Calculating calories burned during exercise

globalc00
globalc00 Posts: 103 Member
in Health and Weight Loss
For treadmill or cycling on a smart trainer, do you just go with the calories burn the machine says or do you use a different method to calculate calories burned or do you just let your activity tracker calculate it?
Obviously there are discrepancies, but trying to figure out which one is more accurate.

Replies

  • nanastaci2020
    nanastaci2020 Posts: 1,072 Member
    Pick one method, use it and check your data over time perhaps 6-8 weeks. Adjust if actual results vary from expected.

    That is the scientific approach.

    Personally I use my Fitbit data, because over the years: it has seemed reliable for me.
  • spiriteagle99
    spiriteagle99 Posts: 3,733 Member
    I use the calories given by MFP for an activity. It is usually pretty close to what the stationary bike gives me. My treadmill is way off in its calorie numbers, but it has no way to input my weight and I think it assumes I weigh 200+ lbs. The calorie burn MFP gives for walks and runs is a bit lower than what my Garmin gives me, but I usually run hills, so my HR goes up a lot more than MFP knows. Over the past several years of mostly maintaining my weight, the MFP numbers have worked well.
  • sijomial
    sijomial Posts: 19,809 Member
    edited October 2020
    If your indoor bike / smart trainer measures your power output (and uses the correct maths - average power in watts X 3.6 per hour = your net calories expended e.g. maintain an average of 200w for an hour would be 720 net cals) then it's just about the most accurate exercise estimate you can get.

    I wouldn't let an activity tracker over-write an accurate estimate with one based on far less reliable and variable metrics such as heart rate. My HR climbs rapidly indoors as I get hot indoors even with a completely steady power output.

    I also wouldn't use MFP's stationary bike categories as they are extremely vague (Chris Froome's "moderate effort" would likely be the same calorie burn as me going flat out!). Definitely don't use the outdoor cycling speed related estimates partly as they are very high even for outdoor riding but also "speed" reported indoors when you aren't actually moving or fighting rolling resistance and aero drag is very exaggerated.

    For the treadmill assuming I'd want to check its estimate against a running mass X distance formula such as weight in lbs X distance in miles X efficiency ratio of 0.63 - if your treadmill doesn't allow you to input your weight then maybe try and find out what standard weight they assume.
  • globalc00
    globalc00 Posts: 103 Member
    My treadmill is very generic and doesn't have weight input. I do however walk on an incline so trying to figure out what effect that has on calorie burn since it is suppose to be more.

    I am wondering if just doing calculation based off heart beat would be accurate. Assuming the heart beat monitor is accurate, I read that using that to calculate calorie burn is the most accurate way. If that is true, than at least I have a constant when I switch between activities.
  • sijomial
    sijomial Posts: 19,809 Member
    globalc00 wrote: »
    My treadmill is very generic and doesn't have weight input. I do however walk on an incline so trying to figure out what effect that has on calorie burn since it is suppose to be more.

    I am wondering if just doing calculation based off heart beat would be accurate. Assuming the heart beat monitor is accurate, I read that using that to calculate calorie burn is the most accurate way. If that is true, than at least I have a constant when I switch between activities.

    The only people who say that are Polar!!
    Heart rate is used as a proxy for oxygen uptake during cardio as it's far more convenient to measure - but people's CV systems are not uniform. Heart rate is extremely variable between people, even people with good fitness levels. Throw people in with different levels of fitness and the differences can be huge between people burning the same calories.

    Even as your fitness level changes your exercise HR will change. Getting fitter not only resulted in my resting HR dropping by 20% but also means I burn 25% more calories at the same HR when exercising.

    If you are fortunate (not an outlier) and you use a HRM for suitable exercise (not strength training, not hard cardio intervals) then you may well approach the level of reasonable estimates and reasonable is often good enough for the purpose of calorie control.

    You can compare your HRM estimates against your bike's power meter estimates to get an idea of how useful/usable it is for you. Be aware the power based estimate is net calories and your HRM is probably giving you a gross cal estimate.
  • karinkrist
    karinkrist Posts: 4 Member
    I just use the MFP app. As you can see from my picture I am not particularly active. But I try to exercise 30-60 minutes every day. Mostly sitting in a chair. Paul Eugene (youtube) has some good routines that are energetic. Not just senior chair stuff. I exercise mostly to try to maintain muscle not weight loss. For maintaining weight I have to count calories. But I see that if you are very active it is hard to determine calories burned. I googled around a bit and there are a lot of discrepancies so I just you the app.
  • globalc00
    globalc00 Posts: 103 Member
    edited October 2020
    sijomial wrote: »

    Even as your fitness level changes your exercise HR will change. Getting fitter not only resulted in my resting HR dropping by 20% but also means I burn 25% more calories at the same HR when exercising.

    I have always been confused about this, maybe you can clarify it for me. If someone who is out of shape walk 1 hour on treadmill at a set speed and incline then this same person becomes more fit, but doesn't lose any weight. Does this person burn more or less calories if he was walking the same amount time at the same speed and incline as before?
  • sijomial
    sijomial Posts: 19,809 Member
    globalc00 wrote: »
    sijomial wrote: »

    Even as your fitness level changes your exercise HR will change. Getting fitter not only resulted in my resting HR dropping by 20% but also means I burn 25% more calories at the same HR when exercising.

    I have always been confused about this, maybe you can clarify it for me. If someone who is out of shape walk 1 hour on treadmill at a set speed and incline then this same person becomes more fit, but doesn't lose any weight. Does this person burn more or less calories if he was walking the same amount time at the same speed and incline as before?

    Think of Physics and not feelings.
    A heavier person doing exactly the same thing as a lighter person will burn more calories for a weight bearing exercise.
    A fitter person will find that level of work easier and have higher capabilities.
    But an unfit person and a fit person doing the same work in a physics sense (same mass moved over same distance) will burn broadly the same calories. There are some tiny efficiency improvements but not significant for simple movements.

    In your same weight but different fitness scenario the fitter person may increase the intensity/speed/distance to allow them to do more work in the same time for the same feeling of effort and burn more calories.

    For example I can cycle at roughly 230watts for 20 minutes working at my maximum sustainable effort level (276cals). A pro rider working at 230watts is literally cruising along easily but we are burning the same calories. But that pro rider has the capability to keep going at 230watts for hours on end or for the same perceived effort level double my calorie burn.

    Where HR as a basis for calories badly falls down is that people's hearts have very different pumping capacity. You train your heart and it gets stronger/pumps more blood with each beat plus you have big genetic differences. If you happen to be average then HR based estimates can be reasonable but it's a wide bell curve.

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