# Human on a treadmill
**URL:** https://boards.straightdope.com/t/human-on-a-treadmill/448641
**Category:** Factual Questions
**Created:** [May 9, 2008, 1:36am UTC](https://boards.straightdope.com/t/human-on-a-treadmill/448641 "2008-05-09T01:36:02Z")
**Posts on this page:** 20
**Page:** 4
### Author:  [@Duhkecco](https://boards.straightdope.com/u/Duhkecco)
#### Post date: [May 9, 2008, 7:56pm UTC](https://boards.straightdope.com/t/human-on-a-treadmill/448641/61 "2008-05-09T19:56:51Z")
[QUOTE=Don’t Call Me Shirley]
The much longer strides involved in running 10mph require you to exert much more effort to counter gravity than the shorter strides of 5mph.
[/quote]
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?
> [@](#):
>
> It takes exactly the same amount of horizontal force to keep your body moving at a constant 10mph, 5mph, and 0mph (neglecting air resistance).
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.
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### Author:  [@RaftPeople](https://boards.straightdope.com/u/RaftPeople)
#### Post date: [May 9, 2008, 8:13pm UTC](https://boards.straightdope.com/t/human-on-a-treadmill/448641/62 "2008-05-09T20:13:29Z")
[QUOTE=DSYoungEsq]
OMG. The lack of understanding of fundamental physics here is enough to make me think that our schools really DO fail us!!!
In each case it doesn’t matter which scenario, the result is identical. Do you comprehend? _ **Identical.** _
[/QUOTE]
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.
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### Author:  [@Chronos](https://boards.straightdope.com/u/Chronos)
#### Post date: [May 9, 2008, 8:18pm UTC](https://boards.straightdope.com/t/human-on-a-treadmill/448641/63 "2008-05-09T20:18:58Z")
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.
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### Author:  [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)
#### Post date: [May 9, 2008, 8:27pm UTC](https://boards.straightdope.com/t/human-on-a-treadmill/448641/64 "2008-05-09T20:27:58Z")
[QUOTE=Chronos]
Wait a minute, here… Don’t most treadmills have a stationary handle that you hold on to?
[/QUOTE]
Most of the ones I’ve seen have a belt on a chain or cable that serves the same purpose.
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### Author:  [@Duhkecco](https://boards.straightdope.com/u/Duhkecco)
#### Post date: [May 9, 2008, 8:30pm UTC](https://boards.straightdope.com/t/human-on-a-treadmill/448641/65 "2008-05-09T20:30:23Z")
[QUOTE=DSYoungEsq]
OMG. The lack of understanding of fundamental physics here is enough to make me think that our schools really DO fail us!!!
[/QUOTE]
Perhaps our schools have failed us in teaching [Kinesiology](http://en.wikipedia.org/wiki/Kinesiology).
Here’s a quote by Owen Anderson:
> [@](#):
>
> When a foot hits the treadmill belt while running, the foot, ankle and shin, being momentarily ‘parts’ of the belt, will move backwards from the centre and mass of the body at the same speed as the belt – 10mph. This must be true unless you think of the human body as a rigid rod without segments or joints, in which case the centre of mass would also move backwards at the same speed. However, research indicates that during treadmill running the shin of the support leg is less erect at contact and moves through a greater range of motion, with a faster overall angular velocity, than in normal running. If footstrike time averages 180 milliseconds (an average for good-quality runners) then the foot could move backwards in relation to the centre of mass by about 2.6 inches during treadmill footstrike. (It will actually be a little less than this, since the centre of mass and upper body will tend to be dragged along at least a little.)
[http://www.pponline.co.uk/encyc/0969.htm](http://www.pponline.co.uk/encyc/0969.htm)
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### Author:  [@DSYoungEsq](https://boards.straightdope.com/u/DSYoungEsq)
#### Post date: [May 9, 2008, 10:01pm UTC](https://boards.straightdope.com/t/human-on-a-treadmill/448641/66 "2008-05-09T22:01:04Z")
stupid capybaras :mad:
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### Author:  [@DSYoungEsq](https://boards.straightdope.com/u/DSYoungEsq)
#### Post date: [May 9, 2008, 10:01pm UTC](https://boards.straightdope.com/t/human-on-a-treadmill/448641/67 "2008-05-09T22:01:28Z")
really stupid capybaras :mad: :mad:
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### Author:  [@DSYoungEsq](https://boards.straightdope.com/u/DSYoungEsq)
#### Post date: [May 9, 2008, 10:00pm UTC](https://boards.straightdope.com/t/human-on-a-treadmill/448641/68 "2008-05-09T22:00:49Z")
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](http://www.pponline.co.uk/encyc/treadmill.html), the good Dr. Anderson makes the following statement:
> [@Owen Anderson](#):
>
> The lower cost of treadmill running is definitely attributable to lack of wind resistance; it may also reflect the biomechanical and kinematic differences between treadmill and ‘normal’ running.
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.
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### Author:  [@Mangetout](https://boards.straightdope.com/u/Mangetout)
#### Post date: [May 9, 2008, 10:15pm UTC](https://boards.straightdope.com/t/human-on-a-treadmill/448641/69 "2008-05-09T22:15:40Z")
[QUOTE=Alex\_Dubinsky]
There’s also hills, road surface, and posture.
No. The difference between walking and running, why running takes so much more energy, is the effects of internal friction, unrecoverable energy to lift your legs, battling your pendulum’s natural period, plus wind and losses from the road surface. All of these things change between roads and treadmills. But treadmills don’t push your legs back. They just fucking don’t.
[/QUOTE]
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.
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### Author:  [@Don\_t\_fight\_the\_hypothetical](https://boards.straightdope.com/u/Don_t_fight_the_hypothetical)
#### Post date: [May 9, 2008, 11:00pm UTC](https://boards.straightdope.com/t/human-on-a-treadmill/448641/70 "2008-05-09T23:00:38Z")
[QUOTE=Hypno-Toad]
Is a person running at 5 MPH on a flat treadmill spending the same effort as a person running 5 MPH on the street?
I don’t think so, but I need a good argument/explanation to demonstrate it to someone else.
[/QUOTE]
It’s harder on the track [according to this article.](http://www.pponline.co.uk/encyc/treadmill.html)
**Bio-mechanically**
> [@](#):
>
> _“When an athlete runs on the track, on roads or on firm ground, their legs create propulsive forces which accelerate their centre of mass and drive it forward. The athlete’s centre of mass is decelerated during each recovery (early-stance) phase of the gait cycle, only to be accelerated forwards again as propulsive forces are created by the stance leg. As they continue to run, centre of mass is accelerated and decelerated over and over again as it moves steadily forwards. When the same athlete runs on a treadmill, centre of mass is static (at least in the forwards-backwards plane). There is no forward progress; instead, the running surface ‘disappears’ behind the athlete. In fact, the treadmill belt moves the athlete’s legs and feet under and behind her centre of mass and, to preserve stability, their key task is to move the support leg back in front of the centre of mass in time for the impact with the treadmill belt. The key function of the leg muscles during treadmill running is not to produce propulsive forces but to re-position the legs so as to keep the centre of mass stable.”_
\*\*
Oxygen-consumption rate\*\*
> [@](#):
>
> _“One of Pugh’s most interesting findings was that the slope of the line linking oxygen consumption with speed was significantly steeper on the track than on the treadmill: put another way, for each unit increase in running speed there was a correspondingly greater increase in oxygen cost during track running than during treadmill running.”_
**And**
> [@](#):
>
> “_Track running leads to greater oxygen debt than treadmill training
> Interestingly, the ‘oxygen debt’ incurred by running 100 metres on the track was 36% greater than in the treadmill condition. Oxygen debt is simply the excess oxygen uptake (above resting oxygen utilisation) that occurs after exercsie is over. It is a somewhat misleading term, because this elevated consumption does not appear to be entirely due to a ‘borrowing’ from the body’s oxygen stores; a better term is excess post-exercise oxygen consumption - EPOC, which is directly related to exercise intensity, in that the higher the intensity the greater the EPOC. Therefore sprinting at 8.5m/sec overground was much more demanding for the Massachusetts athletes than sprinting at the same speed on the treadmill, probably because overground sprinting depleted the leg-muscle cells’ energy stores more than treadmill sprinting so that more oxygen was needed to re-establish normal energy supplies within the muscles._”
The article does suggest that some of this due to wind resistance but the OP put no restrictions on the causes for any differences.
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### Author:  [@Mangetout](https://boards.straightdope.com/u/Mangetout)
#### Post date: [May 9, 2008, 11:10pm UTC](https://boards.straightdope.com/t/human-on-a-treadmill/448641/71 "2008-05-09T23:10:33Z")
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.
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### Author:  [@Don\_t\_Call\_Me\_Shirley](https://boards.straightdope.com/u/Don_t_Call_Me_Shirley)
#### Post date: [May 9, 2008, 11:35pm UTC](https://boards.straightdope.com/t/human-on-a-treadmill/448641/72 "2008-05-09T23:35:19Z")
[QUOTE=Duhkecco]
So, someone who has short legs requires less effort to run at 5mph than someone who has longer legs?
[/quote]
Not sure where you get this from what I said.
> [@](#):
>
> I’m quite sure that a runner’s speed is a combination of stride length and number of strides per unit time.
No disagreement here.
> [@](#):
>
> Also, what is the connection between stride length and “countering” gravity?
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 our schools have failed us in teaching Kinesiology.
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.
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### Author:  [@Jurph](https://boards.straightdope.com/u/Jurph)
#### Post date: [May 9, 2008, 11:42pm UTC](https://boards.straightdope.com/t/human-on-a-treadmill/448641/73 "2008-05-09T23:42:55Z")
[QUOTE=Don’t fight the hypothetical]
The article does suggest that some of this due to wind resistance but the OP put no restrictions on the causes for any differences.
[/QUOTE]
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.
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### Author:  [@Mangetout](https://boards.straightdope.com/u/Mangetout)
#### Post date: [May 10, 2008, 12:17am UTC](https://boards.straightdope.com/t/human-on-a-treadmill/448641/74 "2008-05-10T00:17:51Z")
[QUOTE=Jurph]
Wind resistance matters. Treadmills are easier.
[/QUOTE]
Nobody has overlooked this.
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### Author:  [@DSYoungEsq](https://boards.straightdope.com/u/DSYoungEsq)
#### Post date: [May 10, 2008, 1:44am UTC](https://boards.straightdope.com/t/human-on-a-treadmill/448641/75 "2008-05-10T01:44:33Z")
[QUOTE=Mangetout]
Nobody has overlooked this.
[/QUOTE]
Except possibly Owen Anderson, Ph.D. 😛
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### Author:  [@DSYoungEsq](https://boards.straightdope.com/u/DSYoungEsq)
#### Post date: [May 10, 2008, 1:49am UTC](https://boards.straightdope.com/t/human-on-a-treadmill/448641/76 "2008-05-10T01:49:25Z")
[QUOTE=Don’t fight the hypothetical]
The article does suggest that some of this due to wind resistance but the OP put no restrictions on the causes for any differences.
[/QUOTE]
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.
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### Author:  [@Duhkecco](https://boards.straightdope.com/u/Duhkecco)
#### Post date: [May 10, 2008, 2:40am UTC](https://boards.straightdope.com/t/human-on-a-treadmill/448641/77 "2008-05-10T02:40:40Z")
[QUOTE=Don’t Call Me Shirley]
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.
[/QUOTE]
Okay. Previously, you said:
> [@](#):
>
> The much longer strides involved in running 10mph require you to exert much more effort to counter gravity than the shorter strides of 5mph.
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?
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### Author:  [@RaftPeople](https://boards.straightdope.com/u/RaftPeople)
#### Post date: [May 10, 2008, 2:56am UTC](https://boards.straightdope.com/t/human-on-a-treadmill/448641/78 "2008-05-10T02:56:34Z")
This is just one example of studies of kinematics:
[http://www.blackwell-synergy.com/doi/abs/10.1111/j.1600-0838.2006.00625.x](http://www.blackwell-synergy.com/doi/abs/10.1111/j.1600-0838.2006.00625.x)
> [@](#):
>
> Conventionally motorized treadmills elicit different sprinting kinematics to the over-ground condition. Treadmills powered by a torque motor have been used to assess sprinting power; yet, the kinematics of sprinting on the torque treadmill are unknown. This study compares the sprinting kinematics, during the constant velocity phase, between a conventional treadmill, a torque treadmill and the over-ground condition to assess the suitability of each treadmill for sprinting studies and training. After familiarization, 13 recreationally active males performed multiple sprints at various experimental settings on each surface. Ninety sprints, which attained mean velocities over 7.0 m/s, had their lower-body sagittal plane joint angles during ground contact captured at 250 Hz. These data were low-pass filtered at 10 Hz, and compared with respect to surface, subject and velocity using an ANCOVA statistical model. Sprinting on the conventional treadmill elicited a longer ground contact time, a longer braking phase, a more extended knee at foot strike and a faster extending hip than the torque treadmill and over-ground (all P\<0.05). The torque treadmill obtained an equivalent sprinting technique to the over-ground condition, with the exception of a less extended hip at toe-off, suggesting that it is more appropriate for laboratory sprinting analyses and training than the conventional treadmill.
Here is a recap of what we know:
1. Wind resistance is a factor, but not very interesting because it’s obvious, we want to know if there is something more going on
2. Studies of human motion show differences between treadmill and outdoor
3. Runners on a “torque treadmill” more closely match outdoor motion than a “conventionally motorized treadmill”
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.
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### Author:  [@Alex\_Dubinsky](https://boards.straightdope.com/u/Alex_Dubinsky)
#### Post date: [May 10, 2008, 3:14am UTC](https://boards.straightdope.com/t/human-on-a-treadmill/448641/79 "2008-05-10T03:14:20Z")
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.
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### Author:  [@deanc2000](https://boards.straightdope.com/u/deanc2000)
#### Post date: [May 10, 2008, 4:55am UTC](https://boards.straightdope.com/t/human-on-a-treadmill/448641/80 "2008-05-10T04:55:19Z")
[QUOTE=Hypno-Toad]
Well then I’d be perfectly happy to learn _why_ jogging on a treadmill is easier than the same jogging on the road. Is wind resistance enough to explain it? I always thought it was because I could read a book on the treadmill and distract myself from the effort. But others seem to agree about the less effort on the machine.
[/QUOTE]
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?
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