average heart rate vs calories

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Originally Posted by Max Gosey

I'm sorry but do the math...


Walking vs running at 7.5 mph: You are exercising at 214% of the intensity but are burning 240% of the cals. Do the math in terms of calories per MILE, not calories per minute (with these figures, that number obviously varies). In this situation, you burn 112% as many calories per unit of distance running 7.5 mph as you do walking at 3.5 mph. I could do the math for other figures, but I would assume the patterns are similar.

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#1 that is not my math. it is the math of a guy named David Costil. you should look him up. He is only one of the pioneers of exercise physiology.

#2 My point all along was that you burn more calories running than you do walking over the same given distance

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Originally Posted by Max Gosey

What I want to know is the correlation between cardiovascular fitness and fitness overall: according to someone in this thread, the VO2 max is the main determining factor of fitness and VO2 max increase is specific to the type of exercise.

Bottom line question: if I get my heart in shape by ellipticalizing/stairmastering, will I be no better off skinning up the skin track than if I hadn't exercised at all?

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VO2 max is indeed the detmineing factor of aerobic fitness and there is some cross over between types of aerobic fitness. But you will be more efficient if you do the exercise you want to race/perform etc. This is because those specific muscle will have cellular and neurological adaptaions as well as just plain stronger.

Cardiovascular fitness is more than just your heart. It included the lungs, vessels, nerve transmissions, enzyme activity etc.

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Originally Posted by Max Gosey

Well, actually the answer to this question is obviously no because I'll still be exerting SOME (although not all) of the same motor units with these leg exercises. But let's say I was pedaling with only my shoulders, which got my heart rate up to 160 (where I would assume it would be when I'm skinning)... My heart is obviously more efficient in producing a high stroke volume to supply my muscles with oxygen necessary for ATP production/consumption (eg cardiac output is higher). But the VO2 max is apparently not raised in the same manner with pedaling with shoulders as it would be skinning (or vice versa). What I DO know is that the mitochondrial gains of chronic exercise do not exist for those skinning muscles but do exist for my shoulders in this hypothetical scenario. So obviously the cell is not as efficient in energy metabolism, but at the same time the muscle is not as ischemic as it would be if I were untrained.

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wrong, you will be better off than if you had done nothing. Like I said in the above poitn, there is cross over between differnt types of aerobic activty. But you won't be building efficiency in the specific activity.

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Originally Posted by Max Gosey

Edit: I wonder if hemoglobin's oxygen affinity increases with exercise... (Or if there's a different proportion of heme/myoglobin oxygen ligand receptors that increase the overall oxygen affinity in the blood).

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Not that I know of but possibly. I do know that you will produce more red blood cells in response to aerobic activity

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Originally Posted by The AD

Work is force applied over a distance. It isn't required to be done against gravity.

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Did someone say phyzzaks??

Work is force applied parallel to the direction of travel. The force you apply when running is up-down, but your talking about forward motion, so no work is done in moving yourself horizontally (unless you count air resistance, but if you wear sexy spandex when running then that shouldn't be a problem).

You do a bit of work with every step to lift your body upwards, but gravity has this tendency to pull you back down again and you do an equal amount of negative work when you land your next stride to absorb the impact, so net work done is 0. This work has nothing to do with your forward motion.

sweet. I gotta get to work.

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Originally Posted by davep

Work is force applied parallel to the direction of travel. The force you apply when running is up-down, but your talking about forward motion, so no work is done in moving yourself horizontally

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Honestly I don't know what you're talking about. If your foot didn't impart a horizontal force component to the ground you wouldn't go anywhere. You'd merely be running in place.

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Originally Posted by Viva

Yeah, yeah, yeah. So how does that explain a maximal excercise threshold without achieving a VO2 plateau (i.e., VO2 max)?

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First off, VO2max is mode of exercise dependent, meaning you have different VO2max's for different modes of exercise. So you could have some VO2max for running but be doing a swim test, you cop out before you hit your (running)VO2max because you've reached your VO2max for swimming. This also works for intensity, duration and frequency. Crapping out before your running Vo2max in the same mode, intensity, duration and frequency? Many things could lead to this: The biggest is simply motivation, but most people don't like that answer. Diet, ingest Carbs between 90 and 30 minutes before exercise and you end up making yourself Hypoglycemic, you have a glycemic spike and then come crashing down, leaving yourself with less available glycogen as glycolysis has 'taken a break'. 2-3 hours before exercise or within 15 minutes prior are recommended to avoid this negative affect. The biggest factor will always be mode of exercise, but climate and altitide should also be considered.

Specificity of training, If you want to improve your Skinning, train by Skinning. Sure you'll see V02max improvement from shoulder cycling if you test in shoulder cycling, but you'll see a very small change in your skinning
V02max. Obviously we can't all go skinning whenever we like, so train by trying to use the same muscle groups at the same intensity for the same duration.

Up a hill, down a hill, no work done? You're still making a horizontal displacement, work is done. Climb a mountain slide back down that mountain to the same exact place, you're right no NET work done by the SYSTEM. Keep in mind gravity is a very big part of the system, you do work against gravity on the way up, Don't fight it on the way down resulting in negative work from gravity, this results in no NET work, but you've still done a lot of work to move you mass up that hill.

Here's one for conversation, Lactic Acid has mostly beneficial affects and doens't cause muscle soreness....this could get fun.

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Originally Posted by The AD

Honestly I don't know what you're talking about. If your foot didn't impart a horizontal force component to the ground you wouldn't go anywhere. You'd merely be running in place.

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No, if your foot imparted any average horizontal force on the ground you would constantly accelerate. The total work done in a given stride is 0 if you are going the same speed afterwards. You do a little bit of work when you go from a standstill to a constant pace, and you do an equal but negative amount of work when you come to rest again. (Unless you go uphill, as was pointed out by someone else earlier).

None of this is relavent to the original question of how many calories are burned, since our bodies are spectacularly inefficient. we consume lots of energy (what mntlion is asking about) to do little or no net work (what we're now talking about).

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Originally Posted by davep

No, if your foot imparted any average horizontal force on the ground you would constantly accelerate. The total work done in a given stride is 0 if you are going the same speed afterwards. You do a little bit of work when you go from a standstill to a constant pace, and you do an equal but negative amount of work when you come to rest again. (Unless you go uphill, as was pointed out by someone else earlier).

None of this is relavent to the original question of how many calories are burned, since our bodies are spectacularly inefficient. we consume lots of energy (what mntlion is asking about) to do little or no net work (what we're now talking about).

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Umm, way off. First off, the human body is the most effiecient energy system out there, not positive but i believe we're about 30% effiecient, the average car is about 3% and man's best job so far, the steam engine is around 10%. Not sure that those are accurate, but the point is we're way more effiecient than any machine we've built.

Work is a force applied to an object that causes displacement, when you run, you're making a horizontal displacement. I'd like to ask you what it is that is propelling us forward if we're not doing any net work per stride? So we're doing all the work in that first stride, man i've got a new respect for those marathon runners, able to propel themselve 26.2 miles with a single kick of the leg. The net of a given stride is not Zero for a given speed because you're still moving forward, horizontal displacement. And Net work for humans has nothing to do with caloric energy expenditure because we are people who have to expend energy whether or not we're doing 'positive' or 'negative' work on our system. Yes if you lift an object and drop it to the same place there's not NET work done because there's no NET displacement, but you still had to lift it, gravity took it down.

Edit: if your touchdown horizontal force was exactly equal to but opposite your toe-off horizontal force, why wouldn't you just stop after your first stride? Yes touchdown opposes the forward force you produce, but that's why you supinate on touchdown and roll to pronation through the plant to toe-off in an effort to decrease the negative horizontal forces that are in herent in touchdown.

P.S. you experience far greater vertical forces from running than horizontal, somewhere on order of 9g's, but i can't remember if that's with or without a shoe on. Either way the human body is an incredible creation.

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Originally Posted by fluffballs

I'd like to ask you what it is that is propelling us forward if we're not doing any net work per stride?

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Newton's 2nd law (paraphrase): objects in motion stay in motion. It takes no NET horizontal force for the marathon runner to stay a constant speed throughout his entire run. If the marathon runner were perfectly efficient, he could take his first few strides to get up to speed, then jump on his magical hypothetical frictionless bicycle (or whatever) and coast the remaining 26.2 miles to the finish. All the energy the runner uses in the middle is turned into heat, not work.

You're mixing 'work' with 'expended energy' for the marathon runner, which are not the same thing from a physics perspective. Energy can be turned into work or heat. (Maybe they are used interchangably in human physiology, where the relavent question is how much energy our muscles use, not how much useful work can be extracted from a person).

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Originally Posted by fluffballs

And Net work for humans has nothing to do with caloric energy expenditure because we are people who have to expend energy whether or not we're doing 'positive' or 'negative' work on our system.

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Exactly.

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Originally Posted by fluffballs

i believe we're about 30% effiecient

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That's interesting, I've never done the numbers but that does make sense:
climb 1000m vertical, consume maybe 500calories? ~ 2000000 Joules
net work = mgh = 800000 Joules assuming 80kg mass. that's 40% efficiency, pretty impressive. That surprises me, cool.
(But run 26.2 miles, consume 1500? calories
net work = 0, that's 0% efficiency.)

Dude, we're nerds approaching the same thing from different perspectives. :)

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Originally Posted by davep

Dude, we're nerds approaching the same thing from different perspectives. :)

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Ha, your right in that sense. I think i'm looking at it from more a real world Biomechanics standpoint, and you've got the principals of physics. A marathon runner is not perfectly efficient and this means they must constantly be exerting a horizontal force inorder to keep moving forward, if they were perfect, you're right they could ride that sweet hypothetical bicycle to the finish. If you look at force plate data for constant velocity running you'll see that touchdown horizontal force does not opposite force created by toe-off. I do believe in the real world with imperfect running biomechanics and air-resistance.....there is a Net horizontal force exerted. Because as you know, an object stays in motion in a perfectly fictionless environment with no external forces working on it, this is certainly not the case for running. I think we can both agree that the further you run, the more work you perform, since work is based on displacement. I see what you're saying about interchanging work and energy expenditure, but I will still contend that there is more NET work performed for a longer run because of the external forces.

Edit: I'm not going to re-read my post, but I see what you mean about no NET work done per stride once at a constant velocity. Object is in motion stays in motion, yeah the person is doing 'positive' work with some 'negative' from touchdown, but factor in the 'negative' the environment and you've got no NET work done per stride at a constant velocity. But like we said before, NET work of a system has very little to do with the total work done by the person.