Does throwing a Javelin biomechanically correct increase the throwing distance?

Does throwing a Javelin biomechanically correct increase the throwing distance?

The javelin throw is one of four throwing events in track and field. It has a run up which consists of a serious of cross steps; the delivery which relies on speed, direction and height and the recovery which decreases the momentum preventing disqualification. "Javelin throwing is technically demanding" (Liu, Leigh and Yu, 2010, p. 1459) which is why each section of the skill needs to be technically correct.

 

Figure 1 (Livestrong. 2013).

Looking at biomechanical principles in relation to the javelin throw will focus on improving technique and encouraging specific movement phases. Rules of the sport impact the throw and will impact how the biomechanical aspects can be formed.

Run up-

Propulsive Impulse

Propulsive Impulse is the force that is applied to move forward and accelerate.

While performing  the run up the javelin is moving with you at the speed of your run. When  you then apply extra force through adding muscles the force to accelerate increases. Therefore the faster the run up the further the javelin should go. However this is not always the case  because as you add speed the technical approach to the throw becomes increasingly difficult. To increase the speed of the run up a skill cue could be given around foot placement while running.

If the athlete is landing on the heal of their foot a force is being exerted which "elicits a backward or braking reaction force. Since the force is applied over time, the area under the curve is the braking impulse" (Blazevich, 2010, p. 55). When the foot lands under the body it creates a propulsive reaction force which will increase the speed when running. The smaller the angle between the foot and the ground when you are placing your foot the greater the acceleration gained. This decreases the braking impulse which is a product of applied forces and the time over which it is applied which will slow the running speed.

 

           

Figure 2 (Blazevich, 2010, p. 55).

Every force has an equal and opposite reaction- Ground reaction force

When running the "ground exerts an equal and opposite reaction force" (Blazevich, 2010, p. 45) a force is applied both vertical and horizontal which exerts an equal and opposite reaction. This "accelerates us forward if the force is large enough to overcome our inertia" (Blazevich, 2010, p. 45).
 

A skill cue that could be provided to the athlete to increase their performance of the run up could be to decrease the time that the foot is on the ground. In order to run faster, stance to must be shorter. However when stance time is shorter there is less time to produce an impulse, so the peak force must be higher.

Figure 3 (Tongen, A. and Wunderlich, R., N.D).

 

Figure 3 shows that the vertical ground reaction force is much high and over a much shorter time while running than walking. This increases the speed through using Newtons 3rd law every force has an equal and opposite reaction.

Release-

The second phase of the javelin throw is the release. The release is very technical and involves all body parts.

In preparation to throwing the javelin the athlete should move the javelin to the rear of their right shoulder keeping the arm straight and the palm facing upwards. Accelerate forward while rotating the shoulders to line up with the direction of the throw with the hips remaining forward to maintain approach speed (Stander, 2006). The tip of the javelin should be close to the athlete's head with the point at eye level.

To prepare for the throw the trunk leans back to maximise the pull of the throwing arm. The dominate foot should touch the ground first slightly in front of the hips and shoulders. The dominate arm still fully stretched while bringing the non dominate leg forward and transferring the weight through the hips.

 

Figure 4  & 5 (Stander 2006).

 

Projection speed

 
The release speed has the greatest influence on the distance the javelin will travel. "If an object is thrown through the air, the distance it travels before hitting the ground (the range) will be a function of horizontal velocity and flight time" (Blazevich, 2010, p. 25).

 
Push/Throw

 
There are two ways that an object can be released or moved. There is through a push which movement which "tend to extend all joints in our kinetic chain simultaneously in a single movement" (Blazevich, 2010, p. 196). The push movement in generally done in movements such as a leg press or squat lift exercises. When throwing a javelin the "joints of the kinetic chain extend sequentially" (Blazevich, 2010, p. 198). This makes the javelin a throw movement rather than a push.
 
There are many technical aspects of javelin which can make it difficult to execute correctly. To encourage the athletes to use a throw movement do an experiment with them to increase understanding. Just standing on the spot get them to release the javelin using a push movement. As they are not moving they will not have all the other sequences to think about as well. Once they have done this throw measure it then repeat using a throwing motion. There distance should increase, however they may understand this, they may just find it difficult when performing the movement as a whole. To overcome this pedagogical implication the skill could be broken down and taught in sequential steps.

 
Centre of gravity

 
Your centre of gravity while throwing a javelin should be near the grip, this does not change throughout the different stages of the throw. "The better the push forward with the right leg, the greater the angle between the centre of gravity of the body and the heel of the left foot which may increase the net power of the javelin at release"(Kunz and Kaufmann, 1983, p.203). Research states that there is a positive correlation between the velocity of the centre of gravity of the body and the throwers who throw between the optimal angle of release (Kunz et al, 1983).  When teaching javelin a skill cue to encourage the correct centre of gravity being obtained could be to encourage core strength . Increased core strength will increase hip movement and increase flexibility in the back and shoulders.

Angular Velocity

"Angular velocity is the rate of angular displacement"(HyperPhysics, 2000). The angle the javelin is thrown will greatly impact the distance it travels.

Figure 6 (Blazevich, 2010, p. 26).

Figure 6 shows that if a javelin is thrown at 90° and 0° it will have a range of zero. The optimal angle for throwing a javelin is 45°, this has equal vertical and horizontal velocity and will give the maximum range (Blazevich, 2010). Generally a javelin is thrown at an angle between 30° and 36°, "the faster the javelin is thrown, the lower the trajectory will be" (Stander, 2006). Angle is something that will be impacted on through the way the javelin is being help throughout the run up, and the trunk position in the throwing motion. This may be hard for athletes to change once they have done it this way for awhile. It is best if this is taught from the beginning, however it can be changed through teaching each phase sequentially.

 

 

Figure 7 (Mackenzie, 2014)

Recovery-

The final stage of the javelin throw in the recovery phase. "The left foot remains grounded and the right leg is brought past it to halt the athlete. The amount of space needed to stop before the scratch line depends on the amount of horizontal momentum" (Healthy Living, N.D). Stoping before the line is critical, if the athlete's foot goes over the line elimination will occur.

 

The above clip shows that many professional javelin throwers fall after their throw or they put their hand on the group to help gain control. This is because they have so much forward momentum.  

4.40 - 5.30 minutes

The straight leg that is talked about in the above YouTube clip is similar to the release movement that is done in javelin. The clip states that 5 times the body weight is going through that leg as the high amount of forward momentum is being produced. Having the leg straight increases the release speed and more energy is transferred into the throw. However having the leg straight increase the chance of injury significantly and should not be done.

Equipment

The javelin's design has changed throughout the sport. The original javelin "had the centre of mass at the centre of pressure" (Engineering Sport: The Centre for Sports Engineering Research, 2012). These means that the javelin can be lifted through the air if it is angled appropriately. "As the centre of mass and centre of pressure coincided the pitching moment (how the javelin rotated during flight) completely depended on the way it was thrown" (Engineering Sport: The Centre for Sports Engineering Research, 2012). The flight path of these javelins were very uncontrolled and the nose could point either up or down in flight. Also the javelin would fall out of the sky often landing flat which  resulted in a no throw. (Engineering Sport: The Centre for Sports Engineering Research, 2012).

 
 

Figure 8 (Engineering Sport: The Centre for Sports Engineering Research, 2012)

The redesigned javelin was introduced in 1986, the centre of mass was moved forward by 40mm from where it was at the centre of pressure (Engineering Sport: The Centre for Sports Engineering Research, 2012). The tip of the javelin was also altered with it now being blunter and less aerodynamic (Engineering Sport: The Centre for Sports Engineering Research, 2012). These modifications meant that there was reduction to "the lift on the javelin, bringing down the nose of the javelin and meaning that it will stop climbing and start to descend" (Engineering Sport: The Centre for Sports Engineering Research, 2012). The point in which the nose begins to descend will happen earlier than the old javelin design meaning it will begin to descend earlier resulting in a shorter distance being thrown.

Figure 9 (Engineering Sport: The Centre for Sports Engineering Research, 2012)

Conclusion

Throwing the javelin biomechanically correct does increase the throwing distance. This is shown through looking into each biomechanical aspect and seeing how this correlates with the javelin throw. There are many skill cues that can be given to the athlete to improve their throwing technique. These will provide feedback without confusing them with the biomechanical terms and explanations. Each phase of throwing the javelin requires biomechanical principles to obtain maximum distance. Propulsive impulse is required through the force that is applied. Equal and Opposite reaction is a part of the running style, projection speed impacts the distance of travel, the throw technique using the joints of the kinetic chain extend sequentially, centre of gravity for balance and angular velocity to increase distance.

Applying biomechanical knowledge to increase the javelin throw will be transferable between other athletic events. The principles will stay the same for other throwing events with the optimum angle always being less that 45° as this has equal vertical and horizontal velocity and will give the maximum range (Blazevich, 2010). Using skill cues and catering for individual throwers will encourage changes to technique of the thrower.

Reference List

            Blazevich, A. (2010). Sports biomechanics, the basics: Optimising human performance. A&C Black

            Engineering Sport: The Centre for Sports Engineering Research, (2012). The Story of the Javelin- Bringing it Back Down to Earth. [online] Available at: http://engineeringsport.co.uk/2012/09/21/the-story-of-the-javelin-bringing-it-back-down-to-earth/ [Accessed 16 Jun. 2014].

            Healthy Living, (N.D). Stages of the javelin throw. [online] azcentral. Available at: http://www.lavic.com.au/Portals/43/Documents/Coaching%20Handouts/Javelin1.pdf [Accessed 16 Jun. 2014].

            Kunz, H. and Kaufmann, D. (1983). Cinematographical analysis of javelin throwing technique of decathletes. Brit. J. Sports Med, 17(3), pp.200-204.

            Linthorne. N. (2013) Optimum Angles of Projection in Throws and Jumps, CoachesInfo.com, University of Sydney, Australia

            Liu, H., Leigh, S. and Yu, B. (2010). Sequences of upper and lower extremity motions in javelin throwing. Journal of Sport Science, 28(13), pp.1459-1467.

            Livestrong. (2013). Physics of Javelin Throwing | LIVESTRONG.COM. [Accessed 13 June.2014], from http://www.livestrong.com/article/431055-physics-of-javelin-throwing/

            Mackenzie, B. (2014). Javelin. [online] Brianmac.co.uk. Available at: http://www.brianmac.co.uk/javelin/ [Accessed 16 Jun. 2014].

            Stander. R. (2006) Javelin Throw, Athletics Omnibus, Boland Athletics, Athletics South Africa, Houghton www.bolandathletics.com/5-13 Javelin Throw.pdf (cited 13/6/2014)

            Tongen, A. and Wunderlich, R. (N.D). Biomechanics of Running and Walking. [online] Available at: http://www.mathaware.org/mam/2010/essays/TongenWunderlichRunWalk.pdf [Accessed 13 Jun. 2014].