Interesting Little Training Facts

Off Topic
21

[quote]Charged wrote:
Does anyone know any interesting little facts to do with training,such as… You burn the same calories walking a mile or running a mile.[/quote]

I don’t think this is actually true:

Work is equal to force times distance.

w = f * d

Force = mass times acceleration

f = m * a

Therefore:

work equals mass times acceleration times distance

w = m * a * d

When you throw a ball, it doesn’t continue going in a straight line forever. Gravity, air resistance, etc, all cause it to come to a stop.

The same is true with a car. When you press the gas peddle, the car doesn’t run forever; it needs to consistantly burn fule to keep the car going.

The same principle still applies when you’re talking about a runner. If they stopped running or walking, their body would come to a rest. The act of striding is actually a counter to this effect. Gravity, air resistance, ground resistance, etc, all provide the runner or walker with negative acceleration, whereas their legs provide positive acceleration to counter this, and keep them moving.

The faster you are moving, the more resistance you will encounter, and the more energy you will have to expend to counteract this negative acceleration; as someone said above, this is why cars run more efficiently at slower speeds. Therefore, in the equation

w = m * a * d

mass (m) and distance (d) are the same, but acceleration (a) and therefore work (w) are both higher.

Also, this fails to take into account the increased metabolic rate of a runner as opposed to a walker; the runner’s metabolism will be much higher, and continue to burn hotter, than the walker’s, for something like an hour after the actual exercise is complete.

22

[quote]jp_dubya wrote:
no amount of gym time can overcome a bad diet[/quote]

http://www.T-Nation.com/findArticle.do;jsessionid=D8BF975CB3795FDCF90FDF9DCE030724.hydra?article=06-005-training

CW might disagree that it is possible. There is a 20 year old kid here with pretty good genetics that eats like total garbage and is still staying lean and making good size gains.

Eating like garbage consists of pizza, hamburgers/cheeseburgers, french fries, desserts, ice cream, etc. Kid barely gets 50 quality grams of protien a day, takes no supplements, and has no intention of cleaning up his diet even with my constant ranting.

23

The mechanical definition of work is not applicable to energy expenditure of the muscles. For example, zero work is performed during isometric exercise, but energy expenditure obviously occurs anyway. Also, it is not useful to apply work and power to the body as a whole because it’s also important to consider the virtually constant acceleration of individual body segments.

Running DOES burn more energy per distance than walking for mechanical reasons. Atmospheric resistance and vertical displacement of the body both increase with speed, resulting in greater work performance and energy expenditure.

24

[quote]belligerent wrote:
…
Running DOES burn more energy per distance than walking for mechanical reasons. Atmospheric resistance and vertical displacement of the body both increase with speed, resulting in greater work performance and energy expenditure.
[/quote]

You are ignoring the time component and the speed of each activity.

If it takes me 12 hours to walk a mile I will burn a hell of a lot of calories per mile. Estimate 1000 calories burned in 12 hours.

If I job the mile in 8 minutes I may burn an estimated 200 calories.

The example is ridiculous but it illustrates my point.

You could also say running a mile in 4 minutes probably burns a few more calories than running a mile in 8 minutes.

Just like cars have a speed that is most efficient for gas mileage our bodies likely have a speed that is most efficient.

It is possible that the difference in calories burned between walking and running one mile is very small but the engineer in me tells me the difference exists.

Sorry for starting the hijack.

25

[quote]belligerent wrote:
The mechanical definition of work is not applicable to energy expenditure of the muscles. For example, zero work is performed during isometric exercise, but energy expenditure obviously occurs anyway. Also, it is not useful to apply work and power to the body as a whole because it’s also important to consider the virtually constant acceleration of individual body segments.[/quote]

Of course the mechanical definition of work is applicable; it’s not like the laws of physics change when you pick up a dumbbell or something. The only difference is that the work is somewhat less obvious. For example, say you’re holding a 50 pound dumbbell, just standing there with it. Are you doing work? Yes. Gravity is constantly trying to accelerat it, and you’re constantly trying to decelerat it.

[quote]belligerent wrote:
Running DOES burn more energy per distance than walking for mechanical reasons. Atmospheric resistance and vertical displacement of the body both increase with speed, resulting in greater work performance and energy expenditure.
[/quote]

Exactly.

26

[quote]thomas.galvin wrote:
Of course the mechanical definition of work is applicable; it’s not like the laws of physics change when you pick up a dumbbell or something. The only difference is that the work is somewhat less obvious. For example, say you’re holding a 50 pound dumbbell, just standing there with it. Are you doing work? Yes. Gravity is constantly trying to accelerat it, and you’re constantly trying to decelerat it.
[/quote]

by definition, no, you’re not.

work = force * displacement
(assuming the force is directed in the same direction as the displacement)

force = mass * acceleration

acceleration = [(final velocity) - (initial velocity)]/time

since the dumbell never changes velocity it’s acceleration is zero, thus no force is exerted and no work is done.

Someone posted earlier that you can’t apply the mechanical definition of work to muscular movement. I believe what they meant is that you can’t apply it to the movement of the body as a single unit. Each individual muscle or limb or what have you is in fact accelerating and decelerating constantly in the act of running or walking. However, if you take the whole body as a unit, work is only done when you start your walk/run. Assuming you continue on at a constant pace, you’re no longer accelerating and thus not exerting any force and not doing any work. Obviously this isn’t the case, which is why you have to look at it from the case of each muscle or limb.

If you really want to figure out and compare how much work is done you’d need to look at the acceleration of each foot as it goes from zero velocity (the point at which it changes from swinging forward to swinging backward, or the point your heel hits the ground) to final velocity (ideally the point where you push off with your toes and begin the next step). The mass in the equation stays constant, your body weight. A typical running stride is quite a bit longer than a walking stride and also faster so you have more acceleration, hence more force, hence more work done.

However, that’s the amount of work done per stride. Given the fact that a running stride is longer than a walking stride means you’re going to have fewer overall strides in a run versus a walk. Does this even out the amount of work done? I’m not sure, I don’t have the actual numbers to plug into the formulae, however if you want to go out and measure your foot velocities and accelerations and report back, it would certainly be interesting to see. Bear in mind however that the amount of physical work done by the legs is probably not an accurate representation of the amount of calories burned while doing so. There are lots of other factors involved.

Jay

p.s. sorry for the longwinded post, I’m really bored at work and was in a physics kind of mood.

27

[quote]Zap Branigan wrote:
rrjc5488 wrote:

I highly doubt they made gas consumption a priority anywhere near safety when they established speed limits.

It was the reason given when the federal government mandate a 55 MPH speed limit.[/quote]

Then why is the speed limit higher in more sparsely populated areas than densely populated areas?

28

[quote]chrismcl wrote:
Zap Branigan wrote:
rrjc5488 wrote:

I highly doubt they made gas consumption a priority anywhere near safety when they established speed limits.

It was the reason given when the federal government mandate a 55 MPH speed limit.

Then why is the speed limit higher in more sparsely populated areas than densely populated areas?[/quote]

When the 55mph federal maximum was introduced, the 55 was to save fuel, and the places where it was below 55 was for safety. The different speed limits in different situations were for 2 different purposes.

29

Correct me if I’m wrong, since 11th grade physics class was about 8 years ago, but “force” isn’t just a factor of “mass times acceleration” but also “1/2 of mass times velocity-squares” or F = 1/2 (M * V^2).

So let’s say a 100kg tubby boy was walking at 2 m/s…

F = 1/2 (M * V^2)
= 1/2 (100 * 2^2)
= 1/2 (100 * 4)
= 1/2 (400)
F = 200 N

So his force would be 200 N.

For a kilometer, his total work would be…

W = F * d
= 200 N * 1000 m
= 200 000 j
W = 200 Kj

Total work = 200 Kj

If he ran that same Km at, say, 5 m/s, he would be expending…

F = 1/2mv^2
= 1/2(100)(5^2)
= 1/2(100)(25)
= 1/2(2500)
F = 1250 N

W = Fd
= 1250N * 1000m
= 1 250 000 j
W = 1250 Kj

So by running his big ole butt off for that kilometer, he’s expending about 6 times as much energy…? That doesn’t make sense. Someone with a mechanical engineering degree figure this out and get back to me!

Beef

30

[quote]AlbertaBeef wrote:
Correct me if I’m wrong, since 11th grade physics class was about 8 years ago, but “force” isn’t just a factor of “mass times acceleration” but also “1/2 of mass times velocity-squares” or F = 1/2 (M * V^2).

So let’s say a 100kg tubby boy was walking at 2 m/s…

F = 1/2 (M * V^2)
= 1/2 (100 * 2^2)
= 1/2 (100 * 4)
= 1/2 (400)
F = 200 N

So his force would be 200 N.

For a kilometer, his total work would be…

W = F * d
= 200 N * 1000 m
= 200 000 j
W = 200 Kj

Total work = 200 Kj

If he ran that same Km at, say, 5 m/s, he would be expending…

F = 1/2mv^2
= 1/2(100)(5^2)
= 1/2(100)(25)
= 1/2(2500)
F = 1250 N

W = Fd
= 1250N * 1000m
= 1 250 000 j
W = 1250 Kj

So by running his big ole butt off for that kilometer, he’s expending about 6 times as much energy…? That doesn’t make sense. Someone with a mechanical engineering degree figure this out and get back to me!

Beef[/quote]

The first equation you stated was for kinetic energy, not force.

31

[quote]Charged wrote:
i got it off Charles Staley[/quote]

I think he meant walking and running a brisk mile (both at the same speed). walking becomes less efficient at the speed where you would naturally break into a jog. Running or walking (provided you are not forcing walking at above a natural pace) burn about 1.5-1.6 calories/kilogram per mile.

32

[quote]AlbertaBeef wrote:
Correct me if I’m wrong, since 11th grade physics class was about 8 years ago, but “force” isn’t just a factor of “mass times acceleration” but also “1/2 of mass times velocity-squares” or F = 1/2 (M * V^2).

So let’s say a 100kg tubby boy was walking at 2 m/s…

F = 1/2 (M * V^2)
= 1/2 (100 * 2^2)
= 1/2 (100 * 4)
= 1/2 (400)
F = 200 N

So his force would be 200 N.

For a kilometer, his total work would be…

W = F * d
= 200 N * 1000 m
= 200 000 j
W = 200 Kj

Total work = 200 Kj

If he ran that same Km at, say, 5 m/s, he would be expending…

F = 1/2mv^2
= 1/2(100)(5^2)
= 1/2(100)(25)
= 1/2(2500)
F = 1250 N

W = Fd
= 1250N * 1000m
= 1 250 000 j
W = 1250 Kj

So by running his big ole butt off for that kilometer, he’s expending about 6 times as much energy…? That doesn’t make sense. Someone with a mechanical engineering degree figure this out and get back to me!

Beef[/quote]

Work is done when you accelerate a mass, or lift it. When walking or running, the limbs are accelerating (and decelerating), and rising under your power.

By the way, the static dumbell example does show the flaw when applying this to muscles. Individual muscle fibers contract and relax to statically hold a dumbell, so there is work done on the micro-scale which does not translate to the dumbell-or you could visualize the dumbell rising and falling by very tiny amounts.

33

[quote]thomas.galvin wrote:

Of course the mechanical definition of work is applicable; it’s not like the laws of physics change when you pick up a dumbbell or something. The only difference is that the work is somewhat less obvious. For example, say you’re holding a 50 pound dumbbell, just standing there with it. Are you doing work? Yes. Gravity is constantly trying to accelerat it, and you’re constantly trying to decelerat it.
[/quote]

Let me rephrase my comments. Of course the laws of physics are constant and of course the mechanical definition of work applies to everything. However, you can’t use mechanical work to calculate energy expenditure during exercise.

34

[quote]m0dd3r wrote:
since the dumbell never changes velocity it’s acceleration is zero, thus no force is exerted and no work is done.
[/quote]

Just because the dumbell doesn’t move doesn’t mean that forces aren’t exerted on it. It just means that the forces acting on the object cancel each other out, and thus the object is in equillibrium.

35

I found these statistics using the free Fitday service that I think
might also help settle the debate…

If you run at an average pace of 10 minutes a mile (6 miles per hour),
you would cover the 9.2 miles in 1 hour and 32 minutes, which would
burn a total of 920 calories. If you ran at an average pace of 12
minutes a mile (5 miles per hour) you would burn 860 calories in the 1
hour and 52 minutes it took you.

If you are walking the distance at a “brisk” pace of 3.5 mph, it would
take you about 2 hours and 39 minutes, and you would burn about 530
calories.

The real difference between them is with the run you’d use glycogen and blood glucose for energy and the walk you would be burning bodyfat.

36

[quote]thomas.galvin wrote:
belligerent wrote:
The mechanical definition of work is not applicable to energy expenditure of the muscles. For example, zero work is performed during isometric exercise, but energy expenditure obviously occurs anyway. Also, it is not useful to apply work and power to the body as a whole because it’s also important to consider the virtually constant acceleration of individual body segments.

Of course the mechanical definition of work is applicable; it’s not like the laws of physics change when you pick up a dumbbell or something. The only difference is that the work is somewhat less obvious. For example, say you’re holding a 50 pound dumbbell, just standing there with it. Are you doing work? Yes. Gravity is constantly trying to accelerat it, and you’re constantly trying to decelerat it.[/quote]

Maybe you should go back and read your original post. Work is the application of a force through a distance. Using this logic would be the same as saying that the chair I’m sitting on is working to keep me up. The chair is applying a force on my ass, but it is doing no work.

Energy expenditure and work are not the same thing. Many people have flawed understanding of ‘physics’ work due to improper usage of physics terms such as work, energy, heat, power, etc.

I agree with belligerent that a lot of people are trying to simplify the moving human body into a particle (in other words, create a free body diagram) without understanding some of the assumptions they are making.

I don’t know enough about physics and engineering related to the internal structure of the human body, but I’m pretty sure that Leonardo da Vinci did enough work on the subject to keep you occupied for a couple of years.

37

tastes “great”
“less” filling is all relative and subjective.

Willing to volunteer for extended study