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Asked by lesterjwh to Helen, Jenni, Mark, Martin, Stu on 17 Jun 2011. This question was also asked by leonl001.
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Jenni Tilley answered on 16 Jun 2011:
I have absolutely no idea!
Maybe because it helps them prepare for landing or because of left over momentum from when they left the ground?
Maybe just to show off!?
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Mark Burnley answered on 16 Jun 2011:
The “running several steps in the air” is done in a long jump because at take-off the athlete does not apply the force of the jump through the centre of mass. This means that the body would rotate in the air if the athlete didn’t run (it’s called the 3 and 1/2 hitchkick). Without it, an athlete would land face-down! By rapidly moving the limbs the athlete is transferring the rotation to the arms and legs, so that the trunk stays upright. This is similar to why you will automatically swing your arms if you find yourself over-balancing. What you need to remember is that “angular momentum” is constant for somebody in mid air (it cannot be increased or decreased, just transferred). I wouldn’t recommend trying the hitchkick technique unless you can jump over 7 metres – you won’t have enough time to do 3.5 kicks!
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Comments
Jenni commented on :
ah, so I was nearly there will ‘left over momentum’!
Mark commented on :
Had you removed the “or” and the questionmark from your second sentence I’d have had nothing to post!
Jenni commented on :
I still think it’s really just to show off!