Better way to guess my caloric expenditure?

[Dead Man]

Howdy

I went out for one of my city sprint sessions last night. Since winter hath fallen and daylight riding is basically nonexistant, I go do sprint/interval laps on a 4 mile loop in my town on lit roads after dark. Three or four short but nasty hills, some good cornering, one stop sign and two traffic lights. Come off a side street corner into traffic, race cars down the main drag, bomb a little steep hill into Old Town and hit some corners hard, sprinting hard until about a block breather before burning back up another hill into my neighborhood.. then sit up and try to catch my breath on the backstretch, start ramping up speed for the first corner and do it all over again. It's pretty masochistic. Especially if I have to slow or stop for the two traffic lights- 'cause then I have to sprint as hard as I can off the line on green to get up to speed to merge going over a bridge about 300m down. BURN BABY

Short ride, but it's truly a ride from hell, every time. It's gotta be worth some serious cals. I've never paid any attention to Strava's calorie estimates for my rides, but I'm trying to cut back a pretty big chunk of holiday too-much-eating-not-enough-riding weight, and recently started tracking my input and output.

Strava gave yesterday's ride 479 calories, for 49 minutes of pure hell. "myfitnesspal," on the other hand, gave me 1,028 for the same ride. What gives? Does it not seem like what I describe above should be worth more than a big bowl of cereal?? At the same time, 1028 seems kind of high, for 49 minutes of anything.... but that's gotta be closer than Strava was.

What's a better way to figure this out?

[carpediemracing]

from what I see on my SRM vs MyFitnessPal the latter is really optimistic with calorie burn. I use kJ:cal (1:1, give or take, although the range is apparently .95-1.2:1). I don't ride super hard but I normally have to log my rides using the 10-12 mph ride and then reduce minutes to get the right calorie/kJ number.

Strava, for me, wildly overestimates the wattage for me. I ride mainly on flatter roads when solo so it's the worst for Strava, meaning aero drag a huge factor. If I just went uphill for a whole ride I would guess Strava to be more accurate. I've never used Strava for calorie estimates.

Of course in crits the numbers go out the window. I'll average 170w and Strava will say 470w or something insane.

As for actual calorie numbers it's impossible to say without a lot of information. For me, at 5'7", a typical 175-180 lbs weight, reasonably aero, doing something sort of similar to you, I'm guessing I'd be burning just under 600 cal/hour. In tough races I've broken the 500 cal/hour but peeking through some of my 2014 races it seems that I never go much above about 570-580 kJ for an hour of racing.

[guido]

Buy a power meter.

[JAGI410]

Heart rate monitor might be a better gauge, and it's useful off the bike in other exercises too.

[sandyrs]

from what I see on my SRM vs MyFitnessPal the latter is really optimistic with calorie burn. I use kJ:cal (1:1, give or take, although the range is apparently .95-1.2:1). I don't ride super hard but I normally have to log my rides using the 10-12 mph ride and then reduce minutes to get the right calorie/kJ number.

Strava, for me, wildly overestimates the wattage for me. I ride mainly on flatter roads when solo so it's the worst for Strava, meaning aero drag a huge factor. If I just went uphill for a whole ride I would guess Strava to be more accurate. I've never used Strava for calorie estimates.

Of course in crits the numbers go out the window. I'll average 170w and Strava will say 470w or something insane.

As for actual calorie numbers it's impossible to say without a lot of information. For me, at 5'7", a typical 175-180 lbs weight, reasonably aero, doing something sort of similar to you, I'm guessing I'd be burning just under 600 cal/hour. In tough races I've broken the 500 cal/hour but peeking through some of my 2014 races it seems that I never go much above about 570-580 kJ for an hour of racing.

Funny, Strava criminally underestimates my power output. Probably because I'm 6'5" and on flat roads, I catch more wind than some sedans.

[Jaq]

600 kcals doesn't sound too far off the mark. Most on-line calorie calculators will figure, for 50 minutes of high intensity, 160 pounds body weight, 650 - 750 kcals.

I use 20 kcal/km, or 30 kcal/mile as a conservative estimate.

[dan682]

Looking at my power meter data, I did a crit last spring that lasted 29 minutes.
I did 383kJ of total work, and average heart rate was 86% of my max, and I weigh 145 lbs.

Sounds like you're doing a similar effort, so according to my non-scientific calculations, and assuming you weigh a little bit more, I'd guess you're burning about 700 calories in that workout.

[shovelhd]

Buy a power meter.

This is the only accurate way.

I would guess that the effort is a lot closer to 500kj than 1,000kj.

[ergott]

Even the less accurate powermeters out there will be good enough for what you need. Perhaps invest in a Stages crank arm?