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Head Down

by BASEwiki

Head Down Exits

You have to understand the basic mechanics of things such as body positioning, centre of gravity, and momentum to truly understand what causes BASE jumpers to “go head down”.

The two most common causes are pivoting at the feet, and looking down during the exit!!!! Removing these two scenarios would reduce the number of head down exits by over 90%.

In the very early stages of a BASE jumpers career, most jumpers are taught by their mentors/instructors to keep their head up, looking out at the horizon, and to punch their chest towards it. Why?

Lets delve a little more deeply into pivoting and head down exits.

Pivoting

This occurs when the jumper keeps their feet on the exit point and starts the exiting motion. What follows leads to a head down exit. The feet remain “attached” o the exit and the upper body starts moving forward. Because the feet are fixed, and the upper body is moving, the only option is for the upper body to start moving down. In physics jargon, a “turning moment” is created. The upper body tends to accelerate a little and continues its motionat an ever increasing angle. Typically the jumper will subconsciously feel the upper body impeding the space on the lower body and the natural response is to commence some force by the feet against the object. This force allows the jumper to leave the object and creates some forward throw, thereby moving the body away from the object. However, the downward motion is still evident and as the jumper leaves the object, the upper body is accelerating a little faster (now under the influence of gravitational attraction as well as the original thrust created by the jumpers exit) than the lower body.

The orientation of the body becomes such that the head is laterally lower than the torso and legs. The jumper has achieved a head down position. There is also a correlation between the time difference of commencing the exit and the feet leaving the object - i.e. the longer the feet are left on the object, the greater the angle of orientation of the body.

It is often noted that student jumpers are frightened on their initial jumps. What happens to their limbs when they are scared? They “turn to jelly”. It is very difficult to move “jelly legs” in an appropriate manner.

Another cause of leg pivoting is that sometimes people want to jump “down” instead of up and/or out as they desire to be get to their destination sooner (or some other psychological reason) . They often forget to coordinate their down motion with an out motion which results in the upper body moving first and pivoting to result.

In laymans terms, you leave your legs on the edge, you go head down. The longer you leave them, the worse the head down becomes.

Head Position

The other common factor is head positioning. It is common knowledge that “the body follows the head”. This is true for most people with limited experience. Why? What happens to cause the outcome?

Basically, the human body likes to create an equilibirum where all muscle groups and skeletal structures are balanced and neutral. As one part of the body is moved, the other parts of the body adjacent to it want to either follow that movement, or force it back to something closer to its original position. E.g. If you try to touch the centre of your back by putting your arm/hand over your shoulder, the top and side of the torso tend to contort towards the movement of the arms. On top of the physical factors, there is a psychological component. The mind receives information from the body that something is stretching out of its normal range of movement. Over a long period of time, the mind interprets this data and learns that if it moves other parts to accommodate the original motion, it will reduce the stresses and strains on it.

How does this mumbo jumbo relate to head down positioning? A typical dead down scenario related to head position follows:

a jumper exits in a standard boxman position. Immediately upon exit they look down as fear or a sense of curiosity forces their mind to desire information. They want to see what is below them. An experienced person is able to adjust the angle of their eyes (roll them down), whereas an inexperienced jumper will usually maintain visuals perpendicular to their face (they look straight out) and hence they are forced to move their whole head down. If you touch your chin on your chest whilst maintaining rigidness with the remainder of your body, the muscles in the back of the neck become more strained. Hence the body tries to overcome this by relaxing the neck muscles as well. This is best achieved by de-arching a little and bending slightly forward. The act of de-arching is not too dissimilar to initiating a forward somersault. So now we have created some downward and rotational momentum as well as positioned our upper body downwards. This process continues and leads to a head down position.

How a person reacts to their orientation and positioning will also add to a detract from their scenario. They can make it worse or better by doing the wrong or right things in response to their position. This is where prior experience becomes crucial.

There are other factors that lead to head downs. Slippery and uneven exit points, rushed exits, interference (tripping or exit collisions), intentional head downs, poor aerobatic technique, altering and/or not executing and exit plan as a jumper commences the exit motion, etc.

How to prevent head down exits

There are a number of ways:
  • look out and not down.
  • if you need to look down, learn how to keep the rest of your body position intact whilst you move your head and/or eyes around prior to BASE jumping.
  • exit with your whole body in one coordinated motion.
  • The old adage of “punching your chest out to the horizon, looking up, and keeping a good boxman position” is a good starting point for beginners. This can be modified as experience and skill grows.
  • satisfy the curiosity of what is below an exit point prior to leaveing the edge. This could be achieved by abseiling out or below the exit point or getting a good guide who can explain what is below the exit point.


Submitted by BASEwiki on 2007-06-13 | Last Modified on 2007-07-03

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