9 Fitness Trackers for All Your Fitness Needs

2. Armour39

This is actually the first tracker I used when I started logging my sessions. It’s a chest strap-based monitor, so I only use it for training. UnderArmour recommends getting the chest strap’s sensors wet before wearing; I found that once I was a little sweaty, the sensors had a better connection. Pro tip: I’ve also seen a few people at my gym use their saliva instead of water, as it tranmits an electrical signal better. Gross? Yeah, but you’re about to sweat all over it, right?

To start using Armour39 ($149.99), you click the sensor module into the chest strap, then connect it via the app. The first time you connect the device, it will prompt you to take a 10-minute assessment. It’s good to estable a baseline: then you can go back each month and reassess to compare your results. Once you’ve done the assessment, you can move on to your usual routine. I like that Armour39 tracks heart rate and uses that to calculate intensity — a lot of trackers are distance-based, and since I do a lot of strength training, most of my work can’t be measured in miles. I do like to bike or walk on recovery days, though, so it’s convenient that Armour39 works with MapMyFitness. The pairing of the module and the app felt pretty seamless.

Unique to Armour39 is a metric called “willpower.” This score is a measure of the effort you put into your workout. Your willpower is measured on a scale from 0 to 10, and you can choose to set a target willpower for any session. I’m pretty motivated and competitive (even/especially with myself), so I found it fun to set and try to achieve a target. However, I’d like to know a little bit more about how exactly willpower is calculated.

Armour39 is great for seeing which programs (or even which individual moves within a day’s session) really kick up my heart rate. I like seeing that number spike, and it’s good to see how quickly I recover, too. The module uses Bluetooth, and it can store data to be uploaded to your phone when you’re out of range. It doesn’t track every little stat, but what it does track, it tracks well.

One last thing to keep in mind — Armour39 doesn’t charge via USB or cradle the way some other trackers do — it uses a small CR2032 3V lithium battery, like a watch. The battery life is supposed to be about nine months; I did have a little trouble when my module’s battery died only a few weeks out of the package. However, after a quick chat with the customer service team, a new battery was on its way to me in record time.