful yet.

All the Connect IQ installations happen within Garmin Connect (And Mobile) and then you turn them on and off on the watch ad-hoc.


The Bluetooth connectivity is excellent. When I had the Forerunner 220, it was hit and miss at best – I regularly had to repair the device to get my runs uploaded. With the Garmin Forerunner 235 its MUCH more robust and reliable and I have had no problems with it at all.

Another “smart” addition to the bluetooth connectivity is using “Smart Notifications”. Your phone will pass you the push notifications it receives and display them to you on the watch display (You configure what you receive from which phone apps using Garmin Connect Mobile). You can’t reply to them, but it is enough for you to be able to work out if something needs immediate action or not. Of course, this will only work if you are carrying your phone with you on the run!

Battery Life

I had read bad things about the battery life on the Garmin Forerunner 235, but I have to say it’s not anything I have  had a problem with.

With the following set up, over 4 days constant use, I used 80% of the battery.

  • Backlight lasting 15 seconds with Wrist Turn
  • Smart Notifications on (Receiving about 50-60 per day)
  • Bluetooth always on
  • 24 hour heart rate on
  • Activity tracking on
  • Running 35 miles (4 hours)

That really doesn’t seem too unreasonable to me. It isn’t a hardship to charge it up every few days. We have to charge our phones, tablets, laptops and other devices after all.

It clearly has enough battery to last at least 40 miles which is plenty for me. I reckon if I turned Bluetooth off I’d get a lot more than that too.


  • Great day-to-day watch features
  • Highly configurable alarm
  • Activity tracking and 24 hour heart rate works well
  • Sleep tracking seems pretty accurate
  • Bluetooth connectivity is seamless and excellent
  • Good (in my opinion) battery life


  • Alerts are very quiet
  • Optical HR is highly inconsistent
  • Programmable workouts produce random laps.


Weirdly despite some critical issues at the moment, I still love the Garmin Forerunner 235. It clearly needs to do something with the optical HR which I know is coming, and I will log a support ticket with Garmin about the Workout programming and Alert volume, as when they have cracked those it really will be a top end device.

This review has been entirely based upon my user experience. if you want something more in-depth I can highly recommend DC Rainmaker’s review which really is excellently detailed and doubles up as a practical user guide.

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