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Why do humans swing their arms while walking?

by Yashbhatt
Tags: arms, humans, swing, walking
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Yashbhatt
#1
May15-14, 12:22 AM
P: 145
I have read a number of answers to this question. All have answers like it helps us keep balance etc. . . But there can be a very fundamental reason. Humans evolved from apes. Our ancestors used to walk on on four legs. If we observe a four-legged animal, it walks moving its limbs alternately. So, can we reason that as we evolved from four-legged animals, we have still haven't forgotten moving our limbs alternately?
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Simon Bridge
#2
May15-14, 12:28 AM
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That would suppose that walking is mostly about reflexive movements of the fore and hind limbs - like a wind-up toy. We can check this by observing animals which normally move on four limbs but occasionally on two.

i.e. - when you see monkeys and apes balance on their hind legs to "walk", do they normally wave their arms as well?
What about performing dogs?

Observation seems to support the idea that arm-movements while walking is something that got picked up after a more upright stance was developed. However, there are no single causes for things in evolution.
Yashbhatt
#3
May15-14, 12:36 AM
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Have we found any exact cause for the thing?

Simon Bridge
#4
May15-14, 01:36 AM
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Why do humans swing their arms while walking?

Define "cause". Recall - there is no such thing as a single cause in evolutionary systems.
But the simple answer would be "no".
Why would anyone need an exact cause?
Yashbhatt
#5
May15-14, 03:33 AM
P: 145
Okay. Then let's say need instead of cause. There should be a reason for swinging arms.
Simon Bridge
#6
May15-14, 05:44 AM
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In evolution? - it needs only be passed on to offspring and not actually hurt having offspring.
What's wrong with stability and balance?
russ_watters
#7
May15-14, 06:04 AM
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I'm not sure there needs to be a reason: when you walk, your body twists from side to side, which makes your arms swing on their own unless you stop them.
Borek
#8
May15-14, 06:17 AM
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http://en.wikipedia.org/wiki/Arm_swi...man_locomotion
adjacent
#9
May15-14, 06:20 AM
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Quote Quote by russ_watters View Post
I'm not sure there needs to be a reason: when you walk, your body twists from side to side, which makes your arms swing on their own unless you stop them.
I agree
Borek
#10
May15-14, 07:07 AM
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Quote Quote by russ_watters View Post
I'm not sure there needs to be a reason: when you walk, your body twists from side to side, which makes your arms swing on their own unless you stop them.
Quote Quote by adjacent View Post
I agree
I am not convinced they will swing in a synchronized way on their own. Try to walk keeping your arms fully relaxed - IMHO they start kind of a chaotic dance (and mostly forearms are moving).
Pythagorean
#11
May15-14, 07:13 AM
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On my mobile now, but I'm pretty sure it's just a result of the way the control system evolved in a way that allows limbs to all work together when they have to (not all terrain is flat in the world we evolved in).

So my guess is that it's just a result of one of our driving control systems: central pattern generators, and the lack of perfect isolation in motor cortex. Will look more in depth when I'm at a computer.

edit: ah, my proposition is discussed in Borek's wiki link under "Evolution", considering remnants of quadruped locomotion:

The inter-limb coordination in human locomotion, questioning whether the human gait is based on quadruped locomotion, is another major topic of interest. A recent research indicates that inter-limb coordination during human locomotion is organized in a similar way to that in the cat, promoting the view that the arm swing may be a residual function from quadruped gait.[7] Another work on the control mechanisms of arm movements during walking corroborated the former findings, showing that central pattern generator (CPG) might be involved in cyclic arm swing. However, these findings do not imply vestigiality of arm swing, which appears to be debateful after the 2003 evidences on the function of arm swing in bipedal locomotion.[8]
[7] http://www.ncbi.nlm.nih.gov/pubmed/12183207
[8] http://www.ncbi.nlm.nih.gov/pubmed/12610695
russ_watters
#12
May15-14, 07:37 AM
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Quote Quote by Borek View Post
I am not convinced they will swing in a synchronized way on their own. Try to walk keeping your arms fully relaxed - IMHO they start kind of a chaotic dance (and mostly forearms are moving).
Your wiki says that at least at low speed it is completely passive. Certainly due to geometry there is a natural frequency: Perhaps that's how we find a comfortable walking speed - anything faster requires forced synchronization?

The wiki says "The contribution of active muscle work increases with the walking speed." [above the sync speed]

I would also consider that a separate issue from motion for stability, which almost certainly must be active.
Borek
#13
May15-14, 08:03 AM
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Quote Quote by russ_watters View Post
Certainly due to geometry there is a natural frequency
This is double pendulum, my understanding is that they don't have a natural frequency. Or perhaps they do, but only for very low energies (which can support the idea of arms swinging in a passive way for low speeds).

Looks like it is quite complicated system.
Simon Bridge
#14
May15-14, 07:32 PM
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Anyone here done any military training/service?
One of the things new recruits have to be trained to do is swing their arms in counterpoint to their legs.
Watch people in a crowd and see how complicated the passive motion can be.
Just the idea that there is a single style for humans to walk seem a bit off.
As usual, real life is messy.

Some notes:
Everything on two legs does something extra for balance.
There is an extent to which basic walking motions are built-in - iirc compare Coelacanth swimming motion and land quadrupeds.
Yashbhatt
#15
May16-14, 09:59 AM
P: 145
Hey Borek, the wikipedia article you mentioned also mentions the point I mentioned under the section "evolution". It says it is possible that we might have picked it up from quadrupeds.
harborsparrow
#16
May16-14, 10:06 AM
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The army teaches men who are marching to swing their arms regularly. It makes walking over long distances more efficient. The arms should be swinging opposite to how the feet are going. The opposing movements help the trunk remain stationary relative to the limbs, making the forward motion smoother and using less energy.
Simon Bridge
#17
May16-14, 09:55 PM
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@Yashbhatt: careful of the confirmation bias: it mentions a lot of other things too doesn't it?
Evolution results in a web of cause and effect, not a chain.

Nobody has been saying that there is zero built-in factor for the arm-swinging.
You just may want to be less invested in the idea that you appeared to be in post #1.

You have left a number of questions outstanding...
Why would anyone need an exact cause? (for arm swinging in humans)
What's wrong with stability and balance? (as a reason for favoring arm-swinging)

But I think your question has been answered by now.
Yashbhatt
#18
May16-14, 10:56 PM
P: 145
@Simon Bridge Okay. I agree that there might not be a particular reason. There may be various reasons as the Wikipedia article mentioned.

But there needs to be some stimulus to cause it. If there were no external factors affecting it, then all the random kind of mutations would have survived instead of a few.


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