E-biking Calories: Apple Watch VS Other computers

LiveOnceBeHappy
LiveOnceBeHappy Posts: 448 Member
edited August 2022 in Fitness and Exercise
I have an e-bike, a couple months old. I hit maintenance a few months ago, and I'm finally eating my exercise calories as the app intends.

Calories from the same 40 mile bike ride this morning:

Apple Watch--based on heart rate and also knows my height and weight and age. 1,269 calories.

Strava--based on unknown. It knows my height, weight, age and how far, how fast, and the grade of the ride. 622 calories

My bike's computer (Specialized app)--It knows my height, weight, age, how far, how fast, grade of the ride, and how much assist I accepted from the motor, how hard I peddled. 551 calories.

INSANE! I've been using just the calories from my bike computer (conservative), and I'm holding steady at my weight, but I've also been going over on my daily calories.

Any thoughts on this crazy difference between Apple Watch and the biking apps? Why such a huge difference?

In case you're curious: 5' 2.5", 117.5 lbs, 53 years old, female.

Replies

  • sijomial
    sijomial Posts: 19,809 Member
    Apple watch - heart rate to calories relationship is massively variable and often not a good choice, sometimes a terrible choice!
    HR is very variable due to lots of factors (genetics, fitness level, heat, stress, hydration....). It's also going to be a gross calorie estimate so quite inflated for long duration exercise. I wouldn't use it.

    Height and age are irrelevant.

    As Strava doesn't know how much electric assistance you are getting and your bike computer does I would go with the Specialized estimate.
    Out of interest does your bike computer tell you how much power you put through the pedals?
    (Either in average Watts or total work in KJ.)

    PS - if you provide a link to your Strava ride people would have more data to go on. And/or a screen shot of the bike computer.
  • BrianSharpe
    BrianSharpe Posts: 9,248 Member
    I'd be going with the bike's computer. When I installed a power meter on my road bike a few years ago I was surprised with how much less energy I was expending compared to what my Garmin had estimated without wattage.
  • iancity
    iancity Posts: 26 Member
    DC rainmaker has some great reviews of health/fitness stuff and he NEVER recommends heart rate/calorie info from something on your wrist on a bike ride. Far too many fluctuations - if you want to measure heart rate on a bike ride go for a chest strap.
  • AnnPT77
    AnnPT77 Posts: 34,261 Member
    iancity wrote: »
    DC rainmaker has some great reviews of health/fitness stuff and he NEVER recommends heart rate/calorie info from something on your wrist on a bike ride. Far too many fluctuations - if you want to measure heart rate on a bike ride go for a chest strap.

    FWIW, I do both, at different times, cycling on the same route. I don't get noticeably different calorie-estimate results from wrist HR or chest-belt (run through the same algorithms) on the same route at roughly the same speed. I can imagine that bike position could make a difference, and so do lots of other factors (skin tone, arm hair, etc.).

    I do absolutely need the chest belt for rowing: Random drops in observed HR are common with wristwatch HR only.

    I don't have huge faith in HR based calorie estimates for cycling. Power meter would be more accurate, if someone really wants best accuracy. I'm not willing to spend the $$, so I'm willing to accept my tracker's estimates, though that's in a context where I do have a tested HRmax rather than an age estimate. (My age estimate is around 25bpm too low, which I suspect would throw off calorie estimates quite materially, and divergence from age estimates is quite common in the population.)

    In OP's case, with the E-bike, I'd be even more skeptical of HR-based estimates. Like others, I'd go with the bike's estimate, too, for two reasons: It has the most complete data to estimate with, and it's the lowest (when unsure, I always use the lowest of any available semi-rational exercise calorie estimates).

    Even then, if I wanted to be super accurate, I'd be trying to find out whether the bike's estimate is gross calories (includes baseline calories that would be burned if not cycling) - I'd expect that it is. If it is, then it would make sense - again, if one wants to be stricter about it - to subtract from the estimate the number of calories one would be estimated to burn in that time period if not cycling (BMR plus activity multiplier).

    I don't bother with that degree of precision, personally: My BMR+base activity is estimated only around 60 calories per hour, and that's only maybe 3% of my experiential TDEE. I have bigger errors in other aspects of tracking: This is not a big enough factor to be worth messing with, for me . . . but not everyone is me. 🤷‍♀️

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