So, someone who has short legs requires less effort to run at 5mph than someone who has longer legs?
I’m quite sure that a runner’s speed is a combination of stride length and number of strides per unit time.
Also, what is the connection between stride length and “countering” gravity?
And, ignoring all other forces, such as the friction of the pavement, and the forces within the body itself. The human body isn’t just a lump that is floating along the pavement.
Based on some quick googling, it would appear that studies in kinematic motion comparing treadmill running vs outdoor running show significant differences.
So much so that I didn’t find any that said they were the same. All of the ones I found said that they have found treadmill running to use less energy but that it still is good for a workout.
One key point was that treadmill runners motion was designed to keep the center of mass static in the forward backward plane, whereas outdoor running continuously accelerated and then decelerated the center of mass.
Search for “Anderson” and studies, etc. to learn more about this complex topic.
Wait a minute, here… Don’t most treadmills have a stationary handle that you hold on to? That’s going to make a huge difference in this analysis. Walking (or running, or jogging) on a treadmill while holding onto the stationary handle should be exactly the same as walking (or running, or jogging) down the road while holding onto a handle that’s moving at the same speed down the road. And moving down the road while holding onto a moving handle is not the same thing as moving down the road without the handle.
Most of the ones I’ve seen have a belt on a chain or cable that serves the same purpose.
Perhaps our schools have failed us in teaching Kinesiology.
Here’s a quote by Owen Anderson:
stupid capybaras :mad:
really stupid capybaras :mad: :mad:
His quote does nothing to support any hypothesis that running is fundamentally different on the treadmill than on level ground. I’d have to read the whole report, but you will notice that the questioner who he is answering asserted that there was no significant difference that would occur running on the treadmill. And please note that, while Anderson asserts a physical difference, he doesn’t explain how this relates to anything “easier” about the effort.
Also, he’s paying no attention to the actual physics again. When the runner outdoors has his foot hit the ground, there is going to be a period of time where the foot now becomes “part” of the ground, in the same way that he asserts that the foot becomes “part” of the belt. This will accellerate the foot backward relative to the body’s center of mass, in the same way that the foot accellerates “backward” when it contacts the belt.
And indeed, in this article, the good Dr. Anderson makes the following statement:
Underline added by me.
So despite the (in my mind questionable) claim of different physics (which I believe shows either a lack of understanding, or, more likely, a failure to explain some relevant part of the system), the doctor is not willing to assert that the biomechanical differences result in making treadmill running easier. You will note he doesn’t make that assertion in the answer you linked, either.
There are all sorts of differences between treadmills and roads - spring in the surface, curvature of the belt, inconstant speed of movement, etc, but as I think you’re agreeing - none of that is about the fundamental physics of moving relative to a surface, which behaves the same whether the surface is moving or stationary.
In fact it’s not just that the two things behave the same - they are the same.
It’s harder on the track according to this article.
Bio-mechanically
**
Oxygen-consumption rate**
And
The article does suggest that some of this due to wind resistance but the OP put no restrictions on the causes for any differences.
That article sounds a bit misleading to me. Sure, when you’re running on a road your centre of mass is moving forward and the road is staying still, and when you’re running on a treadmill, it’s the road that’s moving backward relative to the centre of mass.
But those two things are the same. that your centre of mass is stationary relative to the floor (with which you have no interaction) is irrelevant.
There’s no difference, in terms of fundamental physics, between moving on a static surface vs a steadily moving one.
There might be a multitude of practical differences brougth about by mechanical quirks of the machine, but not in terms of basic physics.
Not sure where you get this from what I said.
No disagreement here.
When you are running, both feet are off the ground in mid-stride. In a longer stride, both feet are off the ground for a longer period of time. Hence, more force is needed to stay airborne for longer.
Perhaps so. The fact that there may be physiological reasons (and, I would guess, quite possibly psychological reasons) that running on a road is harder than running on a treadmill, those are not the reasons that people were previously arguing. There were arguments in this thread demonstrating an appalling lack of understanding of basic physics, and that is what **DSYoung **was referring to.
Since the article specifically references sprinting I’ll go ahead and reiterate a pretty fundamental point that a lot of you are wishing away.
Once the Reynolds Number is high enough for drag effects to become predictable, drag force scales with the square of the velocity. 4mph is unlikely to be fast enough for this (4mph is a fast walk for a tall person), but let’s say that 5mph is where drag effects begin. This means that by the time you get up to 10mph, the drag force has quadrupled. An NFL quarterback can sprint at 18mph, so you can probably do 15mph… but the drag force is now nine times greater than the initial drag. Add a 5mph natural headwind, and you’re now sprinting into a 20mph breeze where your drag force is 16 times heavier than the original 5mph trot.
Whatever your feeling on airplanes and treadmills, you have to admit that in a closed indoor gym, running on a treadmill generates no practical headwind. Running on a track – indoor or outdoor – generates a headwind that can be significant. Running outside with wind can potentially be that much worse, since 5mph winds are fairly common.
Wind resistance matters. Treadmills are easier.
Nobody has overlooked this.
Except possibly Owen Anderson, Ph.D. 
Of course, in the later article of his that I quoted from, he’s backed off that and says that the difference only “may” involve biomechanical aspects. And in the even later article, wherein he answers the question from Charles Verrall, he completely waffles on the whole issue, with a mind-numbing batch of folderol about footstrike and treadmill speeds. It’s pretty clear from the description that he either has no idea of the physics of the system, or is not talking about some aspect of that system crucial to the point he is backpedalling from.
Okay. Previously, you said:
So, by extrapolation, a sprinter should have a longer stride than a miler, who should have a longer stride than a marathoner. Is that what you’re saying?
Also, someone who is airborne longer must have gone up higher during the stride, right? When I observe runners, it doesn’t appear to the case that faster runners go up higher than slower runners. (Likewise when observing fast running animals.)
What I am I missing here?
This is just one example of studies of kinematics:
http://www.blackwell-synergy.com/doi/abs/10.1111/j.1600-0838.2006.00625.x
Here is a recap of what we know:
Given that differences in motion will result in differences in energy used, and given that motion is different between different treadmill types and outdoor, I think it’s pretty safe to say that something more complex than simple relative motion is going on.
Walking and running is essentially falling forward and bouncing up (and not pushing forward, except to make up for the energy losses from sticking your foot out in front and not keeping it perfectly rigid). Ideally, ambular motion is perfectly efficient. Like a pendulum or a poll-volter, the body repeatedly trades horizontal momentum for height. It’s a pretty cool system, which is almost as efficient as the wheel.
So in principle, walking on the road and walking on a treadmill both use no energy!
It’s when considering the inefficiencies that differences between the two come out. The regularity and predicatbility of the treadmill allow the runner to be more efficient, to more closely approach 100% energy conversion on each step. There are various reasons for the differences in efficiency, all of which mentioned. An interesting one (though probably not the most important) is that noted by a mentioned study, that on the road your center of gravity has an unideal horizontal wobble to it but on a treadmill it only travels up and down.
I have used treadmills for running on for YEARS. I always run at a 2 slope, though, b/c with the treadmill being perfectly horizontal, there’s that GIVE with every footfall, which actually brings the track to below horizontal for a split second. I think this factor may also explain why treadmills SEEM easier than running on the street, ie on a treadmill at 0 slope, you are actually running slightly down hill because of the GIVE of most treadmills.
So run on a 1 or 2 slope and this will take out this factor. I think running on a treadmill with a slope could actually make it harder than running on the street, but safer b/c of the give of treadmills.
Anyone want to comment?