The most noticeable change from the outgoing Forerunner 35 is the 45’s shape. The previous model employed a square-shaped face; the new version is round, like Garmin’s other watches.
The Forerunner 45 uses a similar silicone strap to Garmin’s more expensive models, with one exception: The straps on the Forerunner 645 and the new Forerunner 245 come with a quick release design that lets you swap different colored bands without using any tools, but the straps on the 45 are screwed onto the body. Garmin sells other colors of bands, but they won’t snap in and out like the Quick Release versions.
While you can’t easily swap out bands, the silicone band is soft and flexible, which makes it comfortable to wear for workouts, dinner dates or just lounging on the couch. The whole thing only weighs 36 grams, so you barely feel it on your wrist.
“It’s so light and low-profile that I don’t even think about it,” our tester says. “Some other watches tend to get caught up when I’m putting on a jacket or button down shirt, but I never had that problem with the 45.”
Garmin says the battery in the Forerunner 45 will last up to a week in smartwatch mode and track 13 hours in GPS mode. Our tester says the battery life was long enough to get him through a week of running without needing a charge. When it did eventually need some juice, it charged quickly. The watch soaked up a full charge in about an hour and a half when it was plugged into a computer.
Garmin didn’t use the same charging clip as on other watches and products, though. The 45 comes with a USB cable that plugs into the back of the watch.
Also on the back of the watch, a heart rate sensor keeps tabs on your pulse. The wrist-based optical heart rate monitor uses LED lights to illuminate how quickly blood flow through veins and capillaries. That data is then used to estimate a person’s heart rate.
The monitor on the Forerunner 45 accurately recorded our testers heart rate. He happened to have a yearly physical while testing the watch, and his resting heart rate estimate from the watch matched the measurement taken by the nurse. But even with the accurate resting heart rate, Garmin includes an important note about heart rate measurement for its watches: There are inherent limitations to the technology, and it’s not meant to be used for medical purposes.
But what most runners want from a running watch is accurate GPS tracking. To that end, the 45 taps into GPS, GLONASS and Galileo satellite systems to you can keep track of your runs no matter where you go. The watch found a satellite signal quickly and was just as accurate as other Garmin watches we’ve tested before, giving our tester the same distance he expected from his normal routes.