HRM and burned calories - run vs bike?!?

Nope, you answered your own question, your running HR is higher, that's all. HR monitors gauge calories burned by duration of activity, HR, your age, your wieght, and sometimes any AT or VO2 data they allow for.

There was a study done a while back that found roughly that for every 4 miles of biking it equals 1 mile of running. I also read an article in Cycle Sport that tried to compare the world class cyclists with other sports. The top runners averaged about 1/4 as many miles in a year.

HRMs are a poor tool to guesstimate calories. Calories are a measurement of work. Effort (HR) gives no real indication of work done.

For example, you are a new runner and you just ran an hour with aveHR 160 and went 4 miles. Fast forward 3 years. You're at the same weight and you run an hour with an aveHR of 160. This time you run 8 miles. Do you think you burned the same number of calories? I'd guess you've burned about double on the later run. How is your HRM to know the difference?

I guess I should have stated this in the first reply, but I'm not a physiologist nor have I studied at all to become one. I am an engineer and have taken a couple Physics courses a long time ago.

I believe that the Forerunner has the potential to be the 2'nd best "common-man" tool to guesstimate calories. The best would be a power meter, but even those will have to assume some things (RMR, for instance).

I'm basing my opinion of this calorie stuff on the assumption that calories burned closely follows work = force x distance.
With a Forerunner, you have the distance and with some acceleration profile combined with persons weight, it could be able to get fairly close to guesstimating the force. I have a FR305 and had a FR201. The 201 provided much more consistent and I'd bet accurate numbers. I'm pretty sure Garmin, with the better sensitivity of the 305 receiver, added in the elevation to the calculations. But, the elevation part is still not very accurate, so the calorie numbers are considerable off. Also, some unit update helped the 305 considerably.

Polar did something right when they funded a college (at least some 3'rd party) to do their research. At one point, I found the paper, but searched again and came up empty. If I remember correctly, they claimed an accuracy of +/- 25% on their formula.

I get the feeling that Garmin hasn't put the same effort in their calorie formula.

I realize that there is some physio stuff that this doesn't account for (heart pumping, lungs breathing, etc), but I believe that these are fairly small and are insignificant in getting the guesstimate within 10%-15%.

One problem with this assumption is that in order to reasonably calculate this using distance (and force for that matter) the measurements would have to be incredibly accurate and precise (which, as you point out, civilian GPS is not) as you would need to calculate the work to move the body forward and up (or down) plus the forces and the constant movement of the centre of mass (up and down/left and right) and the forces involved.

The other problem is that this is assuming that the human body is 100% efficient when it comes to calorie consumption into work, which it is not. Depending on the activity, it may be more or less efficient, but consider how much heat is created during exercise and is simply given off as waste to the environment.

Shane

I don't think distance really matters, I think it's effort x time.

Otherwise biking downhill would burn as much as biking up hill.

gsmacleod: I agree completely. But, I think you can get the accuracy within 85%-90% somewhat fudging these numbers.


BbMoozer: this calculator may help you get in the ballpark. If you google for a calorie calculator you may get some others that may work better. Oddly enough, I bet you won't find many (if any) that uses HR as an input.


kblahetka: The difference in going up/down is the force required. The force required to bike uphill is much greater than that required to go downhill (possibly 0). So, even if the distance is the same, the calories could be much different.


Edited by camy 2007-06-15 9:13 AM

thanks Camy for that site. At least gives a ball park idea.