Question about Bontrager Node 1.1 computer readings
 

I'm using it to track my rides and have noticed a consistent difference between when riding on the trails and on my trainer. For example I'll ride 22 miles and show right around 1250 calories with an average 115 bpm heart rate at an average cadence of 72. When on the trainer riding 20 miles with an average 120 bpm and cadence of 80 and it shows around 700 calories. Am I missing something?

Rich

One thing that is missing is your average speed (the time you spent exercising).

Also, it's possible that the calorie calculation is based on how much time you spend in the various HR zones (which could be quite different for the two rides).

(The calories burned estimation isn't worth much.)

When on the trail speed averages 11 mph; on the trainer it's 16 mph. On what do you base the remark about calories burned not being worthwhile.

I'd guess that the difference is mostly due to a difference in the time spent in the various HR zones.

As far as I've read, it's not very accurate. Except for the ones based on power measurements. (The ones based on HR should be better than without HR.)

Here's some info on how the Garmins do it (the Nodes aren't likely to be as sophisticated):

http://www.dcrainmaker.com/2010/11/h...on-garmin.html

Miles don't matter. What matters is duration and intensity. If doing the same intensity (as measured by HR in this case), for the same duration, the device optimally would show the same calories.

Thanks, that link explains a lot. Riding the bike on the road yields approximately twice as much calories as doing it on the trainer; this corresponds to how the effort seemed to me. The Nodes must use more than just speed and distance. A quote from the article:



These are the factors, plus gender, you enter into the node (which is ANT+ compliant). One of the many outputs are the times spent in each zone.

Rich

The Nodes should be using the HR and the time spent in the HR zones in the calorie estimation.

What I was suggesting in post 2 is that the amount of time you spent in the HR zones is different and that is one reason for the difference in calories.

I came across a search in the archives here http://www.bikeforums.net/archive/in.../t-236011.html Using the formula the numbers are fairly close, calculating the reported (from the Node 1.1) total for 35 day yields 1002 calories per day; with the formula 987 calories per day, a difference of one whole cashew nut....close enough!
:rolleyes:

Makes sense because you can't change the nature of the zones, only one's MHR. This all is very useful. While it's clear there is considerable conjecture it helps me establish just where I want to draw the line for getting a reliable figure.

Rich

It's still hard to know whether the number is close to the real value (I'm somewhat sceptical).

As am I. I'm looking for a consistent and equivalent way of measuring my daily level of effort. I'd like to shoot for and maintain approximately 1200 calories per day exercising to maintain my fitness. The formula in the above link shows a weighting of .63 for AHR, .2 for weight and .2 for age (they add up to more than 1 I realize, but that's the formula). If I did my math correctly decreasing the AHR between 120 and 110 adds 1.8 minutes to a ride for each bpm decrease in AVG BPM, and conversely.

I found out one thing, spinning is the most mind numbing of the three.:bang::bang::bang:

Rich