Wierd calorie stats?

neilus

Hi,
I kinda enjoy keeping track of my bpm and how many calories i burn (so i know know much fudge I can eat!)...but ive recently just started going for an easy spin around town in the evening and it seems im using the same energy as i do on reasonably strenuous mtb routes and im a bit miffed! Eg:
Easy evening ride around town:
8.66km/00:40:35/410Kal/Av. bpm 130/87m height gain: 47.3 Cal/km
Hardish mtb loop (with 4 climbs):
36.92 km/02:58:42/1736Kal/Av. bpm 156/1105m height gain: 47.04 Cal/km
According to this im actually working harder on the first ride !?! It makes no sense whatsoever. The 36km mtb loop isnt brutal by any stretch but it still feels far more strenuous than my leisurely cruise around town...
:?:

Dave_P1

The most accurate way of working out how many calories you've burned is via a power meter or some sort of lab test. Working it out via heart rate isn't always that accurate but it's the next best thing.
Assuming you're not working at a particular effort e.g intervals, you can't calculate your calories per km as you might be going harder for one section that another so I would ignore whatever has given you that result and stick with the total calories burned for the entire ride, rather than breaking it down.

neilus

Cheers Dave. Yeah i figured the cal/km might not be entirely useful though I dont know anywhere near enough about physiology to know why! I guess i'll run a few more experiments. There's always a chunk of the ride between 10 - 25% when bpm goes below 127 which says "not in zone", maybe thats skewing the results?

Dave_P1

What device are you using to monitor and record heart rate?
You're always in a zone, whether it's the zone you want to be in is another matter.

diy

You need to look at the graph its likely that you are having breaks on the MTB - of course the other factor is you haven't told your monitor about the weight of your road bike vs mtb?

But you will usually get better kcal/min burn rates on short rides vs long rides, unless you are road riding. Often when you are dropping down the hill after a climb you'll go for a few mins without pedalling much at all even if you are caning it, most of the work will be twisting, jumping etc and you don't burn much doing that. Alternatively a flat route is constant.

Its easier to burn calories doing an hour of zone 2-3 than 30 mins of zone 4-5.

kajjal

It looks like you are not measuring power accurately. Riding off road is alot harder at any given speed and the speed is alot more variable. Also it takes more effort to manhandle a mountain bike over trails and the obstacles on the trail. In comparison riding a road bike is alot smoother and more consistent with little comparable bike handling needed.

njee20

The bigger issue here is that your device is guessing at calorie consumption using speed as the proxy for work done. It's not actually using your HR (or power, if you had it) for the calculation.

I'll wager According to the device your calorie consumption will be at its highest whilst coasting down hill!

That's how Garmins work at least, and their figures are stupid. Polar have the best guess algorithm, I seem to recall they still give a figure even if you don't use a HRM although. Been a while since I used one.