Varun Patel BIOL438 Professor Rome Questions What are the kinematics of a football throw Does the elbow or wrist have greater end velocity I will be analyzing physical quantities such as velocity acceleration torque and force generated during a football throw ID: 934918
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Slide1
Biomechanics of the Football Throw
Varun PatelBIOL438Professor Rome
Slide2Questions
What are the kinematics of a football throw (Does the elbow or wrist have greater end velocity)?I will be analyzing physical quantities such as velocity, acceleration, torque and force generated during a football throw.
Most of these factors are essential to throwing the perfect spiral.
How does football throw compare with a baseball throw?
We’ll take a deep look into the football throw and
compare that with the baseball pitch.
How does my ball velocity compare with professionals?
Surely, professionals have greater control of their body movement and are able to rotate body parts more rapidly to generate high velocities
Some of it has to do with aerodynamics and ball spin.
Slide3Football Throw Fundamentals
Throw the ball in a half-circle motion to increase centrifugal force on the ball.Rotation of the shoulders will generate torque to speed up the ball.
Ideal release point is ¾ way through the acceleration phase
Roll your fingertips off as you release the ball – index finger should be the last to touch the ball.
Arms must form close to 90 degree angle.
Slide44 Phases of the Football Throw
Early CockingLate CockingAccelerationFollow Through
Slide5Early Cocking
Planting of the quarterback’s rear footMaximal shoulder abductionInternal rotation
Ends when the ball is at shoulder height with the elbow pointing back
Slide6Late Cocking
Ball at shoulder height moving upwardExternal rotation of shoulderBall posterior to the head
Slide7Acceleration
Full rotation of shouldersSnapping of the wristTrunk and leg muscles send power to arms.
Flexion to extension of the elbow – key!
Slide8Follow Through
Arm in horizontal positionHand pronated, shoulder abducted, wrist flexed
Slide9Muscles Activated during Throw
Slide10Muscle Groups II
Rotator Cuff muscles active throughout entire motion (Stabilizers)
Subscapularis
and Pecs active most during acceleration and follow through (accelerators)
Slide11The Role of Joints
Elbow produces valgus torque– caused by upper torso movement and shoulder rotation – helps accelerate the ball. Too much torque (overload) can result in serious injuries.
Glenohumeral
joint – ball and socket joint connecting scapula and
humerus
. Plays a role in arm cocking (in preparation for acceleration). More flexible joints allow greater range of motion.
Slide12Personal (Imperfect) Demonstration
Slide13Ball Movement
Release
Acceleration phase begins
Slide14Calculations
Assumptions: constant acceleration, no air resistance or friction, force acting perpendicular to moment arm.
Y-velocity of ball = 2.1
m/s
X-velocity of ball = 9.7
m/s
Total velocity of ball upon release
= 9.92
m/s
Time of acceleration phase = 0.45 seconds
Force on the ball = ma = (.51 kg)(22.04 m/s^2) =
11.24 N
KE at release = (½)mv^2 = (½)(.51 kg)(9.92 m/s)^2 =
25.09 J
Change in PE =
mgh
= (.51 kg)(9.8 m/s^2)(.23
m
) = 1.15 J
Power = Fv = (11.24 N)(9.92
m/s
) = 111.5 J/
s
Work done = Change in KE + PE =
26.24 J
Ball momentum after release =
mv
= (.51 kg)(9.92
m/s
) = 5.06 kg*
m/s
Torque on the ball = Fr = (11.24 N)(.304
m
) =
3.42 N*
m
Slide15Elbow and Wrist Movement
Wrist reaches a higher speed than elbows
The wrist and ball are the end products of the rotational and linear energy provided from the trunks to the upper body
Wrist has a longer range of motion and more time to accelerate
Elbow needs to generate torque (more-so than speed) to propel the wrist and ball forward
Top wrist speed = 5.1
m/s
Top elbow speed = 3.3
m/s
Elbow
Wrist
Slide16Comparison to Baseball
In baseball…Greater rotational velocities of arm/trunkMore elbow extension necessary.
Higher shoulder rotation angular velocity
Faster kinematics (more force on the ball, faster velocity, greater power relative to previous calculations)
In football…
Rotate shoulders sooner to generate more power
Stand more erect – limits the contribution of lower body
Greater elbow flexion to compensate for lower speeds
Slide17Comparison to Professionals
QB
Average Speed
of Throw
Brett
Farve
66 mph
John Elway
61 mph
Tom Brady
70 mph
Me
22 mph
Why…?
NFL
QB’s
have greater rotational velocity and transfer of momentum
Better hand and foot placements
Can throw better spirals
Slide18Common Injuries
Common Injuries include…
Rotator cuff contusion
Shoulder dislocation
Sternoclavicular
joint separation
Most common injury:
Acromioclavicular
Sprain
Sprain of the AC ligament (intact)
Disruption of AC ligament
Slide19Injuries II
Tear in the
ulnar
collateral ligament (connects ulna to
humerus
):
As a result of overload and too much torque supplied by the elbow.
UCL Injury
Slide20Ball Spin and Aerodynamics
QB must balance forward momentum of ball with forces of gravity and drag.Forces of wind produce a torque that counterbalances gravity – keeps the ball in the air. This torque acts perpendicular to the direction of angular momentum
Wobble occurs as ball spins slightly off axis
Slide21Summary of Findings
What are the kinematics of a football throw?Ball experiences almost 11.2 N of force and I do approximately 26 J of work.
Elbow velocity is slower than wrist and ball velocity
How does a football throw compare to a baseball throw?
Baseball throw has greater rotational velocity and greater elbow extension.
How does my throw compare to that of professionals
Professional quarterbacks can throw at speeds 3x than mine
This is because they are able to better rotate their bodies and impart greater energy to the ball (along with spin)
Slide22Future Studies on Football Throws
Is the speed of a football throw more dependent on technique or arm/shoulder strength?Ex: Bodybuilder with no football experience vs. scrawny high school
QB with
years of experience
Does finger placement affect the ultimate speed of the ball?
Ex: How far the fingers are spaced out
What are the best ways to prevent injuries that quarterbacks often suffer?
Ex: Stretching, better padding, etc
Research Methods
Electromyography to detect muscle recruitment
3D imaging software
Slide23References
"Baseball vs. Football." American Sports Medicine Institute
. Web. 10 Apr. 2012. <
http://www.asmi.org/asmiweb/research/usedarticles/baseballvsfootball.htm
>.
Fleisig
, G., and R. Escamilla. "Biomechanics of the Elbow in the Throwing
Athlete."
Operative
Techniques in Sports Medicine
4.2 (1996): 62-68. Print.
Garrett, William E., and Donald T.
Kirkendall
.
Exercise and Sport Science
. Philadelphia: Lippincott Williams & Wilkins, 2000. Print.
Kelly, B. T. "Shoulder Injuries to Quarterbacks in the National Football League." American Journal of Sports Medicine 32.2 (2004): 328-31. Print.
Kibler
, W. B., A. D.
Sciascia
, T. L.
Uhl
, N.
Tambay
, and T. Cunningham. "
Electromyographic
Analysis of Specific Exercises for Scapular Control in Early Phases of Shoulder Rehabilitation."
The American Journal of Sports Medicine
36.9 (2008): 1789-798. Print.
Slide24Questions?