HLPE3531 Skill
Acquisition and Biomechanics for Physical Educators
This blog has been designed to biomechanically break down
the discus throw and outline how the biomechanics of a person can influence the
performance of the throw.
This blog has been created by Jacob Ellidge
What
biomechanical factors contribute to peak performance in a discus throw?
Discus is a very technical sport that requires a person to
rotate their body to release the discus trying to throw it as fair as they can.
This skill requires the influences of many different biomechanical factors to
allow the performance of a discus to occur successfully. Watkins describes how
important the understanding of biomechanics is when trying to understand the
way a human body moves when participating in variety of different physical
movements (2014). As previously stated, Discus is a very technical movement
pattern, but when it is broken down into smaller segments, the biomechanical
analysis of the throw can help to determine how to create a successful performance.
The biomechanical factors that the throw will be broken into
include:
The Kinetic Chain - Push Like vs Throw Like movement patterns
Newtons Laws
Length of Arm
Angular Velocity
Optimum Angle of Trajectory
These biomechanical factors will be analysed throughout the
blog to try and determine how they influence the overall performance of a
discus throw.
How does the kinetic chain influence the performance of a discus throw? How do Newtons Laws affect the performance of a discus
throw?
The kinetic chain has two types of movement patterns,
including the push-like movement pattern and the throw-like movement pattern
(Blazevich, 2010a). The push-like movement pattern involves the extension of all
joints to occur simultaneously in one movement, such as a shot put or a dart
throw (Blazevich, 2010a). When looking at a discus throw in Figure 1, the body
does not seem to move in one single motion, it tends to wind up, rotate and
then release the discus.
This motion seen in the discus throw is a sequential
movement of the joints, known as the throw-like movement pattern (Blavevich,
2010a). The throw-like movement allows for increased speed created throughout
the movement pattern allowing this speed to be transferred into the discus. The
later part of the extension during the throw allows the velocity to increase
significantly, resulting in a higher velocity when the discus is released
(Blazevich, 2010a). If you were to push
the discus with all joints moving at the same time the discus would travel nowhere
near as fair. Therefore the throw-like movement pattern is an essential part of
the discus to perform at a peak level.
Within the movement of a discus throw the base of support
must be solid, as the performer is rotating on an axis, as seen in figure 1. The
performer starts facing away from where they are going to throw the discus
allowing for rotation to occur. During this rotation of the torso the grounded
knee bends slightly, producing an upwards motion upon release. During this
upward motion the body is applying a force through their grounded leg into the
area they are standing. Newtons third law of motion states that ‘for every
action, there is an equal and opposite reaction’, promoting the thought that the
force the body applies into the ground will react through their body
(Blazevich, 2010b, p. 45). As the performer extends through the movement pattern
the upwards motion will allow the force produced through in the legs to move
through the arm and into the release of the discus. If the throw-like movement
is performed in a manner of smooth flowing, sequential movements, then the
force created will not be lost and the performance shall increase.
The greatest advantage a throw-like movement has over the
push-like movement is that it generates a lot more speed due to the muscle movement
within the body (Blazevich, 2010a). Therefore the higher speed in the discus at
point of release allows for the discus to travel further.
What influence does
arm lengths have on the distance a discus is thrown? How does angular velocity
influence a discus throw? Is it more or less important than the angular
velocity of the arm in determining the release speed?
Discus throwing is a performance of high speed movements within
a limited space, with the final release speed playing are primary role in the
distance the discus is thrown (Dai, et al., 2013).
According research the release of speed is the most critical factor in relation
to the length of a throw (Leigh, Gross, Li,
& Yu, 2008; Bartlett, 1992; Hay, Yu, 1995). It is clear the release
speed is critical within the discus through in order to reach peak performance.
Blazevich defines the release speed as being ‘equal to the speed of the discus immediately
before release’ which is created by the speed of the performer spinning on
their vertical axis with the arm in an outstretched position (2010, p. 16). In Figure
1, the body is shown to spin around the vertical axis of the body. If the
performer creates a fast spin then the discus will be travelling at a higher
speed at the point of release. Therefore the faster the spin is the further the
discus will travel, showing one of the goals of the discus throwing technique
to influence the throwing distance, is to obtain maximum speed (Yu, Broker, & Silvester, 2002) .
The way to create this increase speed of release is more
complicated than just spinning faster. Angular Velocity is, as Blazevich
defines, ‘simply the rate of change in angle of the thrower’ (Blazevich, 2010c,
p.16). To calculate angular velocity the equation (w)= O.t^-1 is used, where is O the symbol for angular displacement
(Blazevich, 2010, p. 17,18). To be able to calculate the release speed of a
discus two things must be known, firstly the angular velocity of the arm and
secondly the length of the arm. It is know that if the arm is swinging faster,
then the discus will also be moving faster. By increasing the distance of the
centre of rotation, this allows for the increase in speed, seen in Figure 2 (Blazevich,
2010c).
Figure
2: Axis of Rotation Source: Blazevich, 2010c
This idea can be transferred to discus,
if the baseball bat was the arm of the person. Therefore by increase the arm
length there will be a greater speed created allowing for a further throw (Blazevich,
2010c). Due to there being little a human can do to increase the arm a person
with a longer arm should have an advantage over a shorter armed person, unless
the angular velocity of the smaller armed person is incredibly better than the longer
armed person. I believe that both the angular velocity
of the arm and the length of the arm are very important. Performers with longer
arms can need to focus on producing force to get their arms moving faster to
create a larger speed of release, while performers with shorter arms must focus
on strategies to get their angular velocity to increase speed of release (Blavevich,
2010c).
What
is the optimum height and angle release for the trajectory of a discus throw,
to cause a throw of maximum distance?
Trajectory is influenced by three factors, the projection
speed, the projection angle and the relative height of release of the
projection. ‘The ultimate goal of the technique in each
throwing event is to obtain the maximum speed and optimum height and angle of
release, which are key factors influencing the throwing distance’ (Yu, Broker, & Silvester, 2002) . The evidence of how
critical the optimum height of release and angle of release is to a discus throw
shows that these factors have a clear link to reaching peak performance. Leigh et al. describe the height of release as
being the vertical distance of from the ground to the point of release of the
discus (2008), with research evidence showing the optimum height of release of
the discus at shoulder height (Leigh, Gross, Li,
& Yu, 2008; Gregor, Whiting, and McCoy, 1985). By allowing the height of
release to be at shoulder height the ability to create the largest speed of
release can occur, therefore sending the discus further in distance travelled (Leigh,
Gross, Li, & Yu, 2008) .
The anlge of release is
determined by ‘the angle between the horizontal and vertical velocity vectors
at the point of release’ and is specfic to each performer as it is associated
to the speed of release (Leigh, Gross, Li, & Yu, 2008; Leigh, Hui, Hubbard,
& Yu, 2010). The optimal release angle for a discus thrower is quiet
individualsied but studies have shown the range to be within 35 to 45 degrees (Leigh, Hui,
Hubbard, & Yu, 2010) .
What have we learnt
about the different biomechanical factors that contribute to peak performance
in a discus throw?
Through this
blog it is clear that the throw-like
movement pattern of the kinetic chain contributes largely in the performance of
a discus throw. This movement allows the sequential motion of the joints to
create the greatest release speed. Newton’s third law of motion allows forces
to be generated through the reaction to the ground allow for increased force transferred
into the discus. Angular motion and arm length combined together to allow for
the release speed to be as large as possible. With increase angular motion and
the longest possible arm length the release speed will be at its greatest,
allowing for peak performance to occur. Finally the optimum height release is
said to be at shoulder height at the point where the discus is leaving the hand,
to allow for the discus to reach the highest release speed and the optimum
angle of release to be created. The optimum angle of release is individual but
is aimed to be between 35 and 45 degrees.
This blog has analysed the discus throw through a
biomechanical approach, and hopefully allows readers to develop their discus
through to reach their peak level of performance.
Reference List
Bartlett, R. M. (1992). The biomechanics of the
discus throw. A review. Journal of Sports Science, 10, 467-510.
Blazevich, A. (2010a). The Kinetic Chain. In Sports
Biomechanics: The Basics (pp. 195-205). London: A&C Black Publishers.
Blazevich, A. (2010b). Newton's Laws. In Sports
Biomechanics: The Basics (pp. 43-50). London: A&C Black Publishers.
Blazevich, A. (2010c). Angular Position, Velocity and
Acceleration. In Sports Biomechanics: The Basics (pp. 15-23). London:
A&C Black Publishers.
Dai, B., Leigh, S., Li, H., Mercer, V., & Yu, B.
(2013). The relationships between technique variability and performance in
discus throwing. Journal of Sports Science, 31(2), 219-228.
Gregor, R. V., Whiting, W. C., & McCoy, R.
(1985). Kinematic analysis of Olympic discus throws. International Journal
of Sports Biomechanics, 1, 131-138.
Hay, J. G., & Yu, B. (1995). Critical
Characteristics of technique in throwing the discus. Journal of Sports
Science, 13, 125-140.
Leigh, S., Gross, M., Li, L., & Yu, B. (2008).
The relationship between discus throwing performance and combinations of
selected technical parameters. Sports Biomechanics, 7(2), 173-193.
Leigh, S., Hui, L., Hubbard, M., & Yu, B. (2010).
Individualized optimal release angles in discus throwing. Journal of
Biomechanics, 43, 540-545.
PYKKA. (n.d.). Fundamental Techniques: Discus
Throw. Retrieved from Virtual Coach:
http://emulate.aponline.gov.in/PYKKA/UserInterface/VirtualCoach/VC/Athletics/Fundamental%20Techniques/dt.html
Watkins, J. (2014). Fundamental Biomechanics of
Sport and Exercise. New York, NY: Hoboken Taylor and Francis.
Yu, B., Broker, J., & Silvester, J. L. (2002).
Athletics. Sports Biomechanics, 1(1), 25-45.
No comments:
Post a Comment