9

I have just recorded two following activities (I am 42 years old and seriously fat / 108 kg):

  • Hike: 9.04 km / 1h20m / 90 m elev. / 1,220 kcal
  • Bike: 20.26 km / 1h25m / 146 m elev. / 837 kcal

Is this kcal burnout on second activity accurate / possible? Only 837 kcal when compared to 1,220 kcal on hiking?

Here is a Strava's (no power meter) screenshot from my hike / walk:

enter image description here

And here is the second activity (bike riding):

enter image description here

For me it was:

  • Hike: a moderate walk, feeling good, no stops, my muscles moving just me
  • Bike: tough ride, a few stops, my muscles moving me and +20 kg bike

How can I burn much less (only 70%) kcal on a really tough bike ride when compare to fairly moderate walk? What am I missing here?

EDIT: To clarify after a great number of even greater comments. Both numbers and "fast" wording are just to underline the difference here. I am not challenging each single kcal burnout on its own. It is only very hard for me to believe / understand that during a fairly simple walk I supposedly burned out 150% of the kcal that I burned during a bike ride from which I returned totally wet and "wasted".

So the real question could be: How can I burn way more calories walking than I burned during biking?

trejder
  • 544
  • 7
  • 19
  • 9
    Bike fitness and walking fitness are different, if you are not trained in cycling the effort will feel harder for the same apparent work. As far as calories burned - without a power meter they are wild guestimates based on a comparison of measured results using a population sample then matching to your metrics. For an average person of average fitness averagely trained in the activity, they might be accurate enough to be useful. (and do read the article about how the US Air Force found there is not such thing as an average person). – mattnz Aug 16 '21 at 21:53
  • 8
    Yes. The bike is the most efficient method of transportation there is. Nothing, absolutely nothing gets you further per energy unit than a bike. Taking your measurement, you can derive a cost of 4'250 Cal/100km, which is equivalent to about 470g fat, or about 0.51 l/100km biofuel (cooking oil). How far can you drive your car with half a liter? – cmaster - reinstate monica Aug 16 '21 at 22:17
  • 2
    Btw, a large fraction of those 850 Cal is due to the height difference. Lifting a mass of 100kg (bike + rider + luggage) 146m heigh consumes about 146 kJ energy. That only translates to 35 Cal at face value, but then you must consider the low efficiency of your muscles (about 25% afaik), so you require about 140 Cal of food for the elevation effect alone. – cmaster - reinstate monica Aug 16 '21 at 22:26
  • 15
    Finally, I don't know how you measured your calories. If it's via a smartphone app or bike computer, those are rough estimates at best (I would guess that those numbers might be a little high, but I may be totally wrong). The only reliable method of measuring expended calories on a bike is by using special power measuring cranks that precisely monitor forces and cadence to derive the actual mechanical work that is done by the rider. – cmaster - reinstate monica Aug 16 '21 at 22:31
  • 2
    @cmaster-reinstatemonica I'm going to be pedantic - power meters can be mounted on cranks, or in pedals, or less commonly in rear hubs. But yes, power meters do provide the most accurate measure of work done on a bike, and from there you can estimate calories burnt with a much smaller prediction interval than estimating it from heart rate. I am under the impression that running power meters are an emerging thing, but I'm not sure if they're as accurate as bicycle PMs. – Weiwen Ng Aug 16 '21 at 23:48
  • 1
    @WeiwenNg Ah, I wasn't aware of the rear hub possibility. Probably a great solution for chain-shift bikes, even though it's not applicable to internal gear hubs. – cmaster - reinstate monica Aug 17 '21 at 06:32
  • 1
    Actually a bicycle is a pretty inefficient method of transportation because humans are inefficient. A velomobile where the “velo” part is replaced with an electric motor would be much more efficient, especially when traveling at similar speeds. – Michael Aug 17 '21 at 07:34
  • 2
    @Michael Ok, you got me. The most efficient method of transportation would be an e-bike in full-electric mode that's charged with solar power. Nevertheless, the additional solar cells, batteries, electronics and motor need to be produced, and the additional motor/battery drive the unsuspended mass of the bike up (i.e. the part that's not cushioned by the riders butt and sinews), decreasing the mechanical efficiency of the bike. Also, non-human powered vehicles have a strong tendency to get much more heavy over time. It starts with a small auxiliary motor, and end ends with a motorbike. – cmaster - reinstate monica Aug 17 '21 at 08:57
  • 2
    What's the source (exact device, calculator, or app) of the calorie estimate? – Chris H Aug 17 '21 at 09:31
  • 3
    I edited and removed the "touring" tag. The question doesn't at all match the tag description. – juhist Aug 17 '21 at 11:02
  • 4
    @Haukinger he's not calling the speed itself fast. But using the word "fast" do show that the number in front is about speed. Common in some languages. – Matsemann Aug 17 '21 at 19:18
  • 5
    Side note: don't get too discouraged by the modest number of calories burned during exercise, as those numbers aren't the whole story. With regular exercise, you'll build muscle, which will act as a continuous calorie-sink, and your metabolism will increase, so you'll be burning additional calories between exercise sessions as well. Those calories aren't counted by your fitness app (AFAIK) but they will count where it matters -- towards improving your health and reducing your weight. – Jeremy Friesner Aug 17 '21 at 19:51
  • 1
    @JeremyFriesner: +1 for don’t get discouraged, but the increase in metabolism from muscles is small, especially if you lose weight overall. The much bigger impact will be because OP will quickly be able to ride much longer and with much higher power output. My 53kg sister is able to burn 1760kcal in 3 hours (172W avg power). – Michael Aug 18 '21 at 06:05
  • 1
    @Matsemann that's rather strange grammar, are you sure that's common in English? It would be very rude to expect readers to guess which language one's writing in while using english words... he's talking about a "fast bike ride", there's nothing else in the sentence "fast" could refer to. – Haukinger Aug 18 '21 at 06:26
  • 3
    @Haukinger in an international forum you should show some more compassion for those not being native speakers and try to read things in good faith, not doing so is rather rude on your part. Especially rude that your first and only comment on this site is coming here telling someone they're slow. Both in Norwegian and German I feel it would be natural to add something after saying "I biked 20km/h", for instance. – Matsemann Aug 18 '21 at 07:10
  • 2
    The OP later calls the exercise "a really tough bike ride". Maybe he means that the bike is really tough, but it sure sounds like he's referring to the ride. – ojs Aug 18 '21 at 07:49
  • Thank you everyone for large number of educating and enlightening comments. Calorie burnout was measured by Strava, so yes, simple app and a huge overestimate. I am aware of that. But both the numbers and the "fast" wording was to underline the difference. I can imagine / understand how it is possible that (according to my overestimating mobile app) I've returned dry from a moderate walk and supposedly burned 150% of calories that I burned during a killer (for me and my weight) bike ride, where I had grasping breath and returned totally wet with all my muscles shaking. That's all. Thank you. – trejder Aug 18 '21 at 14:15
  • 1
    Also: see the answers to this bikes.SE question: How many miles of riding require the same effort as one mile of running? – R. Chung Aug 18 '21 at 14:42

7 Answers7

18

Since the other answers and comments were discussing only your bike trip, I will tackle on your hike values and show why they are probably incorrect.

First of all your activity wasn't a hike, but a walk, since 90m elevation in 9km is just ~1% elevation on average. This distinction could be important if you are using apps like Google Fit or similiar for the calculations of your calories. Depending on what activity you select, it will calculate different values based on some average values they have for these activities and there is a big difference between a hike and a walk.

So let's say you made your walk of 9km in 80 minutes, which is an average speed of ~6.77 km/h. This page (in german) shows a table of calories burned based on your weight and speed of walking. With 100kg and a walking speed of 6.5 km/h it shows 450kcal burned. So in 80 minutes you would burn around 600kcal and if we adjust it to your weight and some elevation you would probably end up at around 700kcal for your trip.

I also found a calculator for calories burned by walking and if I put in your data there I end up with roughly the same value of ~700kcal. So it is safe to assume that your 1,220 kcal are incorrect and to high. If you are using Google Fit or a similiar app, I would suggest to check what activity is logged for this trip and if it is "hike" change it to "walking" and it will recalculate the values and maybe show lower values with are closer to the calculated ones.

sheep
  • 181
  • 3
  • 1
    Damn, we wrote almost the same answer at almost the same time :D But at least we agree with each other. – Michael Aug 17 '21 at 07:56
  • 6
    Nice first answer, and welcome to the site – Andy P Aug 17 '21 at 08:18
  • 8
    Apps relying on the difference between the synonyms "hike" and "walk" in calculations are too dumb to be trusted for anything. Much of the difference is subjective based on fitness, while distance, pace, and climb don't care what label they have. The only real difference is load, but a light day hike pack could weigh less than your load walking home with shopping, or a stroll around a nature reserve with photography gear. The one exception is something like fitness pal, which just uses time and activity type, not gps – Chris H Aug 17 '21 at 09:27
  • 1
    In Chapter 10 McArdle, Katch, & Katch introduce a rule of thumb that running on flat firm ground requires a net energy expenditure of 1 kcal/kg/km. So, a 108kg runner traveling 9km on flat ground expends ~ 9108=972 kcal. We also know that to raise a mass of 108kg 90m in height requires 10890*9.8/1000=95 kilojoules. If gross metabolic efficiency is close to 23.8%, then 1 kJ~1 kcal, so total energy expenditure is 972+95=1067 kcal. (1 food Calorie = 1 kcal). If GME < 23.8%, energy expenditure rises. – R. Chung Aug 18 '21 at 11:03
  • @ChrisH To add to your comment. I've heard that some apps assumes that "walk" is "in the city" streets only and straightens "bouncing GPS path" to the nearest street or path. While "hike" is "in the wilderness" so no artificial straightness happens. This is just an addition, since Strava does not do this and I am getting sometimes really annoying bouncing path. – trejder Aug 18 '21 at 14:23
  • @ChrisH And for fitness-pal-like apps, I have a very bad experience in long walk. For example, I took mine together with Strava and on 7 test walks it showed a greatly reduced steps count in all 7 scenarios. For every of those I am getting 4500-5000 steps per each kilometre which suggest that I have... 1.2 metres long step. Impossible, if not stupid. So, I'd say that no-GPS fitness pals maybe are good for indoor activity. But for outdoor surely correcting measurement based on GPS signal does a good job. – trejder Aug 18 '21 at 14:25
  • @sheep Thank you for a great and detailed answer and welcome to the site. – trejder Aug 18 '21 at 14:26
  • @R.Chung Thanks for this addition. I wasn't aware that such flat/simplified calculation rule exist. It doesn't seem suitable for some serious calculation, but surely is good for a quick compare or verification. The only question is, if that "rule of thumb" works the same / similarly for walking and hiking, as you are saying about running only. – trejder Aug 18 '21 at 14:28
  • 1
    @trejder I haven't used an app recently that does something like that, but it's got a sort of logic to it that means it may well exist. I use a bike computer app that allows manual adjustment of GPS smoothing, also for walking (while we do use the term hiking in British English, we seem to describe things as walks when they'd be hikes in other places), running, and other activities. It does an OK job of calorie estimation, let down by my phone only having gps for altitude. Strava seems reasonably self consistent between activities, even if there's a considerable error overall. – Chris H Aug 18 '21 at 17:08
  • @ChrisH To me the difference between a hike and a walk is more about the environment. A walk involves smooth terrain in an environment basically free of hazards, at most you're carrying water. A hike generally involves uneven terrain where you have to pay attention to the ground, you're in an environment you have to be prepared to take care of yourself and you have to extract yourself, you're carrying food, water and emergency gear. – Loren Pechtel Aug 19 '21 at 02:11
  • @Loren, that's one reasonable interpretation (though here we use "walk" even for quite strenuous terrain with the chance of a scramble). But many "hiking trails" are smooth and easy going. As for load, apart from my point about a walk that involves carrying stuff that's not in service to the exercise, considering the difference in hiking load between an ultralight solo hiker and someone leading a group of kids, with comprehensive group emergency kit, on the same route, and you'll see it can't be inferred from the activity type but can only reasonably be assessed numerically – Chris H Aug 19 '21 at 09:05
  • @ChrisH Sounds like there are cultural differences--I can't picture "walk" being applied to something involving a scramble. I do agree there is overlap between the exertion level of a walk and a hike. – Loren Pechtel Aug 19 '21 at 15:17
  • @Loren don't even think about "winter walking" then, with ice axe and crampons! But those cultural differences reinforce the idea that the semantic difference doesn't work – Chris H Aug 19 '21 at 19:33
  • @ChrisH I can't imagine anyone describing that as "walking"! I would interpret "winter walking" as going into snow mild enough you don't need traction aids. – Loren Pechtel Aug 21 '21 at 00:53
12

The bicycling calories sound about right (maybe a bit too high, but assuming a relatively bad bicycle and higher moving speed between breaks it could work). I think it’s your walking calories which are overestimated. Where did you get the estimate from? Most calorie calculators estimate around 600kcal for your hike, for example this one says 600kcal when set to 6.4km/h and 180cm height: https://keisan.casio.com/exec/system/1350891527

Are you used to bicycling? Is your bike set up correctly? Did you use easy enough gears for the climbs?

For comparison, here is a screenshot of a casual training ride I did a month ago with a power meter. I’m a 67kg, 1.8m male and used a 7kg road bike for this ride. The ride is about twice the distance and elevation of yours, took a bit more time and burned 1010kcal (fairly accurate estimation because of the power meter). The first and last 4km are slow because it’s in the city. I’m physically active but couldn’t train much this year due to injuries.

strava screenshot

Michael
  • 27,311
  • 1
  • 24
  • 86
  • Interesting screenshot, and shows how poor the estimates from online calculators can be. They would have you at ~30kph for that power output on a road bike. – Andy P Aug 17 '21 at 08:29
  • 1
    Yes, the problem with online calculators is that they can only assume a more or less perfect scenario. In my case the first/last kilometers are through the city (only 1 traffic light, but lots of cyclists and other traffic) which completely destroys the average speed. It was also a windy day. I’ve ridden the same route with only 940kcal in a shorter time on other days. On flat terrain without wind I do ride around 30km/h with 155W of power. – Michael Aug 17 '21 at 08:43
  • @AndyP most calculators use an average rate of climb, or a total climb. That doesn't work well because aero loses are so nonlinear. There are calculators that take segments of different inclines which should handle a ride like this better – Chris H Aug 17 '21 at 09:29
  • 1
    @Michael ... which completely destroys the average speed I'm guessing that 200m hill between the 7 and 10 km did quite a bit to knock your average speed down, too. A 200m climb over 3 km is 6.67%, and the bulk of that climb looks to be over 2km, so it's pushing a 10% average grade, and I'd bet there are some 12% or maybe even steeper sections. – Andrew Henle Aug 17 '21 at 15:04
  • 1
    @AndrewHenle: True, but if I cut out the first and last 3km the average speed is 26.6km/h. From after the first steep climb to 3km before the end it’s 29.2km/h. On a different day with less wind and much lower power output (922kcal for the ride) it’s 27.4 and 30.2km/h respectively (and 26.6km/h overall). Kind of shows how little distance, speed and elevation actually tell about the intensity of a ride. – Michael Aug 17 '21 at 18:35
  • @Michael et. all Thank you for your comments. All these numbers (calorie burnout etc.) comes in my case from the same source as your :) (assuming based on your screenshot) -- Strava. I am unable (and there's no need for doing so) to post a screenshot in comment, but I've copied them form exactly the same place -- next to "Show Less" button. Of course, in my case there's no power meter so only "perfect scenario" counts. – trejder Aug 18 '21 at 14:32
  • @trejder: You could add a screenshot of both activities to your question. I just had a look at older workouts before I got the power meter and noticed that Strava’s estimates were too high by ~20% for my bike rides compared to what the power meter says. But that’s actually not too bad, considering it only knows the type of bike (“road bike”), my weight and the weight of the bike. – Michael Aug 18 '21 at 14:44
  • @Michael Screenshots added to question. – trejder Aug 18 '21 at 15:02
8

Using this calculator we can estimate how much power you needed to produce to maintain your average speed of 20.26 km/85 min: I get 38 W, although I might have some of the conditions wrong.

We can then multiply 38 W by your ride time of 85 minutes to get joules of work performed. I get 194 kJ.

Thanks to a neat mathematical coincidence, work performed is roughly equal to calories burned (some calculators treat calories as work + 10%). Based on that, I get about 215 calories burned. Obviously this is much lower than the estimate you got, and some of that difference might be accounted for by headwinds, knobby bike tires, uneven pacing, etc.

Another thing to take into consideration is that unless you are using a power meter on your bike, calorie estimates aren't very reliable. They're probably based on speed over time and heart rate (if that data is available).

In any case, 837 calories doesn't sound low for the time and distance you rode. If you are not bike-fit, then riding can feel like a lot of work.

Adam Rice
  • 29,997
  • 1
  • 47
  • 102
  • I should mention that if your 85-minute ride time includes a significant amount of resting time, that throws the calculations off a lot. – Adam Rice Aug 17 '21 at 01:00
  • 2
    and "resting" covers red light stops, coasting any downhill bits, and tailwind boost. – Criggie Aug 17 '21 at 02:45
  • 2
    I used a different calculator to Adam (bikecalculator.com) and came to 38W and 186kcal. Given the very low speed, I tried switching the calculator to calculate for a MTB and got 80W/385kcal. I'm fairly confident we can say the 837 is a massive overestimate as you'd need to push 170W to do that and I can't think of any way 170W would translate to such a low average speed – Andy P Aug 17 '21 at 08:02
  • @AdamRice "I get 194 kJ. (...) Based on that, I get about 215 calories burned". How can you get 215 kcal out of 194 kJ, if 1 kcal = 4.186798 kJ so 194 kJ is 46.336 kcal? What am I missing here? "In any case, 837 calories doesn't sound low for the time and distance you rode". You say nothing about my walking, but I understand that you suppose that 1,220 sounds way to high for 1h20m time and 9.04 km distance that I walked? – trejder Aug 18 '21 at 14:44
  • 1
    @trejder The bit you are missing is that depending on the individual we're only around 20-25% efficient at turning energy into power at the pedals, so the measured kJ can be multiplied by 4-5. So for sake of convenience we'll say 4.18 and then 4.18kcal burned = 4.18kj at the pedals. Not perfect, but close enough. – Andy P Aug 18 '21 at 15:08
  • I used the Gribble calculator and I'm getting 78 watts, not 38. 78 watts * 5100 seconds = 400 kilojoules. This is a lower bound on energy expended: if the course were not a constant slope the energy expended would be higher. I think 837 kcal is way unrealistic. – R. Chung Aug 19 '21 at 08:38
3

The 837 "calories" (which I assume mean kilocalories) sounds fishy. Usually when riding at 20.26 km/h speed I use 139 watts of power in varying terrain (10 meters of elevation ascent and descent per kilometer). That's only because I'm heavierweight than most. A normal weight person (70 kg) would use around 109 watts of power.

109 watts multiplied by 3600 seconds divided by 0.25 energy efficiency of human is 1570 kJ or 375 kcal. (At 139 watts for 110kg rider, it's 478 kcal.)

You rode the distance very slowly and it didn't seem to be a very hilly route. In fact, at 14.3 km/h. At such speeds, the average power in varying terrain would be 66 watts for 70 kg rider and 88 watts for 110 kg rider. The same calculation (but this time 5100 seconds and not 3600 seconds) gives 321 kcal for 70 kg rider and 428 kcal for 110 kg rider.

No way could you burn 837 kcal even if you're 110 kg.

What you're missing is that a bicycle is an extremely energy efficient form of transportation. Low rolling resistance, ability to coast (well unless you're riding a fixie), ability to move without center of gravity moving upwards and downwards repeatedly, etc.

juhist
  • 18,668
  • 3
  • 27
  • 49
  • 1
    0.25 energy efficiency of human That seems a bit high. For example (page 46 of the PDF link at top: "... the model returns a peak simulated value for thermodynamic efficiency of a little over 0.2 ..." – Andrew Henle Aug 17 '21 at 15:12
  • @AndrewHenle I think 25% is a really good approximation for marginal energy efficiency that ignores the idle energy use, the energy a non-moving human would anyway use. If you consider the total energy efficiency, including the idle energy use, then 20% might be better. – juhist Aug 19 '21 at 08:43
3

It's likely that both the bike and hike calories are overestimates. Many devices use weight and speed to calculate calorie burn, but because they are not measuring any physical output (such as cycling power) can be wildly inaccurate.

In addition, many sites/devices also count a fraction of your BMR corresponding to the time of the activity in the resulting value causing an inflated number.

Andy P
  • 18,268
  • 2
  • 36
  • 69
2

I weigh about the same as you and happen to have a power meter, so I can give an empirical - if anecdotal - answer.

I would likely burn about 850 kcal in the duration of your ride. But my ride would be approx. 35-40 km in length and cover 300-400 meters elevation gain rather than your 146.

I don't mean this in any way to be rude, but your ride was not fast. And mine isn't either. It may have been high effort for you, but if you've only recently started out, you might just be incapable of actual high effort - only effort that feels high. You may huff and puff and get all sweaty, but in reality you might not really be doing much work - just because your body isn't adapted to it.

Your hike is very unlikely to have burned 1200 kcal either. I'd guestimate 600-800, but it's much harder to measure than cycling.

Generally, if you take calorie data from an app on your phone, it's most likely a useless guess. If you use a heart rate monitor, it's gonna be a bit closer, but still way off. I did an experiment once - used a watch and a bike computer at the same time - watch measuring with a HR monitor, bike computer with power meter - and the watch overestimated my effort by about 35%.

If you want accurate data, get a power meter (it's expensive though). Otherwise, either don't pay too much attention to what calories your app tells you you burn, or try to find out an approximate correction rate (it may not be 35% in your case though, depending on devices used).

user622505
  • 326
  • 2
  • 8
0

That sounds about right, maybe a bit high if anything. Here's a ride I did back when I was about 115kg, for something close to what you're saying and I got 750-ish calories from Strava. No power meter back then so numbers are pure guesses, but since I've switched to a power meter the guesses proved a little high.

So, sounds about right, but could be up to 30% high from my experience.

A Ride

throx
  • 256
  • 1
  • 2