What is the Science Behind a Javelin Throw

When Neeraj Chopra bagged India’s only gold medal in Tokyo 2020 Olympics, the whole nation lit up to a festive mood and celebration. Neeraj Chopra secured gold in the men’s javelin throw event and it was also India’s first-ever gold in Athletics.

But, have you ever wondered, what is the science involved behind this sport? How exactly does our body propel a Javelin? Let’s find out.

The underlying objective of the sport is to attain the greatest possible throwing distance or can be stated as ‘the maximization of the throwing distance’. The elements governing this are:

  1. Approach run
  2. Release
  3. Braking (final phase)
  4. The flight of the javelin

For the fulfilment of the objective, an optimal approach velocity and optimal position of the body segments is required at the end of the approach run. The running step consists of a run-up which is followed by the cross over steps. The initial running steps are meant for building the speed and the rhythm of the thrower. The maximum running velocity should optimally lie in the range in order to attain the maximum throwing distance. The cross over steps allows the thrower to land with their weight over the back foot and establish a good position before throwing.

Fig. Approach run (Source: BrianMac)

Apart from the speed of the release, the angle and height of release are also essential in deciding the distance of the throw. The optimal angle of release and optimal angle of height constitute the release phase. The angle of release (α) is defined as the angle between the release velocity and the horizontal line. The angle of attack (β) or the angle of the height is the angle of the longitudinal axis of the javelin and the horizontal line just at the instant of release. These angles are affected by the aerodynamic conditions and further the throwing distance is also governed.

Fig. Trajectory of the javelin throw (Source: Hassan, E.E. 2015)
Fig. Angles during the release phase (Source: worldathletics.org)

In the release phase, the velocity is reduced and further in the braking phase this approach velocity has to be reduced significantly and considerable deceleration should be there. The braking distance should be minimized so that complete deceleration is allowed after the release and the athlete doesn’t cross the foul line.

The release velocity is governed by the fact that how well the impulse transmission takes place to the throwing arm. The momentum built up in the thrower is transferred to the javelin before its release. The phase flight of the javelin starts from the last contact of the javelin with the hand and the first contact of the javelin with the ground. As the javelin loses contact with the athlete, its flight can’t be controlled by the athlete anymore and is governed by aerodynamic factors such as wind velocity. The forces acting on the javelin while the motions are the drag force and the lift force. The drag force is basically a resistive force and acts against the direction of the flight and the lift force acts vertically to the direction of the flight.

Fig. Forces on javelin during flight (Source: chevillat.pagesperso-orange.fr)

Hence, we have discussed briefly the underlying science of javelin throw but can always delve deeper into it.

Hope you all enjoyed reading it! 🙂

References:

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