Revision as of 15:07, 29 May 2016

The Garmin 235, showing the display of heart rate.

I had remarkably high hopes for the Garmin 235. I was naïve enough to think that it would be like the Garmin 225, but with better optical heart rate monitoring, better GPS Accuracy and adding in Connect IQ to boot. Sadly, the GPS accuracy is even worse and the optical heart rate monitoring is still not viable. The 235 has some cool novelties, but if you look at the four basic questions I use to evaluate the foundational capabilities of a running watch, it comes up short.

• How far did I run? This is the most basic question, and sadly the 235 has distinctly grim GPS Accuracy. Even with my low expectations of recent Garmin devices I was rather disappointed. It's possible that the variants of the 235 that lack the optical heart rate monitor (230/630) might do a little better, but I wouldn't expect a huge improvement. Of course, the error that you'll see will depend on the nature of your route. On straight lines and with a clear view of the sky it should do okay, but in tree cover and on twisty courses it's likely to be pretty ugly. How much this will bother you is likely to depend on how what you're using the watch for and the nature of your personality.
• How fast am I running? Knowing how fast you're running can be a nice to know, or it can be vital for your training or race performance. Even the best GPS watches tend to have serious problems with current pace, and the poor accuracy of the 235 exacerbates this. If knowing how fast your running is important to you, then look for a watch that has display of your current Pace From A Footpod.
• Where am I? The 235 has extremely limited support for navigation, but it's better than nothing.
  • Back To Start. This is a simple arrow point to your starting point, so it won't help you backtrack. However, knowing where your hotel is in a strange city or where you parked your car is immensely valuable, especially if you're running a circular route.
  • Back To Waypoint. You can mark a location and use the arrow to point to it later. Again, this is a simple "as the crow flies" pointer.
• What's my cadence? Cadence is one of the most critical and often overlooked aspects of running. If you get your Cadence right, many other things naturally fall into place. . There is support for Cadence from the internal accelerometer, though I find that's not as accurate as the Footpod which it supports. While the 235 has alerts for heart rate, pace, distance, and time, it lacks an alert for Cadence which would have been the most valuable.

The 235 is not a good choice for ultrarunners, as its battery life is too short. You can charge the 235 while you're running, but I'd recommend getting a watch with a longer battery life so you don't have to charge it so often. See Watches for Ultrarunning for more details.

1 Garmin 230/235/630

Garmin produces three similar watches; the base 230, the 235 that adds optical heart rate monitoring to the base 230, and the 630 that adds extra functionality to the base 230. I don't see that the additional price of the 630 is worthwhile.

2 Garmin 235 Pros

• Connect IQ allows the 235 to include rich apps to extend its core functionality. For instance, the ActiFace app makes the activity monitor far more inspiring.
• The 235 is a nice size, looking more like a watch than a brick. I find it a lot more comfortable than the Garmin Fenix 3, [{Garmin Epix]], or Garmin 920XT, though I have rather tiny wrists.
• The color display is bigger than the Garmin 225, though it is neither square nor circular, but flat on the top/bottom and round on the sides, which is odd. Some of the screens end up with the edges cut off, which can make the graphs confusing.
• Like many other recent running watches, and the 235 will act as an activity tracker. I found this is an area where Connect IQ really shines, providing rather more sophisticated visualizations and motivations than other manufacturers. As noted above, I particularly like the ActiFace watch face that displays a graph of your activity level over the last week, and adds badges for things like reaching double your step goal. The 235 will automatically detect when you go to sleep and wake up, rather than having to be told. This makes the sleep tracking a lot more convenient, as I tend to forget. I didn't find the sleep tracking to be as good as the Basis watches, but in the 235 does an acceptable job for casual usage.
• You can enable notifications from your smartphone, which relays the phone's notification messages, such as texts, calls, or other things you've enabled. For instance, it will notify me when someone joins my conference line.
• The 235 has some Firstbeat features that normally require a heart rate strap, such as recovery time, training effect, and V̇O₂max estimation. (See below for the issues with the heart rate accuracy that limits the value of this.)
• The 235 can be charged while running, though the optical heart rate is turned off. This may make it slightly more viable for ultrarunning.
• The 235 can be configured to alert you when a metric is out of range. The alerts include heart rate, pace, distance, and calories. You can also have time-based alerts such as a reminder to take a drink. However, there is no alert for Cadence which is probably the most valuable alerts you could have.
• The 235 will cache the GPS satellite locations for the next few days to reduce startup time. The satellite cash is downloaded when you sync the 235 either via a USB connection or through the Bluetooth sync to a smartphone. I find the faster acquisition is particularly useful when travelling to a new location as older devices can take minutes to get a fix when travelling. I hate standing around on a street corner in the cold, dark, early hours of the morning waiting for my watch to tell me I can start running. I found that the satellite acquisition was on a par with other modern Garmin watches, which means it's extremely rapid when the cache is available, and relatively slow if the cash is expired.
• The 235 will upload your workouts via a Bluetooth link to your smart phone. If you plug the 235 into a computer it will function as a flash drive, giving you direct access to your workouts as '.FIT' files. This provides compatibility with a wide range of software.
• The 235 will record your personal best performances, such as fasted 5K or longest distance. These are a nice novelty, but for most people you won't be setting PR's on a regular enough basis for it to add much value.
• The 235 has a surprisingly nice strap. I sometimes fear that Garmin has a department that specializes in unfriendly and uncomfortable straps. While the 235 is not anything like as nice as a Suunto, it's far better than most Garmin watches.
• The Garmin Connect smartphone app and website are both excellent, and Garmin is continuing to improve them.

3 Garmin 235 Cons

• The GPS Accuracy is terrible. I'll add more details in the near future.
• The Optical Heart Rate Monitoring is also terrible, but it's broadly similar to other systems. See below for details.
• I love the idea of having continuous hear rate monitoring, especially to get things like Resting Heart Rate. However, the poor accuracy limits the value, and the continuous monitoring seems to add problems where the 235 gets "stuck" at a particular value. I'd expected the heart rate data to be used for calorie calculations, but it doesn't seem to have any effect.
• The battery life is annoyingly poor, even for fairly casual running when the watch is used as an activity monitor. I find myself having to charge the 235 far too frequently and it seems to take longer than I'd like to recharge.
• The 235 will automatically pair to a heart rate strap without being in a pairing mode. This means it will link to someone else's strap, which is mightily annoying.
• There's no support for displaying your current Pace From A Footpod while getting all other data from GPS. For situations where pacing is critical, such as running a marathon, this is a must have feature. If you need to know how fast your running, look elsewhere.
• The 235 includes an internal accelerometer to give you an idea of pace and distance while running on a treadmill without a footpod, but I found the accuracy was rather poor. I've yet to come across a watch that can reasonably estimate your pace from the movement of your wrist, nor does it seem likely that this functionality is practical.

4 Optical Heart Rate Monitoring

To analyze the accuracy of the 235's optical heart rate monitor I gathered a little over 20,000 readings and analyzed them in comparison with an ECG-based chest strap heart rate monitor. I created to cross to visualize this comparison. The first graph shows the heart rate measured by the ECG HRM on the horizontal against the Garmin 235 on the vertical. If the two systems match exactly then the point will be on the green line of equality. You can see that many of the points cluster around this green line, but are distributed more widely than I think is acceptable. In addition you can see a cloud of points well away from the green line that represent times when is the 235 was reading a wildly high heart rate. There is some discussion within the running community that these high readings might be the optical system becoming confused by the impact of foot strikes as they tend to be vaguely in the vicinity of Cadence. This graph uses transparent points to give a better impression of the density of data, with black areas having at least 10 data points lining up. There is a blue regression line, which will be aligned with the green line if the system is accurate, but as you can see it is distinctly misaligned. I've also included two red lines that are 25 bpm away from the true value. The second histogram shows the distribution of errors, and includes the erroneous cloud of points is a slight bump to the right of the main spike.

The distribution of readings between the Garmin 235 OHRM vertically and the Garman Ant+ system horizontally.

Here is another view of the same data, showing the greater error.

Of the 20,000 readings, slightly more than 10% were out by more than 25 BPM (demarked by the red lines on the first graph.) The average error (standard deviation) is 19.1 BPM, with an average reading that was 5.7 BPM too high. If you're an experienced runner that has a good idea what your heart rate should be, then you may be able to ignore values that are out by more than 25 bpm. In that case, the standard deviation drops to 4.2 BPM with an average that is 0.03 too low. Of course, if you know your heart rate to within 25 BPM, then the 235 will only get you slightly closer. To give a sense of how the errors manifest themselves, I've included a few anecdotal graphs.

During this run you see the 235 having a couple of major dropouts. For the rest of the run, the 235 roughly tracks the true heart rate.

Here we see the 235 giving an accurate reading, but one that is rather misleading. While I frequently see the 235 displaying a heart rate that is wildly too high or too low, I know I can ignore that information. Where the 235 is more problematic than other optical systems is that it will display a plausible but inaccurate value.

For this run the 235 initially gives an inaccurate reading that is somewhat close to the real heart rate, but then spikes to wildly too high. I tried several times to adjust the tension and position of the 235, but nothing helped.

5 What's Missing

While I don't consider these missing features as 'cons', it's worth understanding the features that are missing compared with other watches. You'll notice that the 235 has a rather short list of missing features ;}

• Altimeter. GPS is far less accurate vertically than horizontally, so a barometric altimeter can provide a much better idea of your ascent and descent. It can also be useful for navigation if you're ascending or descending a mountain. In some races I've been far more interested in how much ascent is left rather than the distance to the top.
• Navigation. The navigation capabilities are useful if there is a risk of getting lost. I've made good use of this feature when running in an unfamiliar city, or when running remote trails. (On a screen this small it might not be much use anyway.)
• Extended battery life. Some porches can extend the battery life by turning the GPS reception off for short periods. This can dramatically reduce GPS accuracy, but it's a useful trade-off for some ultramarathons.
• WiFi Uploads. While the automatic upload of workouts via WiFi is nice, the upload will typically only go to the manufacturer's web site.
• Running Dynamics. Some of the newer Garmin watches can show and record Vertical Oscillation (VO) and Ground Contact Time (GCT). (You can get this with the 630.)
• Web Configuration. Some watches allow you to setup the configuration via a web site, and then download your changes. This is vastly easier than fiddling with the watch.

6 Support This Site

Please support this site This review was made possible by readers like you buying products via my links. I buy all the products I review through normal retail channels, which allows me to create unbiased reviews free from the influence of reciprocity, or the need to keep vendors happy. It also ensures I don't get "reviewer specials" that are better than the retail versions.

7 Visual Comparison

Garmin 235 top	Garmin 235 side	Garmin 225 top	Garmin 225 side	Garmin 620 top	Garmin 620 side
Suunto Ambit3 top	Suunto Ambit3 side	Suunto Ambit2 top	Suunto Ambit2 side	Polar V800 top	Polar V800 side
Garmin Epix top	Garmin Epix side	Leikr 1 top	Leikr 1 side
Polar M400 top	Polar M400 side	TomTom Cardio Runner top	TomTom Cardio Runner side

8 Comparison Table

I evaluate running watches in three distinct ways. Firstly, you can use a watch on its own, without any kind of Footpod. This is probably the most common way runners use their watch, but you miss out on a lot. The second rating is with a standard Footpod that is available quite cheaply. These Footpod's can be reasonably accurate once the calibrated, but calibration is a little tedious. The final evaluation is with the Stryd Footpod, which is vastly more accurate than any other type of Footpod, or and more accurate than GPS. The table below looks at the score, and the value for money of each watch for each of the three conditions. (I’ve also tested the Apple Watch 3, but I’ve not included it in these tables as it’s not really a running watch.)

The score is the sum of how well each watch can answer the four basic questions (how far, how fast, where are you, what's your cadence), plus some bonus points.

1. The "How far you've run" will be based on GPS only for "without Footpod" and "with Standard Footpod", but based on Stryd if supported in the "with Stryd Footpod" table..
2. How fast you're running assumes you're using a Footpod if it's supported, otherwise the rating is 0-2 based on GPS accuracy.
3. The "Where are you?" is based on various navigation features such as back to start, breadcrumbs, and preloaded maps. For some watches, you have to turn GPS off to get the benefit of Stryd, so those watches have worse "where are you scores" with Stryd than without.
4. The cadence score uses 1 point for an internal cadence sensor, 2 points for footpod support, 1 point for support from chest strap cadence, and 1 point for cadence alerts.
5. I give 1-2 bonus points for application support, 1-2 bonus points for data upload, 1-2 bonus points for Optical Heart Rate Monitoring, and 0-1 bonus points for battery life.
6. Value for money is the score divided by the price (at the time I last updated the table.) Your needs may be different, so you might weight the different aspects of the watches differently, or be basing your decision on different criteria totally. Hopefully this table will give you a good starting point for your decision.

8.1 Score Breakdown without a Footpod

8.2 Score Breakdown with a Standard Footpod

8.3 Score Breakdown with a Stryd Footpod

8.4 Basic Features

9 Navigation Features

For "navigation":

• Color Maps gives you full color maps, rather like a smart phone, with roads and paths marked out.
• Track Outline is a display of where you've run, rather like a breadcrumb trail. If there are maps, the outline is superimposed otherwise this is just the outline on its own without any context.
• Course Outline is an outline of a route that can be downloaded. I've found this useful during ultras or in unfamiliar cities where I've needed to know where to go.
• Back To Start is a simple arrow point to your starting point, so it won't help you backtrack.
• Back To Waypoint returns you to a previously marked location using a simple arrow to point.
• Compass. A magnetic compass can help you orient yourself or the map. Without a magnetic compass you have to be moving for the GPS to give you a sense of direction.

(Older Reviews: Polar RC3 GPS, Soleus 1.0, Motorola Motoactv.)