test2 wrote:
My issue is that it isn't clear what force you are talking about.
Just in case I wasn't clear, the force in this case is the force applied by your leg on the ground. If you look at it as a graph of force (y-axis) over time (x-axis) it will be roughly sinusoidal with peaks at each footfall. You can solve W in 2 ways: 1) integrate this graph and multiply by velocity (W=Fvdt), or 2) calculate the average force and multiply by distance.
Done.
It is an absolute fact that there are people who can eat a crapload every day and not gain weight. CICO is not an infallible rule. If it were that simple, then everybody would have 5% body fat.
chupacabra wrote:
test2 wrote:My issue is that it isn't clear what force you are talking about.
Just in case I wasn't clear, the force in this case is the force applied by your leg on the ground. If you look at it as a graph of force (y-axis) over time (x-axis) it will be roughly sinusoidal with peaks at each footfall. You can solve W in 2 ways: 1) integrate this graph and multiply by velocity (W=Fvdt), or 2) calculate the average force and multiply by distance.
Done.
Done? If you did the integration and calculation, show us. You still need to specify the directions of the forces and velocities you're talking about. How would you calculate the "average" force, is it always acting in the same direction, and what distance would you multiply it by?
It's almost like you still think you can throw out some sorta physicsy sounding words and people will think you know what you're talking about even if you don't give any specifics.
Psycho-logist wrote:
It is an absolute fact that there are people who can eat a crapload every day and not gain weight. CICO is not an infallible rule. If it were that simple, then everybody would have 5% body fat.
Someone cannot eat 5k calories a day with a TDEE of 3k calories and not gain weight.
Unless you have some metabolic disorder which doesn't allow you to absorb calories, and these people are probably in medical care for being dangerously underweight.
Yes they can. A healthy metabolism adjusts to your calorie consumption to maintain homeostasis.
There are 3,500 calories in a pound of fat. If I have a TDEE of 2,000 calories and eat 5,500 calories in a day, I am not going to put on a pound of fat instantly.
Psycho-logist wrote:
Yes they can. A healthy metabolism adjusts to your calorie consumption to maintain homeostasis.
There are 3,500 calories in a pound of fat. If I have a TDEE of 2,000 calories and eat 5,500 calories in a day, I am not going to put on a pound of fat instantly.
3500 surplus is rather large and I'm not sure how the body processes large surpluses.
You will, however, put on SOME fat. Which is the point.
You ate more calories than you expend, so some of that is converted to fat mass.
Psycho-logist wrote:
It is an absolute fact that there are people who can eat a crapload every day and not gain weight. CICO is not an infallible rule. If it were that simple, then everybody would have 5% body fat.
Care to elaborate?
So no one who is overweight just eats more and expends less than the calories eaten and expended by the average not over- weight person? It's always: slow vs fast metabolism? I don't think so. People are different, for sure, but you appear to be trying to simplify it in the other direction.
These ALSO are "absolute facts"
1) most people who are not overweight either
A) expend a lot of calories through activity, and/or
b) don't eat a "crapload of calories"
Most people who are overweight either
a) are fairly sedentary, and/or
b) eat way more calories than their activity levels
Psycho-logist wrote:
Look at the research of Dr. Jason Fung. He shows evidence that, for most people, calories in versus calories out doesn't work, because our bodies will always adapt our metabolic rate to match input to output. He also theorizes that insulin resistance is the sole factor explaining obesity, and that obesity can only be reversed by reducing insulin (either through a low-carb diet or, ideally in his mind, through fasting). Using this approach, he has cured type II diabetics through intermittent fasting programs.
a) Nice theory. Too bad he's wrong.
b) People have been cured of t2d by simply reducing calories greatly for a few weeks, and then going on a normal diet. Fasting? isn't that reducing calories (and not just carbs) ?? What was he/you saying about "calories in/out" aren't that important?
then show us wrote:
Done? If you did the integration and calculation, show us. You still need to specify the directions of the forces and velocities you're talking about.
No you don't. Simplify the problem. Model it as a single point mass in 2 dimensions with all forces against the mass summed negative and all forces done by the mass summed positive.
I already showed you the solution symbolically. If you've ever taken a science or upper-level math course you know that solving the problem symbolically is better than anecdotally because it is more general.
W=Fd=mad=mvd/t
where m & d and v/t all end up as constants, making W constant.
It is literally as simple as that. I'm suggesting the graph as an illustration because it might be conceptually easier to understand.
Think about it in terms of lifting the heavy box. You can lift the box slowly or quickly, but either way you accomplish the same amount of work. In the box case you are working against gravity. In the running case, you are working against more complicated forces which can ultimately be modeled as summed in the negative direction. It doesn't matter how fast or slow you move your mass, it takes the same amount of work to get it from A to B.
@chupacabra
what if running faster drastically changes your running form and you become less energy efficient, more vertical bob :^)
I'm just messing.
I believe a better way (more layman) to explain your argument
Running 8 miles fast = more caloric burn per minute
Running 8 miles slow = longer duration of caloric burn
And if normalized, the increased caloric burn per minute cancels the increased duration of caloric burn.
Yea?
You think too much.
obese wrote:
@chupacabra
what if running faster drastically changes your running form and you become less energy efficient, more vertical bob :^)
I'm just messing.
I believe a better way (more layman) to explain your argument
Running 8 miles fast = more caloric burn per minute
Running 8 miles slow = longer duration of caloric burn
And if normalized, the increased caloric burn per minute cancels the increased duration of caloric burn.
Yea?
lol yes exactly. Now get out and run nice and slow, fatty.
chupacabra wrote:
test2 wrote:My issue is that it isn't clear what force you are talking about. Moving on the flat gravity does nothing (it's perpendicular to the direction of motion). If you are going slow, wind resistance is pretty negligible. You shouldn't be scraping your feet against the road so there really isn't any frictional loss. There really isn't any simple force opposing your motion in a way that would be appropriate for that equation.
Mechanically what requires energy are the things that aren't clearly written down in a W = F dot X formula such as bouncing up and down, swinging your legs and arms forward and backward. Obviously these require internal forces but the directions of those forces are complex and there are mechanical losses due to the imperfect elasticity of muscle, tendon etc. There are also presumably biochemical inefficiencies.
Good points. I'll address the 2nd paragraph first.
When you are talking about the same runner, all of the points you bring up are roughly constant between easy pace and fast pace. If we're talking about a 15:00 5ker, you can simplify the problem by assuming all ineffeciencies are roughly the same between 7:00/mile and 5:30/mile. This is reasonable. If you take it to greater extremes, there will be large variation in efficiency between 4:00 pace and walking. But that's not what we're talking about. Most people's mechanics don't change drastically between 7:00 and 5:30 pace.
To your first paragraph, look at F as an average over a period of time. This is easily measurable. Instantaneous forces are difficult do deal with. There is certainly gravitational force (running involves up & down motion) and frictional losses (your shoes allow you to push off the pavement for a reason). But say we're talking 8 miles worth of work? Average force is better.
But we don't need to calculate F to prove that calories/mile is the same. That's the beauty of physics and math. You'll certainly agree that average F is greater at 5:30 pace than 7:00. What W=Fd proves is that if you multiply your average F by 8 miles, W will be the same in both cases.
You are assuming your conclusion when you lump everything into an unknown F which you also assume doesn't vary interestingly with v.
chupacabra wrote:
test2 wrote:My issue is that it isn't clear what force you are talking about.
Just in case I wasn't clear, the force in this case is the force applied by your leg on the ground. If you look at it as a graph of force (y-axis) over time (x-axis) it will be roughly sinusoidal with peaks at each footfall. You can solve W in 2 ways: 1) integrate this graph and multiply by velocity (W=Fvdt), or 2) calculate the average force and multiply by distance.
Done.
I'm not trying to give you a hard time, honestly, but I'm going to go into details.
There are two relevant components to this force trace: one is vertical, the other in the direction you are running. The vertical component of the force averages out to your weight and has no component parallel to your displacement, D, so it drops out of the work equation. The parallel force component integrates to equal wind resistance because there are no other external forces opposing your motion in the parallel direction (I suppose that's Newton's third law). Wind resistance is not constant with velocity (it's a square or cube power I think) so your argument breaks down here.
What I was saying before, though, is that this net force in the direction of motion isn't where you are doing the most work because air drag isn't a big deal at these speeds. Most of your power is lost to friction within your muscles and tendons when bouncing up and down and moving your legs back and forth. These motions are cyclical so they don't go in the direction of net motion so it's not really possible to work them into a single W=F dot X equation. Peace.
chupacabra wrote:
then show us wrote:Done? If you did the integration and calculation, show us. You still need to specify the directions of the forces and velocities you're talking about.
No you don't. Simplify the problem. Model it as a single point mass in 2 dimensions with all forces against the mass summed negative and all forces done by the mass summed positive.
I already showed you the solution symbolically. If you've ever taken a science or upper-level math course you know that solving the problem symbolically is better than anecdotally because it is more general.
W=Fd=mad=mvd/t
where m & d and v/t all end up as constants, making W constant.
It is literally as simple as that. I'm suggesting the graph as an illustration because it might be conceptually easier to understand.
Think about it in terms of lifting the heavy box. You can lift the box slowly or quickly, but either way you accomplish the same amount of work. In the box case you are working against gravity. In the running case, you are working against more complicated forces which can ultimately be modeled as summed in the negative direction. It doesn't matter how fast or slow you move your mass, it takes the same amount of work to get it from A to B.
Are you saying that if I take that box that you wanted us to lift and I picked it up to 3 feet in height, held it for 5 minutes, and then lifted it the remaining amount to put it on the table, that I burned the same amount of calories? What if I hold it for 30 minutes? 1 hour? Once muscle fatigue begins will that change the calorie consumption?
chupacabra wrote:
then show us wrote:Done? If you did the integration and calculation, show us. You still need to specify the directions of the forces and velocities you're talking about.
No you don't. Simplify the problem. Model it as a single point mass in 2 dimensions with all forces against the mass summed negative and all forces done by the mass summed positive.
I already showed you the solution symbolically. If you've ever taken a science or upper-level math course you know that solving the problem symbolically is better than anecdotally because it is more general.
W=Fd=mad=mvd/t
where m & d and v/t all end up as constants, making W constant.
It is literally as simple as that. I'm suggesting the graph as an illustration because it might be conceptually easier to understand.
Think about it in terms of lifting the heavy box. You can lift the box slowly or quickly, but either way you accomplish the same amount of work. In the box case you are working against gravity. In the running case, you are working against more complicated forces which can ultimately be modeled as summed in the negative direction. It doesn't matter how fast or slow you move your mass, it takes the same amount of work to get it from A to B.
I see. You solved it both symbolically and anecdotally. Got it.
(for those of you who are unfamiliar, neither of those are real things)
Carter Rods wrote:
What I have noticed as this:
Take 5k races for the first example:
People who run over 20 tend to be overweight
People who run 17-20 tend to be average or on the heavier side
People who run 15-7 tend to be on the below average to average size
People who run sub 15 tend to have that "runners look": very thin, almost evacuated looking, yet are extremely fit
What I've noticed as well is all these runners tend to have the same diets. In fact, the guys who run really fast, sub 15, tend to eat junk, no healthier, and even more of it! Yet they are very lean. Something about running fast changes the body.
Take marathoners as well:
People who run over 4:00 tend to be overweight
People who run 3:00-4:00 tend to be average or on the heavier side
People who run 2:40-3:00 tend to be a little below average or average
People who run sub 2:40 tend to be very lean, and let's not even get into sub 2:20!
Yet diets remain the same.
So what I am saying is no way is it all calories in versus calories out in the end. These people who train more have to eat more obviously to prevent injury, worse performance, and to keep improving as you need the calories aka energy
BUT I think there is something to making your body run FAST that causes certain metabolism shifts to take place. Your body *just without changing anything* will lean up to make running more efficient on itself. It adapts to its environment. People that jog 100 miles per week at 10:00/mi won't be nearly as lean as people running 100 miles per week at 6:00-7:00/mi, despite eating the same foods and in fact even more calories to make up for the greater energy expenditure. Something about fast running...
You can see this is people who start running, get faster, and never change their diets (like most of us). I've seen people eat standard junk diets and start off overweight and running 25 for 5k, and without changing their diet begin to lean up and run 15 over the course of years. When they get hurt if their diet doesn't change they gain weight. Whether it's due to their body not needing to stay lean anymore to make running (or lack thereof) easier or because they eat poor diets is up for debate. May be both.
So there is something to running fast that makes your body "adapt to its environment" if you will.
Thoughts?
Fast runners were pretty skinny first before they were runners. And they started running early (teenagers).
Slow joggers were overweight first and started running in order to lose weight.
So it's still calories in vs out. But calories out has a lot of fluctuations. The timescale for calories in is however long it takes you to eat. The timescale for calories out is 24 hours. Athletes in general have a higher metabolic rate than non athletes due to their sport/intense exercise routine.
Alan
chupacabra wrote:
Jon Orange wrote:At the speed you are running, there are slight differences.
Heat production comes from the Lactate dehydrogenase reaction of which there is much more in a race than an easy run.
Slight is the key word. Go ahead and calculate the % change in energy requirements for easy (8.6 mph) vs fast running (10.9 mph) due to wind resistance. For practical purposes it is negligible.
You also made a non-sensical argument about heat production. Let me phrase it for you so that you can clarify for all of us: "You burn more calories running faster because of heat production." Please explain yourself.
You can try to confuse the issue with as many physiological ineffeciencies that you want, but you are not addressing the issue, and your inefficiencies are negligible in a practical sense.
The issue is that it is a common misconception that feeling like you are working harder means that you have done more work. If someone lifts 100 lbs from the floor onto a table, they feel like they have done more work than if they use a pulley to accomplish the same task. The pulley makes it easier, but the work done is the same.
It is the same issue here. People feel like they are burning more calories by running faster, but in reality the caloric requirements to move from point A to B are, practically speaking, the same whether you run easy pace or fast pace. That is the point. You are trying to confuse a very simple principle with negligible real world inefficiencies.
If you feel the inefficiencies are not negligible, then it is now up to you to show it. Please present the final answer in as a % change from ideal.
Ok. Change the calculation to comparing a runner doing 4 minute mile to him doing an 8 minute mile? Do you still think the calories burned are:
1, the same?
2, slightly more calories for a 4 minute mile vs an 8 minute mile?
3, a lot more calories?
Uneducated wrote:
And his notion that an average to overweight person can run a 17:30 5k is ridiculous
Any decent young runner with 20% body fat should be able to do that without any trouble.
The idea that people who are running between 17-20 are overweight is equally sensationally hilarious and deluded.
Just have a look at Parkrun times which is a fairly representative cross section of society (from those who choose to run). Around 8% run under 20 minutes. And pretty much 95% of those who do go under 20 minutes are slim (just have a look at the photos on any individual Parkrun facebook page).
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