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Garmin Forerunner 735XT review: A slim, lightweight triathlon watch that's worth the money

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The Good Lightweight and waterproof, and has GPS for tracking a variety of sports and an optical heart-rate sensor. All-day activity tracking, interval training and phone notifications are helpful. There's a multisport mode to time triathlon transitions and easily switch sport profiles. It's compatible with a wide-range of Garmin accessories.

The Bad It's expensive; there's no altimeter for measuring ascent and descent; and battery life may not be long enough for a full Ironman triathlon.

The Bottom Line The Forerunner 735XT is an exceptional watch for serious triathletes, but there are better and cheaper alternatives for both dedicated runners and more casual athletes.

8.0 Overall
  • Design 8
  • Battery 8
  • Performance 9
  • Software 7
  • Features 8

The Garmin Forerunner 235 is one of my favorite running watches and for good reason: It has everything runners need to take their training to the next level. It's not ideal for multisport athletes, though.

The 235 is primarily a running watch, but its more expensive cousin, the Forerunner 735XT, is equally good and better suited for serious triathletes. This watch can track running, cycling, swimming and other sports, includes an optical heart-rate sensor, and has interval training, all-day activity tracking and phone notifications. Its special triathlon feature can time transitions and switch sport profiles with a single button press.

The Forerunner 735XT costs $450, £360 or AU$700. That's a premium of $120, £80 or AU$230 over the 235, but for hardcore triathletes, it's a price I think is well worth paying.

A laundry list of features

The watch is comfortable and lightweight. It feels good on my wrist when training or while wearing it throughout the day. It's a tad lighter (40.2 grams compared to 42 grams) and has less of a bezel, but otherwise the two devices are remarkably similar, but only when it comes to design. Garmin was able to squeeze even more functionality into the 735XT. It has all of the features of the 235 and more -- a lot more.

garmin-forerunner-735xt-01.jpg

The Forerunner 735XT (left) next to the 235 (right).

Sarah Tew/CNET

Here's everything that's different:

  • Added tracking for pool swimming, open water swimming, paddle boarding, rowing, hiking, cross country skiing and strength training
  • Added support for running dynamics (with a special optional heart-rate chest strap, it can measure ground contact time, vertical oscillation, stride length, vertical ratio and more)
  • Added stress score, lactate threshold, functional threshold power and performance condition measurements (when paired with a chest strap)
  • Added Courses, Virtual Partner and Virtual Trainer features to compete against a digital person or past runs
  • Compatible with Garmin Vector pedals, Varia Radar and lights, Shimano Di2 electronic shifters, Varia Vision heads-up display and ANT+ power meters
  • Compatible with Garmin Tri and Swim-HRM straps

Triathlon support

The watch includes a profile specifically for triathlons, along with an auto-multisport feature. That means you can switch between each sport (swimming, biking and running) with a single button press, rather than having to manually stop one and start the other. It also times how long you take during your transition period. This isn't unique -- this mode, or a similar one, is also present on the Garmin Fenix 3/HR, Forerunner 920XT, Polar V800 and Suunto Ambit3.

garmin-forerunner-735xt-01.jpg
Sarah Tew/CNET

You won't have any problems wearing the watch in the pool, the ocean or the shower. The 735XT carries a water-resistant rating of 5 ATM, which means it can withstand depths of up to 50 meters.

The built-in heart-rate sensor doesn't work while swimming, although that's true for most devices. Garmin is instead offering a triathlon bundle for $500 that includes the Swim-HRM (pool) and Tri-HRM (open water) chest straps. Both of these record heart rate data while swimming -- the latter also supports running dynamics -- but the data isn't displayed in real time and will only be available for review after your workout has been completed.

garmin-forerunner-735xt-01.jpg
Sarah Tew/CNET

Missing features

The 735XT doesn't have a barometric altimeter, which is used for measuring altitude. It attempts to measure altitude using the GPS, although I found it wasn't nearly as accurate when compared to the altimeter-equipped Fenix 3.

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