Biomechanics of the Football Throw 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. 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.

Football 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.

4 Phases of the Football Throw Early Cocking Late Cocking Acceleration Follow Through

Early Cocking Planting of the quarterback’s rear foot Maximal shoulder abduction Internal rotation Ends when the ball is at shoulder height with the elbow pointing back

Late Cocking Ball at shoulder height moving upward External rotation of shoulder Ball posterior to the head

Acceleration Full rotation of shoulders Snapping of the wrist Trunk and leg muscles send power to arms. Flexion to extension of the elbow – key!

Follow Through Arm in horizontal position Hand pronated, shoulder abducted, wrist flexed

Muscles Activated during Throw

Muscle Groups II Rotator Cuff muscles active throughout entire motion (Stabilizers) Subscapularis and Pecs active most during acceleration and follow through (accelerators)

The 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.

Personal (Imperfect) Demonstration

Ball Movement  Release  Acceleration phase begins

Calculations 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

Elbow 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

Comparison to Baseball In baseball… Greater rotational velocities of arm/trunk More 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

Comparison 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

Common Injuries Most common injury: Acromioclavicular Sprain 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

Injuries II UCL Injury Tear in the ulnar collateral ligament (connects ulna to humerus): As a result of overload and too much torque supplied by the elbow.

Ball 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

Summary 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)

Future 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

References "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 Medicine36.9 (2008): 1789-798. Print.

Questions?