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Commuting Bicycle commuting is easier than you think, before you know it, you'll be hooked. Learn the tips, hints, equipment, safety requirements for safely riding your bike to work.

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Old 07-24-05, 03:28 PM   #51
dfw
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Quote:
Originally Posted by CdCf
You still don't get it.
My examples were extreme to clearly show how unrealiable average trip speed is for this purpose.
I could've used wind instead. In fact, here's a new example...

Same rider as in previous examples.

Ride #1:
10 km on a flat road with no wind, and then back the same way.
Average speed 31 km/h. Total time 39 min. Total energy 530 kcal.
(Online calculator suggests 1040 kcal for this ride...)
Calorie Calculator reports 600 calories.


Quote:
Ride #2:
10 km on flat road with a 5 m/s headwind followed by riding the same distance back, with a 5 m/s tailwind instead.
Average speed 22 km/h. Total time 54.5 min. Total energy 740 kcal.
(Online calculator suggests 730 kcal for this ride...)

So, average speeds go down while energy spent goes up.
But the online calculator tells you that the first ride used more energy than the second...

And 5 m/s of wind is not at all uncommon!
Calorie Calculator reports 535 calories.

Have you considered maybe the problem lies with the site you are using and not the methodology?
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Old 07-24-05, 04:39 PM   #52
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I'm not "using" a site. I simply took the data and entered into the calculator that was linked to previously in this thread.

I got 630 and 550 respectively, but that doesn't matter.
They still trend the wrong way for these conditions.

Add small hills to this windy ride, and the error will be even greater.

I agree that these calculators can put you in the ballpark, but 100-300 kcal off for single ride easily means the difference between weight loss and no weight loss, if people rely on them. (Three rides a week, with 200 kcal error for each, and you end up with just under a pound of weight loss less per month, if you're unlucky.)
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Old 07-24-05, 06:09 PM   #53
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I don't think anyone said you'd do much better than a ballpark figure. My only point was you're better off measuring speed rather than measuring heart rate. With no other source of info, most people wouldn't even be able to come up with a figure that's within a cab ride of how many calories they are burning. Even if you knew exactly, nobody really knows exactly how many calories they actually metabolize. Common sense should tell you to exercise more or eat less if you are not dropping pounds.
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Old 07-24-05, 08:01 PM   #54
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Well I thought about it and thought about it and lost 3 nights of sleep. I finally decided we are all right.

I ride a wide variety of routes in different weather conditions. I want to know roughly how many calories per hour I burn overall. I figure the estimate might be a little low today, it might be a little high tomorrow, but it will all even out, and I can just think that I burn about 800 calories per hour of riding when I go 16 mph. I want to enter only my body weight aand speed so I have an accurate estimate over time.

Someone else rides the same route every day under similar conditions. They need to know, how many calories do they burn on that daily ride. They need to enter all the variables entered in various posts to get the estimate they want of one particular ride.

Anyone buying this?
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Old 10-03-07, 08:29 AM   #55
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no one's going to read this, right? as the "conversation" ended years ago. But I had to respond to this. Firstly, dfw is right: the number of calories burned is by definition the amount of work you do. Work is force needed to move mass a certain distance -regardless of the speed; that is physics. It takes more force to move a mass up a hill, due to gravity, and to oppose the force of the wind. Conversely, it takes less force when the wind is "at your back" or to go down a hill. When also accounting for our physiology, humans can expend more calories and increase their cardiovascular capacity with interval training.

Coming in at a close second:
Ganesha, as someone who prefers other activities (and is motivated to bike for my green principles) I found your comment a little presumptuous, if not deliberately belittling to novice bikers. Perhaps you're a tri-athlete, but I can imagine that you/at least many other avid bikers, might find it vigorous to keep up with a swimmer as she just warms-up for her real workout. Attitudes like that keep some people from trying new things, which is a shame.

Lastly, I'm assuming that most of us are concerned with calories to "stay in shape"/lose weight. No? Taking the time to calculate wind speed and 5 other variables to get an exact number is ridiculous for the average joe; it just leads to obsessive behavior. I'd suggest getting some reasonable estimate that's enough to plan on how many calories you need to replace -or for motivation to go that extra mile to justify one more Guinness (or a nice wheat beer in my case).
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Old 10-03-07, 09:02 AM   #56
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Originally Posted by CdCf View Post
I'll give you an example.

Take a rider+bike weighing 100 kg.
Let's say this fictional rider is capable of putting out a maximum of 200 W.
His total CdA is 0.4. His bike's Cfr is 0.006.
That's way to complicated for me. I've simplified it to two burgers / hour.
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Old 10-03-07, 09:34 AM   #57
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Lastly, I'm assuming that most of us are concerned with calories to "stay in shape"/lose weight. No? Taking the time to calculate wind speed and 5 other variables to get an exact number is ridiculous for the average joe; it just leads to obsessive behavior.
As well as introducing more errors to what is only ever going to be a back of the envelope calculation despite however many decimal places a web calculator or heart rate monitor gives you.

A power meter will give a correct answer however. If it's accurate, anyway.
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Old 10-03-07, 10:43 AM   #58
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Putting much stock in calorie counting tables falls into the error I call "measure with micrometer, mark with chalk, cut with axe"

In real world conditions, there are enough variables that you will not be able to guess that precisely. On a given day, I might commute on any one of four bikes, and there is a huge amount of difference in the speeds and effort required to get me to work. Factor in wind, temperature, what I'm lugging, etc, and the best you can do is guess roughly.

At the end of the day, it doesn't matter how many calories you burn, so much as calories in roughly equals calories burned.
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Old 10-03-07, 11:34 AM   #59
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I watched "Chasing Lance" the other day. Team Discovery was eating 8-10,000 calories EACH per meal during the Tour win #7.

I'm ready to take up racing!!
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Old 10-03-07, 01:46 PM   #60
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The easiest to remember rule of thumb is "40 calories per mile".

IMO, that's a reasonably accurate number for most folks over most terrain. A little less if you're light, ride where it's flat, or draft a lot. A little more if you're heavy, or ride up and down big hills.
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Old 10-03-07, 03:01 PM   #61
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See if any one of you have the same results.
I have the Suunto T3 Multi Sport and here's what I have after a day's ride to and from work. The stopwatch keeps on going even while stopped at traffic light intersections.
Male: 5' 5"; Age: 48; Weight: 137 lbs.; Bike: Surly Steamroller (47x18); Total Propelled Weight: 181 lbs.
Total GPS Distance: 40.7 miles
Total Commute Time: 2 hrs 58 mins
Total Calories Burned: 1674
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Old 10-03-07, 03:17 PM   #62
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wow, how awesome: people actually read my stuff. And I love what you all wrote. In between these two posts I actually did my errands of the day riding on my sweet beach cruiser which has one gear, fenders, a big, usually full, metal basket in the back, and a mirror that looks like I might've taken it off my car. I sit on this sweet ride with an almost erect back, using petals set so far forward my legs never bend to less than ~85 degrees. I imagine alot of you would have to tie a small parachute to the back of your bike to match my aerodynamics... but the question is, of course, how many more calories have I been burning since I put that mirror on?? I don't think we discussed the friction of the terrain or the specific efficiency of bike's gears and whatnot either, but maybe those were some of those stats dfw was putting up.
Bottom line: do what makes you feel good, from head to toe.
I'm off to the beach.
But just to leave on a contentious note (that's with a virtual wink), I don't know about TWO burgers/hr, maybe one or 2 veggie burgers/hr (and then you'd be a little greener too! -that's with a virtual grin)
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Old 10-03-07, 03:39 PM   #63
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and about 165 calories for an equivalent amount of Amstel Light. Makes you wonder why people drink horrible beer to save 35 calories.

Cause if you drink 20 of them, you have to work out an extra hour.

/cp
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