The Question
How can we optimise the distance of which a javelin travels after release?Introduction
Javelin is a universal sport and originated in Ancient Greece, and since then has been adapted (Nemeth Javelins, n.d.). In modern times, javelin was first included as an event for men in the 1906 Olympics; however, women were not allowed to compete until 1932 (Nemeth Javelins, n.d.). The aim in javelin is to throw the javelin as far as possible from a set point, within set parameters (Stander, 2006). Throughout time, the technique used has changed and still continues to continues to change. Reasons for technique change include safety considerations, injury prevention, and allowing for optimal results (Valleala, 2012). While technique has changed, there are six phases that have been identified to take place during in successful execution of a Javelin throw (Mackenzie, 2002). These phases include:
- Carry Phase,
- Withdrawal Phase,
- Transition Phase,
- Pre-delivery Stride,
- Delivery Phase,
- and Recovery Phase.
Each phase requires a number of steps and skills to be successfully executed in order to progress to the next phase (Mackenzie, 2002). The above question, how can we optimise the distance of which a javelin travels after realease?, will be answered examining the biomechnical principles of a specific technique in each of the six phases.
The Run Up
Carry Phase - Hand position and grip
The carry phase is the phase in which the javelin is held in place and pointed in the direction of the run up (Mackenzie, 2002). The grip and hand position in this phase will determine the way in which the javelin will be released during the delivery phase.
 |
| Figure 1. The three type of grips commonly used in javelin. SOURCE: Stander, 2006. |
There are three different grips commonly used in javelin, and each grip requires a different level of skill (Stander, 2006). The American Grip, as pictured above, requires the lowest level of skill, and the "V" Grip requiring the highest, with an increase in safety risks as difficulty increases (Stander, 2006).
During
the Carry Phase the javelin is held in the hand using one of the above grips,
in which the palm of the carrying hand is facing up. The grip on the javelin
should be relaxed, allowing for the arm and shoulder to be relaxed too. By
having a relaxed grip on the javelin it reduces the tension throughout the
entire body which brings us to Newton’s Third Law of Motion. Newton’s Third Law
states “For every action, there is an
equal and opposite reaction” (Blazevich, 2010). During the Carry Phase the athlete is moving
with the javelin, the force from the foot hitting the ground is transferred through
the body; if the body was kept rigid, including the hand, arm, and shoulder,
this would cause the athlete to run rigidly, and the arm to jerk around while moving.
Allowing the body to be relaxed and absorb the impact of the foot hitting the
ground the the hand, arm, and shoulder may only move slightly. The
athlete will have more control over their body and will move more efficiently during
the carry phase.
Withdrawal Phase - Angle of the hips in regards to the direction of running
During the Withdrawal Phase the athlete drives forward, causing the arm carrying the javelin to be pulled back and increases momentum (Mackenzie, 2002). The athletes posture should change during this phase, which lasts for approximately two strides. This can be seen in the below image.
 |
| Figure 2. Body positioning during the withdrawal phase. SOURCE: http://www.wikihow.com/Throw-a-Javelin |
The hips
during the Withdrawal Phase should be at right angles to the direction in which
the athlete is travelling; this can be seen in the second athlete in the above
picture. Keeping the hips at right angles changes the athlete’s torque, and
distances their centre of mass from their centre of gravity (Valleala, 2012)
. An individual’s centre of mass is the point at which the body’s weight is evenly distributed in any way; it can have an effect on the athlete’s sense of balance if it differs too greatly from the centre of gravity (Blazevich, 2010). The athlete keeps an upright position meaning the centre of mass does not differ too greatly from the centre of gravity. However, the torque of the body has been changed as the position of the hips differs from the position in which the remainder of the body is facing. Torque is an extension of centre of mass, and is the twisting of an object, in this case the hips, to apply force (Blazevich, 2010). This impacts the athlete’s momentum at which they are travelling in preparation to deliver the javelin. Therefore, to allow for minimal impact on the athlete's momentum, the change in position of the hips should be a slow and fluid movement. This will allow for balance to be kept, due to the centre of mass being even.
. An individual’s centre of mass is the point at which the body’s weight is evenly distributed in any way; it can have an effect on the athlete’s sense of balance if it differs too greatly from the centre of gravity (Blazevich, 2010). The athlete keeps an upright position meaning the centre of mass does not differ too greatly from the centre of gravity. However, the torque of the body has been changed as the position of the hips differs from the position in which the remainder of the body is facing. Torque is an extension of centre of mass, and is the twisting of an object, in this case the hips, to apply force (Blazevich, 2010). This impacts the athlete’s momentum at which they are travelling in preparation to deliver the javelin. Therefore, to allow for minimal impact on the athlete's momentum, the change in position of the hips should be a slow and fluid movement. This will allow for balance to be kept, due to the centre of mass being even.
Transition Phase - Placement of the planting foot
The Transition Phase is is the final phase in preparation to begin the delivery (Mackenzie, 2002). This phase requires the athlete to cross their feet over, and stepping forward causing the athlete to lean backwards.
 |
| Figure 3. Foot placement during the Transition Phase. SOURCE: http://www.wikihow.com/Throw-a-Javelin |
Positioning
of the feet during the Transition Phase has a great impact on the potential
outcome of the delivery. For a right-handed athlete, the position of the right
foot during this phase is vital; it changes the position of the athlete’s entire
body. The right foot should be advanced ahead of the left foot, and in turn
ahead of the athlete’s centre of gravity. This advancement should cause the
body to lean at a 115° angle as seen in the above image. A body’s centre of
gravity is the point at which the weight body is evenly distributed in a vertical
manner (Blazevich, 2010); advancing the right foot forward in such a manner
causes the athlete’s centre of gravity to no longer be displaced. In order to
gain place the body leans back at a 115° angle, causing the body’s centre of
mass to be stable.
The Throw
Pre-delivery Stride - Upper body position
This stride is the final step before the javelin is thrown; the body position during this phase important as the direction of the body determines the direction in which the javelin will travel (Unknown, 2015). The
upper body during the pre-delivery stride aligns with the lower body and faces
the direction in which the javelin it to be released [as seen in the above image]. This in turn reduces the athlete’s
moment of inertia as the bodies distance from their centre of rotation is also
reduced. As the upper body is aligned with the hips, the athlete is
likely to be more stable, allowing them to transfer their momentum from their
lower body, to their upper body and eventually to the javelin. This is
successfully achieved due to the reduction in the moment of inertia (Blazevich, 2012).
Delivery Phase - Release angle of the javelin
 |
| Figure 4. Demonstration of the kinetic chain leading up to the delivery. SOURCE: Stander, 2006. |
The Delivery Phase is arguably the most important phase in the process of the javelin throw; it is when the athlete finally releases the javelin. During
the Delivery Phase the entire body works together to deliver the javelin the
optimal distance. This is due to the kinetic chain, in which each part of the
body has previously moved sequentially to achieve the desired outcome [as seen
in the above image], also known as the throw-like movement pattern (Blazevich,
2010). This process can help enable the angle of which the javelin is released.
The javelin should be released when the throwing hand is at its highest point;
however, as well as the height of release, the angle of release and speed of
release will also impact upon the distance achieved by the javelin (Valleala, 2012). These
factors are due to projectile motion, which is also impacted by air resistance
and gravity. In order for the javelin to
travel the optimal distance the projection speed, the speed at which the athlete
is travelling when the javelin is released, must be high (Valleala, 2012). The higher the
projection speed, the further the javelin should travel this is also dependent
on the angle and height of release. The angle and height of release are
dependent on one another; the angle should increases as height of the landing
area increases [an example of this can be seen in Figure 5]. The optimal angle of release would be approximately 35° degrees,
as the javelin is being released at a height greater than that of the landing
area.
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| Figure 5. Projectile motion. SOURCE: Blazevich, 2010. |
Based on the information above we can calculate the distance in which the javelin would travel if it was thrown at a specific angle, height and speed. Below is a table of hypothetical data based on various angles of which the javelin could be thrown at, and the distance it would achieve.
Angle of
Release
|
Height of
Release
|
Speed of
Release
|
Distance
travelled
|
0°
|
1.75 metres
|
6.0 metres
per second
|
3.58 metres
|
15°
|
1.75 metres
|
6.0 metres
per second
|
4.50 metres
|
25°
|
1.75 metres
|
6.0 metres
per second
|
4.95 metres
|
35°
|
1.75 metres
|
6.0 metres
per second
|
5.13 metres
|
45°
|
1.75 metres
|
6.0 metres per second
|
4.96 metres
|
55°
|
1.75 metres
|
6.0 metres
per second
|
4.41 metres
|
75°
|
1.75 metres
|
6.0 metres
per second
|
2.22 metres
|
90°
|
1.75 metres
|
6.0 metres
per second
|
0.00 metres
|
The Follow Through
Recovery Phase - Follow through after javelin release
This final phase is important for many reasons, it helps to reduce injury risk and allows the transfer of momentum to be high (Mackenzie, 2002). During
this final phase the back leg is brought forward to stop the athlete travelling
any further forward (Unknown, 2015). This once again stabilises the athlete, ensuring the do
not go over the fault line and that their centre of mass is evenly distributed.
It allows the athlete to transfer their momentum to throw the javelin
successfully with limited impact on their speed (Blazevich, 2010).
The Answer
The above video demonstrates the six phases of the javelin throw as discussed throughout this post. The key biomechanical principles that need to be considered while attempting a successful execution of the javelin throw are:
- Newton's Third Law of Motion: Every action has an equal and opposite action
- Centre of Mass
- Centre of Gravity
- Torque
- Transfer of Momentum
- Kinetic Energy Chain
- Projectile Motion
If each of these principles are addressed, and the optimal release angle is achieved, than the javelin should travel far. Though, it is important to remember that weather, gravity, and air resistance can all change the optimal outcome and these are often beyond the control of the athlete (Blazevich, 2010). Providing the athlete moves through the six phases, achieving the correct technique, similar to that in the above video, than distance should be optimal for the conditions and injury risk should be reduced (Mackenzie, 2002).
How can we use this information further?
The biomechanical principles identified within the javelin throw could also be applied to other skills or sporting techniques. These include shot put, and the over arm American Football pass (Blazevich, 2010). Both these skills incorporate the kinetic chain using a throw-like movement, and rely on projectile motion to allow the pass or shot put to travel the optimal distance (Blazevich, 2010). Having an understanding of these techniques can allow for the transfer of knowledge in a range of skills, as well as improving performance within javelin.
References
Blavevich, A. J., (2010). Sports Biomechanics The Basics: Optimising human performance (2nd ed.). London: Bloomsbury.
Mackenzie, B. (2002). Javelin. Brian Mac Sports Coach. Retrieved 15 June 2015, from http://www.brianmac.co.uk/javelin
Nemeth Javelins (n.d.). History - Nemeth Javelins. Retrieved from http://www.nemethjavelins.hu/history
Quintic Consultancy (2012, February 9). Javelin throw filmed by Quintic (Slow motion 300fps) [video file]. Retrieved from http://www.youtube.com/watch?v=xlOc6r6Eo8w
Mackenzie, B. (2002). Javelin. Brian Mac Sports Coach. Retrieved 15 June 2015, from http://www.brianmac.co.uk/javelin
Nemeth Javelins (n.d.). History - Nemeth Javelins. Retrieved from http://www.nemethjavelins.hu/history
Quintic Consultancy (2012, February 9). Javelin throw filmed by Quintic (Slow motion 300fps) [video file]. Retrieved from http://www.youtube.com/watch?v=xlOc6r6Eo8w
Stander, R. (2006). Athletics Omnibus - Javelin Throw. Athletics South Africa: Houghton. Accessed at http://www.bolandathletics.com/5-13%20Javelin%20Throw.pdf
Unknown. (2015). How to throw a Javelin. WikiHow. Retrieved 16 June 2015, from http://www.wikihow.com/Throw-a-Javelin
Valleala, R. (2012). Biomechanics in javelin throwing. Retrieved from http://www.kihu.fi/tuotostiedostot/julkinen/2012_val_biomechani_sel72_42228.pdf
