Why do humans spread their arms while jumping off things?

h0m3gr0wn said:
it's for Dynamic stability .Take sky diving for example. You spread your arms and feet to make an Arrow. If the arrow starts to flip sideways, the air resistance against the fletching is greater than the resistance at the nose, and the arrow automatically goes back to its initial orientation. Likewise, skydivers don't want to be tumbling end over end and out of control, so they trail their arms and feet behind them to act like the feathers on the arrow.
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I was going to mention that when i made my first and last solo jump, i didnt spread my arms or better known as the arch, i felt like i got into a fetal positions, while laying sideways to the earth.
 
If I were to make a guess I'd say spreading our limbs allows us to be ready for the landing. If you keep your hands at your side you might find it hard to get them out in front of you fast enough to break your fall. Also a wider leg stance would make you more stable upon landing and allow you to absorb some of the shock by bending your knees.
 
I think it's a couple reasons, but absolutely not bird flapping at all. Not once have I ever instinctually flapped. Just spread my arms out further and further. When jumping from 15+ feet or higher, you know that spreading your arms does two main things. It aids in balance, and sets you up to potentially grab/hit/get tangled in something and potentially slow or stop yourself. It also increases wind resistance thus slowing your terminal velocity.
At less than large heights, the above post is the most widely accepted answer.

Who the hell feels natural flapping? To the person way above who mentioned their baby waving their arms, that's called a tantrum, and flailing limbs is not uncommon.
 
I can speak to this....in my younger days (back in the mid 70's) there was a rock quarry that had been closed for an extended period of time it was purchased by someone with the bright idea to use it for swimming. On the highest side he built a platform that extended out about 20 feet .From the platform to the water was about 35 feet. The highest place to dive or jump was about 50 feet above the water. I always dove head first no problems. The first time I jumped from the platform to land feet first for some reason I extended my arms straight out to form a cross. When I hit the water the sting I felt from the water on the underside of my extended arms was excruciating .....I didn't bring my arms to my side before entering the water.....I didn't make that mistake again My friends and I continued to swim there for several more years till the inevitable happened and someone drowned and just like that it was closed. But the memories I have of people jumping from the platform who,had no business jumping from that height still run through my mind. Even helped rescue a few who from 35 feet would hit the water on their backs or fronts knocking the air out of them...
Good times !
 
oldtimer54 said:
I can speak to this....in my younger days (back in the mid 70's) there was a rock quarry that had been closed for an extended period of time it was purchased by someone with the bright idea to use it for swimming. On the highest side he built a platform that extended out about 20 feet .From the platform to the water was about 35 feet. The highest place to dive or jump was about 50 feet above the water. I always dove head first no problems. The first time I jumped from the platform to land feet first for some reason I extended my arms straight out to form a cross. When I hit the water the sting I felt from the water on the underside of my extended arms was excruciating .....I didn't bring my arms to my side before entering the water.....I didn't make that mistake again My friends and I continued to swim there for several more years till the inevitable happened and someone drowned and just like that it was closed. But the memories I have of people jumping from the platform who,had no business jumping from that height still run through my mind. Even helped rescue a few who from 35 feet would hit the water on their backs or fronts knocking the air out of them...
Good times !
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I did that from a cliff into a lake. It started at about 30 feet and went to about 50 ft. Just above the 50 was a tree that made an s shape and come out over the water. We took a chainsaw and cut it off to make a platform. Close to 60 foot high. I hit arms wide open once and it bruised me. Hurt like hell.

I slo jumped from the lower end with a friend that jumped with me. He shoved shoved me in the air to push himself farther. I went into a tumble and couldn't react. I hit spread leg and rack my nuts. I almost drowned.
 
oldtimer54 said:
I can speak to this....in my younger days (back in the mid 70's) there was a rock quarry that had been closed for an extended period of time it was purchased by someone with the bright idea to use it for swimming. On the highest side he built a platform that extended out about 20 feet .From the platform to the water was about 35 feet. The highest place to dive or jump was about 50 feet above the water. I always dove head first no problems. The first time I jumped from the platform to land feet first for some reason I extended my arms straight out to form a cross. When I hit the water the sting I felt from the water on the underside of my extended arms was excruciating .....I didn't bring my arms to my side before entering the water.....I didn't make that mistake again My friends and I continued to swim there for several more years till the inevitable happened and someone drowned and just like that it was closed. But the memories I have of people jumping from the platform who,had no business jumping from that height still run through my mind. Even helped rescue a few who from 35 feet would hit the water on their backs or fronts knocking the air out of them...
Good times !
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Bexar County?

Rock Quarries, the birth place of the X Games, with added excitement of Rattlesnakes, Cottonmouths, Cactus, Scorpions oh, friendships and fights and always sunburn.

We would always make sure our bicycles were ready to go on Saturday morning! lol
 
qwizoking said:
its actually an attempt at the perfect amount of balance
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Indeed! And a successful one might I add. Look at skateboarders/surfers and how they use their arms to perfectly balance themselves in all sorts of positions they get themselves into. Very hard to do anything on a board and not use your arms. Any 1/2 decent skater/surfer will tell you that :bigjoint:
 
It also slows you down by creating drag. Less noticeable on smaller jumps but if you were to say jump off a roof using your arms and then not using your arms, you'll notice the difference between the two... significantly :bigjoint:
 
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