Surprising comparison between my Charge 2 and DH's Tomtom

macchiatto

This is maybe a pointless post and perhaps the wrong forum since it's about two different brands of trackers but something has piqued my curiosity so I figured I'd post in case any of you have insights.

Do any of you and your SOs have different brands of fitness trackers and get unexpected differences (or similarities!) in your respective results? I just got a Fitbit Charge 2 and my husband just got a Tomtom Spark 3 GPS. We've been using these for a week and I don't know if it's a difference between brands or what but both have HRM and our estimated calories burned have both been running around 2100-2300/day.

That seems crazy to me that our calorie burns would be so similar (mine have tended to be a tad higher even); he's only 2 cm taller than me but he's almost 70 lbs heavier, lots more LBM, and works out a lot harder (esp since I've been sick the past few weeks). Our # of steps aren't that dramatically different either. I'm just wondering if his under-estimates or mine over-estimates or both. Any TDEE calculator we use would say he should be burning a lot more calories than I am.

The one other factor is my resting heart rate is around 70 bpm and his is apparently in the low to mid 50s so maybe that's affecting it? (My guess would be that my TDEE is more like 1900 but I would have thought his would be significantly higher.)

heybales

They all use the same formula for converting steps to distance, distance and time is now pace, and pace and weight is calorie burn.
That comes straight from the chipset that provides the accelerometers now.

That's for your daily non-exercise level activity calorie burn.

So accuracy of seeing impacts to see a step, accuracy of how much impact to decide a distance - both play a part.

The devices can dynamically adjust the stride length based on expected impact and measured impact.
But they can only adjust so far with decent accuracy, the outside ranges get less accurate.
So if your default or manually entered stride length is correct for the majority of your day for pace - you are more accurate.
He could be set lower than correct, so distance is short and calorie burn is lower than reality.


Then when you move into the workouts, more potential variance.
It has to guess when HR is high enough to start using HR-based calorie burn formula, resting HR has some bearing there. But the bottom of that range is more inaccurate - so start using it too soon, inflated calorie burn.

It also has to estimate what your HRmax is, and 220-age is terrible estimate for women, tad better for men, but either can be way off.
And then it has to estimate your fitness level, again by resting HR, and probably some factor of frequency of workouts during the week. That decision of what's a workout could throw off calculations too.

So the difference you are seeing between makes is no different than what 2 people would see using the same device.

You could both be using the exact same Fitbit model, HR accurately seen - and see the exact same results that don't seem correct.

Also, while he may work out more intense, you could be more active during the day despite about the same number of steps. It's been shown that unless workouts are just really long, you get more daily increase to calorie burn by being more active outside of exercise.

macchiatto

That is helpful. Thank you so much!

Also, your last paragraph helps explain some things that had surprised me a little with my own calorie burn (that overall calorie burn isn't that different on run days vs non run days--even yesterday when I had a race in the morning--even when the run days have a higher total step count). Especially since I'm getting over being sick and energy is low, I can see how I am inclined to sit on my butt for longer periods when I pushed myself running in the morning.

macchiatto

Also incidentally, yesterday we ran the 5K race together and we ran together the whole way so that was interesting to compare, too. Step counts were almost identical. His Tomtom estimated he burned over 500 calories during that run (his HR was also higher; averaged 167) while mine estimated 300 calories even (HR averaged 153). (And then somehow later in the day, my run record was showing only 251 calories burned, but that's a separate issue!)

heybales

So step counts the same during the race seems about right - curious if the distance seen for just the race was correct?

When he matches your pace (I'd be assuming that perhaps he goes a tad slower) is it easier for him, or the pace you both do is a workout for him also?
Because that HR does seem high if he was backing off some to match your pace.

Then again - that could be totally backwards, and you are more fit and running longer, and slowing down for him. Nice!

macchiatto

Distance logged was pretty close; my Fitbit said 3.09; his said 3.10.

We've both been working our way back into running recently so currently our training paces are pretty similar (though he also does things like hill sprints, intense stairmill workouts, a lot more strength training, etc., while I just finished re-doing Couch to 5K and then do my physical therapy home program 2x/wk for strength).

For race day, since I'd been sick for 3 weeks/missed a lot of training, I was pretty much running at max effort; it was definitely a workout for him but he could've gone a little faster if we hadn't planned to run this one together.

Two years ago I could actually run much faster than he could. One of our twins decided that he and I were the "speed team" and his brother and DH were the "strength team." But health-wise DH has made some great strides and lost weight since then. I need to up my game.