Inaccurate Calorie Burned

[alex.andujar]

Hello,

I've been using the Blaze for a few weeks now and the calories burned during my workouts are WAY off. The particular program I'm in gives us heart rate monitors so I can see what my heart rate is and calories burned are while working out. For the most part during the workout itself the heart rates match pretty closely. However, upon completion of the workout, the calories burned are so way off. Today for example, the heart monitor showed I burned 1,195 calories during the workout. The Blaze? 686. That's a whopping 509 calorie difference. It's a constant difference of 400-600 calories off from what the heart rate monitor shows. Is there any reason for that inaccuracy? I almost don't trust anything my fitbit says if those numbers are so off track....

[bbarrera]

What type of workout, and how long?

[alex.andujar]

It's all circuit training. 15 stations with a mix of cardio and strength.
You spend 40 seconds at each station and then have a 20-25 seconds to
rest/move to the next station. I typically do 3-4 rounds and the workout is
never longer than an hour and 10 mins. I track it with the circuit training
option in the exercise group but even still it's way off vs. the heart rate
monitor. I know those will always be more accurate but again, it's a
significant difference in calories burned

[Scott_STL]

If you are average height and weight, I would say the Blaze would be closer to your calorie burn. Have you entered all the info into the app to keep track of weight, resting heart rate, height?

[bbarrera]

@alex.andujar its hard to know what to believe in this situation. When walking to get back into shape, Fitbit had good estimates without using HR. At that time I was counting calories and dropped 20 lbs, about 1 lb per week. So I know the non-HR calorie estimates were good for walking. But then I started cycling and tried the Surge and Blaze and they didn't correctly estimate calorie burn, in fact using my iPhone 5s as step tracker (Fitbit app's MobileTrack feature) gave better calorie burn estimates, without HR, than Surge/Blaze. All I did was let my iPhone5s-in-my-cycling-jersey-pocket track "steps" and give those to Fitbit app. And yes, I got better calorie burn estimates than with Surge/Blaze and verified by losing another 10 lbs (1lb/week).

What app is giving the calorie burn from the chest strap HR data?

A simple way to cross-check the two is by using this online calculator:

http://www.acaloriecalculator.com/calories-burned-calculator/

it uses the Compendium of Physical Activity catalog of MET values to estimate burn based on:

- your weight

- duration

- specific activity

Just enter your weight, 1 hour and 10 minutes, and then click on "Calculate Calories Burned in Activities" button. Now scroll down the page (or search) to the "circuit training, including kettlebells, some aerobic movement with minimal rest, general, vigorous intensity" item. I weigh 205 and get 868 calories. Thats a rough estimate, based on averages, and a rather loose description of the activity. 

Note that if you train hard and get good at doing something, like I've done with cycling over the last year, then you may no longer be average and the Compendium based estimates will be off. And for other reasons you may not be average (too heavy, too out-of-shape, very fit individual, etc.), so take those estimates with a grain of salt.

[alex.andujar]

@Scott_STL I would say I'm technically average height and weight (5'11, 183 lbs) but my body fat percentage is upwards of 21%. I've so far entered everything I can in - age, gender, height, weight, body fat percent, etc. The weird thing is my girlfriend also has a Blaze and does the same class with me. Oftentimes the calories burned on hers are off but only slightly - usually 50-100 calories as opposed to the 400-600 calories for me. 

[alex.andujar]

@bbarrera interesting...thanks for providing that website. The rough estimate is in the middle of both the Blaze and strap on HR monitor (it's a Garmin - I forget the model). On average the Blaze usually has me around 600 cals burned, the HR monitor about 900, and the website said 775. At 183 but 21% body fat it's possible that it's on that higher end since I'm not in as good of shape as I used to be. I mentioned to the other poster in the thread that the weird thing is that my girlfriend also takes the class and also has a Blaze but she usually only shows a difference of 50-100 calories burned as opposed to the huge difference I have. I did also notice today that the heart rate monitor showed me at 160 bpm meanwhile the Blaze showed 83 bpm. I definitely sided with the strap on monitor for that one because I was halfway through circuit one and I could feel my heart pounding. In any case, I'll continue to keep an eye on it and probably just assume the true calories burned is in the middle of the Blaze and strap on HR monitor. Thanks!

[bbarrera]

@alex.andujar optical HRMs on the wrist are in a really bad location for a variety of activities that involve non-rhythmic movement, or doing things that like lifting weights or bending your wrist. When I'm working out with a barbell or dumbbell, every wrist optical HRM I've tried will record HR in 60-100bpm range when in fact I'm 120-170bpm. It is unfortunate the Blaze doesn't support Bluetooth chest straps, for these types of situations. 

[Scott_STL]

Since you have entered in all the info about yourself into the app I can only think of one thing to explain the error with the Blaze. And this may affect men more than women, my wrist gets pretty sweaty during my workouts, especially with my 3-rd party watch band to protect the Blaze, I have notice my heart rate reading well under my own heart rate (I could feel it beating in my neck) so I check the old fashioned way with a 10 second count and figured I would dry off the Blaze and my wrist and presto.  The Blaze had a huge increase in my hr measurement. Try taking a towel with you or use your shirt and give it a wipe down on the green lights and your wrist and see if that helps.  There is a little bit of a delay in the new measurement but give it 20 seconds and it should work. 

[bbarrera]

I've seen a lot of errors while using barbells and dumbbells, due to wrist tension and movement. This is a known issue with inaccurate HR tracking and listed as such in the Fitbit help docs on HR. I see 60-80bpm readings when in fact my HR is 120-170bpm. 

Sweat hasn't been a major issue for me, I cycle road bikes in 90 degree heat and spin in the gym. The Blaze generally follows my HR despite a lot of sweat on my wrist. My wrist are relaxed and not moving while cycling and spinning. 

[AlejandraFitbit]

A warm welcome to the Community @alex.andujar, @Scott_STL and @alex.andujar thanks for stopping by.

I would like to know if you keep having inquiries about your calories burned? If you do, I recommend taking a look at the How does Fitbit estimate how many calories I've burned? article, where you will be able to find more information about how the trackers estimate calories.

Catch you later. 

[Kesha1]

My fit bit is not on my arm, however it shows 800 plus calories burned today. Yesterday, it showed over 1800 and I didn't wear or pick it up. 

[bbarrera]

The Fitbit app uses your weight and age to estimate "basal metabolic rate" (BMR), which is the calories you burn just being alive. My BMR is about 1890 calories per day, so the Fitbit app will show 79 calories burned per hour just for being alive and not moving. That will show up with or without a tracker on your arm.