Caution FitBit HR Wearers - Don't Trust That Your Heart Rate is Accurate!

In the effort to track calorie burn and activity, I have seen many patients coming in wearing a FitBit HR.  So, I decided to get one myself to check it out.

I use a Garmin to track my heart rate during exercise, which requires a sometimes uncomfortable chest strap, so the idea of tracking my heart rate with my neat little FitBit HR wrist band was very appealing indeed.

Unfortunately, what I have found is very disappointing - for me, the FitBit is completely useless to track higher heart rates (and based on online reviews and even lawsuits in the US, I am not the only one).

When I am at rest, my FitBit HR measures my heart rate very well.   Now, watch what happens when I put the pedal to the metal on my spin bike.  Pictured below is my Garmin (white watch, left), measuring my heart rate via the chest strap; on the right is my FitBit HR.

While my actual heart rate was 167, my FitBit HR registered only 108.  

This is beyond shockingly inaccurate and actually quite dangerous - for example, if a person with a heart condition has been advised to keep their heart rate under a certain target, the FitBit HR could dramatically underestimate their actual heart rate and mislead the person to think they are under their maximum target when they are not.

When I drove my output near my max with a heart rate of 180, the FitBitHR didn't register at all, which is safer, as at least it is not misleading the wearer with a wildly incorrect heart rate:

***NOTE: Discuss with your doctor to find out what your appropriate target and/or maximum heart rate should be before embarking on an exercise program. ***

It was only after I had stopped my exercise and my heart rate came down into the 120s that the FitBitHR became accurate again:

 

For those who are wondering if the problem could be the Garmin, it's not - I checked each of these heart rates manually against my own pulse, and the Garmin was accurate (though it too can be inaccurate, for example if you are in a cold environment and/or not sweating).  I have also carried out this experiment with different activities, and yes, I have also tried moving the FitBit HR further up my wrist. The results are the same.

The reason for the inaccuracy comes from the technology used to monitor HR.  While the Garmin strap uses electrical activity from the heart measured via the chest strap, the FitBit HR use optical technology to measure heart rate.  This involves using a LED light to illuminate your capillaries (tiny blood vessels) as blood runs past.  Capillary blood flow isn't as distinctly pulsatile as the bigger blood vessels (arteries), and at higher heart rates, it may be very difficult for this technology to distinguish higher heart rates.    I have not tested any of the other wrist devices using optical technology out there, but I suspect they may be at risk of similar inaccuracies.

What I do like about my FitBit HR is the sleep tracker, and the pedometer (step counter) - though both of these features have their limitations as well.

Thus, please exercise caution in your interpretation of your FitBit HR data - your heart rate, particularly during activity, may be highly inaccurate.

***NOTE: Before starting any moderate or vigorous exercise program, be sure to speak with your doctor.***


Thanks so much to Ryan, Jacqueline, and friends for the fabulous discussion that led to this blog post.

Follow me on twitter! @drsuepedersen

www.drsue.ca © 2016

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#Active365 Goes Public!

Here's a chance to get motivated to stick with those New Year's resolutions you're trying to keep.

Lisa Taylor, a Calgary high school teacher (and, I'm proud to say, my amazing sister), launched a Twitter initiative #active365 to help her phys ed students feel inspired to engage in daily physical activity.  When they get active, they take a picture and post it on Twitter - this gets their classmates hyped about being active, stimulates some friendly competition - and Miss Taylor even gives them bonus marks towards their report card!

We are now taking #active365 outside of gym class and to the general public!  Here's your chance to get friends, family, and work colleagues involved and see who can rack up the most #active365 tweets each week, each month, and for all of 2016.  Being #active365 will mean different things to different people - it can mean walking to work or school instead of taking a bus or car; taking the stairs instead of the elevator; taking your kids for a swim in the local pool; going to the gym; ice skating; starting a new exercise class... use your imagination!  You can choose to tweet with or without a picture, but be sure to describe what you did!

So start racking up those bonus marks to your health - let's tweet up #active365 and motivate each other every day of the year!

I would love to know when my readers are Tweeting at #active365 - my Twitter handle is @drsuepedersen - please add it to your Tweet so I can cheer you on!

Important note: Be sure to discuss with your doctor before starting any new activity or exercise program. 

Follow me on twitter! @drsuepedersen

www.drsue.ca © 2016

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