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Biomechanical Analysis of a Discus Throw

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by Molly Pesarchick on 10 December 2010

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Transcript of Biomechanical Analysis of a Discus Throw

Biomechanical Analysis of a Discus Throw

By: Molly Pesarchick, Caitlin Schellin, & Lindsey Guth Basics of Discus:
Discus throwing is a track and field event.
The basic objective of the event is to see which athlete can throw their discus further using proper technique.
Discus has been a part of the modern Summer Olympic Games since the first Olympiad in 1896.
Women’s discus was not added to the Olympic games until 1928. Critical Instances and Critical Phases of the Throw:
The discus throw is broken down into 6 critical instances throughout the movement so that it is easier to learn/analyze.
These instances help break the movement into its 5 phases. Disc Regulation:
Men- 2kg and a diameter of 220mm.
Women- 1kg and a diameter of 181mm.
High Schools: Boys- 1.616kg, Girls- 1kg
Critical Instance One: Maximum Back Swing
Loading of the core muscles and provides potential initial torque for the movement
Stability is increased by extending the arms out to the sides and bending the knees. Critical Instance Two: Right Foot Take Off
Beginning of the path across the ring
All of the throwers weight is on the left leg and he/she begins to rotate
Core remains coiled
Arms fully extended to provide counterbalance for the reduced base of support The phase between the first two critical instances is referred to as the initial double-support phase. The increase in speed of the discus during this phase is one of the factors credited with an increase in total distance of the throw. (Yu, 2002) Critical Instance Three: Left Foot Take-Off
The thrower uses his or her left foot to push off and rotate their body even further.
The thrower should maintain a fully coiled core and should keep his/her arm extended to the rear. Both of these aspects are crucial for building up kinetic and potential energy.
Vertical ground reaction impulse on the left foot is directly correlated with distance - Yu, Broker, and Silvester (2002) The phase between the second and third critical instances is referred to as the Single Support Phase. This is in reference to the thrower having only one leg worth of support throughout this part of the motion. Critical Instance Four: Right-Foot Touchdown
The body accelerates during this instance and travels closer to the front of the ring
Once the right foot lands it plants and pivots but remains in the same place until the final release
The torso of the body is leaned forward and the thrower compensates by bending the knees and lowering his/her center of gravity The Phase between the third and fourth critical instances is referred to as the Flight Phase. The speed obtained during this phase is crucial to the total distance traveled due to the momentum stored up in the body before the release of the disc. Critical Instance Five: Left-Foot Touchdown
Places the thrower in his/her final position at the front of the ring.
The throwers body should be perpendicular with the front of the ring.
Upper body should still be facing the back of the ring waiting to unleash all of the kinetic energy and torque stored up in the body
The knees should be bent to load the muscles for final delivery.
The phase between the fourth and fifth critical instances is referred to as the Second Double Support Phase. It is thought that this is the most important time to increase vertical velocity, since it is the phase that immediately precedes the release. -Leigh & Yu (2007) Critical Instance Six: The Release
During the release, the thrower has uses all of his/her stored up momentum and rotates the body toward the front, uncoiling the body, hips first, then the mid-torso, the left elbow, then the chest, and finally the throwing arm. The phase between the fifth and sixth critical instances is referred to as the Delivery Phase. This is the final motion where the disc is sent into flight. After the release of the disc the thrower will often spin/hop in a circle on his/her left leg to try to remain in the ring.
This is an effort to control the leftover momentum after release.
The throw is disqualitfied if he/she steps outside of the ring. Release Phase:
Separation angles
Hip-shoulder
Shoulder-arm
Horizontal release velocity
Impulse-momentum: Ft= mv Release Phase Cont:
Trunk forward-backward tilt
Vertical Velocity
Release angle

Release angle
Release speed
Aerodynamic distance
Optimal release angle Stretch Reflex:
Contraction to resist a stretch detected by the muscle spindle proprioceptor
More force Rules and Regulations:
Discus Cage:
shape of the cage has to be a 'U'
width of the mouth of the cage has to be 6 m and around 7 m in front of the middle of the throwing circle
height of the netting panels or draped netting at the lowest point has to be a minimum 4 m
circle is 2.5 m in diameter Rules and Regulations Cont.
Athlete must stand in the circle
Top of the rim cannot be touched, the inner part of the rim can be touched
Athlete cannot touch the ground outside the circle during the throw
Prior to the disk hitting the ground, the athlete cannot go out of the circle
Fouls Muscles Involved:
Discus throw encompasses every part of the body
Muscles include: Arm, abdomen, back and legs
biceps
triceps
deltoids
pectoralis
latissimus dorsi
subscapularis
teres major
erector spinae
trapezius
adductor muscles Injury:
knee
elbow
rotator cuff of the shoulder
preventable measures Training:

full body weight-training program. Strengthening your upper body muscles will improve your throwing abilities.
Your core and lower back muscles are crucial for generating power. The action requires you to generate power from your legs, through the core, and use the power with your upper body for the release and throw.
Add power training after building a strength foundation through weight training. Training Continued:
Plyometric drills will improve power in your legs.
Master the technique involved in the throwing motion.
Use drills for power and glide positions. Start with grip and release training.
Master the standing throw, then work on the spin.Visualization training involves the use of mental imagery. Mental training is believed to strengthen your performance and overcome challenges. Center of mass:
the mean location of all the mass in a system
crucial for maintaining one’s balance.
If the athlete is off balance then the outcome of the throw will not produce its optimal distance. Momentum:
The 2.5-meter distance across the throwing circle is a run-up area wherein throwers are allowed to develop as much energy or momentum as possible.
momentum-developing techniques as the discus throw begins:
     1. Body mass movement from the right leg to the left leg.
     2. Push off of the right leg just before pickup (minimal force).
     3. Left foot/leg pulling action as it pulls the body left at the start of the throw.
     4. Sweeping left arm.
     5. Body lean or moving the line of gravity beyond the base of support.
     6. Sweeping right leg.
     7. Thrust of the left leg and foot.
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