Calories cycling

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yirara
yirara Posts: 9,389 Member
edited May 2021 in Fitness and Exercise
I have a good grasp on walking and running calories. Cycling remains an enigma though. Yesterday I took my racebike over small 40km at low speed (rubbish weather) flat terrain in just below two hours. My garmin watch gave me 540 calories for it (gross? Not sure). For now I always used an arbitrary 65kcal net per 5km cycling, which is more than this. Btw, a powermeter is above my paygrade, and I can’t use cleats anyway. Suggestions?
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  • BrianSharpe
    BrianSharpe Posts: 9,249 Member
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    Installing a powermeter was a real eyeopener for me. Itbasically cut my calories expenditure in half from what my Garmin had been estimating (from around 32 cal / km commuting at 25 km/h -relatively flat - to around 17 cal/km). I bought the Stages one which replaces your left crank arm, you could use it with flat pedals but I'm not sure how that might impact accuracy.
  • sijomial
    sijomial Posts: 19,811 Member
    edited May 2021
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    Yes probably a gross calorie estimate, I believe it's only a net calorie estimate when it's connected to a power meter.

    Before I got my PM both my Garmin Edge (with HRM input) and Strava gave pretty reasonable (but gross) calorie estimates for my roadbikes. Within the realms of reasonable which tends to be good enough for purpose.
    Both will take your type of bike, the elevation and your weight into account, they can't know anything about your aero of course and wind strength/direction.
    I would speculate roughly 10 - 15% too high for me and that's far, far better than the unrealistic estimates from MFP which compared to my accurate PM numbers are more like 40% too high.
    I found them too generous for hybrid and MTB bikes though.

    I wouldn't use an arbitrary calories per distance calc but I don't have much flat terrain where I live and my speed varies a lot (aero becomes a more dominant factor at speed compared to rolling resistance at low speed, the power and calories required to overcome wind resistance goes up at the cube of the speed ).

    Do you have any access to a PM equipped indoor bikes at a gym perhaps? It's a useful comparison exercise to compare accurate numbers from a PM to what your HRM might be guessing.
  • yirara
    yirara Posts: 9,389 Member
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    Thanks guys. My arbitrary guess was 13cal/km net at 20kmh with not the lightest bike. Garmin gives me 10.5cal/km net. My thinking was that if I cycle 20kmh then 260 net calories per hour wouldn't be toooo high, considering there's always wind, and taking difference in difficulty of cycling vs running into account. 1hr running would give me about 400 calories (I'm a super slow runner). And walking an hour about 140ish.

    No, I don't have access to a gym with a PM bike. I'd have to sign a one year contract right away, and gyms aren't even open yet. I've not even looked at what MFP is offering as I know it will be waaaay off.
  • NorthCascades
    NorthCascades Posts: 10,970 Member
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    How long did it take to ride 40k?

    There's really no rule of thumb for cycling especially by distance. So many things can affect energy use by so much that is not going to work. You can guesstimate by time and perceived intensity.
  • yirara
    yirara Posts: 9,389 Member
    edited May 2021
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    NorthCascades wrote: »
    How long did it take to ride 40k?

    There's really no rule of thumb for cycling especially by distance. So many things can affect energy use by so much that is not going to work. You can guesstimate by time and perceived intensity.

    Like I said, it wasn't fast. Just 20km/h. My muscles felt very weak and it was raining. Not a good combination. Cycling continuously at that speed is more exhausting than walking, but easier than running.
  • sijomial
    sijomial Posts: 19,811 Member
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    260 net cals / hr is a very low power output, roughly 73watt average. I would be surprised if a regular cyclist wouldn't push out more power than that. Even bearing in mind that's not a quick speed for flat terrain.

    Weight of your bike isn't much of a factor apart from when riding hills and acceleration. On the flat at a steady speed weight of the bike is pretty irrelevant.

    I agree 260cals/hour wouldn't be toooo high. :smiley:
  • yirara
    yirara Posts: 9,389 Member
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    Thanks a lot, sijomial. Yes, i think 80 watts would roughly be a speed of just above 20km/h. What I find fascinating is that my Garmin for once underestimates instead of overestimating. That's the first time I've ever seen this on ANY tracker. That's why I started to doubt my own numbers. :D
  • Jthanmyfitnesspal
    Jthanmyfitnesspal Posts: 3,521 Member
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    FWIW, I believe the Garmin cycling estimate for me on the bike with a HR strap but no power meter. I am a male with average build, and I think that helps these algorithms a lot. Why do I believe them? Because I'm maintaining my weight quite well.

    Where Garmin is failing is on my swim days. Although it counts the lengths and strokes and knows my weight, the calorie estimate is definitely too low! (Compared with many different charts for swimming.) Not only that, the algorithm takes away from my step calories on days where I swim.
  • heybales
    heybales Posts: 18,842 Member
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    My FR310XT with attached power meter keeps it's own calorie estimate, even while it logs the PM info and will display the KJ. I guess because older model device.

    Now KJ is net calories basically, and Garmin's estimate (by HR FirstBeat method) is gross.

    Accounting for that difference (which I do when I correct the workout to the PM numbers since I know what Garmin is going to do with MFP sync), the Garmin is always high.

    1.5 hr workout is usually about 200 cal over.

    I'm not sure why the HR method is so bad on that, or perhaps it's actually doing like it does for running, it mixes HR-based and cycling formula based calories. I can get an calorie figure when I forget my HRM.
    For running it's inflated too, but not as much - and actually during cooler fall season it's about right on when I'm not so hot with elevated HR.

    Ditto that unlike running, you can't do a per distance calorie burn for cycling.
    Strava KJ estimate has been pretty decent if you have total weight of bike & accessories/clothes, and your weight correct.
  • yirara
    yirara Posts: 9,389 Member
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    Thanks guys. I don't really cycle a lot. I do cycle because I don't have a car and want to go to places. Mainly geocaching. And when a cache you really want that find is 20km away from the nearest train station, and you're tight as a *kitten* and don't want to take the bus from that station then cycling is the way to go :D
  • NorthCascades
    NorthCascades Posts: 10,970 Member
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    yirara wrote: »
    I have a good grasp on walking and running calories. Cycling remains an enigma though. Yesterday I took my racebike over small 40km at low speed (rubbish weather) flat terrain in just below two hours. My garmin watch gave me 540 calories for it (gross? Not sure). For now I always used an arbitrary 65kcal net per 5km cycling, which is more than this. Btw, a powermeter is above my paygrade, and I can’t use cleats anyway. Suggestions?

    Just to clarify: you can have a power meter in the wheel or other places, and use whatever pedals you like. Not saying you should, mostly posting in case anybody else with the same question reads this thread.
  • yirara
    yirara Posts: 9,389 Member
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    NorthCascades wrote: »
    yirara wrote: »
    I have a good grasp on walking and running calories. Cycling remains an enigma though. Yesterday I took my racebike over small 40km at low speed (rubbish weather) flat terrain in just below two hours. My garmin watch gave me 540 calories for it (gross? Not sure). For now I always used an arbitrary 65kcal net per 5km cycling, which is more than this. Btw, a powermeter is above my paygrade, and I can’t use cleats anyway. Suggestions?

    Just to clarify: you can have a power meter in the wheel or other places, and use whatever pedals you like. Not saying you should, mostly posting in case anybody else with the same question reads this thread.

    True. But it's still above my pay grade. I know there's a fairly cheap kind of funnel solution, but then I'd still need hardware to use with it, like a bike computer. Thus that's a big no. Plus I cycle far too little. I might do a tour of 40-100km once every 2-4 weeks. Thus...
  • heybales
    heybales Posts: 18,842 Member
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    Strava app on your phone, using the phone GPS for route logging, with correctly setup body and bike weight - and you'll be given a calorie burn that is as good an estimate as you'll get.
  • robertw486
    robertw486 Posts: 2,388 Member
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    I've just stuck with Strava myself, and accept that it still has flaws based on wind, some GPS error, etc. Overall it tracked in line with my weight and intake much better than any other app I tried. I suspect that it may track a little to the higher side in regards to power and calorie burn, but nothing even close to many of the other apps.

    Short of meters, there are just far too many variables on a bike to get really close.
  • yirara
    yirara Posts: 9,389 Member
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    Hmm.. can I use Strava in the background, and use google maps for navigation on the same phone? As I'm usually cycling from coordinate to coordinate Strava would not help for navitation.
  • Jthanmyfitnesspal
    Jthanmyfitnesspal Posts: 3,521 Member
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    I think a bicycle power meter is one of those very-tempting items for a fairly dedicated fitness or competitive cyclist. If you're riding around for fun or for transportation, there is little point in having one.

    I note that it has it's own inaccuracy in terms of estimating calorie burn: It measures the actual energy you applied to the bike. Your calorie burn is computed by multiplying this number by an efficiency factor that varies person-to-person and even over time, depending on your fitness level.
  • NorthCascades
    NorthCascades Posts: 10,970 Member
    edited May 2021
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    yirara wrote: »
    NorthCascades wrote: »
    yirara wrote: »
    I have a good grasp on walking and running calories. Cycling remains an enigma though. Yesterday I took my racebike over small 40km at low speed (rubbish weather) flat terrain in just below two hours. My garmin watch gave me 540 calories for it (gross? Not sure). For now I always used an arbitrary 65kcal net per 5km cycling, which is more than this. Btw, a powermeter is above my paygrade, and I can’t use cleats anyway. Suggestions?

    Just to clarify: you can have a power meter in the wheel or other places, and use whatever pedals you like. Not saying you should, mostly posting in case anybody else with the same question reads this thread.

    True. But it's still above my pay grade. I know there's a fairly cheap kind of funnel solution, but then I'd still need hardware to use with it, like a bike computer. Thus that's a big no. Plus I cycle far too little. I might do a tour of 40-100km once every 2-4 weeks. Thus...

    Funnel?

    Edit to add: I use my watch as a bike computer to collect the data. A lot of people use their phones for that purpose, on the handlebars or tucked away in a pocket. It's fine to not want one, they're a lot of money.
  • NorthCascades
    NorthCascades Posts: 10,970 Member
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    Jthanmyfitnesspal wrote: »
    I think a bicycle power meter is one of those very-tempting items for a fairly dedicated fitness or competitive cyclist. If you're riding around for fun or for transportation, there is little point in having one.

    I note that it has it's own inaccuracy in terms of estimating calorie burn: It measures the actual energy you applied to the bike. Your calorie burn is computed by multiplying this number by an efficiency factor that varies person-to-person and even over time, depending on your fitness level.

    Again, simply for the purpose of clarification, the maximum error using a power meter for bike calories is +/- 2.5%. Because that efficiency factor on a bike varies incredibly little between humans. Using my after work ride yesterday as an example, the PM says 789 kCal, the truth is it could have been anywhere from 770 to 808 kCal.

    I'm not saying anybody in this thread should buy one, I'm clearing up the science. 🙂
  • Jthanmyfitnesspal
    Jthanmyfitnesspal Posts: 3,521 Member
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    I think the reason many people say what @NorthCascades is saying about efficiency comes from the paper "No Differences in Cycling Efficiency Between World-Class and Recreational Cyclists," Mosley, et. al,Int. J. Sports Med (2004). (And other papers like it.)

    I've posted this before, but the problem with this paper's title is that it really means that the average efficiency of each population is about the same. But the paper also shows that there is wide variation between individuals. For illustration, here's a figure from the paper that shows that the "GE165" varies from person to person from 14 to 22%.

    8rj8ru5prybr.png

    The GE165 is defined as

    ((Work Rate [W]/Energy Expended [J/s]) * 100%, as measured for an individual at a power output of 165W
  • heybales
    heybales Posts: 18,842 Member
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    yirara wrote: »
    Hmm.. can I use Strava in the background, and use google maps for navigation on the same phone? As I'm usually cycling from coordinate to coordinate Strava would not help for navitation.

    Oh yes, just start the workout and let it log away.
    Probably some settings to prevent or lessen any interrupting pop-ups.

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