Question #2: Why is this important?
In order to put first things first and, in order to be as confusing as possible, I will answer the second question first!
The Objective –Get More Height
One of the objectives in diving is to attempt to get as much height off the diving board as possible. More height equals harder dives, and harder dives – done properly, mean higher scores. Where a diver’s knee and hurdle leg finish at the top of the hurdle is a major factor in how much height they get off the diving board, and the direction of this height.
As a diver executes the hurdle, the knee is lifted upward in conjunction with the armswing. At the height, or top of the hurdle, the diver will then drop to the diving board. If the knee is not lifted high enough, the diver will have too much forward momentum and many things can happen, most of them bad.
This occurs many times with former gymnasts turned divers, who attempt to use a take off similar to that used on a vault, or that used in the floor exercise. The idea for a gymnast is to use their forward momentum to help carry them through the exercise, or trick. This is the opposite of what a diver is trying to achieve on springboard.
The idea for a diver is to have their body, their weight, and their momentum dropping close to straight down from the top of the hurdle, to a point on the end of the diving board. As this weight and momentum bends the board, an angle is created and the spring from the board will carry them a safe distance for the dive (Image #2 - Bending the Diving Board).
In order to achieve this, the diver must drop from the top of the hurdle in balance, without much forward momentum. This effect can be achieved by lifting the hurdle leg to the optimal position.
The Hurdle – Proper Position
Now to answer the first question, a diver’s knee and hurdle leg should be perpendicular to the body at the top of the hurdle. What this means is that if the body of a diver is moving vertically up from the board, then the hurdle leg should extend – at the very least, straight out from the body of the diver, creating a 90 degree angle between the leg and the upper body (Image #1 – Hurdle Angle).
The reason for this is that the direction the diver lifts his or her leg in the hurdle, will help determine the direction that the rest of the body will follow. The higher the knee and the leg move and finish, and closer to and past the 90 degree angle, the higher the diver will go.
Refering back to the example of a gymnast; have you ever seen a gymnast lifting their knee during a floor exercise? It doesn’t happen because this would stop the gymnasts forward momentum.
A diver on the other hand wants to go up relatively straight, and come down the same way.
By staying consistent with hurdle position, a diver can consistently stay in balance and allow the springboard to do what is was designed for: gain as much height as possible and move the diver a safe distance from the board.