Biomechanics of a Javelin Throw

The javelin throw is a track and field sport in which a 2.5 m (8 ft 2 inch) long spear-shaped javelin is thrown with the intention that it must cover the maximum possible distance. The winner of the event is decided on the basis of the distance covered by the javelin thrown by the participants. The muscle coordination and the technique implemented during the javelin throw is somewhat considered complicated. This is the reason why one must refer to the proper biomechanics involved in the sport to achieve a good throw as well as to avoid muscle pull and other injuries. The distance covered by a javelin after a throw depends on three major factors, namely, the height of the release, the angle of the release, and the velocity of the release. The most important factor to improve the throw is the velocity at which a javelin is thrown. Usually, the release velocity of a javelin is approximately equal to 6 meters per second. When the velocity with which the javelin is thrown is increased, the distance covered by the javelin increases significantly. For instance, an increase of 1 meter per second in the release velocity increases the throw distance by approximately 5 meters. A good throw in the javelin does not depend on the strength, but it depends on the correct implementation of the throwing technique. The javelin throw is one of the most critical overhand throw sports. It requires movement of the entire body. During the throw, the arm muscles get involved only after the major muscles of the feet, legs, hips, and torso have properly transferred the motion. The player must keep his/her arm as relaxed as possible to achieve a good throw. The javelin throw world record is 98.48 meters, which was established by Jan Zelezny of the Czech Republic in the year 1996.

Phases of Javelin Throw

There are four main phases of a javelin throw, namely, approach run, crossover phase, release phase,

Approach Run

The prime phase of the javelin throw is the approach run. Here, the javelin thrower tends to take six to ten running steps before he actually throws the javelin. The javelin is held in the dominant hand and is positioned above the shoulder. In this phase, the glenohumeral joint and the humeroulnar joint are extended and flexed at an angle equal to 90 degrees. This helps the player build speed and generate the momentum required for the throw. Major muscles used are the soleus, gastrocnemius, hamstrings, quadriceps, and gluteus maximus.

Crossover Phase

In this particular phase, the thrower tends to pull and position the javelin behind his/her body and tends to take two or three running steps. This is known as a crossover step. During the crossover phase, the player’s body is aligned to one side, and the javelin’s tip is maintained at eye level. This helps the thrower build speed and configure the best possible release position. The second last crossover step is known as the penultimate or impulse step, where the entire weight of the player’s body gets concentrated on his/her back foot. The upper trunk tends to rotate 90 degrees, and the player prepares to release the javelin in the air. Two key points to be properly maintained during the crossover phase of javelin throw are momentum in the body and the position of the javelin. If the player takes a jump during the impulse step of the crossover phase, he/she tends to lose a portion of the force possessed by the athlete. This is because the horizontal forces get converted into vertical forces. Vertical forces lead to an unstable throw and a significant decrease in velocity.

Release Phase

The release phase mainly involves the transfer of momentum and full body rotation. A majority of factors that primarily affect the javelin throw are contained in the release phase. The release phase is divided into two basic parts, namely, the single-legged support phase and the double legged support phase. The first part of the release phase, i.e., the single-legged support phase involves the shifting of the thrower’s centre of mass over the back of the leg. The double legged support phase is also known as the plant phase. It helps the athlete transfer momentum generated during the approach run to the different parts of the body such as the torso, shoulders, arms, hand, etc. The momentum transferred to the upper body can be described as the whipped transfer of energy from hip to shoulder, which further gets linked to the player’s elbow and the hand holding the javelin. The front leg is extended to ensure a high point of release. As the hips rotate, the thrower stretches his/her rectus abdominous. The chest of the athlete faces the sky. The non-dominant hand of the thrower generates a counterforce called the block. The athlete’s glenohumeral joint gets blocked horizontally by the rhomboids and the trapezius muscle. This causes the athlete to form a backward C shape. The throwing arm is raised above the shoulder at the end of the release phase, the elbow rotates in the outward direction, and the javelin is released with force. The optimal angle of release lies between 33 degrees and 39 degrees. The movement of the fingers causes the javelin to rotate clockwise. The rotation induces stability in the javelin and helps in an appropriate landing. The prime muscles used by the player during the release phase include gastrocnemius, soleus, quadriceps, hamstrings, rectus abdominous, triceps, and rhomboids.

Recovery Phase

The recovery phase is one of the most important phases of the javelin throw. It begins as soon as the javelin leaves the thrower’s hand. Implementation of proper biomechanics and technique in the recovery phase helps to reduce the risk of injury and allows proper deceleration of the body. Here, the player brings his back leg in the front to block any further movement that can cause penalty or foul. The body tends to decelerate gradually and dissipates energy in the surrounding. The primary muscles used during the recovery phase are the quadriceps, gastrocnemius, and hamstrings.