Cycling calorie counts?

gdyment wrote: »

Calories: 1,216 C
Work: 1,597 kJ

I am curious why it is calculating 1597 kj for that ride (which is spot on what I would predict based on the avg and NP), but then says 1216 calories. Perhaps it is calculating it off heart rate instead of power, but your cycle computer should NOT be doing that if it has power available. Your cycle computer should be simply taking that KJ value and calling it calories (KJ expended and calories burned are close enough to the same that they just take one for the other)

glevinso wrote: »

gdyment wrote: »

Calories: 1,216 C
Work: 1,597 kJ

I am curious why it is calculating 1597 kj for that ride (which is spot on what I would predict based on the avg and NP), but then says 1216 calories. Perhaps it is calculating it off heart rate instead of power, but your cycle computer should NOT be doing that if it has power available. Your cycle computer should be simply taking that KJ value and calling it calories (KJ expended and calories burned are close enough to the same that they just take one for the other)

Just to ditto the curiousity. Especially as converting the kJ number to calories produces a result that actually looks pretty reasonable.

I wore my HRM for the first time on a fairly tough ride on Saturday (62 miles, 2500+ ft, 19+ mph winds) and averaged close to 16 mph. HRM said only 1311 calories, which seemed very low for the conditions.

I have a mini portable pedal cycle and although I can keep a good pace for at least an hour, my heart rate only goes up to about 110-120. I know its better than nothing and I can do it while watching TV and such so I only count 1 calorie a minute and don't eat them back. Some days I can pedal 3-4 hours.. But I still don't feel like it does more than fidgeting.

I also commute to work by bike April to November. My ride is short enough that time is almost equal to transit and long enough that I get 500 - 600 extra calories to play with a day. I also ride longer distances on the weekend. I generally find MFP really over estimates the calories burned compared to what my HRM tells me. MFP is closest in the spring when I'm out of shape and in the fall when it is colder and windier.

My ride to work is 11 km with a 92 m elevation gain. Home is the exact reverse. Weight has also varied between 190 lbs and 220 lbs. It has taken me anywhere from 28 minutes (home) to 45 min (to work) mostly depending on wind and traffic lights. Wind is the big variable. I've logged between 225 cal (August, tailwind and green lights) and 400 cal (April, headwind and pain :-) ).

Since I've found time dependent on external factors, I like to challenge myself with HR, particularly average HR.

I've also found that for the longer rides (plus 3 hrs), there is a limit to calories I eat back. I never log more than 1500 cal per ride.

Another:

Calories: 5,246 C

Normalized Power (NP): 167 W
Intensity Factor (IF): 0.834
Training Stress Score (TSS): 361.0
Work: 2,749 kJ

Still would love to know where Garmin is pulling the Calories from. It's not even in the ballpark.

I've noticed garmin / strava is way off on calories sometimes when it should be a straight kj to cal conversion. I'm typically doing endurance efforts around 210-240 watts which is ~750-800ish kilojoules an hour.

Example here doing some threshold intervals:
https://www.strava.com/activities/312835740
1009 kj's burned, strava reports 1,125 calories. Even with a slight variance in efficiency that's pretty far off as it shouldn't be more than a 3-4% difference in work energy vs calories burned.