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Power meter owners: do you ever ride for kJ?

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Power meter owners: do you ever ride for kJ?

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Old 08-11-08, 06:41 AM
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Power meter owners: do you ever ride for kJ?

On my commutes, a couple times per week, I find myself trying to crack 300kJ before I arrive at my destination, just for a threshold/VO2 workout. Does anyone else try burn a certain number of kJ before a landmark?
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Old 08-11-08, 06:43 AM
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I don't but my coach says he uses that as the marker to determine the effort I put out for the week...

Edit...I use it to determine how many S'mores I can eat...
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Old 08-11-08, 06:43 AM
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all the time, but I do mine more for kJ/time on the bike than a physical landmark
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Old 08-11-08, 07:00 AM
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Originally Posted by MDcatV View Post
all the time, but I do mine more for kJ/time on the bike than a physical landmark
average power?

I guess it's still trying to get somewhere as inefficiently as possible though
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Old 08-11-08, 07:05 AM
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Old 08-11-08, 07:08 AM
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Not sure if I should say yes or no to this. Never X kJ in Y distance. I do watch it and stretch my ride out if I want to burn more depending on my diet for the week. I do find myself watching the kJ and thinking "Ah... another 15-20 minutes maybe" Likewise, I find it easier to think of "average watts" easier in kJ/hr vs watts. I "feel right" on long rides at 850 kJ/hr. Not sure what that is in actual watts, but I guess it's around 240-245? If I'm pushing 900+/hr I will back off on endurance days.
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Old 08-11-08, 07:08 AM
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ive recently been looking at it a lot more because of my weight loss plan but I havent used it as a marker yet.
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Old 08-11-08, 07:10 AM
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Now that I'm doing base in preparation for next season (working on my "endurance" limiter), I ride for kJ, slowly building up the amount of work I do per ride. Need to train my body to utilize different fuel sources.
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Old 08-11-08, 07:11 AM
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Originally Posted by bdcheung View Post
Need to train my body to utilize different fuel sources.
Can we train it to utilize ice cream? That would be cool.
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Old 08-11-08, 07:14 AM
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That's basically what I'm trying to do... my body burns through glycogen stores just fine, but doesn't seem to like using fat as fuel.
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Old 08-11-08, 07:26 AM
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During base training, sometimes I'll try to beat 1750 or 3500 (roughly half-pound or pound of fat)
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Old 08-11-08, 07:52 AM
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I'll target the number of KJ's to determine how many beers I get to drink.
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Old 08-11-08, 07:53 AM
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^^ or how many beers you won't have to drink to get tanked.
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Old 08-11-08, 08:01 AM
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Yeah, I've certainly tracked kJ for most rides, for Calories burned estimates.

This is really just more of a "Crap, how can I burn another 80kJ if I've only got a mile left?" Oh yeah, afterburners.
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Old 08-11-08, 08:01 AM
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I consider it as a target for each ride I do. I set minimums for the week and for the longer rides. This is mostly about weight control/loss.

I need to see at least 3000kj on any Saturday or Sunday ride. If I am under than I will add on a bit of time until I meet that minimum. If I am spent before this I start looking at my food.
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Old 08-11-08, 08:03 AM
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Originally Posted by NomadVW View Post
Can we train it to utilize ice cream? That would be cool.
Or french fries.

WR, I use TSS & IF as markers for a workout. I think kJ may not tell the whole story for a VO2Max workout - you probably need to DL the wattage graph to make sure it was an actual interval.

Is this really about how many calories you will let yourself chomp down @ dinner?
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Old 08-11-08, 08:14 AM
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Originally Posted by simplyred View Post
Or french fries.

WR, I use TSS & IF as markers for a workout. I think kJ may not tell the whole story for a VO2Max workout - you probably need to DL the wattage graph to make sure it was an actual interval.

Is this really about how many calories you will let yourself chomp down @ dinner?
Yeah, TSS & IF are great after a ride, but during the ride, kJ is right there. Also, this is a known course, it's short (6 miles), with pretty consistent winds. If a front comes through and changes the wind, I can see it in the energy spent though.

I really only ever target kJ on my commute, and only once or twice/week. It's nice to see that I can get over 600kJ in my round-trip commute.
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Old 08-11-08, 08:18 AM
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I burned 371 kJ this morning on my 6 mile commute
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Old 08-11-08, 08:18 AM
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Originally Posted by waterrockets View Post
Yeah, TSS & IF are great after a ride, but during the ride, kJ is right there. Also, this is a known course, it's short (6 miles), with pretty consistent winds. If a front comes through and changes the wind, I can see it in the energy spent though.

I really only ever target kJ on my commute, and only once or twice/week. It's nice to see that I can get over 600kJ in my round-trip commute.
That's right... hmm.. honestly, I can't say that I've ever put my display to show kJ. How sensitive is it? How is it calculated?

Those are some serious calories burned/day. Excluding your training - you're up to -3000kJ/wk!! That's like one day of food deficit!
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Old 08-11-08, 08:27 AM
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kJ is a fairly accurate number. The estimation comes in converting kJ to Calories burned. There are about 4kJ in a kcal. Note 1kcal is equal to one dietary Calorie. The human body is about 25% efficient when burning calories aerobically. This means that the # of kJ put into your rear wheel on a ride is roughly equal to the # of Calories you used to do it.

Of course this all goes out the window if you're doing anaerobic work, but it's still fun to see.

For the record, I think anaerobic respiration is about 1/8 as efficient as aerobic, so burning 20kJ in a sprint actually uses 160 Calories.
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Old 08-11-08, 08:46 AM
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Originally Posted by bdcheung View Post
I burned 371 kJ this morning on my 6 mile commute
Really? How much do you weigh, and what was your NP?

Here's my 304kJ commute this morning 6.17 miles (road closure required a bit more distance). On the way home, I'll probably get 320-340kJ with the headwind.

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Old 08-11-08, 09:00 AM
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Originally Posted by simplyred View Post
That's right... hmm.. honestly, I can't say that I've ever put my display to show kJ. How sensitive is it? How is it calculated?
It updates for each kJ, every few seconds when I'm working hard.

To calculate, work = torque * angle moved, and those are the core measurements taken by the PowerTap hub.
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Old 08-11-08, 09:01 AM
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I weigh 67 kilos, bike is probably 7.5-8 kilos, and the gear I was carrying is probably another 2-3 kilos.

I don't know what NP is - don't have the software to give me that at work.

Here's the ride, though:http://www.mapmyride.com/route/us/va...n/156907274627
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Old 08-11-08, 09:50 AM
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Originally Posted by brianappleby View Post
kJ is a fairly accurate number. The estimation comes in converting kJ to Calories burned. There are about 4kJ in a kcal. Note 1kcal is equal to one dietary Calorie. The human body is about 25% efficient when burning calories aerobically. This means that the # of kJ put into your rear wheel on a ride is roughly equal to the # of Calories you used to do it.

Of course this all goes out the window if you're doing anaerobic work, but it's still fun to see.

For the record, I think anaerobic respiration is about 1/8 as efficient as aerobic, so burning 20kJ in a sprint actually uses 160 Calories.
"kJ is a fairly accurate number." Providing your power meter is accurate. - TF
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Old 08-11-08, 10:06 AM
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Originally Posted by waterrockets View Post
On my commutes, a couple times per week, I find myself trying to crack 300kJ before I arrive at my destination, just for a threshold/VO2 workout. Does anyone else try burn a certain number of kJ before a landmark?
I have a habit of topping off my kJ at the end of a ride. I always aim to do 2000+ kJ of work, regardless of whether I'm doing intervals, or tempo, or whatever.

I've been averaging 12000 - 13000 kJ/week, while riding ~14 hrs.

Unlike you, however, I don't ramp it up to make my goal, I'll just add a few minutes easy instead.
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