My Fitbit Air test revealed the flaws of calorie counting with a health tracker – here’s why

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ZDNET’s key takeaways

• I examined the Fitbit Air’s coronary heart charge knowledge. 
• I in contrast it in opposition to the Polar H10 chest strap, a dependable coronary heart charge monitor.  
• The Fitbit Air is sweet for coronary heart charge checks, however not as correct as a calorie counter. 
  

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Simply how correct is that well being tracker round your wrist? The reality is, you do not actually know. The businesses that create these gadgets equip them with sensors that detect each coronary heart charge spike or dip, however their trackers are designed for basic, leisure use. Inaccuracies occur. 

Nonetheless, most of the high well being trackers on the market are surprisingly correct, and technological advances have introduced every new era somewhat nearer to the gold normal of train and coronary heart charge monitoring. 

I examined this out on the Fitbit Air, one of many health world’s larger releases of the 12 months. Utilizing the Polar H10 chest strap as a management, I recorded my fitness center exercise to see how the gadgets in contrast. Whereas the Polar H10 chest strap can also be a client product, it is usually thought of the gold normal of coronary heart charge monitoring for its technical accuracy. One research discovered that the chest strap confirmed “virtually good settlement” with a reference Lead II ECG system, for instance. 

My exercise routine included each a energy coaching and treadmill session, my typical mix of weight coaching and cardio. Here is the breakdown. 

On the treadmill

I began out strolling, checking the in-the-moment coronary heart charge measurements on each the Polar and the Google Well being app. Toggling between the 2, the Fitbit Air was inside one or two factors of the Polar chest strap. 

As I began to run, the Polar instantly tracked this improve in coronary heart charge because the Fitbit Air’s readings lagged behind. For instance, as I started operating, Polar captured a coronary heart charge of 141. In that very same minute, the Fitbit Air recorded a coronary heart charge of 109. The following minute, Polar recorded 128 bpm, whereas Fitbit recorded 112 bpm. 

After some calibration, the Fitbit Air caught as much as my Polar chest strap’s coronary heart charge readings. The gadgets displayed the identical coronary heart charge knowledge whereas retaining a gentle tempo, however rising or reducing my velocity resulted in some momentary discrepancies within the knowledge. 

This is smart, because the Polar chest strap is nearer to the center than the Fitbit and makes use of electrodes to measure exercise and coronary heart charge, so these adjustments might be shortly recorded, whereas the Fitbit Air has to attend for that coronary heart charge change to make its means from the center to the wrist, making a lapse in knowledge reporting time. 

Listed here are the 2 coronary heart charge graphs, displaying comparable metrics however the barely completely different timing, as talked about above. 

The guts charge metrics carried out swimmingly with below 2.5% error. The Fitbit Air underestimated energy burned by almost 12% throughout my treadmill session. These trackers calculate energy burned by a components that components in coronary heart charge, weight, age, intercourse, exercise depth, and extra. It isn’t so simple as gathering coronary heart charge knowledge, so errors can compound, as we’ll proceed to see in my energy coaching knowledge. 

Power coaching 

To check Fitbit Air’s accuracy to the H10 chest strap, I used each gadgets to trace my full physique exercise on the fitness center. This consisted of lat pulldowns, dumbbell squats to shoulder presses, dumbbell lateral raises, stability ball workouts, and the hip abductor machine. 

In each workouts, the minimal and common coronary heart charge datapoints are essentially the most correct. Energy burned and max coronary heart charge have a higher deviation from the chest strap, with energy burned tripling its inaccuracy from my treadmill session. 

In contrast to within the first check, the utmost coronary heart charge is off by 11% on this check. This might point out that the Fitbit Air is lacking transient spikes in coronary heart charge throughout shorter bursts of depth, as my coronary heart charge rose and fell in between my energy coaching workouts and breaks. 

As a result of my energy coaching periods concerned a number of quick bursts of upper depth after which dips again to a baseline, the Fitbit Air could have missed the peaks of those max coronary heart charge spikes. The second check proves that the utmost coronary heart charge is extra unreliable in weight coaching periods than it’s in regular periods, like a treadmill or cardio train. 

The underside line

I will begin out by disclaiming that two exams is just not sufficient to attract sturdy conclusions on the general accuracy of the Fitbit Air. This was an newbie check at my native fitness center — not a trial in a lab. Nonetheless, this check has helped me perceive well being trackers in a brand new means. 

For instance, wrist or finger-worn well being trackers aren’t going to seize the quickest fluctuations in coronary heart charge, due to their place on the physique. They’re farther away from the center, so it takes somewhat longer for blood to pump to those extremities and mirror essentially the most momentary coronary heart charge fluctuations. 

This leads to a tool that will not at all times seize the subtlest adjustments in coronary heart charge or mirror them in your exercise stats. Go for a coronary heart charge monitor if that is one thing you worth throughout coaching. 

The Fitbit Air ended up recording largely correct coronary heart charge knowledge that matched the chest strap’s graphs total. Regardless of the energy coaching’s most coronary heart charge knowledge’s 11% deviation from the Polar chest strap, the gadget recorded coronary heart charge knowledge with low inaccuracy. I used to be very impressed by these datapoints and would advocate the Fitbit Air as a dependable well being tracker for these very causes. 

However for calorie monitoring… that is one other story. It is troublesome already to calculate energy burned, and every tracker will calculate it otherwise. I did not count on the Fitbit Air to be 11% to 30% off in its energy burned estimations, nevertheless. In case you are utilizing the gadget for weight loss program or weight administration, I might advocate taking these datapoints as ballpark estimations slightly than goal factors.