Fitbit Charge 2 HR: An indispensable tool for lifestyle optimization

Truth be told, I’ve mostly owned Fitbit products as wearable activity trackers.  I’ve owned a Fitbit Ultra and a Fitbit One that lasted me a combined 4+ years and a Basis Peak that lasted about 8 months before I got tired of it.  I wanted to upgrade to something that had heart rate as a measure but the Basis wasn’t very good at measuring heart rate, particularly during exercise.  The interface wasn’t that great either so it ended up in a junk drawer.

Activity trackers have come along way from the days of the pedometer, which is what my Ultra and One effectively were.  The Basis Peak measured more data, but accessing this data wasn’t exactly user friendly and the product was recalled after I had stopped using it for a year and a half.  I’m not a big fan of wearing watches or rings, so most of the wearables on the market were just not for me.  That all changed when a friend showed me the new Fitbit interface for the wrist wearables.

What was once a way to increase the number of steps you take in a day is now a powerful tool to take control over your health.  The new Fitbit app when combined with one of the wearables that measures heart rate may completely change the game, at least until Apple copies their interface and gets their continuous blood glucose monitoring clinically accurate and available.  Currently, the Apple app is second rate and the sleep data is relatively useless, imo.

So I decided to get the Fitbit Charge 2 HR and after playing with it for a few months I’m more than pleased with the purchase.  There are a few things I’d change but I don’t know that most people use activity trackers in the way I use them.  I’m primarily focused on optimizing my circadian rhythms, but I don’t like wearing rings and I’m not entirely sold on measuring core body temperature with the Oura Ring.

With the Fitbit Charge 2 HR costing $120 and the Oura Ring costing $300, the decision isn’t all that difficult to make.  So what exactly does the new Fitbit Charge 2 HR have going for it and how do I use that data?  Let’s jump in and see.

Variables I use on the Charge 2 HR

All the things the Fitbit Charge 2 HR measures are available from the home screen of the app.  I don’t use all of the info, just steps, heart rate, exercise, sleep, and every now and again I try to get 250 steps every hour during the day to reduce sitting time.


I use a good amount of the data that the Charge collects, but I don’t use the weight, hydration, or the meal data(Not pictured) as I do time-restricted feeding and I’m no longer trying to lose weight.  These variables are simply not necessary for my goal of circadian optimization.

To access deeper data on each variable, you simply click on it from the home screen and a new screen appears with more information on that specific variable.


The first variable I use the Charge for is steps.  This is simple, I want to make sure I’m getting the proper number of steps per day and have since I bought my first Fitbit in 2012.  Back then, I realized that one of the drivers of my inability to maintain a healthy weight was that I was only somewhat active during weekdays and nearly completely sedentary on the weekends, save for when I’d go disc golfing or to the beach.

I kinda got the hunch that this was a problem, especially during the winter when I’d put on more weight.  I bought the Fitbit Ultra to test this out in February of 2012 and my winter inactivity, particularly on the weekends, stuck out like a sore thumb.  I started logging my steps, put my lower limit at 10k/day, and I lost an easy 10 lbs.

Fast forward to now, and I get way more steps, I’m below my initial target weight, and I’m a little more sophisticated in my step analysis.  I’m more interested in when I’m getting my steps and how that affects my sleep.


Overall,  I just try to crush my steps.  As you can see below, I’ve averaged over 17k steps since I’ve owned my first Fitbit, which is over 6 years ago.  I access this by going to COMMUNITY>FRIENDS>Click my own name.


Heart Rate

The most attractive option that I looked forward to when purchasing the Charge 2 HR is the heart rate feature.  My Basis Peak did this poorly and according to clients the earlier versions on the Fitbit weren’t much better.  I’m all in with how well the Charge 2 measures heart rate.  It appears to be pretty accurate, even with exercise.  It does get a little spotty with intense exercise using the arms, but for the most part it’s accurate if you remember to tighten the band.

I use this feature a lot to monitor what my heart rate’s doing throughout the day, which gives me a pretty good idea of how well my autonomic nervous system is functioning.  The Fitbit app gives you a pretty readable graph showing you how your heart rate tracks throughout the day and gives you a reading of your resting heart rate that you can track daily, weekly, or monthly.


I use this data for several things.  It’s useful to gauge if I’m overdoing my exercise as, generally speaking, overtraining increases resting heart rate.  Heart rate also gives an added level of precision for estimating daily calorie burn, which I use to estimate carbohydrate need.  Additionally, I use it to gauge the progress of my cardiovascular training program by comparing heart rate trends between different weeks, as shown below.


On the left is a baseline week before I began ramping up my cardiovascular training program.  On the right is a few weeks later.  In between I tweaked a few things and I was rewarded with a lower resting heart rate, indicating improvement in my autonomic nervous system..  Additionally, my cardiorespiratory fitness, as measured by VO2max, improved.


Note: Notice that dip to 54bpm just prior to my resting heart rate of 63bpm?  That’s what we call a vacation, folks.  A lot of things change resting heart rate including diet, alcohol, stress level, sleep, infections, etc.

VO2max is an estimate of the maximum volume of oxygen you consume per unit mass per minute.  In effect, it’s a measure of mitochondrial function since oxygen is consumed in the mitochondria.  Greater and more efficient mitochondria help you age better, increasing your healthspan.  I’ve also measured this on a treadmill with a heart rate strap which puts me dead in the middle of the range at 47mL/kg/min, so it appears to be an accurate range.

The final thing I use the heart rate data for is to make sure I’m winding down at the end of the day.  This is crucially important for optimizing sleep, which I’ll cover after exercise.


Exercise is another useful variable that I measure.  Oddly enough, I never really cared to measure it on previous Fitbit products before I got the Charge.  That’s primarily because the Ultra and One didn’t have heart rate data so I really had no way of measuring progress or monitoring how exercise was affecting the rest of my day.

The Fitbit Charge does a great job of estimating exercise, I don’t even need to tell it that I’m exercising, it figures it out via my heart rate.  Right now I’m typically playing around on an elliptical machine, and after inputting that info once the Charge knows when I’m doing the elliptical.  It’s made one error in predicting I was cycling when I was actually mowing the lawn, but I don’t really consider that exercise anyway.  It seems to measure long walks in the same way, but a longer walk does count as moderate to vigorous physical activity.

Below you can see my exercise data from an elliptical interval session.  I’m interested in seeing my heart rate drop a specific amount during recovery from each interval and at the completion of exercise.  Most people don’t care about that info, but other info that people are concerned with such as calories burned, average heart rate, and the percentage of time you’re in each heart rate zone are also available.


My only knock on this is that I wish the heart rate graph had a better legend and the ability to zoom for both the heart rate and timing.  Since I’m not an athlete that data isn’t necessary, but it would be nice.  Truth be told, I look directly at the watch during my recovery interval to make sure my heart rate drops appropriately before my next work interval, so it’s not that big of a deal.

The cool thing about the Charge 2 HR is that, while it doesn’t have a GPS, it can piggyback on to the GPS from your phone.  I still haven’t played around with this feature as I haven’t had the chance to run outside yet.   I have plans do this once the opportunity presents itself.  I prefer to run outside, but my schedule makes that difficult to do at the time I want to do my cardiovascular exercise.


Sleep is the variable I was really interested in measuring with the Charge because I know how important sleep is.  I wake up pretty easily every morning, refreshed and without the need for stimulants.  But I wanted to know if this was just because I was accustomed to that level of sleep and it felt normal to me or if it was because I was getting enough good quality sleep.

With this variable, Fitbit doesn’t disappoint.  The layout is similar to a hypnogram which shows you where you are in each sleep stage throughout the night.  It also gives you total sleep time, how much time you spent in each stage, and a percentage breakdown for each stage of sleep.

Overall my sleep was probably better than most but needed a little tweaking.  Digging in to what a good night’s sleep looks like and tweaking the things I know modulate the different aspects of sleep have allowed me to improve my sleep in 2 important ways.

First, my average amount of sleep every week has increased a bit as I’ve challenged myself to be more strict on sleep hygiene and the things I know will optimize my sleep.  Second, when I do get shorter sleep, my duration of REM and NREM sleep tends to stay pretty consistent while my light sleep takes a hit.  Ideally I’ll always get enough sleep.  But based on what I’ve read, I’m pretty sure losing light sleep is better than losing either REM or NREM sleep.

Of the variables I measure, I manipulate most variables based off how my sleep is going.  It helps me change my daily routine as well as analyze training load to optimize my overall health.

Things that Fitbit should add…

While I am a big fan of the Charge 2 HR, Fitbit could certainly improve this product.  First, body temperature data would be useful.  The problem is that skin temperature doesn’t always correlate to core body temperature which is ultimately what you want to know.  Second, I’d like to follow my heart rate variability(HRV).

HRV is a measure of how well your autonomic nervous system is working and can be used to determine daily training load as well as identifying days where it would be important to lay off altogether and just veg.  I regularly measure mine each morning with an app but this begins to get cumbersome and I stop doing it for a while.  I would definitely use it if it were part of the Fitbit data.

The Oura Ring contains both of these measures in their product.  I’m pretty sure the HRV is accurate, but the body temperature information may not be as reliable.  They also only take HRV data throughout the night and body temperature when skin temperature correlates to core body temperature.  While this likely improves the sleep data, I’d want to follow daily variation for the more than 100% mark up in price.

Another useful measure would be light exposure or a way to enter it.  I’d like to know how much light exposure I’m getting throughout the day as well as when I get first and last exposure.  In clinical studies, the Actiwatch does this to a pretty good degree, but a significant problem is that I wear blue blocking glasses at night so this would need to allow a way to input this information in addition to measuring light where it’s worn.

Finally, I would like the ability to measure variables known to affect sleep such as coffee consumption, alcohol consuption and when I eat.  Granted, I could do this by entering it in the nutrition data, but I would want it plotted in a way where I could see how they affect my sleep so I can fine tune when and how much I consume.  I’m pretty sure I’ve got this down, but being able to access the data would allow me to confirm this.


I am more than happy with my purchase of a Fitbit Charge 2 HR.  While I’m not a fan of wearing a watch, my job basically requires me to do so.  Rather than just wear some random Timex, I like the idea of gathering data that I can use to optimize my health.  Many of the previous Fitbit watch wearables didn’t have a time display so I really had no use for them.

In my opinion, Fitbit has made major upgrades to the new wearables and their user interface is much better than the iWatch.  While the Charge 2 HR does show me texts and phone calls, I really don’t care about that type of thing if the data it collects isn’t actionable or user friendly.  Personally, I feel the iWatch sleep data is a mess and have no interest in moving in to that type of wearable until they get continuous blood glucose monitoring accurate enough to include as part of the package.

There are some drawbacks to the Fitbit Charge, but these are minor and likely not things the vast majority of people are interested in.  I do believe they should be addressed as interest in circadian rhythms grows.  There have been 2 validation studies using the previous Fitbit Charge for measuring circadian rhythms, so this is obviously something Fitbit is interested in doing.

Overall the Fitbit Charge 2 HR has allowed me to tweak several lifestyle factors that have improved my sleep and well-being.  Being already healthy for the most part, I think people at the lower ends of the health spectrum will get tremendous value and returns from the purchase of a Fitbit Charge 2 HR.  I’ve already begun using it with clients and the feedback certainly generates greater buy-in for things like time-restricted feeding, increasing physical activity, and paying attention to variables important to regulating circadian rhythms.

I recommend the Fitbit Charge 2 HR for anyone looking to improve their overall health and well-being.


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