Thunderdome 2015 » Printable Version of Topic » Physics question: inclined treadmill

Forum: General Stuff
Topic: Physics question: inclined treadmill
started by: thibodeaux

Posted by thibodeaux on Oct. 30 2015,09:31

Same as climbing a hill? Discuss.

Posted by Malcolm on Oct. 30 2015,09:37

(thibodeaux @ Oct. 30 2015,11:31)

QUOTE

Same as climbing a hill? Discuss.

If we're talking physics, no hill is that uniform, regular, or perfectly flat.

Posted by GORDON on Oct. 30 2015,09:54

With treadmills, inclined or not, they always felt different to me because you aren't moving your own body weight around, you are just moving your legs to keep from flying off.

Plus the micro-muscular adjustments Malcolm mentioned.

You are a magnificent pedant and said "same," which means equal, so I say "no."

Posted by TheCatt on Oct. 30 2015,10:30

(Malcolm @ Oct. 30 2015,12:37)

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(thibodeaux @ Oct. 30 2015,11:31)

QUOTE

Same as climbing a hill? Discuss.

If we're talking physics, no hill is that uniform, regular, or perfectly flat.

That's a stupid fucking answer.

Just make some assumptions. So yes: uniform, flat, regular hill (paved/graded road) versus treadmill.

Well, the first difference is wind resistance, which varies based on speed and shape, and doesn't apply to treadmill.

Removing that. I know that treadmill running on an incline is harder than no incline, so it's definitely something. My gut tells me it isn't the same. While I am propelling myself "up" in some sense, and losing that altitude as my foot comes down the treadmill, it doesn't feel like it could be an accurate representation of going only up a hill.

Also, if I stand still, and jump, I don't go up at all after landing. But the treadmill would think I went up.

I dunno, but my gut says it's not the same.

Posted by Malcolm on Oct. 30 2015,10:35

QUOTE

Just make some assumptions. So yes: uniform, flat, regular hill (paved/graded road) versus treadmill.

I only see those sorts of conditions on bike paths that were recently paved.

QUOTE

Well, the first difference is wind resistance, which varies based on speed and shape, and doesn't apply to treadmill.

The treadmill is moving you forward (if you're stationary), and if the wind's blowing against you while you're outside on it, that's added resistance to you "climbing" it.

The difference maybe where the power comes from. < Here >.

QUOTE

The kinematics in the runners frame of reference look the same. This is not the cause of the difference in perceived difficulty.

I have always assumed that the difference in difficulty was two fold:

Wind resistance is not really negligible.
The treadmill presents a very uniform reliable surface and the runner need not lift her legs as high to insure non-tripping progress.
Also modern treadmill are designed to be relatively easy on the knees, and the accomplish this by having a slightly springy feeling which presumably returns some energy to the runner.

Posted by TheCatt on Oct. 30 2015,16:32

So, instead of trying to answer the question, you google it? Pretty sure Thib knows how to google.

Posted by Malcolm on Oct. 30 2015,18:12

(TheCatt @ Oct. 30 2015,18:32)

QUOTE

So, instead of trying to answer the question, you google it? Pretty sure Thib knows how to google.

I provided two answers (surface integrity and why wind counts) then googled and picked the first relevant result page. It happened to have my two points plus another.

Posted by GORDON on Oct. 30 2015,18:27

(GORDON @ Oct. 30 2015,12:54)

QUOTE

With treadmills, inclined or not, they always felt different to me because you aren't moving your own body weight around, you are just moving your legs to keep from flying off.

I still suspect this is the best answer. You aren't pushing 100+ pounds of torso, head, and arms on a treadmill, you are just keeping yourself stationary and not flying backwards. Since drafting is a thing among long distance runners, I have to say lack of wind resistance alone means "not same."

Posted by thibodeaux on Oct. 30 2015,18:47

I suspect that you do indeed do less work on the treadmill because your body doesn't move. Particularly on the incline, you're not adding potential energy to your body by moving it up against gravity.

But I'm not convinced 100%. I imagine there ought to be a way to measure it but I dunno.

Posted by Malcolm on Oct. 31 2015,10:37

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Particularly on the incline, you're not adding potential energy to your body by moving it up against gravity.

Doesn't the potential go down if you don't move? Aren't you working to keep it level?

QUOTE

You aren't pushing 100+ pounds of torso, head, and arms on a treadmill, you are just keeping yourself stationary and not flying backwards.

Are we talking an incline or totally flat? Either way, you're still moving the same mass as the tread pushes you back and/or down and you have to make progress to maintain position.

QUOTE

Since drafting is a thing among long distance runners, I have to say lack of wind resistance alone means "not same."

You can sort of replicate this if you have something ahead of you on the tread that's nice enough to cut through the air the same way another person does. I can also put you on a treadmill in a wind tunnel.

A treadmill has a truer, more consistent surface on average than your typical patch of ground, provides mechanical advantages when modern science says to ease up on the joints, and forces you to run in a relatively narrow corridor. Is it the same as < running up that hill >? Nah, probably easier. In spite of the controlled environment you get and how much the injury potential is cut, there's a reason shit like the Iron Man and Olympic races aren't done on machines.

Posted by TheCatt on Oct. 31 2015,10:49

I'd like to see it quantified, if possible. The wind stuff has been studied a fair amount, and I'm comfortable with what I've read. But I'd like to know about the incline stuff. I couldn't find any good google resources.

Posted by thibodeaux on Oct. 31 2015,10:50

(Malcolm @ Oct. 31 2015,13:37)

QUOTE

Particularly on the incline, you're not adding potential energy to your body by moving it up against gravity.

Doesn't the potential go down if you don't move? Aren't you working to keep it level?

Obviously moving your legs your doing work. But I don't think it's as much.

Posted by Malcolm on Oct. 31 2015,11:00

How much a difference in energy output are you thinking? 10%? Less, more?

Posted by GORDON on Oct. 31 2015,11:49

On a treadmill, you need to pick up your feet and move them forward, but once your foot is down you don't need to do anything to push your leg back, the treadmill is doing that work for you. No way it is the same.

Posted by thibodeaux on Nov. 01 2015,09:28

(Malcolm @ Oct. 31 2015,14:00)

QUOTE

How much a difference in energy output are you thinking? 10%? Less, more?

I dunno. The main reason I was thinking about it was there's a guy at the gym who puts on a heavy backpack and walks on an inclined treadmill. And I'm pretty sure the backpack is useless.

Posted by GORDON on Nov. 01 2015,11:02

I think you're going to have to build a robot to do it and measure the work performed.

You might end up getting paid off/murdered by Big Treadmill to keep the results a secret.

I want 10%.

Posted by Malcolm on Nov. 01 2015,11:23

(thibodeaux @ Nov. 01 2015,11:28)

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(Malcolm @ Oct. 31 2015,14:00)

QUOTE

How much a difference in energy output are you thinking? 10%? Less, more?

I dunno. The main reason I was thinking about it was there's a guy at the gym who puts on a heavy backpack and walks on an inclined treadmill. And I'm pretty sure the backpack is useless.

Depends on the incline. The more towards 90 it is, obviously the more work trig says he's doing. I was thinking more the running/jogging angle. Once you slow down, treadmills and real hills get further and further apart. Additionally, putting on a heavy pack is going to shift your center of gravity.

Unless his form is quite good and consistent, I bet his legs are cheating, a lot, for his core on up. He's probably doing more work overall than without a pack, but not nearly as much as he thinks or a straight energy equation would have you believe. Also, why the fuck would you put on a pack versus upping the incline/resistance levels?

Posted by thibodeaux on Nov. 01 2015,11:30

(Malcolm @ Nov. 01 2015,14:23)

QUOTE

Also, why the fuck would you put on a pack versus upping the incline/resistance levels?

Because most the stuff people do in the gym is retarded

Posted by TheCatt on Nov. 01 2015,11:34

(thibodeaux @ Nov. 01 2015,12:28)

QUOTE

(Malcolm @ Oct. 31 2015,14:00)

QUOTE

How much a difference in energy output are you thinking? 10%? Less, more?

I dunno. The main reason I was thinking about it was there's a guy at the gym who puts on a heavy backpack and walks on an inclined treadmill. And I'm pretty sure the backpack is useless.

I'm doing to disagree. If the incline makes it harder (which objectively it does), then why does it make it harder? Either 1) You're overcoming some amount of gravity for the additional force or 2)

And the gravity would be acting on your body, thus backpack helps.

Perhaps he does a lot of hiking, so having the additional weight is his way of training at a given speed for hiking at certain grade. I understand it.

Posted by thibodeaux on Nov. 01 2015,15:54

I'm about 90% convinced the only thing the incline does is make you lift your legs higher. A backpack wouldn't add any work to that.

Posted by TPRJones on Nov. 01 2015,16:08

Even though you seem to be staying mostly in the same place, you are indeed pushing your torso up and putting potential energy into it with each stride on an inclined treadmill. Just as much as you would with each stride on a hill with the same angle of inclination. The difference is that with the hill you just keep adding more and more potential as you go up while on the treadmill it keeps getting immediately leached back out between strides as your center of gravity shifts back down the incline of the treadmill. That energy is converted into a small amount of kinetic energy that makes it easier for the motor to turn the belt for that part of the cycle.

QUOTE

On a treadmill, you need to pick up your feet and move them forward, but once your foot is down you don't need to do anything to push your leg back, the treadmill is doing that work for you.

You also don't have to push your leg back while running normally, either, as momentum takes care of that for you. You can fall forward with very little effort; your torso is going to keep going forward while that foot is planted whether you push or not. The work is in keeping your torso off the ground and getting your other leg up there in time to take the weight of lifting your torso and keeping things going.

Unless we're talking about stair climbing. Then there's a lot more active pushing going on. But mostly up, not so much forward.

Posted by GORDON on Nov. 01 2015,16:24

(TPRJones @ Nov. 01 2015,19:08)

QUOTE

On a treadmill, you need to pick up your feet and move them forward, but once your foot is down you don't need to do anything to push your leg back, the treadmill is doing that work for you.

You need to keep adding energy to that motion to maintain that velocity. The treadmill is doing that with electricity from outside your body. Maybe if the treadmill wasn't plugged in.....

Posted by TPRJones on Nov. 01 2015,16:28

On a treadmill you are putting in that bit of energy needed to maintain forward momentum. It's just countered by the backwards motion of the treadmill.

You can test this by coming to a sudden stop on a moving treadmill and see what happens.

If the treadmill were doing anything to keep you moving "forward" then you'd fall off the other end.

Posted by GORDON on Nov. 01 2015,17:04

You aren't picking up what I am putting down.

Posted by TheCatt on Nov. 01 2015,18:03

(thibodeaux @ Nov. 01 2015,18:54)

QUOTE

I'm about 90% convinced the only thing the incline does is make you lift your legs higher. A backpack wouldn't add any work to that.

I'm 90% convinced otherwise. Bet?

Posted by thibodeaux on Nov. 02 2015,13:54

(TheCatt @ Nov. 01 2015,21:03)

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(thibodeaux @ Nov. 01 2015,18:54)

QUOTE

I'm about 90% convinced the only thing the incline does is make you lift your legs higher. A backpack wouldn't add any work to that.

I'm 90% convinced otherwise. Bet?

how do you prove it?

Posted by TheCatt on Nov. 02 2015,18:08

(thibodeaux @ Nov. 02 2015,16:54)

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(TheCatt @ Nov. 01 2015,21:03)

QUOTE

(thibodeaux @ Nov. 01 2015,18:54)

QUOTE

I'm about 90% convinced the only thing the incline does is make you lift your legs higher. A backpack wouldn't add any work to that.

I'm 90% convinced otherwise. Bet?

how do you prove it?

Yeah, I'm not sure. My first though is that you'd need something that measured center of gravity, and change thereof. Say, measuring where a person's belly button is at each incline setting. I would think that the higher incline would result in more variance in belly button height than the lower incline would, showing that the body itself is gaining/losing potential energy.

Posted by thibodeaux on Nov. 02 2015,18:30

I'd be satisfied with just measuring overall "effort" (whatever that is) in these two scenarios:

1. walking on an inclined treadmill
2. walking an equivalent distance on a ramp

make the angle the same, the surface as close (bouncy rubber, whatever) to minimize differences.

Posted by Malcolm on Nov. 02 2015,19:05

Need a big-ass ramp.

Posted by TheCatt on Nov. 03 2015,06:51

(thibodeaux @ Nov. 02 2015,21:30)

QUOTE

I don't think that answers your question though. I'm not arguing it's 1:1, I'm arguing that it's harder, and not just due to lifting your feet higher.

I think you'd have to measure energy output: 1) weighted (backpack) and 2) unweighted in different situations: a) standing, b) walking on no incline, c) walking on incline.

Posted by thibodeaux on Nov. 03 2015,15:53

I just think it's fucking stupid to wear a backpack on a treadmill. Okay???

Posted by GORDON on Nov. 03 2015,16:03

Miniturized walking robots, battery operated. A step counter. One inclined looped track, with an elevation reset in there somewhere. One on an inclined treadmill walking in place.

Run 100 batteries through each of them, until the battery is drained. Compare how many steps each robot took before its battery died. By the end one will have averaged more steps over the other... or not. Who knows. Old lady science... you gotta hold on tight. Whichever took fewer steps overall drained more battery with each step.

Posted by TheCatt on Nov. 03 2015,16:25

(thibodeaux @ Nov. 03 2015,18:53)

QUOTE

I just think it's fucking stupid to wear a backpack on a treadmill. Okay???

That's just like, your opinion, man.

Posted by TheCatt on Nov. 03 2015,16:26

(GORDON @ Nov. 03 2015,19:03)

QUOTE

Problem with robots is that they are designed to walk a given way. The question is whether humans are adapting their gait to the surface in a way that is different than a true incline.

Posted by GORDON on Nov. 03 2015,16:35

I can't think of any other way to measure the treadmill effort except by a set amount of energy consumed compared to how much work gets done. I don't know how to measure that in a human, so a small machine should be able to simulate it and you can measure batteries vs: work performed.

Posted by Malcolm on Nov. 03 2015,16:40

Reverse the problem. Hook the treadmills to a battery each. Get two dudes that weigh and walk the same. The treadmill that runs out of power first is doing more work for the person.

Posted by TheCatt on Nov. 03 2015,16:43

(GORDON @ Nov. 03 2015,19:35)

QUOTE

Posted by GORDON on Nov. 03 2015,16:44

Goddam. Well I guess there's that, but wouldn't you need like 2 identical people doing an actual incline vs. an inclined treadmill?

Posted by TheCatt on Nov. 03 2015,16:46

(GORDON @ Nov. 03 2015,19:44)

QUOTE

Goddam. Well I guess there's that, but wouldn't you need like 2 identical people doing an actual incline vs. an inclined treadmill?

Couldn't you just use the same person with repeated trials?

Posted by GORDON on Nov. 03 2015,16:47

(TheCatt @ Nov. 03 2015,19:46)

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(GORDON @ Nov. 03 2015,19:44)

QUOTE

Goddam. Well I guess there's that, but wouldn't you need like 2 identical people doing an actual incline vs. an inclined treadmill?

Couldn't you just use the same person with repeated trials?

yeah but they would be in better shape the second time.

Posted by Malcolm on Nov. 03 2015,16:48

(GORDON @ Nov. 03 2015,18:47)

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(TheCatt @ Nov. 03 2015,19:46)

QUOTE

(GORDON @ Nov. 03 2015,19:44)

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Goddam. Well I guess there's that, but wouldn't you need like 2 identical people doing an actual incline vs. an inclined treadmill?

Couldn't you just use the same person with repeated trials?

yeah but they would be in better shape the second time.

Doesn't matter. If they weigh the same and walk the same, it's all mass.

Posted by TheCatt on Nov. 03 2015,17:07

(GORDON @ Nov. 03 2015,19:47)

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(TheCatt @ Nov. 03 2015,19:46)

QUOTE

(GORDON @ Nov. 03 2015,19:44)

QUOTE

Goddam. Well I guess there's that, but wouldn't you need like 2 identical people doing an actual incline vs. an inclined treadmill?

Couldn't you just use the same person with repeated trials?

yeah but they would be in better shape the second time.

Thus the repeated trials

Posted by GORDON on Nov. 03 2015,17:30

wink.