Fitbit vs Garmin Heart Rate

[Chitsman]

I have a Fitbit Blaze and Garmin that I use for cycling. I have noticed that on almost every ride my Fitbit is reporting a max heart rate that is 40-50 bpm faster than the Garmin using a chest strap. (Example: 199 bpm Fitbit v 158 bpm Garmin)

Why is there a difference?
Do I have a faulty Fitbit?
Is there a setting I need to change on the Fitbit app?

Any help or explanation would be helpful.

[Rich_Laue]

The biggest distance I see is that the two units use entirely different technology, and both types of technology in general, by independent testing have been found to be off at times. The chest must be used with some type of electrical get, to get accurate readings, especially with a hairy chest like I have.

The bigger question would be which is correct?

[bbarrera]

@Chitsman The chest strap is gold standard for consumer devices, and has been proven in study after study. Even publications like Wall Street Journal have recently compared chest strap to EKG and shown accuracy. As Rich mentions, on cold or extremely dry days you may need to wet terminals, in those cases many people just lick or moisten with wet finger (although electrode gel is cheap and a great option). I only have to moisten termainsl a couple times a year, and even then, if I don't bother within 5-10 minutes I'm getting accurate readings.

Unfortunately when cycling I've had trouble with HR accuracy of optical wrist technology from Fitbit and Apple. There are some optical devices that I've tried that are more accurate, either due to technology or placement (above/below elbow). With optical it is dependent on both the device and individual user.

I train at heart rate threshold, and therefore always use chest strap as it measures electrical impulses that cause heart to beat and is almost always accurate (rare exceptions noted above). Optical technologies like Fitbit use LEDs and a sensor to measure blood flow in your wrist, its less exact vs EKG or chest strap, however generally very good for resting heart rate and steady state cardio. 

You didn't mention if HR accuracy is a priority. Fitbit's approach is to come close on average HR, which doesn't help me (interval training around threshold) but might be just fine if you aren't riding as hard, or not interested in beat-by-beat accuracy. If you just want a decent estimate of calories burned then optical wrist HRM is often just fine for cycling.

I suggest you call Fitbit support and discuss to see about a replacement in case your unit is faulty. In addition there are some wearing tips you could try:

http://help.fitbit.com/articles/en_US/Help_article/Heart-rate-FAQs?p=blaze&c=Topics%3AAccuracy&l=en_...

Hope that helps, again I'd suggest calling Fitbit support to discuss.

[Chitsman]

Thank you for your reply. I am inclined to i.e. be that my chest strap is the more accurate.

I recently had heart valve repair surgery. Since the surgery I have restarted my cycling training. I purchased the Fitbit to help monitor my hedRt after the surgery, both on and off the bike. I find that in the situation with my cycling, the Fitbit is much less reliable than my chest strap. But the reliability makes me question all the heart data I get from the Fitbit. I wish this was not the case. Unfortunately, I do not know of any other device that will give me more accurate data throughout the day.

I am a bit of a data junkie, so accuracy is important to me, otherwise what is the point?

[Chitsman]

While I do not use an electrical gel on the leads of my chest strap, I do wet them with water for conductivity. I never have an issue with getting a reading from my strap.

As to which is more accurate? Due to the really high readings from the Fitbit, I have to believe the chest strap is the more accurate of the two.

[Chitsman]

As an example, my max heart rate is 166. My Fitbit regularly records a max in the 180's to 199. My strap will record 150's to 160's.

I have tried wearing the Fitbit higher on my arm, and the readings seem to be about the same.

[bbarrera]

Keep in mind Fitbit is not a medical device. 

All the technical reviews that I've read indicate Fitbit is pretty good at resting heart rate. And I've seen the same. To my engineering thought process, it seems reasonable to believe that resting heart rate is much easier for wrist-based optical sensors as the arm is not moving. Why? Arm movements cause outside light to reach the sensor which adds "noise" to the sensor signal. There are other errors, such as physiological and others. I've definitely seen accuracy issues creep in when wrists are bent (restricts blood flow) while lifting barbells or dumbbells, or if I shine a bright light toward sensor while flexing wrist. And I've seen reviews where optical sensor picks up on running stride instead of actual heart rate.

Again, resting heart rate is pretty good on these devices as it operates under fairly ideal conditions while on your wrist. Just keep in mind Fitbit is not a medical device. AliveCor's Kardia is worth taking a look at if you are looking for FDA certified mobile EKG (attached to phone and also wrist band).

[Rich_Laue]

It's the gold standard, not because it is perfect but it is the closest, Accuracy of both types is very dependant on the way it is written and the contact to the skin.