Biomechanics of a Pull in Ultimate Shannon Tsai

Biomechanics of a Pull in Ultimate Shannon Tsai Professor Rome Spring 2012

Types of throws in Ultimate “Normal” throws �Backhand �Forehand- “flick” �Thumber �Push pass �Pull Inverted Throws �Hammer �Scoober

Research Questions 1. How does each body component contribute to generating energy for the pull? a) Which component contributes the most work/energy to the pull? 2. How can you increase the distance of a pull? a) b) How do you increase the spin on the disc? How do you increase the release velocity? 3. What is the energy distribution for the pull? a) How much is going into rotational energy vs. translational?

Flight of the Frisbee �Two main principles: 1) Aerodynamic lift 2) Angular momentum for stability �Bernoulli’s principle: The pressure within a fluid decreases as the its velocity increases �Therefore, as long as v 1 > v 2, we can generate lift �These requirements are maintained as long as the frisbee stays flat and has translational KE F

How do we get distance? 1. Increase release velocity 2. Increase Lift: disc will stay afloat and continue to travel further FL = ½ρv 2 Ac. L Must overcome gravitational force: Fg = mg 3. Increase angular momentum � Reduces drag on disc due to wobble � Maintains disc in stable form to maximize lift, allowing for longer hang time

Biomechanics of the Pull �Main components: torso, shoulder, elbow, wrist �Three stages: Large windup phase 2. Power throw 3. Follow through 1. �Power throw follows a kinetic chain

The Pull

Phases of the Power Throw 1. Full wind-up- twisted torso, bent elbows, 2. 3. 4. 5. shoulder extended across the body Torso unfurls Shoulder swings around Elbow is brought into the plane of the shoulder Forearm swings around to fully extend arm, disc is released

The Kinetic Chain �Each motion builds on the previous- translation of velocity from one joint to the next �Generation of high velocity at end-point accomplished by the acceleration and deceleration of adjoining links �Effective transfer is achieved by tightening muscles How does each component contribute to the pull? �Look at work generated by each link in the chain

Velocity of muscle during pull

Some Calculations Muscles � Work = KE of muscle at release � KE = ½ mv 2 � Mass of segment (m) = mtotal * body segment proportion � mtotal = 50 kg � v = velocity when a = 0 � Power= Force * velocity � Force= m * acceleration Peak Body Velocity segment (m/s) proportion Disc � Mass of disc (m) =. 175 kg � Radius of disc (r) =. 273 m � Rotational velocity (ω) = 71. 4 rad/s � Translational velocity (v) = 17. 4 m/s � Ketranslational = ½ mv 2 = 26. 5 J � KErotational = ½ Iω2 = 4. 2 J 2 Kinetic I = ½ mr Acceleratio Forc Power Energy (J) n (m/s 2) e (N) (W) Torso 3. 5 . 497 152. 2 30. 2 750. 2625. 3 1 Should er 4. 1 . 028 11. 8 67. 6 94. 6 388. 0

Work Generated �Data only tells you how much energy is coming out from each component; does not tell you how much work each component is doing �Need to look at how much energy is comes out from each part and extrapolate information from there to know how much each part is actually contributing

Wrist Only Frisbee (at release) �Translational velocity: 4. 6 m/s �Angular velocity: 35. 7 rad/s �Translational KE: 1. 82 J �Rotational KE: 1. 04 J Wrist Peak Velocity (m/s) Body segment proportion Kinetic Energy (J) 3. 22 . 006 2. 43 Acceleratio Forc n (m/s 2) e (N) 45. 0 21. 4 Power (W) 68. 5

Wrist + Elbow Frisbee (at release) �Translational velocity: 7. 6 m/s �Angular velocity: 38. 3 rad/s �Translational KE: 5. 054 J Peak Velocity (m/s) Body segment proportion Kinetic Acceleratio Forc Power Energy n (m/s 2) KE: e (N) 1. 2 J (W) �Rotational (J) Elbow 6. 30 . 022 1. 55 38. 5 42. 4 71. 2 Wrist 1. 68 . 006 9. 42 75. 7 35. 9 226. 5

Shoulder + Elbow + Wrist Frisbee (at release) �Translational velocity: 10. 5 m/s �Angular velocity: 60. 4 rad/s �Translational KE: 9. 70 J Peak Velocity (m/s) Body segment proportion Kinetic Acceleratio Forc �Rotational KE: Energy n (m/s 2) e (N) (J) Power 2. 97 J (W) Should er . 83 . 028 11. 8 32. 0 44. 8 37. 2 Elbow 2. 24 . 022 25. 4 38. 5 59. 2 132. 4

Putting it All Together Wrist + Elbow + Shoulder Full Pull From Wrist From Disc Kinetic Power Translational Rotational Energy (J) (W) KE (J) 2. 43 68. 5 1. 82 1. 04 9. 42 226. 5 5. 05 1. 2 14. 3 40. 8 293. 2 689. 7 26. 5 2. 97 4. 2 �See a dip in the velocity vs. time curve after the elbow snap �Lots of translational KE added from adding elbow, but little rotational energy is added �Shoulder does not generate very much power, but adds a lot to rotational KE �Large increase in overall power and KE from

Possible Error �Do not take into account torque/rotational motion � 3 D motion, but tracking is in 2 D �Hard to isolate specific components of the kinetic chain �Inconsistent technique

Conclusions 1. How does each body component contribute to generating energy for the pull? a) a) Which component contributes the most work/energy to the pull? Torso generates the most energy/power, but very inefficient Which component contributes the least? Shoulder contributes the least 2. What is the energy distribution for the pull? a) How much is going into rotational energy vs. translational? ~1/6 of energy is rotational energy. To make disc go further, translational KE is still the bigger contributor and most important aspect

Conclusions (cont. ) 3. How can you increase the distance of a pull? a) How do you increase the spin on the disc? Increase wrist snap, Fact the wrist snaps BEFORE release is significant- wrist snap is where all of the transfer of rotational KE must occur. a) How do you increase the release velocity? Increase elbow snap, Snapping at elbow transfers translational KE to the disc- dip in velocity vs. time graph Both of these depend on energy transfer from previous component of the kinetic chain. Lots of inefficiency in energy transfer from core to shoulder

Future Studies �Take shot from above to get a better measure of rotation and torque �How does lower body play into kinetic chain? �Does shifting of weight from one leg to another get translated into the torso? If so, how efficient? �Are the inefficiencies in energy transfer due to weaker muscles or improper technique? Which plays a greater role?

References � "Frisbee Flight Simulation and Throw Biomechanics. " Sports Biomechanics Lab. 2003 <http: //biosport. ucdavis. edu/research-projects/frisbeeflight-simulation-and-throw-biomechanics/frisbee-flight -simulation-and-throw-biomechanics>. � Lorenz, Ralph D. , and John D. Anderson. "Spinning Flight: Dynamics of Frisbees, Boomerangs, Samaras, and Skipping Stones. " Physics Today 60. 12 (2007): 61 � Morrison, V. R. "The Physics of Frisbees. " Journal of Classical Mechanics and Relativity 8. 48 (2005). � "Supplemental Content. " National Center for Biotechnology Information. U. S. National Library of Medicine. <http: //www. ncbi. nlm. nih. gov/pubmed/8784962>.