Treadmills - How the heck?

[Orbert]

Until my recent adventures in heart disease, I'd never set foot on a treadmill, but I enjoyed scoffing at people who used them and thought they were actually getting exercise.  I now have to reevaluate that position.

My logic was as follows: When you're actually walking or running, you're not just moving your legs, you're using them to propel your body forward in space.  This takes energy, and that energy comes from your legs.  If you're on a treadmill, your legs are moving, but your body is remaining relatively stationary.  You aren't spending any of that energy that would normally be used to move the mass of your body.  So the treadmill may say you've walked five miles, but it's not the same amount of exercise as actually walking five miles.  All you did was move your legs the equivalent of what they'd do if you'd walked five miles.

Similarly, you can vary the slope, but it's not the same thing.  If you actually walk up a 3% uphill grade, your body is being raised three feet for every 100 feet forward you walk.  But if you're on a treadmill set for a 3% grade, all you're doing is walking on a belt that has been slanted a little bit.  You're not actually spending the extra energy to raise your altitude.

So... why is it that it's actually harder to walk on the treadmill when it's set to a 3% grade?  It definitely seems like it is.  And if that's true, then I'm willing to entertain the notion that I'm wrong about the other thing.  Do you actually spend as much energy walking five miles on a treadmill as you would walking five miles outdoors?  It doesn't seem possible.  How the heck does that work?

[Chino]

With an incline you are picking your feet up higher with each forward step than you would while walking level. It's the same concept as steps beeing more tiring than walking on flat ground, except you are on a treadmill.

Even though yur body remains stationary in the sense you aren't moving along a horizontal plane, you are still moving it vertically. While walking on flat ground you propel yourself forward , on a treadmil you propel yourself up, then catch your full body weight when you come down. It's easier to understand if you think of running on a treadmill. Between each step there is a moment when you are not in contact with the belt at all. You essentially jumped, spending energy to get off the belt, and again when you have to land and catch yourself.

[Fiery Winds]

I think it's just the frame of reference and you're still expending the same amount of energy.

[jingle.boy]

Relative to the moving treadmill belt, you are moving forward.  Relative to the rest of the world, you're stationary.  Your mind knows the difference, I'm not sure your cardiovascular system does. 

[lordxizor]

Relative to the moving treadmill belt, you are moving forward.  Relative to the rest of the world, you're stationary.  Your mind knows the difference, I'm not sure your cardiovascular system does. 

Basically this. Your legs are propelling you forward, it's just that the treadmill happens to be propelling you backward at the same rate. You'd fall off the back if you weren't propelling yourself forward. Same with the incline. Your legs are pushing you upward while the treadmill is pulling you back down at the same rate. There is something about a treadmill that is slightly more difficult than just walking. I can't really explain it either. Maybe it's that you're just not as comfortable walking on it as you are walking on the ground. Therefore you're using more muscles to help balance yourself and make sure you don't fall off.

[rumborak]

From the energy point of view, the treadmill is burning off the energy at the same rate you're putting it in, essentially through internal friction. It's like walking up a dune, where you don't move much but expend a lot of energy.
The reason why it feels unnatural is IMHO because in normal gait your position and speed can be variable to a large degree. On a treadmill you have to be very precise to not drift in any direction.

rumborak

[7StringedBeast]

If you run a mile on a treadmill you are doing less work on your body than running a mile on ground.  So to make up for this, just run farther on the treadmill.

[TempusVox]

The reason why it feels unnatural is IMHO because in normal gait your position and speed can be variable to a large degree. On a treadmill you have to be very precise to not drift in any direction.

rumborak

While I don't have any facts to support this, I agree completely. It seems to me that on a treadmill, you also must account for balance and the precise steps you must take to stay in time with your pace, and not to drift. Not having any natural variability in speed is a huge factor I think.

[ZirconBlue]

From the energy point of view, the treadmill is burning off the energy at the same rate you're putting it in, essentially through internal friction. It's like walking up a dune, where you don't move much but expend a lot of energy.
The reason why it feels unnatural is IMHO because in normal gait your position and speed can be variable to a large degree. On a treadmill you have to be very precise to not drift in any direction.

rumborak

Yep.  Essentially, while you're putting in the same energy you would to walk on a normal surface, the motor of the treadmill is also putting in about the same amount of energy to move you back to where you were. 

[MetalJunkie]

But would an airplane take off from one?

[lordxizor]

But would an airplane take off from one?

No. An airplane requires air flow over the wings, no just fast moving wheels.

[7StringedBeast]

But would an airplane take off from one?

I just saw this on Myth Busters!  Yes a plane could take off from a treadmill moving the opposite way!

[Derango]

But would an airplane take off from one?

Oh Geeze...here we go.