Biomechanics of Baseball Pitching - cpb-us … · Pitching Basics •Extremely explosive and...
Transcript of Biomechanics of Baseball Pitching - cpb-us … · Pitching Basics •Extremely explosive and...
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Biomechanics of
Baseball Pitching Saeed Mohammad
Biology 438
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Pitching Basics
• Extremely explosive and unnatural motion
• Several factors go into a good pitch – e.g. Velocity,
Movement, and Position
• Velocity pitch – fastball
• Movement pitch - curveball
• Many different pitching styles, but all follow a similar
basic concept
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Six Phases of Motion
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1. Wind-Up
• Leg raise and straight posture do work against gravity and store potential energy
for upcoming lateral motion
• Arms remain stationary and at front
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2. Stride
• Beginning of the conversion of potential energy into mechanical energy
• Abduction of the shoulder (Deltoid) muscles raises the elbows to prepare
for cocking motion
• Ends with foot plant
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3. Cocking Phase
• Maximal external rotation of the shoulder (Infraspinitus and teres minor
muscles stabilize humerus rotation)
• Foot plant begins action of the ‘kinetic chain’
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4. Acceleration
• Kinetic Chain: Foot plant Trunk Rotation Shoulder Rotation Elbow
translation Wrist Translation
• Extensor (tricep) muscles allow for rapid forearm extension
• Internal angular velocity at the shoulder: ~7600 deg/sec
• Internal angular velocity at the elbow: ~2500 deg/sec
• Force on the Ulnar Collateral Ligament can reach 60N
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Arm Deceleration
• Post-release deceleration of arm, supraspinitus muscle contracts to decelerate
internal rotation
• Pitching muscles begin to relax
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Follow Through
• Natural momentum-guided motion
• Back leg raises to stabilize position
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Important Pitching
Muscles
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Pitching Muscles
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Pitch Comparison
• Fastball: Thrown for speed, the fastball is the most
common pitch and sacrifices lateral motion for
precision and speed
• Curveball: A generally slower pitch that sacrifices
speed for a drastic change in position. Typical
curveball pitching motion involves wrist flexion
immediately prior to ball release
• Task: using the kinetic chain paradigm, analyze the
differences in velocity between the shoulder, elbow and
wrist in both the fastball and curveball
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Fastball Arm
Velocities
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Calculations
• Force of chain on ball = ma = (4.96kg+.149kg)(36m/s2) = 185.5N
• KE = 1/2mv2 = ½(.149kg+4.96kg)(14.6m/s)2 = 545 Joules
• U = mgh = (.149kg)(9.8m/s2)(1.62m) = 2.4 Joules
• Work = ΔKE + ΔU = (545J) + (2.4J) = 547.4 Joules
• Momentum prior to release = mv = (4.96kg+.149kg)(14.6m/s) = 74.6 Ns
• Momentum of ball after release = mv = (.149kg)(36.1m/s) = 5.4 Ns
• Conservation of momentum states that Ben should be moving at around .84m/s after throw. Logger Pro calculated 1.13m/s so, not far off
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Fastball
Acceleration
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Calculations (cont.)
• Assume: Force is always acting perpendicular to the
moment arm (which it is not)
• Arm length: ~.7m
• Arm mass: ~6% of body weight,
so, (82.6kg)(.06) = 4.96kg
• Acceleration from cocking to release: 36 m/s2
• Τ = F x r = (4.96kg)(36m/s2)(.53m) = 94.6 Nm
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Curveball Arm
Velocities
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Calculations
• Force of chain on ball = (4.96+.149kg)(68.4m/s2) = 352.5N
• KE = ½ mv2 = (1/2)(4.96kg.149kg)(12.1m/s)2 = 374 Joules
• U = 2.4 Joules
• Work = ΔKE + ΔU = (374J) + (2.4J) = 376.4 Joules
• Momentum prior to release = mv = (4.96kg+.149kg)(12.1m/s) = 61.8 Ns
• Momentum of ball after release = mv = (.149kg)(25m/s) = 3.7 Ns
• So: Ben’s velocity after should be .70m/s, Logger Pro calculated .86m/s, so again pretty close
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Curveball
Acceleration
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Calculations (cont.)
• Same assumption as before; force is always
perpendicular to the moment arm
• Acceleration from cocking to release in curve:
68.4m/s2
• T = F x r = (4.96kg)(68.4m/s2)(.6m) = 203.6 Nm
• Moment-arm assumption really comes into play in this
case
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Common Injuries: UCL
• Due to the unnatural motion of pitching, injury is exceedingly common.
• A very common injury involves damage to the UCL, which can reach its ultimate tensile strength
• Over many throws, the UCL can become frayed or torn
• Tommy John surgery
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Common Injuries:
Rotator Cuff
• During cocking and deceleration, extreme stress is placed on the muscles of the rotator cuff
• Rotator cuff injury usually involves injuries in the tendons of the supraspinitus or infraspinitus muscles, which stabilize the glenohumeral joint during deceleration
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Limitations
• The majority of the momentum that goes into a pitch comes from the rotation of the trunk
• By studying the linear movement of the shoulder, elbow and wrist, only the final portion of the kinetic chain is analyzed
• 2D analysis is limiting
• Future analysis might use motion capture to look at the rotational kinematics of the trunk during pitching, as well as analyzing the rotation of the arm in more depth
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Future Goals
• The biomechanics of pitching has been studied in
depth, however pitching injuries remain extremely
common
• There is a dichotomy within pitching biomechanics
between altering mechanics to improve output and
altering mechanics to lessen the occurrence of injury
• Future studies might look to elucidate changes in form
that can lessen the stress of the pitching motion on
commonly injured structures, while maintaining peak
performance
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In Action
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References
Blake, Chris. "The Kinetic Chain: Strength and Conditioning of the Baseball Athlete." New England Musculoskeletal Institute at the UConn Health Center. University of Connecticut Health Center. Web. 16 Apr. 2011. <http://nemsi.uchc.edu/clinical_services/orthopaedic/sportsmedicine/baseball_training/index.html>.
Dubin, Joshua. "Medial Epicondylitis." Dubin Chiropractic. Web. 16 Apr. 2011. <http://www.dubinchiro.com/features/pitcher1.html>.
Fleisig, G. S., J. R. Andrews, C. J. Dillman, and R. F. Escamilla. "Kinetics of Baseball Pitching with Implications About Injury Mechanisms." The American Journal of Sports Medicine 23.2 (1995): 233-39. Print.
Fleisig, G. S. "Kinetic Comparison Among the Fastball, Curveball, Change-up, and Slider in Collegiate Baseball Pitchers." American Journal of Sports Medicine 34.3 (2005): 423-30. Print.
Hung, George K., and Jani Macari. Pallis. Biomedical Engineering Principles in Sports. New York: Kluwer Academic/Plenum, 2004. Print.
Nissen, C. W., M. Westwell, S. Ounpuu, M. Patel, M. Solomito, and J. Tate. "A Biomechanical Comparison of the Fastball and Curveball in Adolescent Baseball Pitchers." The American Journal of Sports Medicine 37.8 (2009): 1492-498. Print.
"Rotator Cuff Injury, Symptoms and Treatment." The Virtual Sports Injury Clinic - Sports Injuries, Symptoms, Diagnosis and Treatment. Web. 16 Apr. 2011. <http://www.sportsinjuryclinic.net/cybertherapist/back/shoulder/rotatorcuff.htm>.