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The Field House
How much horizontal rotation do you need?
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HighJumpCoach
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Joined: 11 Apr 2008
Posts: 7
Location: Hillsborough, NJ

PostPosted: Tue Mar 09, 2010 10:17 am    Post subject: How much horizontal rotation do you need? Reply with quote

A very important question that is asked only infrequently is "How much horizontal rotation do you need?


Horizontal rotation is sometimes referred to as rotation about the bar. It is the rotation that causes the jumper to rotate from a vertical orientation at takeoff, through a horizontal position above the bar, and then up-side-down into the pit.


This rotation is originates during the takeoff drive as the sum of two separate rotations:


1. Lateral rotation, which is rotation in the plane formed by the hips and shoulders (at their orientation at takeoff). Lateral rotation supplies the bulk of the rotation about the bar. Lateral rotation is sometimes called cartwheeling rotation. The axis of this rotation is front to back.


2. Somersaulting rotation, which is rotation in the plane formed by the spine and sternum (breastbone, also as they are oriented at takeoff). Somersaulting rotation, when used, provides only a small fraction of the rotation about the bar. Indeed, I consider using any somersaulting rotation at all to be an advanced technique, thus somersaulting rotation will not be discussed in this post. I would, in fact, avoid somersaulting rotation unless analysis of your bar clearance clearly shows that it is necessary. The axis of this rotation is side to side.


So, what is the proper amount of rotation about the bar? The correct amount is: just enough to rotate your body to a horizontal orientation at the moment the center of mass reaches it's apex (highest point). If everything else is done correctly, the apex of the flight will be directly above the center of the bar.


Executed in this way, your body can be held in a gently arched position throughout the flight and all parts of your body will clear the bar by approximately the same amount (lumps, bumps, and other projections from the underside of your body not withstanding).


Some will claim that you should lift your feet at the last moment, but in my opinion raising your feet is unnecessary at best, and counterproductive at worst. This is because raising your feet will drop your butt, and when the jump is really close you can't time this well enough to avoid catching something on the bar. Better to get your rotation about the bar exactly right and avoid the need to lift the feet.


Clearly, if you bend your knee too much you will have to straighten your knees so they are in better alignment with the arch in the remainder of your body. I think it is better to travel over the bar with your body in one flowing arch throughout the flight and avoid "drooping calves" altogether.


This isn't the whole story, but I'll start there and invite discussion. I'm sure I'll get some disagreement, because some people still think that a very arched body, and the resulting increase in rotation rate that it causes, is necessary. It is not; but more on that later.


Glen Stone
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