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Yesterday I completed my first Duathlon- a 5K, 13 miles on the bike and another 5K. It took me 2 hours and 40 minutes. (Hey, I'm 66- I was grateful to finish.)
So... the usual exercise calculators say I burned about 1,000 calories given my body weight of 125 lbs. (Which is why you should never, ever think exercise alone is enough to lose weight- I think I could make that up with a bag of Doritos.)
But, if I remember my Physics from eons ago- calories are a unit of energy. One other measure is the foot-pound, which is the energy it takes to move one pound of mass a distance of one foot. If I convert everything I did to foot-pounds and then convert it to kilocalories I get something around 3,900 even neglecting the weight of the bike. (For those of you who don't know, what we call a "calorie" in the US is really 1,000 calories, thus a kilocalorie.)
So, why the difference? You can guess which number I like better.
Yesterday I completed my first Duathlon- a 5K, 13 miles on the bike and another 5K. It took me 2 hours and 40 minutes. (Hey, I'm 66- I was grateful to finish.)
So... the usual exercise calculators say I burned about 1,000 calories given my body weight of 125 lbs. (Which is why you should never, ever think exercise alone is enough to lose weight- I think I could make that up with a bag of Doritos.)
But, if I remember my Physics from eons ago- calories are a unit of energy. One other measure is the foot-pound, which is the energy it takes to move one pound of mass a distance of one foot. If I convert everything I did to foot-pounds and then convert it to kilocalories I get something around 3,900 even neglecting the weight of the bike. (For those of you who don't know, what we call a "calorie" in the US is really 1,000 calories, thus a kilocalorie.)
So, why the difference? You can guess which number I like better.
1,000 sounds about right. 100 calories per mile running, about. So 600 calories there, probably a bit less at 125 pounds but we're just talking very roughly. Cycling is mostly dependent on speed, maybe 30 calories a mile. Another 400 or so.
It's certainly not 3,900 however you got that. That's not even plausible, sorry.
But, if I remember my Physics from eons ago- calories are a unit of energy. One other measure is the foot-pound, which is the energy it takes to move one pound of mass a distance of one foot. If I convert everything I did to foot-pounds and then convert it to kilocalories I get something around 3,900 even neglecting the weight of the bike. (For those of you who don't know, what we call a "calorie" in the US is really 1,000 calories, thus a kilocalorie.)
So, why the difference? You can guess which number I like better.
Efficiencies.
You burn 78 KCal per mile running (KCal = 0.63 x mass[lb] x distance[mi]). There's 488 KCal.
Biking is more difficult. Gears, wind resistance. Basically it's Watts/hr = Calories/hr, but you could back into the Watts knowing roughly your coefficient of drag, which you can roughly guess with how you ride your bike, and speed - if it's a flat course, weight doesn't matter unless your climbing or descending.
Then it's Watts[average] x duration[hrs] x 3.6 = KCal
For example, a couple weeks ago I took a nice, easy 2 hour bike ride (average 12 mph). That's about 140W average using guesses. So 1008 KCal.
But, if I remember my Physics from eons ago- calories are a unit of energy. One other measure is the foot-pound, which is the energy it takes to move one pound of mass a distance of one foot. If I convert everything I did to foot-pounds and then convert it to kilocalories I get something around 3,900 even neglecting the weight of the bike. (For those of you who don't know, what we call a "calorie" in the US is really 1,000 calories, thus a kilocalorie.)
So, why the difference? You can guess which number I like better.
That's not quite right. A foot-pound can be thought of as the amount of energy to raise a pound one foot up. In other words, pushing a pound with the same force as you would need to over come gravity. Running or riding a bike on flat ground doesn't take nearly the energy as going straight up the same distance.
That's not quite right. A foot-pound can be thought of as the amount of energy to raise a pound one foot up. In other words, pushing a pound with the same force as you would need to overcome gravity. Running or riding a bike on flat ground doesn't take nearly the energy as going straight up the same distance.
Ah, THAT's the difference! I was looking for an explanation from someone who could go into the physics behind it.
I think I've eaten more than enough calories to make up for the exertion but would still do it all over again.
You burn 78 KCal per mile running (KCal = 0.63 x mass[lb] x distance[mi]). There's 488 KCal.
Biking is more difficult. Gears, wind resistance. Basically it's Watts/hr = Calories/hr, but you could back into the Watts knowing roughly your coefficient of drag, which you can roughly guess with how you ride your bike, and speed - if it's a flat course, weight doesn't matter unless your climbing or descending.
Then it's Watts[average] x duration[hrs] x 3.6 = KCal
For example, a couple weeks ago I took a nice, easy 2 hour bike ride (average 12 mph). That's about 140W average using guesses. So 1008 KCal.
Unless you're riding a rusy beach cruiser it's not 140 watts at 12 mph unless you've got a lot of wind or a lot of elevation change. On a road bike, more like 60 watts.
It's fairly accurate, although maybe not at 60 watts. Long easy ride I might do 3-4 hours at 120-140 watts, average 15-16 mph on a road bike. Wind does have an effect particularly crosswinds. Unless the wind direction changes, which often it does, the headwind on the way out is a tailwind on the way back which sort of equals it out. You might ride out at 20 mph at 120 watts with a tailwind and then come back at 11 mph at 120 watts with a headwind. Crosswind though, well, you're fighting that both ways.
Just as an example of how much speed matters though...
60 watts - 12 mph
120 watts - 15 mph
250 watts - 20 mph
1000 watts - 32
(hands on bars, not in the drops)
At least from that calculator, although I can tell you on the high end it's not accurate. Amateur racing the sprints are generally going that fast and this isn't the pros where there's organized sprint trains with guys who can put out 800 watts for a minute or two to ramp the speeds up. But then an organized sprint at that level is generally going 40-45 mph. It's accurate-ish in the normal 150-300 watt range though which is where 90% of riders are going to be who care about such things as watts for longer efforts.
Also on the road of course the average speed is lower than spreadsheet land. There's corners, stop signs, red lights, which inevitable lower the actual average speed.
Congratulations most 66 year olds would not even attempt to start. From experience 1,000 calories sounds about right but these calculations are always very approximate you have also left you heart rate out of the calculations.
Can't outrun a bad diet.
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