Introduction
A thorough understanding of the processes and
biomechanical principles will assist athletes and coaches in improving the
results. The javelin throw has many aspects which can affect the throwing
distance. These variables are both small and large scale contributing equally
to the optimal performance of the javelin throw. The following blog will
analyse some factors which contribute to the optimal performance including
grip, run up, release along with external factors such as equipment influences.
The video below is the optimal biomechanical
performance which we aim to replicate.
The technique in the above picture will now be broken down and discussed.
The
approach:
To
ensure a natural running action, the javelin is carried at head height, roughly
parallel to the ground, with the arm bent and elbow pointing forward. The use
of a relaxed grip, wrist, and shoulder allow the hips and shoulders to face
forward as the athlete reaches optimal speed. (Stander, 2006)
Step
1 and 2:
Once
optimal speed is reached; the javelin is moved over the throwing shoulder until
the arm is straight, with the palm facing upward and at shoulder height. To
ensure the approach speed is maintained it is important to rotate the shoulders
to line up with the direction of the throw while the hips remain forward.
(Stander, 2006)
Step
3:
The tip
of the javelin should be raised to the height of the athletes head, with the
point at ear level. The head should remain facing forward, watching in the
direction of the throw. (Stander, 2006)
Step
4: the drive
This
step should be long and low to the ground in preparation of the throw. The
upper body leans back to allow for the pull of the throwing arm. The dominant
foot should hit the ground heal first, slightly in front of the hip and
shoulder. The throwing arm is fully extended with a closed wrist and upward
facing palm, javelin point remains at eye level. (Stander, 2006)
Step
5:
Non-dominant
leg lands straight and flat pointing forwards, weight is transferred and
accelerates through the hips. The throwing arm is fully extended, and the free
arm remains relaxed. This finishing position is known as the power position.
(Stander, 2006)
The
power position:
-
Body
is arched
-
Head
faces direction of throw
-
Shoulders
and javelin parallel
-
High
throwing hand, palm facing upward, wrist closed
-
Non
dominant leg forward and straight
-
slightly
bent dominant leg
-
Chin
is vertically in line with right knee and toes (Stander, 2006, p.4)
The
throw:
Momentum
travels from the dominant leg up through the hips and shoulders due to the
abrupt straightening of the non-dominant leg. The hips, chest, and shoulders
rotate quickly, in a sequential motion. The throwing elbow then follows which
causes the arm to be whipped over in a rapid forward motion; releasing the fingers
causes the javelin to rotate ensuring stability during flight. (Stander, 2006)
Grip:
The
javelin should lie in the hand in the direction of which it will be thrown with
a flexible yet firm grip (along the length of palm rather than across). The
hand should be at the rear of the cord with at least one finger behind the
binding. The below diagram demonstrated three of the most common grips.
(Stander, 2006, p.1)
Run-up:
The first
phase of the javelin throw is the run up. The speed of the run up contributes
greatly to the distance the javelin may travel. The given run up area ‘should be not more than 36.50m
but not less than 30m and should be marked by two parallel lines 50mm in width
and 4m apart.’ (Stander, 2006, p. 1)
Propulsive Impulse
Propulsive Impulse is the force that is applied to
move forward and accelerate an object (Blazevich, 2012). This is important as
the speed at which an object, in this case the javelin, leaves the hand of the
thrower, immediately before release (release speed), will influence the
distance in which it travels. From these points it can be assumed that simply increasing the speed of
the run up will increase the distance the javelin may travel, however this is
not always true. Through increasing the speed of the run up the technical
aspects of the release may be compromised, therefore appropriate running
technique must be adapted. If the thrower is landing on the heal of their foot
a breaking impulse is applied to the athlete; while this will not stop the
athlete it will slow the running speed. However moving the leg backward and
downward applies a propulsive impulse. Ensuring the propulsive impulse is much
greater than the breaking impulse will generate a faster running speed. ‘The
breaking impulse is usually greater when the foot lands further in front of the
body; there is a trade-off where a small breaking force is useful but a large
force, generated when the foot lands well in front of the body’s centre of
mass, is detrimental.’ (Blazevich, 2012, p.57) Therefore the skill que
necessary when increasing the run up speed of a javelin thrower should be in
relation to foot placement. The front foot must land close to the torso opposed
to being stretched in front of the body; while the back leg must extend far
beyond the body as it provides greater time for force application (Blazevich,
2012).
(Blazevich, 2012, p. 57).
Newton’s third law - Ground reaction force
Newton’s third law states that, ‘for every action, there is an equal and
opposite reaction’ (Blazevich, 2012, p.45).
(Blazevich, 2012, p.45)
While running, we generate both vertical and
horizontal force, meanwhile the ground also exerts an equal and opposite
reaction (shown in the above figure) which allows the runner to accelerate
forwards. (Blazevich, 2012) By applying a greater force to the ground, the
force which is received back is greater, therefore providing greater
acceleration. The use of a greater force is also necessary as gravity is
constantly pushing downward, proving an initial force will result in longer
‘flight time’. As the sum of forces dictate acceleration, it is vital to apply
a large horizontal/vertical force while running; in addition lower body mass
can contribute to faster running speeds. (Blazevich, 2012)
(Tongen &
Wunderlich, n.d., p.2).
This figure demonstrates that vertical ground reaction force (VGRF) is
greater and over a shorter time span for running, compared to walking.
Therefore an additional skill cue to improve the run up speed of the thrower
should be to decrease ground-foot contact time and lower body mass, so long as
this does not adversely affect the speed of the run up or performance of the
throw.
Release
The second phase of the javelin throw
is the release. The release is very technical and involves all body parts.
Projection speed
The release speed is an
important aspect and influences the distance the javelin will travel greatly. "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). The release speed is a result of the
biomechanical influences discussed below.
Push/Throw
For an object to be released or moved there are only two ways that this
can happen. Option one is a push movement which "tends to extend all
joints in our kinetic chain simultaneously in a single movement"
(Blazevich, 2010, p. 196). Option two is a throw movement where the "joints
of the kinetic chain extend sequentially" (Blazevich, 2010, p. 198). Through
these explanations javelin is defined as being a throw movement more so than a
push movement.
As explained previously, there are many variables which can make
executing the javelin throw correctly difficult. To overcome this pedagogical implication the
skill could be broken down and taught in consecutive steps.
Centre of gravity
While throwing a javelin the athletes centre of gravity should be near
the grip, this does not change throughout the throw sequence. In 1986, the
javelin was redesigned with centre of gravity moved 4cm forward so it didn’t
coincide with the centre of pressure (Engineering Sport:
The Centre for Sports Engineering Research, 2012). The redesigned javelin introduced cord
to promote athletes to grip the centre of gravity. This is a good teaching
skill to encourage an athletes grip to be near the javelin’s centre of gravity.
Kunz et al (1983) states that there is a
positive relationship between velocity and the javelins centre of gravity.
Angular Velocity
“Angular Velocity is the rate of change in angle of the thrower”
(Blazevich, 2012, p. 16). Using the torso and dominant arm, the thrower can
increase their angular velocity to then increase the speed of release (Dearmond
& Semenick, 1989). During the run up stage, the athlete’s shoulders are
almost parallel to the throwing section, this provides enough rotational
movement to maximise and increase their angular velocity (Navarro,
1998). The dominant arm is also
pulled back to the maximum external rotation of the upper arm in the run up to
create an arched position. This arched position also known as the power
position is the maximum angle that can be reached to increase the rate of
change for the thrower.
Angle of Release
The angle the javelin is thrown will significantly influence the
distance it travels. To achieve a
high velocity at the release point of the javelin, a throw-like movement
pattern is necessary. The video below demonstrates the correct technique. The
run-up provides momentum to the thrower which is then passed to the upper body
and arms. In the final stage of the throw motion, momentum is transferred to
the proximal segments of the throwing arm which allows the transfer of momentum
along the arm; resulting in a high velocity of the javelin. In combination with transfer of momentum, the
use of elastic energy is important in increasing the velocity of the throw. Having the throwing arm bent to
begin with allows the tendons in the arm to use their elasticity to recoil the
arm into a throw-like movement at a fast pace. This throw movement uses the
simultaneous joints involved to cumulate their forces and generate a high
overall force which will result in a fast paced throw. These simultaneous joint
rotations will also result in a straight line movement, resulting in the throw
being more accurate and travel further. (Blazevich, 2012). The below video shows a mash up of many professional javelin throwers that use the optimal biomechanical performance for throwing a javelin. In this video you can see that they all have a similar angle of release.
(Blazevich, 2010, p. 26).
If the javelin is thrown at the optimal angle of 45° as seen in the
figure above, the javelin is more likely to travel a further distance. Throwing
at a 45° angle provides the javelin an equal vertical and horizontal velocity
which will give it the maximum range (Blazevich, 2010). As seen in the table
below, as the angle increases the further the javelin flies, but it is
understood that an angle greater than 45° is disadvantageous (World of Javelin,
2010).
Release Angle (°)
|
Distance (m)
|
||
30
|
63.94
|
65.37
|
58.37
|
31
|
65.08
|
66.49
|
59.45
|
32
|
66.16
|
67.55
|
60.47
|
33
|
67.18
|
68.55
|
61.44
|
34
|
68.13
|
69.49
|
62.35
|
35
|
69.02
|
70.36
|
63.22
|
36
|
69.85
|
71.16
|
64.02
|
37
|
70.61
|
71.9
|
64.77
|
38
|
71.3
|
72.56
|
65.46
|
39
|
71.91
|
73.15
|
66.09
|
40
|
72.45
|
73.67
|
66.66
|
41
|
72.91
|
74.11
|
67.16
|
42
|
73.3
|
74.46
|
67.6
|
Attack Angle (°)
|
0
|
5
|
5
|
Wind
|
No wind
|
No wind
|
2 m/s head wind
|
Constant: Javelin
= Tailwind, Weight = 800g, No Wind, Release Velocity = 26 m/s
|
|||
Equipment
As stated above, the
javelin has been redesigned and was introduced in 1986. The previous javelin
design was often described as having an uncontrollable flight path often
resulting in a flat land (Engineering Sport: The Centre for Sports
Engineering Research, 2012).
The javelin that was introduced in 1986 had the centre of mass moved forward by 4cm as seen in the below picture and the tip was
altered to be less aerodynamic (Engineering Sport: The Centre for Sports
Engineering Research, 2012). These modifications allowed the athlete to control
the flight path of the javelin more accurately and the javelin would begin to
descend earlier (Engineering Sport: The Centre for Sports Engineering Research,
2012). The javelin descending earlier will result in shorter distances being
thrown, this was modified because the javelin distances were beginning to
become longer than many athletic stadiums can accommodate (Engineering Sport:
The Centre for Sports Engineering Research, 2012).
(Engineering Sport: The Centre for Sports Engineering Research, 2012)
The answer:
The javelin throw can be maximised by applying correct
biomechanical technique to all aspects and stages of the throw. A thorough
understanding of each of the phases of the javelin throw and their individual
importance to the overall performance will assist throwers in developing there
technique and performance. The ability to evaluate and change each of the
phases without affecting another will result in a biomechanically correct
performance. To create a great foundation for the javelin throw, the athlete
must first understand the importance of speed throughout the approach phase and
how to maximise their running speed. Ultimately, an increase in running speed,
while maintaining all other variables, will increase the distance of the throw.
The distance the javelin travels can also be maximised through understanding of
the optimal release angle. Through implementing a throw-like movement pattern,
the force generated throughout the run up is transferred to the javelin
(transfer of momentum) which maximises the velocity of the throw. The optimal
release angle of the javelin is understood to be 45°, as
this provides equal vertical and horizontal velocity, resulting in the maximum
range (Blazevich, 2012). Athletes also need to understand the biomechanical
reasoning behind this optimal release angle and disadvantages associated with
greater angles.
How can we use this?
Through
understanding the biomechanical principals of a given sport or sports skill,
both coaches and athlete can develop and constantly analyse the best technique
which is biomechanically possible for the athlete. The biomechanical principals
utilised in a particular sport are often transferable to a number of others.
Biomechanical understanding of the Javelin throw is transferable to many other
athletic events and sports which implement projectile motion. The basic
principles used to maximise the distance of the javelin throw apply to many other
throwing events such as discuss and shotput. The speed at which an object is
released will determine the distance in which it will travel, not only in
javelin but shotput and discuss also. Similarly the optimal release angle of
less than 45° in the javelin throw is also relevant to other
throwing events as it ensures equal vertical and horizontal velocity; giving
the maximum range to the object. Biomechanical understanding of the run up
phase of the javelin throw is also transferable to many other sports, for
example the cricket run up/bowling action. Athletes who have a thorough biomechanical
understanding within their chosen sport will possess greater skills within the
given sport and have the ability to further enhance their performance.
References
Blazevich, A. (2010). Sports biomechanics, the basics:
Optimising human performance. A&C Black
Blazevich, A. J. (2012). Sports biomechanics: the basics:
optimising human performance. A&C Black.
Dearmond,
R. and Semenick, D. (1989). SPORTS PERFORMANCE SERIES: The javelin throw: a
kinesiological analysis with recommendations for strength and conditioning
programming. National Strength & Conditioning Association Journal,
11(2), p.4.
Engineering
Sport: The Centre for Sports Engineering Research,. (2012). The Story of the
Javelin- Bringing it Back Down to Earth. Retrieved 16 June 2015, from http://engineeringsport.co.uk/2012/09/21/the-story-of-the-javelin-bringing-it-back-down-to-earth/
Javelin,
J. (2010). Biomechanics: Angle of release | World of Javelin. Worldofjavelin.com.
Retrieved 16 June 2015, from http://www.worldofjavelin.com/posts/biomechanics-angle-of-release/
Navarro, e., Cabrero, o., Vizcaíno, f., &
Vera, p. (1998). A three-dimensional analysis of the angular velocities of
segments in javelin throwing. In isbs-conference
proceedings archive (vol. 1,
no. 1).
Stander.
R. (2006) Javelin Throw, Athletics Omnibus, Boland Athletics, Athletics South
Africa, Houghton. Retrieved 16 June 2015, from www.bolandathletics.com/5-13
Javelin Throw.pdf
The
Conversation,. (2014). Science of the spear: biomechanics of a javelin throw.
Retrieved 16 June 2015, from http://theconversation.com/science-of-the-spear-biomechanics-of-a-javelin-throw-29782
Tongen,
A. and Wunderlich, R. (N.D). Biomechanics
of Running and Walking. Retrieved 18
June 2015, from
http://www.mathaware.org/mam/2010/essays/TongenWunderlichRunWalk.pdf
Vallela,
R. (2012). Biomechanics in Javelin Thrower (1st ed.). Finland: Kihu -
Research Institute for Olympic Sports. Retrieved 16 June, from http://www.kihu.fi/tuotostiedostot/julkinen/2012_val_biomechani_sel72_42228.pdf
