Fitbit's thin Alta tracker dropped around this time last year, and the company is already making an update to it. Today, Fitbit announced the new Alta HR, a nearly identical version of the original wristband that now includes a heart rate monitor inside of it.

Fitbit claims the Alta HR is the slimmest wristband with a pulse tracker, and it's certainly the thinnest heart rate monitor-equipped wristband I've used so far. According to Fitbit, the original $129 Alta and its $150 Charge 2 are its two best-selling trackers, and many customers flocked to the Alta for its design. But Fitbit also explained customers wanted more from the little wristband, and the most requested feature was a heart rate monitor.

The Charge 2 was Fitbit's thinnest wristband containing a heart rate monitor, so the company had to shrink the internals to get everything to fit in the Alta. As a result, the internals are 25 percent smaller than those of the Charge 2, and spotting the difference between an Alta HR and an original Alta is difficult. They both have rectangular OLED displays that you can tap to scroll through various screens filled with activity stats, but the main visual difference is in the band. The Alta HR's strap is slightly textured and has been reinforced with two watch-like security buckles that help fasten the device properly to your wrist. Fit is key to wrist-bound heart rate monitors; not only is the Alta HR available in small, large, and extra-large sizes, but those extra fasteners let you secure the band just tight enough to get an accurate pulse reading.

Valentina Palladino

Valentina Palladino

Valentina Palladino

Valentina Palladino

An improved band makes it easier to fasten around your wrist tightly.

Fitbit also claims the Alta HR consumes less battery life thanks to its shrunken guts. The company estimates the HR will get up to seven days of battery life on a single charge, and that's with continuous heart rate monitoring throughout the day and night. Like the original Alta, the Alta HR can track sleep as well as daily steps, calories, and distance. But the Alta HR will be able to use heart rate measurements taken during sleep to inform new sleep statistics and insights.

According to Fitbit, the device's heart rate monitor actually does more work now while you're asleep than when you're awake so it can estimate how long you're in the various sleep stages: deep, light, and REM sleep. The information from the device's heart rate monitor and accelerometer, plus your heart rate variability data, all get analyzed using machine-learning algorithms to give you sleep insights in the app that can help you sleep better. These insights will get better over time as you log more hours awake and asleep while wearing the Alta HR, but from the moment you start using the device, your data informs sleep insights. For example, let's say you've been running about three to four times each week for the past month. During a week you haven't slept well, a sleep insight card may show you that you generally sleep better on the days that you run, prompting you to try to log a run today in the hope that you'll sleep better tonight.

Sleep is the reason Fitbit, and particularly the Alta HR, may one-up most of the competition. Most other fitness trackers that monitor sleep only do so using the accelerometer in the device—if you move too much at night, it assumes you didn't sleep well. Movement is not the best indicator of a good night's sleep, but analyzing movement with heart rate data taken throughout the night makes that sleep data more useful. The HR still won't be able to give you a perfect picture of your sleep quality, but it will give you a better picture than one painted with movement alone.

Also, the Alta HR's thin and light design makes it easy to sleep with. Any of the fitness trackers I've tried that can track sleep have made it into my bed whilst on my wrist for multiple nights, and some are easier to wear than others. The best ones that have included pulse monitors have been thinner devices including the Charge 2 and Garmin's Vivosmart HR—but even those are bulky compared to the Alta HR. We'll fully review the device in the coming weeks, but Fitbit appears to have made one of the most friendly and effective sleep-tracking wristbands available with the Alta HR (if it works as advertised).

The Alta HR also has all the features of the original Alta, including automatic activity tracking, smartphone notifications, interchangeable bands in leather, sport, and metal styles, and a water-resistant design. As far as we know, Fitbit will continue to sell the original Alta at $129, while the Alta HR will be available at the end of March for $150. Fitbit's new sleep statistics and insights will be available for the Blaze and the Charge 2, in addition to the Alta HR, at the end of March as well.