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Calorie discrepancy between Garmin Connect and Strava....

E65RossE65Ross Posts: 23
edited September 2015 in Training, fitness and health
Don't desperately need to know but which do you think the more accurate. Now I'm a very light rider (53kgs). Last 2 rides I've worn my HRM and did the following.....

70.08 miles with 4000ft of climb at 16.3mph, average HR 130bpm (but I did stop twice for 5-10mins). Garmin connect says 1399 calories and Strava says 2566

Today just a gentle recovery ride..... Flatter route 22.1 miles at 17mph with 1000ft climb, average HR 129bpm. Garmin says 465 calories and Strava says 758 calories.

I'm inclined to think strava is more accurate..... But then I would! 465 calories for 22 miles at 17mph average just seems absurdly low!

Any thoughts?

Many thanks

Posts

  • bobmcstuffbobmcstuff Posts: 9,137
    465 calories for less than an hour and a half at a recovery pace doesn't sound unreasonable to me. 758 sounds high, assuming it really was a gentle recovery pace for you.

    I assume you're aware they're using a fundamentally different basis for the estimate - Strava uses its internal power model (unless you have a power meter, when it'll use your actual power) and makes an estimate of calories based on that. The issue with that is it can't account for wind/weather conditions etc. (unless you do have a power meter), and is reliant on your weight entered being accurate. Whereas the Garmin uses the Firstbeat algorithm (different version depending on which Garmin device you have), which is supposedly one of the most accurate waya of determining calorie burn outside of a lab (see this excellent DCRainmaker article for more detail). The advantage of the HR method is that it can account for say, cycling into a 20mph headwind (whereas the Strava model pretty much just assumes you're being lazy and slow!), or vice-versa if you have a big tailwind, are riding in a group or otherwise are getting a lot of drafting assistance it can account for the fact you're working less hard.

    Personally I look at the Garmin calc using the HR method because a) it's more conservative and b) I like that it can account for differences in weather and terrain etc.. They do line up sometimes - generally I find for flat-ish steady rides without much wind the numbers can get pretty close together.

    Bottom line is that both of them are just estimates with their own positives and negatives, so you need to take them both with a pretty big pinch of salt.
  • bobmcstuffbobmcstuff Posts: 9,137
    Also as a general rule of thumb I find ~400 calories/hr for easy rides (Z2) and ~600 calories/hr for harder rides to be reasonable. Potentially a bit more for hard turbo intervals or hard chaingangs but I find those are reasonable rules of thumb. I am heavier than you though, at around 70kg, so generally speaking I would burn more calories to drag myself round the same course (especially if it's hilly!).
  • cougiecougie Posts: 22,512
    For running the average bloke burns about 100 cals per mile. You're a lot lighter so you wily burn less.

    Assume cycling is 4 to 5 times more efficient than running. So your 70 miler would be about 14 miles worth of running. So 1400 cals. So garmin is much closer to the calc than strava.

    I blame our bodies for being too efficient.
  • rafletcherrafletcher Posts: 1,235

    Any thoughts?

    Yep - why are you bothering with it at all? :roll:
  • E65RossE65Ross Posts: 23

    Any thoughts?

    Yep - why are you bothering with it at all? :roll:

    To better know how much i should be eating for recovery etc.

    Or to know how much cake I can have without becoming a fat b*stard
  • buckmulliganbuckmulligan Posts: 1,031
    edited August 2015
    I've always found my Garmin's calorie data to be pretty believable. Can't really comment on whether the 1400 or 465 calorie estimates are accurate for those rides, it seems a little on the low side, but you'd have a better idea of your relative perceived effort.

    Just a thought, but do you have the resting and maximum heart rate values set up properly on your device? IIRC these are crucial to getting accurate calorie burn estimates on Garmin devices. All of the Firstbeat calorie calculations are carried out by the device and written into the FIT files. Garmin Connect basically just displays what is written in the FIT files, no server-side post-hoc analysis is done at all.

    I'd rate Strava's calorie burn estimates somewhere between "random number generator" and "wishful thinking". IMO it's not worth the screen space used to display it, I'd rather have a little smiley face or a thumbs up!

    [edited to add]: just seen that your average HR was ~130 bpm, in which case I'd say 465 calories is probably a good estimate for someone with a high max heart rate (180+). If your max heart rate is lower, then I think you're likely to have burnt more calories than this. If the 65 in your username is your age then your max heart rate is likely to be much lower and you can probably bump them up a bit, but the easiest way is to make sure your HR values are set properly.

    Also, I noticed that you don't explicitly say that you're using a Garmin device, is this the case? If not, then I guess maybe there is some server side calorie calculations on Garmin Connect, so make sure your HR values are set up correctly on your profile there too.
  • buckmulliganbuckmulligan Posts: 1,031

    Any thoughts?

    Yep - why are you bothering with it at all? :roll:

    Why are you bothering with that comment at all, complete waste of everyone's time.
  • wongataawongataa Posts: 906
    I have found that Strava's calorie calculation is in the same ballpark as what my Edge 800 calculates my calories usage to be. I use a HRM and don't have a power meter. The numbers are not the same but usually pretty close.
  • stu-bimstu-bim Posts: 406
    I don't have a HRM and garmin is usually 3 or 4 times strava for long rides
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  • buckmulliganbuckmulligan Posts: 1,031
    I don't have a HRM and garmin is usually 3 or 4 times strava for long rides

    Again, I'd question whether you have the correct user profile parameters (e.g. weight, HR values) put into both of these systems. With that large a discrepancy, something is clearly drastically amiss.

    If people are just going to guess at these values, or better yet, just leave them as default, then of course the values you get out of it (i.e. Calories) is going to be complete garbage.
  • stu-bimstu-bim Posts: 406
    I don't have a HRM and garmin is usually 3 or 4 times strava for long rides

    Again, I'd question whether you have the correct user profile parameters (e.g. weight, HR values) put into both of these systems. With that large a discrepancy, something is clearly drastically amiss.

    If people are just going to guess at these values, or better yet, just leave them as default, then of course the values you get out of it (i.e. Calories) is going to be complete garbage.


    I don't use an HRM and my weight is the same in both
    Raleigh RX 2.0
    Diamondback Outlook
    Planet X Pro Carbon
  • wongataawongataa Posts: 906
    I don't have a HRM and garmin is usually 3 or 4 times strava for long rides

    Again, I'd question whether you have the correct user profile parameters (e.g. weight, HR values) put into both of these systems. With that large a discrepancy, something is clearly drastically amiss.

    If people are just going to guess at these values, or better yet, just leave them as default, then of course the values you get out of it (i.e. Calories) is going to be complete garbage.


    I don't use an HRM and my weight is the same in both
    If you don't use a HRM then any calorie figures will be even more unreliable. Garmin say for their algorithms that you need HR data to get reasonably realistic numbers calorie out.
  • t4tomot4tomo Posts: 2,643

    Bottom line is that both of them are just estimates with their own positives and negatives, so you need to take them both with a pretty big pinch of salt.
    But not too big a pinch, as too much salt is bad for you :D
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  • bobmcstuffbobmcstuff Posts: 9,137
    I don't have a HRM and garmin is usually 3 or 4 times strava for long rides

    Again, I'd question whether you have the correct user profile parameters (e.g. weight, HR values) put into both of these systems. With that large a discrepancy, something is clearly drastically amiss.

    If people are just going to guess at these values, or better yet, just leave them as default, then of course the values you get out of it (i.e. Calories) is going to be complete garbage.


    I don't use an HRM and my weight is the same in both
    If you don't use a HRM then any calorie figures will be even more unreliable. Garmin say for their algorithms that you need HR data to get reasonably realistic numbers calorie out.

    Garmin without HR just does a distance/time estimate which I find only really matches up with the HR estimate if the ride is flat-ish and steady (I have logged rides on fitbit just to see and that's the method fitbit uses). It falls down with anything resembling intervals, wind or difficult terrain. Strava as above uses its internal power model, as mentioned above.
  • I have a similar problem, but the other way round.

    I have a Garmin 800, I'm 99kg and for example, a recent ride had Garmin Connect at 2500 calories and Strava at 1500.

    Which was also different from the amount on the device itself.

    To be honest I don't pay much attention to it, other than to justify what I eat for the rest of the day. :D
  • keef66keef66 Posts: 13,123
    I use an Edge Touring Plus with HRM and think it's calorie figures are pretty believable.

    I was shocked when I corrected my weight having lost around 8 kg; it tells me I have to go a lot further / faster now to burn the same number of calories now I'm not lugging around the extra weight! Makes sense I suppose.

    I don't make any use of the information; I'm finding that sticking to the 5:2 diet is keeping me at my target bodyweight.
  • fenixfenix Posts: 5,437
    Looked at a turbo session from yesterday using my powermeter.

    Trainerroad gives me 630 calories.

    Strava gives me two readings - 701 for calories and 628cal for work done ?

    I'm going with the trainerroad reading anyway for a fairly hard hours session. Seems about right.
  • RutlandGavRutlandGav Posts: 144
    That Garmin connect figure sounds very low, though i am much heavier than you 85kg - was 95kg back in feb.

    Assuming a power meter is not available, what do you reckon to sense checking the numbers on an exercise bike at the gym? One would have thought it is possible to make those things fairly accurate, since you are essentially pedalling into an alternator, , thus forming a stationary power meter.

    My polar HRM, after setting up the profile , gives a burn rate for me of around 600-700 cal/hr, which isn't far off what the gym equipment was saying. I saw near 200w and 800 cal hr at 140bpm at the gym, but in practice i'll probably slack off and take short breaks in reality, so the Polar numbers seem plausible.
  • E65RossE65Ross Posts: 23
    When I use trainerroad for sessions the garmin links up with that using the power meter and seems far more realistic. I think it's just because my heart rate is generally quite low for the effort I'm putting in.... From my running days I think my cardio system is stronger than my legs!

    For the record my FTP is only 206 but that's around 3.85W/kg.

    I've also got virtual training, I'll have to do a ride and see how many calories that comes up at and compare to when km out there!
  • Just to finish this thread off for anyone interested it appears strava is more accurate than my garmin edge when used with the HRM.

    I wanted to get a guide to which was more accurate and so I did a "virtual ride" for 4hrs 20mins on a route I've ridden before which was around 71 miles with just over 5k ft of climb.

    Riding it on the turbo at an effort which felt like I normally ride my long rides (and keeping a check on my heart rate) with the power meter hooked up to the garmin would give more accurate measurements than just going for a ride.

    In the end it was 2258 calories which works out at a shade over 500 calories per hour. My average heart rate was 127bpm. Doing a ride at that heart rate without the power meter yields far, far lower readings so it looks like the circa 30 calories per mile I thought was about right for my general endurance rides.

    Cheers!

    Ps - that was a long stint in the garage!!
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