MAHARASHTRAACADEMY OF ENGINEERING
AND EDUCATIONAL RESEARCH’S
MAHARASHTRA INSTITUTE OF TECHNOLOGY
PUNE
DEPARTMENT OF MECHANICAL ENGINEERING
TECHNICAL PAPER PRESENTATION ON
BIOMECHANICS OF PITCHING
SUBMITTED BY
MIHIR SATISH ADIVAREKAR
T.E. MECH- I
ROLL NO- 8012
UNIVERSITYEXAM NO. T-3020801
T.P.P. GUIDE
PROF. (Mrs.) S.B.DESAI
ACKNOWLEDGEMENT
I take this opportunity to thank our Head of Department Prof. P. B. Joshi and my T.P.P. guide Prof.(Mrs.) S.B.Desai for their valuable guidance and for providing all the necessary facilities, which were indispensable in the completion of this Technical Paper Presentation.
I also acknowledge with a deep sense of gratitude, the encouragement from Dr. Shridhar Chiplunkar (M.D. D.P.T.B..M.Tech. F.S.S. (Sports Medicine) ) .
I am also thankful to all the staff members of the Mechanical Engineering Department
I would also like to thank the college for providing the required magazines, books for collecting information related to this Technical Paper Presentation.
Finally, I express my gratitude towards my friends for their valuable comments and suggestions.
Mihir Adivarekar
(Exam seat no. T-3020801)
CERTIFICATE
This is to certify that
MIHIR SATISH ADIVAREKAR University Seat No. T-3020801
Roll No - 8012
Of T.E. Mechanical successfully completed ‘Technical Paper Presentation’ on
BIOMECHANICS OF PITCHING
to my satisfaction and submitted the same during the academic year 2008-2009 towards the partial fulfillment of Third Year Of Mechanical Engineering Of University Of Puneunder the Department of Mechanical Engineering, Maharashtra Institute of Technology, Pune.
Prof.(Mrs.)S.B.Desai Prof. P.B. Joshi
(T.P.P. Guide) (Head of the Department)
Abstract
It is a commonly held perception amongst biomechanists, sports medicine practitioners, baseball coaches and players, that an individual baseball player’s style of throwing or pitching influences their performance and susceptibility to injury. With the results of a series of focus groups with baseball managers and pitching coaches in mind, the available scientific literature was reviewed regarding the contribution of individual aspects ofpitching and throwing mechanics to potential for injury and performance. After a discussion of the limitations of kinematics and kinetic analyses, the individual aspects of pitching mechanics are discussed under arbitrary headings: Arm rotation; Arm horizontal abduction , Arm abduction .
More research is needed to identify factors related to these injuries. A biomechanical model of the shoulder with detailed structures may find direct relation of the force and torque at the shoulder to these injuries. Studies correlating kinematics and incidence of injury would also be helpful.
A pitcher’s performance and a pitcher’s throwing movement is a very important part of baseball. The performance of a pitcher ultimately determines the outcome of the game. Also overuse or repetitive motion injuries are common in pitchers. Therefore, the purpose of this study was to compare the kinematics performance and muscle activity of pitching. , improving qualitative understanding of the pitching motion ,
analysis of the resultant jointforces and torques created in pitching .
CONTENTS OF REPORT
Sr. No. / Topic / Page No.1 / Biomechanics : Principles & Methods. / 5
2 / Biomechanics of Baseball Pitching. / 6
3 / Six Phases of Pitching / 7
4 / Shoulder / 10
5 / Engineering Principles
(a) Kinematics Analysis & Quantification / 11
(b) Kinetics Analysis & Quantification / 16
6. / Conclusion / 19
7. / References / 20
Biomechanics: Principles and Methods
The term biomechanics represents a rather broad area; the definition of which is accepted as "the application of engineering principles to biological systems". The engineering principles that are of fundamental importance in biomechanics are those relating to force. Biological systems are continually under the influence of forces. One category of force acting upon the body is external which includes gravity, impacts, or load. External forces result in internal forces which may be categorized as compressive and tensile, bending, shear, and torsion. Internal and external forces are varied relative to the response that they will effect.
From a mechanical standpoint, biomechanical analysis of performance consists of two basic areas, kinematics and kinetics. Kinematics and kinetics directly relate to the analysis of the motion and the forces associated with motion, respectively. Kinematics and kinetic analyses are conducted by modeling the human body or body segments as rigid links and using kinematics and anthropometric data.
Kinematics, sometimes referred to as the "geometry of motion", describes fundamental motion characteristics in terms of displacement, velocity, and acceleration, independent of the forces that cause the motion. Kinematics and kinetic variables are generally described in terms of a Cartesian coordinate reference system consisting of three orthogonal axes . Using such a coordinate system, the motion of any body segment may be completely defined in three dimensional space by a set of 15 kinematics variables.
Kinetic analysis refers to those analyses which focus upon the forces and
energetics (intra- and intersegmental energy flows) associated with motion. Most often,
for applications in the area of performance biomechanics, kinetics are obtained indirectly
by calculating joint reaction forces and net muscle moments.
Biomechanics of Baseball Pitching
In baseball, pitch is the act of throwing a baseball toward home plate to start a play. The term comes from the Knickerbocker Rules. Originally, the ball had to be literally "pitched" underhand, as with pitching horseshoes.
Baseball pitching is one of the most demanding activities in sports on the human body. In an activity where maximum speeds have been measured at 100 mph, the demand on the throwing arm is great, especially at the shoulder and elbow. While maximizing the speed of the ball is not the ultimate goal of pitching, it often improves the chances for getting the hitter out. Pitchers throw a variety of pitches, each of which has a slightly different velocity, trajectory, movement, hand position, wrist position and/or arm angle
The biomechanics of pitching have been studied extensively.The emphasis of this study is mostly concerned with kinematics & kinetics of shoulder.
Six Phases Of Pitching
1. Windup
While pitching , the pitcher initiates the throw by stepping backward with what will become the stride foot/leg .When the weight is shifted back from the stride foot to the supporting foot, the windup is initiated. It is important for the pitcher to achieve a good balanced position when the knee of the stride leg has reached it maximum height. From this position, the delivery of the ball to the catcher is initiated.
2.Stride
After the windup, the supporting leg is flexed, lowering the bodyand the left foot/leg is moved to- ward the plate.. Thekey element is to keep the trunk back as much as possible to retain its potential for contributing to the velocity of the pitch (Figure ). As the striding leg moves downward and toward the catcher, the hand/ball breaks from the glove and moves in a down/upward motion in rhythm with the body. Removal of the ball from the glove when the stride is initiated . This co- ordination is one of the most critical aspects of throwing (Figure ).
. 3.Arm Cocking
Once the stride toward the plate is completed, the trunk moves laterally toward the catcher and hip rotation is initiated.Trunk rotation follows the hip but, in highly skilled pitchers, hyper ex-tension of the upper trunk occurs ait is rotated around to face the plateAs the trunk is undergoing rotationand extension, the upper arm is flexed at the elbow, and the shoulder undergoes external rotation (cocking of the arm )
4.Arm Acceleration
The arm acceleration phase starts when the humerus begins to internally rotate about the shoulder. By extending the arm at the elbow, the pitcher can reduce the inertia that must be rotated at the shoulder. With less inertia, the internal rotation torque generated at the shoulder can accelerate the arm to a greater angular velocity.When the ball is released, the trunk is flexed, the arm is almost in a fully extended position at the el- bow, and the shoulder is undergoing internal rotation. The arm acceleration phase ends with the release of the ball
5.Arm Deceleration
After ball release, the arm continues to extend at the elbow and internally rotate at the shoulder. These two motions may help settle a controversy that has existed in baseball since slow-motion video was first introduced. .In the arm deceleration phase, shoulder internal rotation angular velocity decreases to zero from its maximum value observed near the time of ball release. Arm deceleration ends when the arm has reached an internal rotation position of proximately
6.Follow-Through
The importance of a good follow-through is often overlooked. Although a good follow- through cannot directly improve the throw, it is critical in minimizing the
risk of injury.
The Shoulder
The shoulder is an engineering marvel, designed to allow humans to maximize use of the opposable thumb and hand in three-dimensional space. The combined movements of four distinct ligaments and many tendons and muscles working synergistically —allow the arm to be positioned in space. There must be a balance between mobility and stability to maintain proper function, and it is this balance that embodies the biomechanics of the shoulder complex.
It is the ball and socket joint, which has three rotations and no translations. Clinically, shoulder motions are defined as flexion / extension, abduction / adduction, horizontal abduction /adduction, and external rotation / internal rotation. The first three rotations are not independent, as only two of them are needed to determine the position of the humerus. External/internal rotation is needed to determine the rotation of the humerus about its long axis.
ENGINEERING PRINCIPLES
Kinematics
Kinematics is the study of body movement with an emphasis on theanalysis and description of ‘how’ the body moves rather than what causesthe movement. Here we would like to know how each body segment movesduring baseball pitching. We also would like to know their relative motions,which define the motion of the joint connecting two adjacent segments.In determining kinematics parameters, the initial step is to define a spatialreference system. In the ASMI studies the global reference system is definedby a vertical axis, Z, a horizontal axis in the direction of pitching (to homeplate), X, and a horizontal axis perpendicular to the X direction, Y (parallelto the line connecting first and third base). Fig. depicts this convention.The origin of the coordinate system is based on the calibration cubepreviously discussed. Let’s call this coordinate system the global coordinatesystem since it is still relative to the lab or baseball field.
Second, a local reference or coordinate system is defined for each bodysegment. For the trunk, the X axis is defined from the leading shoulder to thethrowing shoulder, the Z axis is defined as pointing to the superior, and theY axis is defined as pointing to the anterior for the right-handed pitcher andto the posterior for the left-handed pitcher .
Global Reference system Local Reference System
Shoulder abduction is defined as the angle between the humerus and the inferior direction of the trunk (represented by the line connecting the middle point of the two shoulder markers and the middle point of the two hip markers) in the trunk’s frontal plane. Shoulder horizontal abduction is defined as the angle between the humerus and a line connecting the two shoulder markers in the trunk’s transverse plane. Third, shoulder external rotation is defined as the rotation of the upper arm about its own long axis.
Fig: Motion definitions at the throwing shoulder (in degrees): (a) shoulder abduction, (b) shoulder external rotation and (c) shoulder horizontal adduction.
Quantification
Figs. (a), (b) and (c) show the shoulder motion during baseball pitching, normalized from foot contact to ball release. The radius of a circle represents the time in milliseconds. Curves show the shoulder motion versus time during a pitch for a right-handed pitcher. The throwing shoulder was abducted to about 90 degrees during the wind-up phase and remained relatively constant at approximately 100 degrees until the ball release phase
(Fig. a ).
Fig.(a):Shoulder abduction in degrees , time in milliseconds.
The shoulder was externally rotated about 50 degrees at foot contact, and continued to rotate to approximately 180 degrees of external rotation during arm cocking phase (Fig. b ) the maximum external rotation the throwing shoulder started internal rotation. It internally rotated about 60 degrees in less than 10 milliseconds during the arm acceleration phase, and continued its internal rotation during the arm deceleration phase, eventually reaching zero degrees shortly after ball release.
The throwing shoulder is horizontally abducted during the stride phase and reaches approximately 30 degrees of horizontal abduction at foot contact (Fig. c). It horizontally adducted during arm cocking and abducted during arm acceleration phase,
reaching approximately zero degrees horizontal adduction at ball release. After ball release, the arm continues to horizontally adduct reaching 40 degrees of horizontal adduction during the arm deceleration phase.
Fig.(b): Shoulder external / internal rotation
Fig.(c):Shoulder Horizontal Abduction
Kinetics
Kinetics is the study of forces and moments of force applied to a body. Here we are interested in the forces and moments of force applied to the elbow, shoulder and other joints during baseball pitching. If we have a full description of body movements (positions, velocities and accelerations), accurate anthropometric measurements, including body segment’s mass, moment inertia, location of the mass center and external forces applied to the body, the forces and moments of forces applied to the joint can be
calculated. During baseball pitching, external forces include gravitational force, ground reaction force and the ball’s resistive force. An inverse dynamic model is used to perform such a calculation. Let’s assume that the hand and ball are one body before ball release. Forces can be determined using Newton’s second law.
where
m is the mass of a body segment, gis the acceleration due to the gravity, a is the acceleration vector of the segment’s mass center, I is the moment of inertia , d is the vector of the moment arm of force Ri about the moment inertia, mass center, and α is the angular acceleration vector.
Quantification
Kinetics equations discussed were used to calculate the forces and torques applied to the forearm at the wrist by the hand and ball before ball release and by the hand after ball release, to the forearm at the elbow and to the upper arm at the shoulder. The mass of a baseball is about 0.14175 kg. Table 9.1 lists these parameters used in calculating forces and torques. Moment of inertia values were scaled by the pitcher’s height (h, in meters) and mass (m, in kg).
Forces and Torques at the Shoulder
Three forces at the shoulder were determined: theanterior/posterior,superior/inferior and proximal forces applied to the upper arm at the shoulder (Fig. a). The peak anterior shear force was 280 N during the arm cocking phases, and the peak posterior force occurred during the arm deceleration phase, reaching 295 N. The peak superior force occurred during the arm cocking phase, reaching 250 N while the maximum inferior force occurred during the arm deceleration phase reaching 230 N.
(Fig. b) shows the abduction torque, horizontal adduction torque and internal rotation torque applied to the upper arm at the shoulder. The peak abduction torque occurred during the arm cocking phase, reaching 45 Nm . The maximum adduction torque was 70 Nm , which occurred during the arm deceleration phase. The peak horizontal adduction torque occurred during the arm cocking phase, reaching 65 Nm . The maximum horizontal torque was 63 Nm , which occurred the arm deceleration phase. The maximum internal rotation torque was 52 Nm during the arm cocking phase.
Fig(a): Forces applied to the upper arm at the shoulder Torques applied to the upper arm at the shoulder
Conclusion
Based upon the qualitative and quantitative information presented on pitching, it can be concluded that throwing a baseball at maximum velocity is one of the most highly dynamic skills in all sports. Kinematics & kinetics analysis of a shoulder shows that,two critical instants; one during arm cocking and the deceleration phase, had high forces and torques at the shoulder. Because of the highly mobile nature of this joint, great care and physical preparation of the shoulder are required before and during participation in throwing events that need maximum velocity. Upon present physical preparation and rehabilitation of throwers, greater understanding of the specific "loads" and muscular responses that occur during these types of highly dynamic activities will be required. Applications in all of these areas will continue not only to improve qualitative understanding of the pitching motion but alsoto improve as scientific methods of analyzing human movement.
References
1. Introduction to Sports Biomechanics .
–Roger Bartlett .
First published 1997 by E & FN Spon, an imprint of Chapman & Hall
This edition published in the Taylor & Francis e-Library, 2002.
2. Sports Biomechanics
Reducing Injury & Improving Performance.
-Roger Bartlett .
First published 1999 by E & FN Spon, an imprint of Routledge
This edition published in the Taylor & Francis e-Library, 2005.
3. Biomechanics-Principles & Applications.
- Daniel J. Schneck .
- Joseph D. Bronzino .
2003 by CRC Press LLC
This material was originally published in Vol. 1 of The Biomedical Engineering Handbook, 2nd ed.,
4. Research Study
(a) Biomechanics of Pitching with emphasis upon Shoulder Kinematics.
-Charles J. Dilman ,Glenn S. Fleisig, James R. Andrews
This paper was published in August 1993 of Journal of Orthopedic & Sports Physical Therapy
(b) Baseball throwing mechanics as they relate to pathology and performance
-Rod Whiteley ,University of Sydney ,Australia .
This paper was published in March 2007 in Journal of Sports Science & Medicine.
1