What's Cool In Road Cycling

Polar RCX5: The Ultimate Heart Rate System

Polar was the pioneer in portable heart rate monitors for athletes, and continues to set the benchmark for heart rate devices. Their latest launch is the top-shelf RCX5, featuring just about every possible training feature in a sleek unit that is perfectly designed for cyclists on and off the bike.

Having been in cycling since the mid-1980s and being a scientific geek for at least as long if not longer, I have personally owned or professionally used nearly every generation of Polar watches. Like collecting hockey cards or comic books, I wish I had kept all of them so that I can set up a museum display in my lab! While old tech has an aura of its own, I’m always happy whenever a new toy lands on my desk. With that in mind, I spent a month putting the new Polar RCX5 through its paces.


The RCX5 comes with everything you need to turn your bike, body, and laptop into a cycling cyborg. The RCX5 package is customizable, and accessories include a handlebar mount, speed and cadence sensors, the s3 Stride sensor, the G5 GPS transmitter, the new Hybrid HR transmitter that can give good signals while swimming, and the data stick for downloading to polarpersonaltrainer.com.


Loaded with Features
When it comes to heart rate monitors, I’m of the sentiment that there are only two types of market out there. On the one hand, there’s the large majority who simply want to see their heart rate while exercising. These folks likely have no desire to record their heart rate, download their exercise file, or really do any secondary analysis. For this market, a dead simple heart rate monitor that simply tells heart rate is ideal and all that is necessary.

At the other extreme are folks like you reading this review! My theory with this demographic is that, if you’re going to have any kind of bells and whistles beyond the basic reading of heart rate, you might as well go all out and have as much functionality and interactivity as possible. The RCX5 certainly fulfills this goal by having a full slate of heart rate and cycle computer features, with additional expansion capabilities through compatibility with a wide array of optional accessories. You can choose to purchase the RCX5 in Multi, Run, or Bike configurations depending on what accessories you desire.

All the usual cycle computer features, such as speed, distance, trip, and cadence are available. Ditto for recording features such as lap times and time spent in 5 heart rate zones that you can customize. A variety of interval workouts of different work and rest durations can also be set up on the watch as audio and visual reminders and timers. Finally, Polar has integrated a vast array of tests for everything from estimated fitness through to recovery. The possibilities are too extensive to list and review in detail. However, some highlights in terms of functions:


• The famous big red button is now a much more subdued small blue rectangle, It is angled at about 45 degree angle from the main face of the watch, and remains easy to push while riding with fingerless gloves. In my experience, this is the first Polar watch where I haven’t accidentally pressed the red button in everyday use, which can get incredibly aggravating when you find yourself with hours of “ghost” data.

• For recording laps, a great new feature is the Heart Touch, where you can mark a new lap simply by holding the watch next to the transmitter. This is great for training in the winter with gloves or any time you do not want to be fiddling with buttons. You can also customize this Heart Touch to show the time, activate the backlight, change training view, or show training limits.

• The Zone Optimizer feature can take some of the guesswork out of training. Rather than static heart rate zones that do not change day to day regardless of your fitness or fatigue, The Zone Optimizer tracks your heart rate and heart rate variability in the first 5 minutes of your workout, prompting you to ride for 2 min each in your Zones 1 and 2, followed by 1 min in Zone 3. From this, an algorithm adjusts your 5 heart training zones for that workout.


• The RCX5 can display 4 lines of data at a time. Pretty much any data you can think of can be displayed, from the usual speed and distance, lap and total times, through to different heart rate metrics (max, average, current) and energy burned (kcalories). Each of the lines of data have a similar size though, so none necessarily pop out at you. However, the large watch face makes the screen quite easy to view and the display is very readable.

• You can switch easily between up to 6 Training Views, each with 4 lines of customizable data. Furthermore, there are additional settings for 2 bikes, running, swimming, and other sports. The unique aspect of the RCX5 is that, even in the middle of a workout, you can switch between bikes or the multisport settings, permitting you to log a dual workout within the same file.

• The soft fabric Wearlink HR strap from Polar is simply the most comfortable strap I have used. It conforms well to the body, and can therefore be snugged up really tight so there’s no risk of slipping, but yet not restrict breathing or feel uncomfortable at the same time. The RCX5’s new “Hybrid” transmitter is the first from Polar that is designed to provide clean signals while swimming.

Ease of Use
Loads of features are pointless if the unit itself is difficult to navigate or to set. The Polar system shines in this respect, thanks to easy two-way communication with the polarpersonaltrainer.com on-line training log software. You can adjust pretty much everything directly using the watch by itself, but it can be annoying pushing all those watch buttons on a continual basis. I personally found the buttons so well placed on the RCX5 that the watch simple to configure on its own.

We will have a more in-depth review of Polar’s online training tracking software, polarpersonaltrainer.com, in another article, because it has been extensively updated and improved. The main thing to note, as it relates to the RCX5, is that data transfer using the data stick is simple to use and foolproof.

Briefly, PolarPersonalTrainer.com can provide nearly every type of heart-rate based training analysis that you can desire. Polarpersonaltrainer.com has added GPS viewing to its features, so each downloaded file includes an integrated view of the ride on Google Maps set to the terrain map view. Start, finish, and each lap are clearly marked, and the entire map can be zoomed in and out. This is a huge improvement over downloading it and then opening it up separately on Google Earth. For someone who’s travelling as much as I will be this coming year, GPS is a perfect way for keeping a scrapbook of great rides in different parts of the world.

Another nice feature of polarpersonaltrainer.com is the algorithm calculating Training Load. This gives each workout a numerical value based on effort and duration, so that you can track your long-term training stress and give some insight into your state of fitness or fatigue.

The optional S3 Stride+ sensor provides information on stride length and cadence, and has also undergone a slimming diet and a more secure attachment design compared to the previous Polar footpod sensors.

G5 GPS = Goodness
For me, though, the real star of the show is Polar’s new G5 GPS sensor, which is compatible with both the RCX5 and RS800CX watches. I really loved using the previous G3 model, preferring it to the traditional speed sensor. That’s because I can use it with any bike at my disposal, rather than having to buy a separate speed sensor for each bike.

The G5 marks a major improvement over the G3 in my opinion, due to its ridiculously small and light (46 g including the rechargeable battery, whereas the G3 was ~50 g without the single AA battery) design. It’s about the size of a large USB memory drive and approximately half to a third of the overall size of the G3, being all but unnoticeable when tossed into a jersey pocket or hydration pack. For multisport athletes, the included armband holds the G5 securely. The G5 has a claimed battery life of 20 hours, and I’ve used it for at least 15 h between charges without coming close to running it down.

The G5 GPS sensor take up pretty much no space and doesn’t flop around in your pocket while standing on the bike. I found it insanely reliable, and quickly ditched the actual bike speed sensor in favour of just using the G5 all the time regardless of bike or sport.

Another improvement with the G5 GPS is that the noticeable time lag I experienced with the G3 seems to have disappeared. With the G3, I found a slight time lag of about 5 s with speed changes before the GPS speed catches up. So you can be at the bottom of a steep roller before the speed reading goes up, and vice versa in that there’s a few seconds lag after you start climbing before the speed drops. I’ve been riding for the past weeks with the G5 GPS right next to my regular PowerTap SL+ hub-based sensor and Joule 2.0 computer, and the speed responds as fast with the G5 as the SL+ hub. Of note of course is that the G5 and RCX5 works as a GPS recorder only, and that it doesn’t provide navigational abilities.

This is usually the point in the review where we’d show a pic of the whole bike computer setup. But since you can just wear the watch on your wrist and stuff the G5 in a pocket, there’s nothing to actually see and you can end up with full functionality with the cleanest look around!

GPS Practical Advantages
In addition to the functionality of GPS itself, the G5 has a whole host of practical advantages:

• For the multisport crowd, the GPS provides a seamless equipment transition between running and biking.

• The GPS also permits a full range of speed and distance tracking for cross-training, from hiking, snowshoeing, skiing, through to kayaking (it’s water-resistant, but keep it in a waterproof pouch regardless!).

• Having as many bikes as I do, it’s a ridiculous expense to equip each of them with a speed sensor. Having the GPS also gives me extra geek points for tracking speed and distance data for the times when I’m running with the cross bike or portaging the mountain bike, along with my commuting and casual errand biking too.

• The speed sensors have non-replaceable batteries, so they’re dead and done once the batteries wear out and you need to buy a complete new sensor. Therefore, combined with the multiple bikes issue, the higher initial cost of the GPS unit will pay for itself.

• Hands up who actually goes to the full effort of measuring the circumference of each bike’s main wheels, let alone different wheelsets with different tires? I thought so, since I’m a science data geek and I still generally just set all of my bike computers to a default 2096 mm circumference for road tires. With the GPS, there’s no need for calibration between bikes and wheelsets or tires.

Godzilla versus King Kong: RCX5 versus RS800CX
Polar positions the RS800CX as the top model in its line, and the RCX5 slots just below it. Realistically, both are top-flight monitors that are useful for either cyclists or multisport athletes, although the RCX5 seems marketed a bit more for multisport. Brass tacks time though: which are the real deciding points when choosing between these two models?

• First off, if you already own a RS800CX, a RCX5 is largely redundant.

• Both are compatible with the same accessories (G5 GPS, speed and cadence sensors, S3 stride sensor for running), so a wash there. Both can record data at multiple frequencies, from 1 s to 60 s intervals.

• If style above all is your deciding factor and this is going to be your main watch on and off the bike, I think the RS800CX looks a lot better off the bike. The RCX5 looks a bit too much like Polar’s old Accurex model in its utilitarian design. On the plus side, the RCX5’s “big red button” is the first Polar model I’ve ever used where I don’t get accidental pressing of the button in everyday use.

• The RS800CX features altimeter data that is not available on the RCX5.

• Both watches are highly customizable, in terms of what data you want displayed. The larger face of the RCX5 permits 4 lines of data as opposed to the 3 on the RS800CX.

• The RS800CX can be downloaded to polarpersonaltrainer.com, Polar’s Pro Trainer 5 software, or exported and then opened up in third party software like TrainingPeaks and WKO+. RCX5 can be downloaded to polarpersonaltrainer.com, or then exported to a file on your computer and then opened up in TrainingPeaks and WKO+. Thus, both are equally accessible across multiple software platforms.

• The RCX5 has new features that are major ergonomic improvements. The memory capacity is higher (I logged 20h worth of HR and GPS data with recording set at 2 s intervals), and features like the Zone Optimizer, Race Pace and the Heart Touch can help with your training, pacing, and also makes the watch itself much easier to use.

• The RS800CX has an OwnOptimizer test feature that analyzes your training status in the morning by examining your heart rate variability at rest. The RCX5 does not have this feature, but similar information can be gained using the Zone Optimizer feature during training, or by analyzing the Training Load information on polarpersonaltrainer.com.

• The RCX5 can switch sports/bikes in the middle of a workout or race, which makes it ideally suited to multisport athletes. In contrast, this would require stopping a file, starting another one, and ultimately many more button pushes with the RS800CX.

So at the end of the day, I found the two watches pretty similar in terms of being fully loaded and excellent watches. Your choice between them really comes down to personal preference.

Is the Polar RCX5 the ultimate training watch? There are other systems out there with close to the same general features for less cost. However, I think it’s fair to say that Polar remains firmly at the head of the pack, thanks to its comprehensive array of features, its compatibility with accessories (GPS, speed, cadence, stride sensor), and the easy two-way interface with the polarpersonaltrainer.com software. If you’re committed to heart-rate based training, the combination of the watch and software gives you everything you need to analyze your training and performance. Put everything together and there really isn’t anything that you would be lacking in terms of cycling computer or heart rate function.

Note: If you have other experiences with gear, or something to add, drop us a line. We don’t claim to know everything (we just imply it at times). Give us a pat on the back if you like the reviews, or a slap in the head if you feel the need!

PezCycling News and the author ask that you contact the manufacturers before using any products we test here. Only the manufacturer can provide accurate and complete information on proper use and or installation of products as well as any conditional information or product limits that may limit their use.

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