Quote:
Originally Posted by Vinman
Okay, but alotta times, the end-point of maximum exercise during testing occurs in the absence of a VO2 plateau. Perhaps VO2 max is determining so some, but I say it isn't a constant.
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Quote:
Originally Posted by Vinman
Okay, but alotta times, the end-point of maximum exercise during testing occurs in the absence of a VO2 plateau. Perhaps VO2 max is determining so some, but I say it isn't a constant.
Thanks HomieQuote:
Originally Posted by homerjay
Quote:
Originally Posted by homerjay
There is a time component to work though
"Work: Energy change over a period of time as a result of a force acting though a displacement in the direction of the force. Work is also the time integral of power.
Work is expressed in Newton Meters or the amount of energy per distance and power is the rate at which the work is done.
this shit makes my head hurt.... nevermind. I conceed to being stupid and will return to looking at Beavers padded room posts from now on.
work is newton meters, power is netwon meters per second, minute, hour, year......Like above power or impulse= work/time. 'Energy change over a period of time' just symantics meaning, it takes time to do the work, but doesn't matter how long that time is.
VO2max is your body's ability to use the oxygen you give it, not it's ability to get the oxygen. This means how efficient your cardovascular system is working, and then how efficiently your energy systems are able to use the oxygen. This is dependent on substrate levels, pH, temperature, muscle fiber type, which are all affected by training and individual differences. With VO2max incorporating all of this, it is the limiting factor to exercise.
Another way to look at it is swimming is the least efficient form of locomotion! Something I heard, so not sure it's true, but it sounds reasonable: of all the Olympic sports swimming is the least efficient (in terms of distance traveled versus work) and cycling is the most efficient. Obviously this is only counting sports where the work is done by the athlete is opposed to gravity, wind, etc.Quote:
Originally Posted by fluffballs
I would say swimming a mile at 3 mph (a 20 minute mile) is much more difficult than running a mile at 10 mph (a 6 minute mile).
Yeah, yeah, yeah. So how does that explain a maximal excercise threshold without achieving a VO2 plateau (i.e., VO2 max)?Quote:
Originally Posted by fluffballs
Actaully no work is done walking from point a to point b if there is no change of elevation. If you walk down a hill negative work is done. So using "work " is a non starter. The amount of energy expended is realted to the work done divided by the efficiency.
Work is force applied over a distance. It isn't required to be done against gravity.Quote:
Originally Posted by DougW
So...then... a woman's breast-sag isn't dependant upon her VO2 max?Quote:
Originally Posted by The AD
Does a woman running a mile without a sports bra burn more calories than one wearing a sports bra?
No, but the spectators do.Quote:
Originally Posted by The AD
Your right, memory failed me, you can do work against friction as long as there is movement.Quote:
Originally Posted by The AD
But you would still expend energy pushing on a 10000lb rock even though no work was done as it did not move. There I have my picky technical point after all. My work here is done.
Chicks bouncing their boobies while running give me a 10000 lb rock.Quote:
Originally Posted by DougW
Uhh...what, Bullet?
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.Quote:
Originally Posted by Vinman
Don't have to think of it in terms of physics... Anybody remember conversions in high school science? That's exactly what this is.
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?
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.
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).
Let's explore this issue of generic vs specific exercise for specific activities...
And hot DAMN, do I want to take this class!
VO2 max is one of the measurable standards used to determine fitness, but I argue that it's not absolute.Quote:
Originally Posted by Max Gosey
Did AKPM write this for you???!Quote:
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?
VO2 max stays the same. It's a measurment of one's ability to use O2. I'm not sure what you're getting at here, but consider that because your shoulders and arms are far less massive than your leg, butt, back, abdominal, etc., muscles, there's less O2 demand because fewer muscles are being used. Even with comensurate increases to the concentration of mitocondria, you're not going to have the same demand for O2.Quote:
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).
You mean with training? No. If you mean during the course of excercise, maybe if the blood becomes acidic enough, but then you've got other problems.Quote:
Edit: I wonder if hemoglobin's oxygen affinity increases with exercise...
One thing that does happen with long-term training is the development of new vascular tissue so that the trained muscle gets a better blood supply.
Okay. Ask questions.Quote:
Let's explore this issue of generic vs specific exercise for specific activities...
#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.Quote:
Originally Posted by Max Gosey
#2 My point all along was that you burn more calories running than you do walking over the same given distance
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.Quote:
Originally Posted by Max Gosey
Cardiovascular fitness is more than just your heart. It included the lungs, vessels, nerve transmissions, enzyme activity etc.
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.Quote:
Originally Posted by Max Gosey
Not that I know of but possibly. I do know that you will produce more red blood cells in response to aerobic activityQuote:
Originally Posted by Max Gosey
Did someone say phyzzaks??Quote:
Originally Posted by The AD
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.
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.Quote:
Originally Posted by davep
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.Quote:
Originally Posted by Viva
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.
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).Quote:
Originally Posted by The AD
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).
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.Quote:
Originally Posted by davep
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.
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.Quote:
Originally Posted by fluffballs
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).
Exactly.Quote:
Originally Posted by fluffballs
That's interesting, I've never done the numbers but that does make sense:Quote:
Originally Posted by fluffballs
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. :)
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.Quote:
Originally Posted by davep
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.