Fitness review: Fitbit Charge 2 HR

Our reviewer puts his own health under the microscope while using Fitbit’s Charge 2 HR over three months

Fitbit Charge 2 HR
(Photo by Aiza Castillo-Domingo)

Fitness wearables have witnessed a steady technological improvement over the past couple of years. From simple pedometers and accelerometers, we’ve seen GPS and heart rate-tracking tools added to these devices. Samsung, Withings, Jawbone and Fitbit have all been active in this space for nearly five years. They’ve all got well-designed websites with uber-fit models rocking their gear in a variety of scenarios. But just how much benefit does a heart rate-tracking wearable really offer someone with ordinary levels of fitness? How accurate are wearables? I’ve been wearing the Fitbit Charge 2 HR for a little more than two months now – here’s the data given to me by the device.

Charge 2 HR
The Charge 2 HR reads changes in flow through the skin’s blood capillaries to provide a real-time heart rate (Picture: Aiza Castillo-Domingo)

1Heart rate study

Charge 2 HR
These screenshots are from the Fitbit Android app. The left shows my heart rate over the duration of this moderate 15-minute workout. It correlates with the second window, which is the rate of burning calories per minute. The third shows the workout in context of that day

The Charge 2 HR has a pair of rapidly blinking green LED lights around a sensor on its underside. The lights bounce back off your skin into the sensor, and the change in blood flow – which is driven by the heart – is used to calculate your beats per minute in real time. When using a Life Fitness crosstrainer (AKA elliptical machine) in the gym, I found the results were nearly in line with what the display was telling me, based on recording my heart beat recorded through grasping two handles.

Peak indicates times when your heart is working at 85 per cent of what the Charge 2 HR has calculated as my maximum rate. Cardio is 70-85 per cent, which is intense but not gut-bursting, while fat burn is 50-69 per cent. As you can see, this elliptical workout in December was hardly an intense on. 

Here’s how I fared at last night’s Bodycombat group workout class, which comprises jabbing, elbowing, kneeing and kicking the air over nearly an hour:

Charge 2 HR
I averaged lower in terms of calories per minute, but hit a peak heart rate 10bpm above the elliptical workout. The massive dip was due to my having to rest (it was my first BC class in months)

Here are the zones my heart was in last week:

Charge 2 HR
The app shows you how much time your heart was in peak, cardio and fat-burning mode on a weekly, monthly and yearly basis

Football is a brutal sport for your body. Aside from the knee and ankle injuries that result from having to sprint, stop and adjust your feet in an instant – aside from mistimed, malicious and accidental tackles – the sport also takes a toll on the heart. I wore the Charge HR 2 during 16 football matches over a two-month period, each lasting an hour and taking place over two months.

As the previous graph illustrates, Monday and Wednesday stand out as the days when I played football. Let’s compare the two games:

Charge 2 HR
Monday’s game (top) began on a tough note in a four-aside match, which involves more running. In the Wednesday match, I slowly built up intensity due to a niggling foot issue from the Monday game. Major dips in the graph indicate time spent in goal

The in-game dips on the graph occur when I played in goal. It should be noted that in the Monday session I played about 20 minutes of four-aside football before commencing a five vs four game for more than an hour immediately afterward – harder running for a longer period is the reason for more calories burnt.

Now, let’s look at the figures from my first match wearing the Charge 2 HR in the last week of December:

Charge 2 HR
I spend more than half of this match last year in the peak zone

The most glaring stat here is the amount of red – more than half the workout was spent in peak zone, which indicates my heart was pumping at close to full capacity over 30 minutes. Was I working harder in that game? Perhaps. However, it could also be that my ticker didn’t need to work as hard last week as it did in the last week of December. My resting heart rate then averaged nearly 67 versus last week when it averaged a little over 59.

Why does resting heart rate matter? Because this is the minimum speed your ticker needs to deliver blood around your body when it’s inactive – i.e. you’re at the desk or asleep. If you wear the Charge 2 HR enough while asleep, working out and at rest, the app gives you a cardio fitness score (factoring in what you’ve entered as your current weight). At the moment, I’m 43-47: average, but nearly good (at the upper end). To contrast, the current US marathon record holder hovers somewhere around 81.

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Over time, the reduction in average resting heart rate is a positive indicator of one’s health improving

What activities is the Charge 2 HR not so good for? Seeing as one’s hands are still will pedaling on a stationary exercise bike in the gym, it’s understandable that the device isn’t able to track this workout. However, I still tried to manually begin the exercise by starting it on the device: 

Fitbit Charge 2 HR
The device can store up to seven pre-selected workouts. Unfortunately, it can’t track your workout on a gym bike. Lower text is blurry because it was strolling

As this mode needs to work with GPS to track your pace, the results of the ‘workout’ were literally all over the place. Following a 20-minute ride, here’s what the app had to report:

Charge 2 HR
According to the GPS, I cycled a weird polygon-shaped route at a speed of less than 0.1mph for 20 minutes. Not very impressive…

Other activities that won’t be tracked by the Fitbit include swing yoga and swimming (the device isn’t waterproof, so don’t even try it).


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I had a longer period of motionless sleep following a Bodycombat session and full work day (left) than after a lazy Saturday spent at home

The Charge 2 HR’s built-in accelerometer monitors your sleep, showing you how both the total number of hours and quality of sleep based on your movement. You can study trends in your sleep over time and even draw up correlations related to diet and/or exercise – for example, I found that my restlessness at night tended to be higher when I’d had a late meal. However, a late workout saw me sleep far more still. Here’s a comparison of the charts from Saturday night and Monday night:

The last day of the weekend was extremely relaxed, most of it spent on a couch binge-watching films. Perhaps that’s why my unconscious self spent the night tossing and turning, according to my Fitbit. The fact is that, despite only half an hour more sleep after a far busier Sunday, which encompassed dealing with deadlines at the office, driving to and back from work, going for a fairly intense Bodycombat class, I feel far more rested the next day.

Being tapped on the wrist is also a nicer way to be woken up than the harsh ringing of a smartphone speaker. You can shake your wrist or rap fingers on the display to snooze, but it takes a press of the device’s single button to disable the alarm. The only downside is on the app-side; it takes a minute for the sync to send the change of time or schedule for alarms to the device, so there’s potential for mistakes to be made if you’re setting this in a hurry.

3Challenges and guidance

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Stunning panoramic photos from some of the world’s most picturesque walking spots are unlocked as you cross various thresholds. The milestones are based on your personal weekly average, so not everyone has the same challenge

One of the clever things Fitbit has done is invest in its app. The difference between this and the likes of Samsung shows, with a number of challenges you can partake in. These may be against your fellow Fitbit-wearing friends or for yourself. 

Challenges are unlockable based on your completion of the easier ones.

In addition to the personal challenges, there are also a few that pit you against Fitbit friends. I’m currently three days into the Workweek Hustle and about 5,000 steps ahead of one rival. Whenever one of us crosses a certain threshold or achieves a badge, the other is notified via a shared messaging window. You can also “cheer” these achievements. It’s not going to get you ripped, but it’s a great way to squeeze out a couple of extra strolls around the office for us desk drones. The app and device encourage walking on an hourly basis from 9am to 6pm (by default). A little buzz on the wrist and you’re asked “Wanna stroll?” (If you haven’t moved at all) or “150 steps to win the hour” (if you’ve moved a bit).

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Fitstar includes a range of easy-to-follow video tutorials, but the most complex routines require a premium subscription. However, the app pulls data from Fitbit so it knows how effectively you’ve been working

Fitbit has also developed a companion app, Fitstar, to guides you with video training on everything from burpees to press-ups. You can pick between a male and female trainer and the exercises include simple moves such as reverse shoulder rolls and more complex actions like three-point jump lunges. A few are free, but the bulk of the guided videos require a premium subscription, which is Dh29 a month or Dh147 per year. Is this good value? That depends on your own motivation and learning style. Bear in mind that equally qualified trainers are available on YouTube for free.  

4Battery life and other notes

I can go about two-and-a-half days out of the Charge 2 HR without needing to place it in the charging clip. This is above average for a device that is always tracking your heart beat. The charging accessory has also improved from the first Flex, where you had to remove the device from the wrist band and put it in a cradle. 

The Charge 2 HR is available in a variety of coloured bands. Thankfully, it’s easy to change these so you could replace a worn-down piece after it’s been through a lot.