Diving

Diving

Diving refers to the sport of acrobatically jumping or falling into water. Diving is an internationally-recognized sport that is part of the Olympic Games. In addition, unstructured and non-competitive diving is a common recreational pastime in places where swimming is popular.
While not a particularly popular participant sport, diving is one of the more popular Olympic sports with spectators. Successful competitors possess many of the same characteristics as gymnasts and competitive cheerleaders, including strength, flexibility,kinaesthetic judgment and air awareness.
In the recent past, the success and prominence of Greg Louganis led to American strength internationally. More recently, the greatest diving nation has been China, which came to prominence several decades ago when the sport was revolutionized by national coach Boxi Liang. China has lost few world titles since. Other powers are generally those which import Chinese coaches, including Australia and Canada.

Competitive Diving

Most diving competitions consist of three disciplines: 1m, 3m and tower, aka platform. Competitive athletes are divided by gender, and often by age groups as well. In tower events, competitors are allowed to perform their dives on either the five, seven and a half (generally just called seven) or ten metre towers, although high level meets, including the Olympic Games and world championships, usually require all dives to be executed from the ten metre.
One and three meter dives are performed from a springboard. Five through ten meter dives are performed from concrete or wooden platforms, and such platforms also exist at one and three metre heights as training tools.
Divers must perform a set number of dives according to various established requirements, including somersaults and twists in various directions and from different starting positions (see Components of a Dive below). Divers are judged on whether and how well they completed all aspects of the dive, the conformance of their body to the requirements of the nominated dive, and the amount of splash created by their entry to the water (less being better). A perfect entry, with no splash, is called a "rip," after the loud tearing or clapping sound it creates (as well as the sometimes painful bursting feeling on the hands of the diver). A really bad entry, with lots of splash, is called a "smack," after the loud smacking sound it creates (as well as the always painful feeling it leaves on the whole body of the diver) Theoretically, a score out of ten is supposed to be broken down into three points for the takeoff, three for the flight, and three for the entry, with one more available to give the judges flexibility. However, since judges must give their scores instantaneously, they base their scores more on a gut instinct and overall impression than actual calculations.
The raw score is multiplied by a difficulty factor, derived from the number and combination of movements attempted. The diver with the highest total score after a sequence of dives (which depend on age group and skill level in elite competition) is declared the winner.While diving is closely related to gymnastics, it differs in one large way: Male and female gymnasts compete vastly different skills on vastly different apparatus, while male and female divers compete the same dives on the same boards. Women are often required to perform one fewer dive than men (10 as opposed to 11, or 5 as opposed to 6), but there has been a movement in recent years to change this fact.

Mechanics of Diving

At the moment of take-off, two critical aspects of the dive are determined, and cannot subsequently be altered during the the execution. One is the trajectory of the dive, and the other is the magnitude of the angular momentum.
The speed of rotation - and therefore the total amount of rotation - may be varied from moment to moment by changing the shape of the body, in accordance with the law of conservation of angular momentum.
The center of mass of the diver follows a parabolic path in free-fall under the influence of gravity (ignoring the effects of air resistance, which are negligible at the speeds involved).

Trajectory

Since the parabola is symmetrical, the travel away from the board as the diver passes it is twice the amount of the forward travel at the peak of the flight. Excessive forward distance to the entry point is penalised when scoring a dive, but obviously an adequate clearance from the diving board is essential on safety grounds.
The greatest possible height that can be achieved is desirable for several reasons:
The height attained is itself one of the factors that the judges will reward.
A greater height gives a longer flight time and therefore longer to execute the moves.
For any given clearance when passing the board, the forward travel distance to the entry point will be less for a higher trajectory.

Control of rotation

The magnitude of angular momentum remains constant throughout the dive, but since
Angular momentum = rotational velocity X Moment of Inertia,
and Moment of Intertia is larger when the body has an increased radius,
...the speed of rotation may be increased by moving the body into a compact shape, and reduced by opening out into a straight position.
Since the tucked shape is the most compact, it gives the most control over rotational speed, and dives in this position are easier to perform. Dives in the straight position are hardest, since there is almost no scope for altering the speed, so the angular momentum must be created at take-off with a very high degree of accuracy. (A small amount of control is available by moving the position of the arms and by a slight hollowing of the back).
Notice that the opening of the body for the entry does not stop the rotation, but merely slows it down. The vertical entry achieved by expert divers is largely an illusion created by starting the entry slightly short of vertical, so that the legs are vertical as they disappear beneath the surface. A small amount of additional tuning is available by 'entry save' techniques, whereby underwater movements of the upper body and arms against the viscosity of the water affect the postion of the legs