I'm not very mathematical either so this may be totally wrong, but what about using one of those calories/activity calculators online and increasing you're weight by 75 lbs? That will increase your calories burned, and it might be somewhere in the ballpark. Then you can manually enter your calories burned on spark people.
Remember, probably neither those calculators, nor sparkpeople, take into account drag, rolling resistance, etc for just yourself and your bike.
But also, those speed ratings on sparkpeople are not accurate for the bike becuase they don't take into account your slope. Riding at 20 mph on a flat surface would be VERY different from averaging 20mph on a hilly course, the latter burning more cals. In fact, on a hilly course you'll almost always go slower, but you won't burn less calories than a course of the same length but flatter.
Just curious if anyone has any insight here. I often bike with my almost 40 pound three year old in a 35 pound trailer behind my bike? Does anyone have a good way of figuring out extra calories burned with the trailer as opposed to without? I found a site where someone had extrapolated this whole calories per pound per minute type of thing and it seem to make sense but my brain isn't that mathematical. According to his calculations the extra weight alone causes an increase of 40% and, he says, figuring in the extra drag and rolling resistance etc.. that he calls it double. Here's that site http://www.palmbeachbiketours.com/2008/06/ 23/calories-burned-while-pulling-a-bik e-trailer/ Myself, I have just been using the correct number of minutes and bumping it up a speed category here on sparkpeople. I know that none of this is exact but I'm just wondering if that gives me even close to a round about number...
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