It is important to consider four principal elements in jumping ‘s biomechanics: preparation, impulse (or take-off), suspension and landing.
Preparation consists of bending the lower limbs and throwing the arms simultaneously as far behind the trunk as possible.
Impulse is about brusquely and quickly extending the lower limbs by energetically raising the arms forward.
Suspension or hang time begins at the moment the body leaves the ground following the impulse created by the lower limbs. During this period, the lower limbs are placed in the most favorable position to clear the obstacle, with the arms lowered along the body.
The Landing’s goal is to effectively cancel out the speed of impulse so that the body recovers its upright position by regaining contact with the ground. It begins at the moment the feet touch the ground after suspension. The body lands inclined to a degree depending on the kind of jump just performed or the body’s position during suspension. The lower limbs bend without exaggeration to absorb shock. The arms, lowered during suspension, are used during landing to ensure balance.
The role played by the arms during jumps is very important.
During preparation, the back-swing of the arms, much like the flexion of the lower limbs, is a relatively slow and supple move.
During impulse, the movement of the arms is brusque and rapid and the forward elevation must coincide exactly with the extension of the lower limbs. This condition is essential for the impulse to produce its maximal effect, meaning to relay the greatest possible extension to the body. Arms are raised semi-flexed in front of the body, almost horizontally.
There can be no pause separating those two phases of preparation and impulse. In other words, the flexion of the lower limbs with the throwing of the arms backwards on one hand, and the extension of the lower limbs with the elevations of the arms on the other hand, must constitute a constant back-and-forth movement, this in order to use one of the main qualities of the muscles: elasticity.
During suspension, the arms lower or are even sometimes vigorously thrown backwards to communicate to the body a new impulse effort.
Finally, during the landing, the role of the arms consists of helping reestablish final balance. They serve as balancing aides to prevent the body from falling forward, backwards or sideways. Their position cannot be decided in advance, as it depends on the body’s incline or its degree of equilibrium upon contact with the ground.