kilojoules and Kcals....what gives?

[Hysbrian]

Ok so this came up this morning on my group ride. My polar HRM gives me a running total of how many cals I have burnt as I ride. Today was an easy ride of 1 hr 45mins at an avg hr of 147 and it says that I burnt 1142 kcals. To me that seems a little high. But what I don't get is how this converts to kilojoules. I thought that they were the same thing, are they?
I thought that I would just post it up here, but now i need to shower.

[zank]

1142 "Nutritional" calories = 1142 kcal = 4778.1 kilojoule

1 kcal = 4.184 kilojoule

1 cal = 4.184 joule

[Dr. Doofus]

the rub is that the efficiency of most cyclists makes a kjoule roughly, roughly equal a calorie....

brian, if you're an elite rider, which you are, and you rode for 1:45, then it is highly likely that you burned around 1100 calories...if you are, say 165 pounds, then that would work out to be about a 180w average, which would be easy for a cat with a LT power of 360w....


even though doof finally got the ridley set up today, thanks to the 125 stem from herr jerk...he had to do 1:30 of tempo on the friggin trainer, cause ms. doof's starter went and we're down to one car for the weekend and there were time issues invloved which mean no outside ride...and doof sucked sucked sucked sucked...doof had been getting 3.4-3.5 w/kilo for those tempos, and today he barely pushed our 3.0...and yesterday was a rest day...some days you just don't have it


but yeah, you probably did burn 1100 calories

[zank]

Doofman, I'm sorry, but I don't understand. A joule is a unit of energy. It is the amount of energy it takes to raise the temperature of 1 g of water 1 degree Celcius. 4.184 joules equals 1 calorie. Efficiency does not play into the conversion. Can you help me understand what you mean?

[EdK]

The total energy expenditure displayed by the SRM represents
the mechanical work input to the bicycle. Physiological studies
show that the human body is about 25% efficient in producing
mechanical energy on a bike, so a measured mechanical
expenditure of 1000kJ uses about 4000kJ of food energy. Food
is most often measured in kiloCalories, most commonly
abbreviated “Cal”. 1 Cal = 4.2 kJ, so the 1000kJ of mechanical
work consumes about 4000kJ or close to 1000Cal of food
energy. Your body can only regenerate properly if your energy
intake is greater than or equal to your energy demand. For
serious cyclists, this may mean 4500-6000 Cal per day of energy
intake. (250W for 4 hours riding is 3600 kJ of work = 3600 Cal
burned, plus 100 Cal/hour for basal metabolism). Cyclists
wishing to lose weight should train their fat metabolism system,
and avoid carbohydrate-rich meals except before and after
training. ´

[zank]

Ahh, I got it. Thanks for the help!

[Hysbrian]

The total energy expenditure displayed by the SRM represents
the mechanical work input to the bicycle. Physiological studies
show that the human body is about 25% efficient in producing
mechanical energy on a bike, so a measured mechanical
expenditure of 1000kJ uses about 4000kJ of food energy. Food
is most often measured in kiloCalories, most commonly
abbreviated “Cal”. 1 Cal = 4.2 kJ, so the 1000kJ of mechanical
work consumes about 4000kJ or close to 1000Cal of food
energy. Your body can only regenerate properly if your energy
intake is greater than or equal to your energy demand. For
serious cyclists, this may mean 4500-6000 Cal per day of energy
intake. (250W for 4 hours riding is 3600 kJ of work = 3600 Cal
burned, plus 100 Cal/hour for basal metabolism). Cyclists
wishing to lose weight should train their fat metabolism system,
and avoid carbohydrate-rich meals except before and after
training. ´

Had to read it twice, but it makes sense. Thanks.

Yo Doof! Sometimes you just got to rock it on the trainer, MP, but hey its better then not riding at all.

[ada@prorider.or]

The total energy expenditure displayed by the SRM represents
the mechanical work input to the bicycle. Physiological studies
show that the human body is about 25% efficient in producing
mechanical energy on a bike, so a measured mechanical
expenditure of 1000kJ uses about 4000kJ of food energy. Food
is most often measured in kiloCalories, most commonly
abbreviated “Cal”. 1 Cal = 4.2 kJ, so the 1000kJ of mechanical
work consumes about 4000kJ or close to 1000Cal of food
energy. Your body can only regenerate properly if your energy
intake is greater than or equal to your energy demand. For
serious cyclists, this may mean 4500-6000 Cal per day of energy
intake. (250W for 4 hours riding is 3600 kJ of work = 3600 Cal
burned, plus 100 Cal/hour for basal metabolism). Cyclists
wishing to lose weight should train their fat metabolism system,
and avoid carbohydrate-rich meals except before and after
training. ´

ooh that´s why i train to get more eff. 20 %
so hiep hiep i have to buy less food

well now you know hard ettape tour 12000cal a day

[Tom]

So, backing up on that 250W*4 hour = 3600 calories, I take yesterday's HRM numbers. 2.3 hours, 2200 calories. I come out with 265W average.

NFW! I'm fat, out of shape and it comes up with 3.4 watts/kilo.

The moral of the story? Figure out how to convince Karen I really <need> an SRM wheel.

Yeah, right. Every bottom feeding moron that doesn't have a frigging clue what goes on in a race needs this. I'm the idiot that singlehandedly blocks the fast guys by mistake.

But, on the other hand...