Physics question: inclined treadmill

Post by **thibodeaux** » Fri Oct 30, 2015 12:31 pm

Same as climbing a hill? Discuss.

Malcolm · Post by **Malcolm** » Fri Oct 30, 2015 12:37 pm

thibodeaux wrote:Same as climbing a hill? Discuss.

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

Edited By Malcolm on 1446223084

Post by **GORDON** » Fri Oct 30, 2015 12:54 pm

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."

Post by **TheCatt** » Fri Oct 30, 2015 1:30 pm

Malcolm wrote:
thibodeaux wrote: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.

Malcolm · Post by **Malcolm** » Fri Oct 30, 2015 1:35 pm

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.

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.

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.

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Post by **TheCatt** » Fri Oct 30, 2015 7:32 pm

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

Malcolm · Post by **Malcolm** » Fri Oct 30, 2015 9:12 pm

TheCatt wrote: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.

Post by **GORDON** » Fri Oct 30, 2015 9:27 pm

GORDON wrote: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."

Post by **thibodeaux** » Fri Oct 30, 2015 9:47 pm

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.

Malcolm · Post by **Malcolm** » Sat Oct 31, 2015 1:37 pm

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?

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.

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.

Post by **TheCatt** » Sat Oct 31, 2015 1:49 pm

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.

Post by **thibodeaux** » Sat Oct 31, 2015 1:50 pm

Malcolm wrote:
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.

Malcolm · Post by **Malcolm** » Sat Oct 31, 2015 2:00 pm

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

Post by **GORDON** » Sat Oct 31, 2015 2:49 pm

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.

Post by **thibodeaux** » Sun Nov 01, 2015 12:28 pm

Malcolm wrote: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.

Post by **GORDON** » Sun Nov 01, 2015 2:02 pm

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%.

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Malcolm · Post by **Malcolm** » Sun Nov 01, 2015 2:23 pm

thibodeaux wrote:
Malcolm wrote: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?

Post by **thibodeaux** » Sun Nov 01, 2015 2:30 pm

Malcolm wrote: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

Post by **TheCatt** » Sun Nov 01, 2015 2:34 pm

thibodeaux wrote:
Malcolm wrote: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.

Post by **thibodeaux** » Sun Nov 01, 2015 6:54 pm

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.