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Discussion Starter · #1 ·
Is there any way to estimate calories burned or kJ(lets assume for ease of discussion these are very close, no fancy equations) output of mtb rides based off info from a road bike Powertap?

I know some HRMs can do this based on avg per hour but I do not have this feature on my HRM.

Anyway, on road rides in L2 I typically produce 600-650 kJ per hour and closer to 700/hr if it as a hard ride with L3/L4 on rolling hills. I have been estimating a hard mtn ride with lots of L3/SST climbing on a singlespeed as 600-625 calories per hour due to the extra coasting on MTB compared to road.

For example:
Todays ride was 5 hours, 60 miles MTB with a good bit of hard climbing and holding tempo on flats. I estimated calories burned at 3200. Am I on the right track here? Anyone been able to compare kJ output on similar effort road and MTB rides? Thanks.
 

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I actually found that hard (ish) mtb rides the kj burn was not too far off from the HRM calories burned estimation. Races actually sometimes kj's was slightly higher than calories.

I'm using the new Garmin 500/800, though ,and the HR based calorie computation is way under shooting what the kj burn is (odd).

Not sure if that helps, but if you're using a HRM like a Garmin 305/705 I'd assume the kj burn for mtbing is a lot closer to what calorie burn it spits out than say for road riding.
 

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Discussion Starter · #3 ·
Ok, so the HRM calorie estimation function is suspect. No surprise there.

Maybe it would be better phrased like this:

For a hard paced rolling 2 hour ride would the kJ for a mtn ride be similar to a road ride of the same perceived exertion? Seems like it would be close, coasting would decrease the calorie burn but the bursty nature of MTB would increase it maybe breaking even.
 

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I think miss rides a lot answered your question and is almost certainly basing her info using data she sees on a mtb power meter (true kj data) as compared to the heart rate monitor data. I don't have a powertap on the mtb, but for quite some time manually input my mtb workouts into the WKO+ software to track my training stress score. Paying attention to this over time, I concluded that time on the mtb was usually more taxing than time on the road. Remember on the mtb you are typically getting a much more significant upper body and core workout, are standing more, etc. Over time that ads up to more work, even if you "feel" the effort is about the same.
 

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Just ran a quick skim of my personal data (not scientific, but will help). Mountain bike 'rides' compared to road 'rides' no matter intensity tend to come out about 8-10% lower kJ / hour. IF can be similar for the rides, but tend to spend more time pedaling on the road with a flatter power curve vs, the stochastic bursts and off time on the mountain bike.

On the opposite end of the spectrum, all my mountain bike races come out higher kJ count than my road races for given time length. That's primarily because mountain bike races are FULL GAS from start to finish, while there's loads of sitting in and soft pedaling in even the hardest road races.
 
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