Why did fitness apps seem to misrepresent calories burned between a bicycle ride and hike workout?

Question

I've been an avid fitness practitioner for about 14 years now. For the last 7 ish years, I've run 3-4 times per week and up until a recent injury, I was running for an hour at a time, usually about 7-10 minute pace depending on various factors. I also lift weights at the gym 3-4 times per week for 1-2 hrs per session and have slowly built up a pretty fit base doing that for over a decade. Last, I hike almost every weekend as well. I state all of this for a specific reason so you know my background to prepare for the question.

I've recently gotten into cycling due to its lower impact. Today, I rode my road bike for 1 hour and 14 minutes, and tracked it with the "MapMyRide" app. The app has my age and weight, GPS enabled, and so on. I know that running for a given length of time at a given exercise intensity level generally burns more calories than bicycling. MapMyRide stated that I burned 430 calories and traveled 11.91 miles on the bicycle, avg speed 9.6 mph and high speed of 23 mph. During the course of this ride, on probably 4-5 hills, I was at near max heartrate and breathing very heavy. I was dripping in sweat. The workout in general felt more like a High Intensity Interval workout, because on the hills, the intensity was high, flat ground it was moderate, and descents, it was probably almost none. I do feel engagement in my upper body when I ride as well, as my triceps will be toned and slightly fatigued after, compared with a run.

I then went on a relatively light intensity hike. The hike lasted 1 hour and 34 minutes, was 8693 steps, 3.5 miles, and it said that my girlfriend (it was her phone) who is 50lbs lighter than I am, burned 464 calories on that hike. I'm not a pro exercise physiologist but I do know that heavier folks generally burn more calories for a given exercise intensity over a duration, at least when walking or running. So if anything, I likely burned more calories than her during our hike.

This seems incredibly off. Not one time did my heart rate rise significantly during the hike, I never entered even the "fat burning zone", was never out of breath, never broke a sweat, and it was what I would consider to be very low intensity. Whereas, the bicycle ride I really strained. My question is, am I probably right in assuming that the calories burned during the hike are inflated by the app in this case? Or perhaps the MapMyRide app gave me a low number for my ride? Again, I didn't do this in a lab, but I've been working out long enough to know when I am exerting more energy and working harder than when I am not, and that bike ride was much harder for my body physically than the hike was.

Or am I missing something? Do you have any suggestions on why the above situation occurred, how I may be able to fine tune the apps, or perhaps a more accurate way to measure? I know there are a lot of variables at play here and these apps make approximations, so feel free to just throw some ideas out there.

Answer 1

If an app tells you how many calories you burned, it's telling you its estimate on how many calories you burned. The more data you can feed into the app the more accurate it will be but it's still an estimate. If the app was not measuring heart rate and elevation, the estimate is going to be off.

Additionally, many calorie estimates include an "effort factor" when you select an exercise. If your app is only measuring distance and time, it may ask you if you got from point A to point B by biking, running, or skateboarding; all would burn different amounts of calories. So when you tell the app I went from A -> B and was running it gives you a different number than if you went from A -> B sprinting.

I know hiking is a weird one. Was it a hike? Or was it a nice walk through the forest. You averaged about 16.69 min/km? MyFitnessPal has three different categories for hiking, for example, for an hour at my weight (217 lb) I get:

• Hiking, Climbing Hills (Carrying 10-20 lb) = 719 calories
• Hiking, Climbing Hills (Carrying <10 lb) = 699 calories
• Hiking, Cross Country = 591 calories
• Walking, 10.5 min/km, uphill = 591 calories
• Walking, 15 min/km, leisurely = 295 calories

So, yes, the app inflates calories burned by taking an estimate at the effort you put in. You can make the estimate more accurate by providing more data (like heart rate).

Answer 2

The app have no idea what was your heart rate because phones have no heart rate sensors. The app must make some assumption, and if it assume you have a 10 kg light road bike, and you have some 30 kg heavy old city bike, this assumptions will be very off. If you're not used to cycling, you might have max HR when the other cyclist wouldn't even notice there's an ascent. It's the difference between cycling me 4 years ago and now.

With the assumption that cycling burns 4 times less calories pro mile than hiking / running and the comparable time of the activity, the calories estimation is plausible. With other apps, in case they allow you to say what kind of bike you have, you might get better estimates, but without HR it's more like guessing.

And even with HR sensor, it's still an estimation. Hearts are bigger and slower, and they can pump blood like crazy, but when the lungs aren't able to provide enough oxygen, the blood will not be saturated enough and your body won't have enough full to burn calories.

After all, the calories burned are only the fun factor statistic, that shouldn't be taken too seriously. Listen your body to know, how much you need to eat, not your watch or app ;)