How much easier is a treadmill?

oldguy wrote:

The effect of wind resistance on energy expenditure at a given running speed, especially at higher speeds, is HUGE. Also, modern treadmills typically have very forgiving running surfaces, much like "tuned" indoor tracks.

The energy required to overcome wind resistance is a very small part of the total energy you must expend to run 10mph. Running on a treadmill is different in subtle ways from running outside. We've spent years optimizing our efficiency for running outside, so those subtle differences on the treadmill are much more likely to make us less efficient than more efficient. And I believe that efficiency difference is a much bigger factor than the wind resistance advantage.

That being said, the person that said it's silly to come up with a bunch of physics arguments as to why treadmill running is easier or harder, because the most likely explanation is that they are calibrated wrong, is absolutely right. Have you ever used a wheel on a treadmill you've run on to check its calibration? Why do you have so much faith that it is telling you the correct speed?

[quote]jerk wrote:

"Room temperature" is usually around 22 degrees celsius (63 degrees fahrenheit, for those of you who still use that shit).

[quote]2xTrinity wrote:

22 degrees C works out to 71.6 F. No really relevant, but this mistake bothered me.

ckalafarski wrote:

Anyway, i've been trying to figure out a good way to quantitatively determine the amount of work you do when on a treadmill (the road is easy, Force=mass*acceleration=weight, and work=Force*distace).

If the above were true riding a bike at 15mph and running 15mph would require the same effort. Sorry, it's not that simple.

dukerdog- Right, but then you'd be ignoring the mechanical advantage of the bike (machine). There isn't a logical parallel when using a TM. I think you bring up a valid point about efficiency being attuned to what you practice. TM running may be slightly less efficient if you always run on the roads simply because you're forced to stay at a specific pace and cannot vary in subtle amounts as you do over land. This may explain in a small way why I hate shifting over to TM running in early winter and yet also hate shifting back over to the roads in early Spring. (I try to do both in the Winter, but...)

Personally, I think the number one effect is pyschological. Someone mentioned surface softness. I imagine that this can have an effect if it's a very soft bed as you may have to increase the vertical component, but I tend not to notice. That is, my TM seems much more firm than grass, although softer than asphalt.

dukerdog wrote:

The energy required to overcome wind resistance is a very small part of the total energy you must expend to run 10mph.

Even if you're talking about 5% of the total energy expended, that's costing you about 18 seconds per mile at 10mph. That, in my book, is a huge difference.

Does anyone really doubt the advantage of running with a 10 to 15 mph tailwind?

dukerdog wrote:

If the above were true riding a bike at 15mph and running 15mph would require the same effort. Sorry, it's not that simple.

err...not quite what i said. Riding a bike 15 miles and running 15 miles (assuming the bike weighs nothing, just for the sake of convenience) do take the same amount of work, but less force. The bike has a mechanical advantage, though. Just like lifting a 5 kg box 10 meter in the air, or pushing it up a 50 meter ramp until its 10 meters high. Both take the same total work, but different amounts of force. (W1=50N*10m=500J, W2=10N*50m=500J) mechanical adv. of 5.

If you know physics you know what im trying to say

ckalafarski wrote:

Riding a bike 15 miles and running 15 miles (assuming the bike weighs nothing, just for the sake of convenience) do take the same amount of work, but less force. . . . If you know physics you know what im trying to say

Sorry, but that's not at all correct.

[If you know physics you know what im trying to say]

I know physics, but I don't have any idea what you're trying to say, only what you actually said. There's an old saying in physics, "If you can't explain it, you don't understand it."

Phred Physics wrote:

"If you can't explain it, you don't understand it."

we say that in my prof as well.

oldguy wrote:

Even if you're talking about 5% of the total energy expended, that's costing you about 18 seconds per mile at 10mph. That, in my book, is a huge difference.

I agree that a 10mph tailwind could probably make a 15-20 second per mile difference. My point is that most of the other 95% is all about running efficiency. It doesn't take much to screw that up and quickly negate 15-20 seconds.

ckalafarski, all of your equations and most of your thought process is correct. The only thing you missed is that acceleration=0. Once you are moving at 10mph it doesn't require any acceleration to keep going 10mph. Same is true on the treadmill at 0mph.

Maybe this will help some of you understand the physics involved here:

Imagine you are inside a very long train and the train is moving at 10 mph. If you run at 10mph in the opposite direction and look through the window, what do you see? The train station! You are not moving relative to the earth.

There you have it, the long train is the treadmill. The floor of the train is NOT assisting you. You still need to run at 10mph to stay in place (in the train station).

If it is very hot where the treadmill is (75-78 degrees) the energy needed to dissipate heat is much more than the energy needed to overcome wind resistence. That may make the workout harder. If the temp is 65, the workout may be easier than running outside. Treadmill running is not easier or harder than running outside, it is just different, just as each run you do outside is different.

Jim:

In a previous reply your stated:

Everytime you stride forward, bringing your center of mass over your foot plant, you are accelerating your mass. It then decelerates as you coast through the air (no way to apply force mid-air).

I think what some others are addressing is that when running on the road, your decleration between push-off and your next foot strike determines the distance you travel. However in this phase of your stride, the treadmill continues at the same pace. It does not decelerate. Therfore on a treadmill the distance between foot strikes is farther than on the road, which results in a greater distance being covered for the same amount of energy required to accelerate your mass over your foot strike.

Could this be a source of discrepanices? Is it a significant variable? Very interested to hear replies.

Much easier on the legs and you can make it as hard[or easy]as you like.

Closet Treadmiller wrote:

I think what some others are addressing is that when running on the road, your decleration between push-off and your next foot strike determines the distance you travel. However in this phase of your stride, the treadmill continues at the same pace. It does not decelerate.

No, the treadmill doesn't, but the runner does with respect to the belt. I know this is hard to visualize because everyone keeps thinking in terms of your body being stationary in the room. It really isn't stationary. The accel/decel is not huge once you're running along at a steady pace and you tend not to notice it. Do you really FEEL like you're slowing down between footplants? Probably not, but you are. Air resistance is a factor here as air drag is roughly proportional to the square of velocity (not precisely in this case, JTD has some interesting data on the subject). As mentioned earlier though, this can be corrected for with the 1% incline.

The scenario using the train is very good. It is funny that I was going to describe a similar situation using a huge flat bed truck. What is the difference between running on that train in the opposite direction and running on a treadmill? In both cases, the train or treadmill "appears" to be pulling your legs back behind you. It "appears" that the surface continues to move while you glide through the air in way that is different from road running. Is anyone willing to say that running along the floor of a very long box car is fundamentally different than running along a road? What if the train was VERY long, like 25,000 miles, and wrapped all around the Earth so that the engine was connected to the caboose from behind. Wouldn't that make it just a HUGE treadmill?

I re-read my post and there is something misleading that I need to correct regarding the TM runner decelerating. Imagine that instead of the 1% incline for the wind correction you correct it by using a large fan that is blowing air head-on at the same velocity as you're running. The decel now is as stated. The 1% incline confuses the matter because you're adding a little extra vertical component to compensate for the drag caused by the wind. The workload may be the same but the mechanisms are different.

In any case, I think the psychological aspects are the real issues. Once you've corrected for wind resistance and calibrated the unit, asuming similar temp, humidty, etc., there can still be huge variations INSIDE YOUR HEAD. That part we haven't quantified (not yet anyway).

If you want to make it easier, turn around and run with the belt instead of against it, and if you want it easier yet, just set the incline up so that you're running downhill.

The train analogy is still no better than thinking about the treadmill. My contentions would be the same for the train. Less force needs to be supplied. The body is not decelerating and the ground moving beneath helps the active movement of bringing the foot backward vs. your center of gravity.

I have found a couple of sources that support that but I'm looking for a definative study. If you can show mw one that shows the same degree of muscle stimulation to cover the same stride length I would say "uncle".

ok, let me explain physics so any idiot can understand it.

have you ever considered why in a moving car, when you pour a drink, it doesn't go flying on your shirt? or why even though the earth is spinning at an incredible rate you don't go flying off?

this is called momentum, that's why you have to push forward not just jump up to run on a treadmill. the difference in effort is 99% wind resistance