Hence the gliding motion described in sightings?
http://www.physorg.com/news168027773.html
Out on a limb: Arm-swinging riddle is answered
July 28th, 2009 The shadow of a woman is seen on a wall
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The shadow of a woman is seen on a wall. Biomedical researchers on Wednesday said they could explain why we swing our arms when we walk, a practice that has long piqued scientific curiosity.
Biomedical researchers on Wednesday said they could explain why we swing our arms when we walk, a practice that has long piqued scientific curiosity.
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Swinging one's arms comes at a cost. We need muscles to do it, and we need to provide energy in the form of food for those muscles. So what's the advantage?
Little or none, some experts have said, contending that arm-swinging, like our appendix, is an evolutionary relic from when we used to go about on all fours.
But a trio of specialists from the United States and the Netherlands have put the question to rigorous tests.
They built a mechanical model to get an idea of the dynamics of arm-swinging and then recruited 10 volunteers, who were asked to walk with a normal swing, an opposite-to-normal swing, with their arms folded or held by their sides.
The metabolic cost of this activity was derived from oxygen consumption and carbon dioxide (CO2) production as the human guinea pigs breathed in and out.
Arm-swinging turned out to be a plus, rather than a negative, the investigators found.
For one thing, it is surprisingly, er, "'armless" in energy costs, requiring little torque, or rotational twist, from the shoulder muscles.
Holding one's arms as one walks requires 12 percent more metabolic energy, compared with swinging them.
The arms' pendulum swing also helps dampen the bobbly up-and-down motion of walking, which is itself an energy drain for the muscles of the lower legs.
If you hold your arms while walking, this movement, called vertical ground reaction moment, rises by a whopping 63 percent.
Should you prefer to walk with an opposite-to-normal swing -- meaning that your right arm moves in sync with your right leg and your left arm is matched to the motion of your left leg -- the energy cost of using your shoulder muscles will fall.
The downside, though, is that opposite-to-normal swing forces up the metabolic rate by a quarter.
The study, headed by Steven Collins at the University of Michigan at Ann Arbor, says we should give the thumb's-up to arm swinging.
"Rather than a facultative relic of the locomotion needs of our quadrupedal ancestors, arm swinging is an integral part of the energy economy of human gait," says the paper.
It appears in Proceedings of the Royal Society B, the biological research journal of the Royal Society, Britain's de-facto academy of sciences.
© 2009 AFP
Full Version: Scientists Unravel Human Arm Swing
This reminded me of my recent post where I speculate that Patty back-cups her hand in order to make a more controlled swing and efficiently turn back towards the viewer:
QUOTE
This has probably been covered before, but here's something I noticed while watching the P/G film stabilization here:
http://www.bigfootencounters.com/files/mk_davis_pgf.gif
During the sequence when 'she' turns to look back she makes one full arm swing while she turns to look at the camera and one consecutive swing immediately after she has turned her head and torso back to continue walking.
If you look at her arm-hand plane prior to both of those swings they pretty much line up at say 0 degrees, then when she turns to look, during that swing you'll notice that her hand has started to cup to maybe 15 degrees( from the straight plane of her forearm as compared to the earlier arm swings) her arm swings back more towards her posterior and the swing is slightly more exaggerated. Next she turns her head and torso back away from the viewer but as she does so completes the backward movement of the next arm swing and the wrist bends and the fingers look to be at an angle of at least 45 if not 90 degrees to the forearm plane.
If you stand holding your arm out in front of yourself at approximately 45 degrees from the vertical plane of your body and flex your hand downward at 90 degrees you mostly feel only your forearm muscles flex, but if you put your arm at 45 degrees towards your backside and then flex your wrist ( upward like Patty does) you feel your forearms, triceps, deltoids and even some in the trapezoid muscles ( you can also feel the bicep stretching). Basically holding your arm in that position and flexing just the hand involves all the arm muscles and the shoulder muscles that support it, as opposed to only the forearm when the hand is held in front.
Now try the "Patty walk" and turn to look with and without flexing the hand. You should notice that flexing the hand and therefore the entire arm/ shoulder muscles gives you much greater control over your turn especially when you move most of your torso, keeping your natural neck rotation to a minimum ( like Patty). This is because the 'dead weight' of a normal swing, although easier in normal walking is a burden when turning the upper body, but by flexing all of the arm muscles it allows for more controlled swinging and takes advantage of centrifugal force to some extent to help turn the mass of the upper body/torso.
I mention this because if that is a man in a suit, he would have to have some type of prosthesis to extend his arm that low and even with an advanced prosthesis, getting the wrist to bend and especially do it at the exactly appropriate time would be quite an acoomplishment...just something I noticed, comments welcome.
http://www.bigfootencounters.com/files/mk_davis_pgf.gif
During the sequence when 'she' turns to look back she makes one full arm swing while she turns to look at the camera and one consecutive swing immediately after she has turned her head and torso back to continue walking.
If you look at her arm-hand plane prior to both of those swings they pretty much line up at say 0 degrees, then when she turns to look, during that swing you'll notice that her hand has started to cup to maybe 15 degrees( from the straight plane of her forearm as compared to the earlier arm swings) her arm swings back more towards her posterior and the swing is slightly more exaggerated. Next she turns her head and torso back away from the viewer but as she does so completes the backward movement of the next arm swing and the wrist bends and the fingers look to be at an angle of at least 45 if not 90 degrees to the forearm plane.
If you stand holding your arm out in front of yourself at approximately 45 degrees from the vertical plane of your body and flex your hand downward at 90 degrees you mostly feel only your forearm muscles flex, but if you put your arm at 45 degrees towards your backside and then flex your wrist ( upward like Patty does) you feel your forearms, triceps, deltoids and even some in the trapezoid muscles ( you can also feel the bicep stretching). Basically holding your arm in that position and flexing just the hand involves all the arm muscles and the shoulder muscles that support it, as opposed to only the forearm when the hand is held in front.
Now try the "Patty walk" and turn to look with and without flexing the hand. You should notice that flexing the hand and therefore the entire arm/ shoulder muscles gives you much greater control over your turn especially when you move most of your torso, keeping your natural neck rotation to a minimum ( like Patty). This is because the 'dead weight' of a normal swing, although easier in normal walking is a burden when turning the upper body, but by flexing all of the arm muscles it allows for more controlled swinging and takes advantage of centrifugal force to some extent to help turn the mass of the upper body/torso.
I mention this because if that is a man in a suit, he would have to have some type of prosthesis to extend his arm that low and even with an advanced prosthesis, getting the wrist to bend and especially do it at the exactly appropriate time would be quite an acoomplishment...just something I noticed, comments welcome.
Arm swing? Hell, I unraveled that when my dad watched me break the slideing window with my pellet gun. Didn't need no scientist there, just an ice bag
As much as I like physorg.com I gotta call BS. I walk a minimum of 5 miles a day with a GPS watch to measure pace. Arm swing is for speed, simply put. It also relieves the hip muscles from stress. The forward momentum generated by arm swinging relieves the hip muscles from doing all the work and picks up the speed by 20 to 30 per cent.
QUOTE
Holding one's arms as one walks requires 12 percent more metabolic energy, compared with swinging them.
Are you sure you aren't picking up that speed due to the extra energy you have available to use by not trying to hold your arms still? Would adding handweights, of significant weight, add an even greater increase in speed, or would you slow down due to energy needed to swing the weights?
QUOTE(moregon @ Aug 15 2009, 03:39 AM) 
Are you sure you aren't picking up that speed due to the extra energy you have available to use by not trying to hold your arms still? Would adding handweights, of significant weight, add an even greater increase in speed, or would you slow down due to energy needed to swing the weights?
I don't think so. It might be true if you're walking 20 miles across the Serengeti with little food. I've experimented a lot and as I said I have a GPS pacer. I haven't used handweights since they look so dorky
The speed you pick up with aggressive arm swinging is significant.I guess I just disagreed with their conclusion:
QUOTE
"Rather than a facultative relic of the locomotion needs of our quadrupedal ancestors, arm swinging is an integral part of the energy economy of human gait," says the paper.
They're jumping to that conclusion. If they had done a study showing that arm swinging increased speed (which I can attest to), they could have said "Arm swinging is an integral part of the human ability to cover long distances quickly". That's all I'm saying. It may just as well have been an evolutionary advantage to gain speed without breaking into a run which risks more injuries.
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