​Garmin Forerunner 235 review

The Garmin Forerunner 235 is the company's latest running watch with wrist-based heart rate monitoring built in. Coming less than a year after the Forerunner 225, it may seem like a simple incremental update.

But under-the-hood, Garmin has made big changes, cutting out Mio's tried and tested heart rate sensor in favour of its own tech.

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It's a big step and risky one. And if you've read our Garmin Vivosmart HR review you'll know that we found substantial issues with its optical technology. But has it fixed them for the Forerunner 235? You'll have to read on to find out.

Garmin Forerunner 235: Design

Visually, the Forerunner 235's design isn't any kind of departure from Garmin's range of running watches, but it's still a fine looking device. We tested the version with the teal strap, which looks superb, and we were perfectly happy wearing it out and about. Sure, it might look a little silly with a suit, but it's actually one of the least offensive specialist sports watches out there.

It's light, too. Weighing just 42g it's easy to strap on and forget about, and was a welcome relief from other Garmin sports watches, especially the ridiculous Fenix 3 that we tested it against. If there's a downside to the Forerunner's svelte weight it feels a tad plasticky and flimsy, but that shouldn't put anyone off buying.

The Forerunner 235 boasts a 1.23-inch colour LCD screen with a resolution of 215 x 180 pixels. It's not winning any awards for visual prowess, but it does the job of displaying the time (it's always on so works as a proper watch) and stats such as running distance, time and pace and heart rate zones, where it uses the colour screen to best effect.

The strap is rubber with plenty of holes for adjustment, but the strap can be a tad annoying. The loop that tucks in the excess strap can slip back towards the buckle, leaving you with a flappy bit of rubber, which needs some adjustment every time you put it on.

That's not the only irritating quirk of the design. The start run button is positioned towards the top left and we found it snagged when putting on jackets and coats, inadvertently starting exercise sessions, which we'd then have to manually discard. We're not sure why it's such an issue with the 235, as it's not something that we've found with any of Garmin's other Forerunners. Perhaps it's a symptom of mid-winter wear.

There's no built in memory so you can't add your own music to finally leave your smartphone at home, and that's still the biggest plus for the TomTom Spark.

Garmin Forerunner 235: Running metrics

Forerunner watches are complicated affairs these days – and that's certainly true for the Forerunner 235. Part fitness tracker with a smattering of smartwatch skills, there's a lot going on under the hood, but let's start the review with its strongest suit: sports tracking.

The Forerunner has four sport modes: running, running indoor (GPS turned off), bike and a catch-all free tracking setting.

It's quick to access the modes by pressing the main button on the top right, and you'll have to stand around for a bit while it gets a GPS lock. We're pleased to say that the Garmin Forerunner 235 was consistently lightning quick to get its GPS connection, and outperformed the Fenix 3, which often left us standing in the street getting cold before getting a lock.

The run tracking is extremely comprehensive, although falls short of the metrics captured by the flagship Garmin Forerunner 630. You get pace, distance, time and calories (of course) as well as average heart rate, max heart rate, cadence and Training Effect (TE) which rates how effective the session was for you out of five. It's a great line up of features that caters for everyone short of elite athletes. All the snazzy VO2 analysis is left to the bigger, badder Garmins, although recovery time recommendations do feature after workout sessions.

You can access most of these metrics mid-run and you can tap the up or down button to control the metrics shown on screen. Cycle right through and you'll get a big heart rate screen, with an arrow that displays your current zone. This is a fantastic addition, but we'll come onto its usefulness in the next section.

Another feature worth highlighting is the Forerunner 235's ability to load workouts synced from the Garmin Connect web app. In the tool you can build workouts, setting your desired warm up time, workout time, distance or intensity, and warm down period, and have it sent to the watch.

To load a session head to the main menu and on the watch and choose Workouts to load your training plan. The watch will guide you through, ensuring you warm up properly and stick to your goals.

It's a nifty system, but we have to say that the TomTom Spark boasts a load more interesting workout features straight from the watch. With no web set up required, you can load previous routes and ghost runs, racing your previous PBs with live details on the wrist. There's nothing like this in the Garmin ecosystem, and that's a real shame.

Garmin Forerunner 235: HR accuracy

With an optical sensor built into the Forerunner 235, the natural thing to question is whether it's finally possible to ditch the chest strap. We took it out for some detailed analysis against a chest strap and we can thoroughly conclude….drum roll please…no, it's not – for serious runners at least.

The data was slightly odd, and we found that the Forerunner 235's HR reading was very slow to get up to speed at the beginning of runs. Most sessions saw it lag 20-30bpm behind the Fenix 3 with a paired chest strap for the first five to ten minutes, before it caught up. So long as your pace remained steady, it would then stay fairly close to the strap reading.

However, if you then stopped and restarted, the Forerunner would take more time to calibrate to your heart rate once again.

The graphs below show the Garmin Forerunner 235 versus a Fenix 3 with chest strap on the same run.

For the most part the graphs follow each other closely but on both charts you can see an unnatural curve at the beginning of the run and after the rest period. This shows the lag that we described, although anecdotally from a number of runs with the two devices, it spent most of the run within five beats of the strap.

It's certainly not strong enough for tracking high intensity interval sessions (HIIT) or getting really granular with your sessions. We'd cautiously use it as a guide to our effort during long runs.

We don't have enough data yet to ascertain whether the Forerunner 235 is more or less accurate than the Forerunner 225, which uses Mio's technology rather than its own – but we're working on drilling down into that soon.

At this point it's worth taking a minute to process all this information. It's important to remember that you can pair a Garmin chest strap with the Forerunner 235, so you can still get the benefits of the device and accurate training tracking. But that means you're buying the Forerunner 235 for its 24/7 abilities – so if you're not interested that that aspect, pick a cheaper Garmin tracker such as the Forerunner 230.

And there's one more aspect to consider. If you want HR data to colour your workouts stats but can live without top accuracy then the Forerunner's HR data is good enough. Just don't rely on it.

Garmin Forerunner 235: Activity tracking

As well as hardcore run tracking, the Forerunner 235 is also designed to be used as a daily activity tracker. This isn't new ground for running watches – most Forerunners do it, as does the TomTom Spark. However, the Forerunner 235 really raises the bar, for a number of reasons.

Firstly, the design helps. By actually looking decent and not horrifically bulky, you might actually be tempted to wear the Forerunner 235 all-day, every day. Wearing it to bed may be a step too far, but it's possible. You could never say that about the TomTom Spark.

The next reason for its fitness tracking success is technological. Unlike the Spark or any of the other Forerunners, the 235 makes use of the optical HR sensor 24/7, and will keep a record of your heart rate throughout the day. Tap the down button and you'll be treated to a read out of your heart rate over the last 4 hours, with current and resting heart rate called out. It's easy to keep an eye on your stats – but our only complaint is that resting heart rate isn't called out within the app, and it can't be tracked over time.

Tap down again, and you'll get a breakdown of your steps, progress against the step goal, distance travelled in your day and calories burned.

That's not the summation of the activity tracking, and you'll see extra metrics in the Garmin Connect app. From there head to the Snapshots screen and swipe through to view active calories, sleep (and a summary of the last seven days), activities and weekly intensity minutes.

All-in-all the activity tracking is highly impressive and certainly one of the best we've seen from a dedicated running watch. The leader in this respect is the Fitbit Surge, which has the benefit of the company's expertise in activity tracking, but can't hold a candle to the Forerunner when it comes to real training.

Garmin Forerunner 235: Notifications

The Forerunner 235 is also capable of displaying notifications and calendar updates from a connected smartphone, meaning you can see calls, texts and other messages straight from the wrist.

While it doesn't offer any of the finesse or customisation options of a proper smartwatch, it's a simple yet effective system that ensures you're less likely to miss calls and saves you time reaching for your smartphone needlessly.

You only get the first line of a message or text, so it's hardly a proper smartwatch competitor, but works well enough.

If you press the down button and cycle past the fitness tracking screens you'll see a breakdown of your day's calendar appointments and get a weather forecast, too. Keep cycling through and you'll see a list of notifications, and pressing the run button means you can recall them straight from the watch, so you can see what you missed.

It's a surprisingly complete and useful array of smart features for such a fitness focused running watch, and for that we applaud Garmin's simple approach.

Garmin Forerunner 235: App

The Garmin Forerunner 235 is compatible with the Garmin Connect mobile app– available for iOS and Android – and you can also use it with a PC/Mac if you install the Express software.

We've written about Garmin Connect extensively, and the mobile and web services are completely different. The web tool is fantastic and filled with incredibly detailed tools for building workouts, setting routes and getting the most out of your data.

The mobile app, on the other hand, is a slightly different beast. Designed for digesting post-workout and daily activity data, it's not the best designed experience, and it can be a downright confusing at times.

But you can't say it's not in-depth. In Snapshots you can swipe through seven pages of activity data, and you can review pages of data on runs and cycles and look at graphs on aspects of your performance, too. It's messy, it's overwhelming, but it doesn't disappoint when it comes to the nitty-gritty.

Garmin Forerunner 235: Battery life

The Garmin Forerunner 235's battery life is highly impressive and lasted over a week on a single charge, with a couple of runs thrown in. A 5 mile run hardly made a dent on the battery – roughly 5% in total – so we'd have no qualms in recommending it for ultrarunners.