Biomechanics of Throwing

Introduction
• The action of propelling an object or ball using a throw which involves
linked motion of the whole body.
• Throwing is a total body activity.It is a elaborate,synchronous progression
of body movement that starts in the legs and trunk and proceeds to the
upper extremity and produce ballistic motion of the upper extremity &
concludes to the rapid propulsion of ball.
• Sports involving throwing motion-
baseball,american football,tennis,racket,javelin throwing,hand ball
throwing,cricket,swimming and volleyball.
• Types of throwing movements-
Underarm throwing
Sidearm throwing
Overarm throwing

Phase of throwing
1. Windup: begins with maximum foot lift and ends with hand
separation.
2. Stride: front foot moves downwards.
3. Arm cocking: pelvis and upper trunk rotation and maximal ER
occurs.
4. Arm acceleration: from maximum ER to ball release.
5. Arm deceleration: from ball release to end range IR
6. Follow through: from maximal IR until pitcher regains balanced
position.

Duration of throwing phases
• 6 phases takes less then 2 seconds to occur.
• First 3 phases-wind up,early cocking and late cocking takes
approximately 1.5 sec in total.
• 4rth phase-acceleration-0.05 seconds
Greatest angular velocities and largest rotation occurs
during this phase.
• Final two phases-last approximately-0.35 sec.

Wind up phase
Windup phase-puts the
thrower in good
starting position.
• Starts with starts of
motion & ends with
maximum knee lift of
the stride leg.
• Duration-0.5-1.0s

kinematics
• lead leg is lifted by concentric contraction of hip flexors(rectus femoris,iliopsoas &
sartorius).
• Lead leg faces the target.
• Stance leg bend slightly,controlled by eccentric contractions from the quadriceps
muscle & remain in a fairly fixed position due to isometric contraction of the
quadriceps until a balanced position is achieved.
• Hip abductor(gluteus medius,minimus & TFL) of stance leg also contract
isometrically to prevent downward tilting of opposite side of the pelvis.
• Hip extensors of the stance contract both eccentrically & isometrically to stabilize
hip flexion.
• Shoulder-partially flexed & abducted(held in this position by anterior and middle
deltoids,supraspinatus & clavicular portion of pectoralis major.
• Elbow-flexion(45deg) is maintained by isometric contraction of elbow
flexors(biceps,brachialis and brachioradialis).

Stride phase
• Begins at the end of the windup
phase,when the lead leg begins to fall &
move towards the target & two arm
separates from each other.
• Thrower turns the lead side target.
• This phase ends when the lead foot first
contacts the ground.
• Duration-0.50-0.75s
• Ending of the phase ends when lead foot
contacts the ground.

kinematics
• Hip-Eccentric contraction of the hip flexors of the lead leg,concentric
contraction from the stance leg hip abductor helps to lengthen the stride.
• As the lead leg falls downward and forward the lead hip begins to rotates
externally(g.max,sartorius and other 6 deep external rotators) and stance
hip extends due to concentric contraction of the hip extensors(G.max and
hamstrings).
• Trunk tilted sideways away from the target.
• Stride length depends on the type of throw.
• Pitching-70-80% of the atheletes height.
• Position of the lead knee is flexed approximately 45-55 degrees at foot
contact
• Lead foot-should placed directly in front of the rear foot towards the
direction of throw.
• Elastic energy generated in the legs,trunk & arm during the sride phase is
transferred to the subsequent phases of throw.

• Shoulder-both shoulder abduct,externally rotates & horizontally abduct
owing to concentric muscle action.
• At lead foot foot contact-shoulder abduction-80-100 degrees(deltoid &
supraspinatus are responsible for abduction.Upper trapezius and serratus
anterior upwardly rotate & position the glenoid for the humeral head.
• Throwing arm is positioned slightly behind the trunk(horizontly abducted)
& in football throwing slightly anterior.
• At shoulder posterior deltoid,lattismus dorsi,infraspinatus & teres minor
works to bring the arm posteriorly and in externally rotated position.
• Rhomboids & middle trapezius retracts the scapula.
• Elbow-approximately-80-100 degrees.
• Forearm rotated up,approching vertical position.
• Finger extension and wrist flexion.

Arm-cocking phase
• Begins at lead foot contact and
ends at maximum shoulder
external rotation.
• Duration-0.10-0.15sec

kinematics
• Upper body is rotated to face the target
• Quadriceps of the lead leg initially contracts eccentrically to decelerates knee flexion and
then concentrically and isometrically to stablilize the lead leg during the cocking phase.
• Throwers body is fully stretched out in the direction of the target.
• Ankle of the stance leg planter flexed & leaves the contact this motion occurs concurrent
with pelvic rotation,just after foot contact.
• Pelvis continues transverse motion,hip internally rotates,occurs approximately 0.03-0.05
sec after baseball pitching-max rotation-700deg/sec.
• Trunk muscles are on stretch-recoil & the subsequent shoulder rotation.
• Upper trunk rotates in reverse direction to the rotation of the pelvis.
• Upper torso angular velocity is maximum during this phase-900-1300deg/sec is achieved.
• Abdominals & oblique muscles is placed on stretch during trunk hyperextension.
• Trunk rotates to face the target,throwing shoulder horizontally adducts,moving from
position of 20-30degrees of horizontal abduction at the lead foot contact to a position of
15-20 degrees of horizontal adduction at the time of maximum shoulder external rotation.

• Shoulder-This leads to maximum shoulder horizontal adduction velocity
relative to the trunk is approximately-500-600 degrees/sec.
• Pectoralis major anterior deltoids(horizontal adductors initially contracts
eccentrically then isometrically to stabilize to allow the arm to move with
the trunk,cocentrically to provide dynamic horizontal adduction at the
shoulder.
• Shoulder girdle muscles(levator scapulae,s.anterior,trapezius,rhomboids
& p.minor) work.
• Serratus anterior is more active to provide both stabilisation &
protraction to the scapula.
• All muscles stabilize the scapula & provides position of the glenoid for
the subsequent action of the humeral head.
• Throughout arm cocking phase shoulder remains abducted approx 80-
100degrees.
• External rotation-165-180degrees(inc. stretch on anterior capsule).

Elbow-90 degrees about 30ms
before maximum shoulder external
rotation.triceps contract
eccentrically then isometrically in
resisting centripital elbow flexion
then triceps contract concentrically
to aid in elbow extension.
Pitcher arm legs behind as the
trunk rapidly rotates forward to
phase the hitter,generating a peak
angular velocity of around
6000deg/sec,occuring 0.03 to 0.05
sec after lead foot contact,followed
by peak torso angular velocity of
nearly 1200 deg/sec,occuring 0.05
to 0.07 sec after lead foot contact.

Arm acceleration phase
• Trunk flexes forward to neutral
position from extended position.
• Begins with maximal shoulder
external rotation and ends at ball
release.
• This phase is very rapid phase.
• Shoulder abduction is 90 degrees
during this phase.
• Duration-This phase lasts 0.03 to
0.05 sec.

kinematics
• Elbow extension begins prior to internal rotation allows throwers to reduce
rotational inertia about the arm longitudinal axis & therefore allowing
greater internal rotational velocity of approximately 7000-8000 deg/sec in
pitching.
• Subscapularis is most active followed by lattismus dorsi & pectoralis major.
• Trunk flex forward from a vertical position approx-25-40 degrees.
• Throwing shoulder remains abducted approx 80-100 degrees throughout
acceleration phase which implies strong position for the shoulder.
• Shoulder movement remains same but trunk position changes with the
throwing type.(overhead-trunk sideways,sidearm-trunk vertical)
• Rotator cuff and scapular muscles demonstrate high activity to control
humeral head & scapular stabilization.
• Elbow extension due to centrifugal force at elbow as trunk & arm rotates-
2100deg/sec

• Increase triceps and anconeous activity also acts as arm stabilizer.
• Elbow angular velocity is due to rotatory action of other parts of the body
such as hips,trunk & shoulder.
• Ball release-elbow is fully extended & slightly anterior at release elbow
flexed to 20-30 degrees & horizontal adduction5-20 degrees.(inc.varus
force can cause wedging of olecranon fossa.
• Elbow extension-from 80degrees to 20 degrees due to centrifugal force.
• Increase activity of elbow flexors-adds compressive force ans stability &
control rate of elbow extension.
• Hand moves from hyperextended wrist position at maximum shoulder
external rotation to a neutral wrist position at ball release.wrist flexors
active during throwing activity initiates eccentric then concentric
contraction,pronator teres is also active.
• Internal rotators contract concentrically to generate peak internal rotation
angular velocity of approx.6500 deg/sec near ball release,

Arm deceleration phase
• Duration-0.03 to
0.05 sec.
• From ball
release to
maximum
internal rotation
trunk continues
to flexion.

kinematics
• Lead knee and throwing elbow extends.
• Pronation due to activation of pronator teres.
• Upward reaction of the flexing trunk & hip.
• Large eccentric load at elbow & shoulder to decelerate the arm.
• Biceps and supinator also eccentrically loaded.
• Elbow extension terminates at 15-25degrees(triceps active)
• Posterior shoulder muscles stop the shoulder
distraction(infraspinatus,lattismus dorsi and posterior deltoid)
• Lower trapezius,Serratus anterior & rhomboids are quite active providing
posterior motion.
• Rotator cuff muscle limits anterior translation,adduction and shoulder
internal rotation.
• Wrist and finger flexors have very high eccentric activity.
• Shoulder and elbow torque is more during slider.(>15-20% compressive
force)
• Maximum shoulder adduction torque of approximately 80-110 Nm are
produced to resist shoulder abduction & superior humeral head translation.

Follow through phase
• Begins at the time of maximum
shoulder internal rotation and
ends when completes its
movement across the body &
position is obtained
• Last less than 1 sec.

kinematics
• maximum shoulder internal rotation and ends when arm
completes its movement across the body and atheletes in in
balanced position.
• Forearm rotated in pronation.

Kinetic chain in overhead pitching
• Consists of linked motion of hips & trunk and culminates with a ballistic motion of the
upper extremity to propel the ball.
• All phases are intricately coupled,resulting in efficient generation & transfer of energy
from body into arm & ultimately,the hand & ball.
• The legs & trunk serves as the main force generators of the kinetic chain,scapula is in
facilitating this energy transfer distally to the hand.
• Kibler & chandler-20% decrease in kinetic energy delivered from hip & trunk to the arm
requires a 34% increase in the rotational velocity of the shoulder to impart the same
amount of force to the hand.
• Improvement in velocity also reduces kinetic contributions of the shoulder to produce
top velocity.
• Time between front foot contact and ball release-0.145sec.

Wind up-wind up & stride position the body to optimally generate the forces &
power required to achieve top velocity.
• The pitcher keeps his center of gravity over his back leg to allow generation of
maximum momentum once forward motion is initiated.
• If the pitchers body and momentum falls prematurely,the kinetic chain will be
distrupted & greater shoulder force will be required to propel the ball at top
velocity.
Early cocking/stride-the stride functions to increase the distance over which linear
and angular trunk motion occurs,allowing for increased energy production for
transfer to the upper extremity.
• The stance knee & hip extend & lead to the initiation of pelvic rotation &
forward tilt,followed by upper torso rotation.Pelvis achieves maximum
rotational velocities of 400 to 700 degrees per second during this phase.
• The lead foot should land in line with stance foot,pointing towards home plate
or in a few degrees of internal rotation. If the foot lands too closed (stride foot
in front of stance foot),pelvis rotation may be limited causing pitcher to throw
across the body.

Late cocking-pelvis reaches its maximum rotation & the upper torso continues to rotate & tilt forward and
forward and laterally.
• Maximum shoulder internal rotation torque occurs just before maximum shoulder external rotation.
• Near the end of arm cocking(64% of time from foot contact until ball release),maximum valgus torque
is experienced at elbow.
• Flexors and pronator muscles generates a counter varus torque(64 Nm).adaptive increase in elevation
and upward rotation scapula is important,ensuring sufficient subacromial space to accommodate the
80-100 of humeral abduction in throwing position without impingement.
• The rotator cuff muscles provide a compressive force of 550 to 770N to resist shoulder distraction
caused by the torque of the rapidly rotating upper torso.
• The biceps muscle reaches peak activity as it flexes the elbow,limits anterior translation and
provides a compressive force on the humeral head.
• As the shoulder approaches maximum external rotation,the subscapularis,pectoralis major and
lattissmus dorsi are eccentrically contracting applying a stabilizing anterior force to the anterior force
to the glenohumeral joint,and halting external rotation.
• Increased amount of shoulder external rotation help to allow the accelerating forces to act over the
longest distance,allowing greater prestretch & elastic energy transfer to the ball during accleration.

• Acceleration phase-the trunk continues to rotate & tilt,initiating the
transfer of potential energy through upper extremity.
• The scapula protracts to maintain a stable base as the humerus undergoes
horizontal adduction and violent internal rotation. This rapid motion
delivers the arm from as much as 175 degrees of external rotation to 100
deg of internal rotation(at ball release) in only 42-58 milliseconds.
• A decreased time to maximum shoulder internal rotation & increased
trunk tilt at ball release have been associated with an increase in ball
velocity.
• Internal rotation velocities as high as 7000 to 9000 degrees per second
have been reported.
• Elbow extension results from a combination of the centrifugal force
generated by a rotating torso and concentric contraction of the triceps;
immediately followed by shoulder internal rotation.
• The biceps brachii supplies elbow flexion torque,reaching a maximum
value of 61Nm just before the ball release

• Maximum elbow extension angular velocity occurs just before ball
release & may reach mean angular velocity of 2251 degrees per
second.Ball release is aided by wrist flexion to neutral in the 20 ms
proceeding release and radioulnar pronation to 90 degrees in 10ms
prior to release.
• Concentric rectus femoris contraction contributes to lead leg hip
flexion & knee extension,providing a stable front side help to create
increased angular momentum of the trunk.
• Increased forward trunk tilt allows the pitching extremity to
accelerates through a greater distance allowing more force to be
trnsferred to the ball.
• Maximal angular velocity 300-450degrees per second at ball
release.

Deceleration-this is the most violent phase of throwing cycle,resulting
in the greatest amount of joint loading encountered during
throwing.
• Excessive posterior(400N) and inferior shear forces(300 N)occur,as
do elevate compressive forces(>1000 N) & adduction torques.
• The massive eccentric contractile requirements of the posterior
shoulder capsular & soft tissues reactions commonly seen in
throwers & for glenohumeral interenal rotation deficit seen inj
pitchers.
Follow through-culminates with the pitcher in fielding position.
• The decrease joint loading and minimal forces during this phase
render it an unlikely culprit for injury.

kinetics
• The leg and trunk serves as the main force generators of kinetic
chain.
• Scapula is the key transferring energy distally to the hand . So,any
scapular dysfunction prohibits optimum energy transfer.
• 20% decrease in kinetic energy delivered from hip and trunk to the
arm requires 34% inc. in rotational velocity of the shoulder to
impart the same amount of force to hand.
• Transfer of power from the point of plant foot to the tip of throwing
hand is the process that relies on strength,flexibility and ROM of
the foot,ankle,knee,thigh,hip,core,chest,shoulder,elbow,forearm
and hand.problem in any part can lead to problem in energy
transfer.

Kinetics of scapular position
• Provides stable platform for the humeral head during rotation and
elevation,while transferring kinetic energy from the lower extremity and
trunk to lower extremity.
• Kibler found that only half of the kinetic energy generated by lower limb
and trunk rotation & is transferred to the upper limb through the
scapulothoracic joint which is a part of kinetic chain.
• Throwers develops chronic adaptations for more efficient performance of
the throwing motion.
• Throwing atheletes have increased upward rotation,internal rotation and
retraction.Loss of upward rotation in throwing injury leads to associated
with impingement of subacromial structures.
• Fatigue also adversely affects scapular movement which leads to decrease
external rotation and posterior rotation and posterior tipping and upward
rotation of the scapula.(dec.approximately in 5 innings).
• Internal rotation increases with scapular elevations.
• Increase in retraction may facilitates a maximum cocking position for
subsequent explosive acceleration during the throwing motion.

• Elite pitchers can generate ball velocity that exceeds
144.8km/hr in order to create this velocity,the shoulder
rotates at an angular velocity of upto 7000deg/sec.
• At ball release distractive forces at the shoulder 950N.
• At deceleration phase-compressive forces created by
rotator cuff muscles & deltoid are in the range of 1090N
and posterior shear forces of upto 400N.
• If compressive force do not counteract high distractive
force,injuries wiil occur.

Increased pitching velocity and
accuracy depends on
• Lead knee flexion
• Forward trunk tilt
• Peak elbow external rotation
• Maximum pelvic angular velocity.
• Synchronicity and coordination between
upper and lower extremity.
• Body height and weight.
• Bone length.
• Specific arm position timing of ball release.

ELECTROMYOGRAPIC
CHANGES DURING
THROWING

Wind up
• Lead knee lifted controlled by concentric of hip flexors
and stance leg bend controlled by eccentic contraction of
quadriceps and remain in fixed postion by contraction of
quadriceps.
• Hip abductors of stance leg contract isometrically to
prevent downward tilting of opposite side pelvic.
• Hip extensors contract both eccentrically and isometrically
to stabilize hip flexors.
• Shoulder activity during the wind up is generally very low
due to the low movements.

• The greatest activity is from upper trapezius, serratus
anterior and anterior deltoids.
• All contract concentrically to upwardly rotate and
elevate the scapula and abduct the shoulder as the arm
is initially brought overhead, and then contract
eccentrically to control downward scapular rotational
and shoulder adduction as the hands are lowered to
approximately chest level.
• The muscles of the rotator cuff, which has dual
function as glenohumeral joint compressors and
rotators, have their lowest activity during this phase.

• Low shoulder activity given that shoulder forces and
torques generated during this phase are low.
• Elbow in flexed and is maintained by isometric
contraction of elbow flexors.

Stride phase
• Hip flexors eccentrically contract control leg lowering.
• Concentric contraction of stance leg hip abductors lengthen the stride.
• Forward movement is initiated by some degree by hip abductors
followed by knee and hip extensors from stance leg.
• As the lead legs falls downward the lead hip externally rotate and
stance hip internally rotate.
• Stance hip also extend due to concentric contraction from hip
extensors.
• Through out this phase trunk is tilted slightly sideways away from
target.
• Stride length is approximately 70 to 80% of athletes height.
• Lead foot should be slightly flexed and point inward.

• The scapula upwardly rotates, elevates and retracts.
• Shoulder abduct, externally rotate and horizontally abduct due to
concentric activity of deltoid, supraspinatus, infraspinatus, serratus
anterior and upper trapezius.
• More muscles are activated and to a higher degree during the stride
compared with wind up.
• The supraspinatus has its highest activity during this phase as it
works not only to abduct the shoulder but also to help compress and
stabilize the glenohumeral joint.
• The deltoid also exhibit high activity to initiate and maintain the
shoulder in abducted position.

• Throwing arm position should be slightly behind the trunk.
• Posterior deltoid, latissmus dorsi, teres major and posterior
rotator cuff muscles are responsible for horizontally abducting
the shoulder while romboidus and middle trapezius retract the
scapula.
• Elbow flexors muscles of throwing arm contract eccentrically
and isometrically in controlling elbow flexion.
• Wrist and fingers extensors have very high activity as wrist has
to move from a position of slight flexion to position of
hyperextension.
• These muscles work concentrically as they work against
gravity as throwing hand facing downward.

Arm cocking phase
• Quadriceps of lead leg initially contract eccentrically to decelerate knee
flexion then contract eccentrically to decelerate knee flexion then contract
isometrically to stabilize the lead leg.
• The abdominal and oblique muscles are stretched due hyperextension of
lumbar trunk that occurs as the upper torso rotates.
• During this phase the kinetic energy that is generated from the larger lower
extermity and trunk segments is transferred up the body to the smaller upper
extremity segments.
• High to very high shoulder muscle activity is needed during this
phase to keep the arm moving with the rotating trunk as well as to
control the resulting shoulder external rotation which peaks near180
degrees.
• Moderate activity is needed by the deltoid to maintain the shoulder at approx
90 deg of abduction throughout the phase.

• Activity from pectoralis major and anterior deltoid is needed during
this phase to horizontally adduct the shoulder to a peak angular
velocity of approx 600deg/sec from a position of approx 20 deg of
horizontal abduction at lead foot contact to a position of approx 20
deg of horizontal adduction at maximum shoulder external rotation.
• Large compressive force of approx 80% of body weight is generated
by trunk onto upper extremity at the shoulder to resist the large
centrifugal force that is generated as arm rotates forward with the
trunk.
• The rotator cuff muscles achieve high to very high activity to resist
glenohumeral distraction and enhance glenohumeral stability.

• The posterior cuff muscles and latissimus dorsi also generate
posterior force to humeral head, which help resist anterior
humeral head translation and perhaps helps unload the
anterior capsule and anterior band of the inferior glenohumeral
ligament.
• Peak shoulder internal rotation torque of 65 to 70 Nm is
generated near the time of maximum shoulder external
rotation.
• High to very high activity is generated by shoulder internal rotators
which contract eccentically to control rate of shoulder external
rotation.
• Dual function of pectoralis major as it contracts concentrically to
horizontally adduct the shoulder and eccentrically to control
shoulder external rotation maintain normal length by length tension
relationship maintain constant length and in effect contracting
isometrically.

• Same occur with subscapularis as it contracts concentrically to aid in
horizontal adduction and eccentrically to help control external rotation
and in effect contracting isometrically.
• Scapular protractors are active especially during this phase to resist
scapular retraction by contracting eccentrically and isometrically
during early part of phase and contract concentrically during the latter
part of this phase to protract the scapula.
• Serratus anterior generate maximum activity during this phase.
• Both the triceps brachii (long head) and biceps brachii (both heads)
cross the shoulder, they both generate moderate activity during this
phase to provide additional stabilization to the shoulder.
• High eccentric contractions by the triceps brachii are needed to help
control the rate of elbow flexion that occurs throughout the initial 80%
of this phase.

• High triceps activity is also needed to initiate and
accelerate elbow extension, which occurs during the final
20% of this phase as the shoulder continues externally
rotating during this phase.
• Triceps initially contracts eccentrically to control elbow
flexion early in the phase and contracts concentrically to
initiate elbow extension later in the phase.
• The infraspinatus not only helps externally rotate and
compress the glenohumeral joint but also helps generate a
small posterior force on the humeral head this posterior
force on the humeral head helps resist anterior humeral
head translation and unloads strain on the anterior capsule
during arm cocking.

Arm acceleration
• Like the arm-cocking phase, high to very high activity is
generated from the glenohumeral and scapula muscles
during this phase in order to accelerate the arm forward.
• Elbow extension initially begins during the arm-cocking
phase.
• Kinetic energy that is transferred from the lower extremities
and trunk to the arm is used to help generate a peak elbow
extension angular velocity of approximately 2300 deg/sec
during this phase.

• Moderate activity is generated by the deltoids to help
produce a fairly constant shoulder abduction of
approximately 90 to 100 degrees, which is maintained
regardless of throwing style (e.g., overhand, sidearm).
• The glenohumeral internal rotators (subscapularis,
pectoralis major, and latissimus dorsi) have their highest
activity during this phase
as they contract concentrically to generate a peak internal
rotation angular velocity of approximately 6500 deg/sec
near ball release.

• With these rapid arm movements, which are generated
to accelerate the arm forward, the scapular muscles
also generate high activity, to help maintain proper
position of the glenoid relative to the rapidly moving
humeral head.
• Strengthening the scapular musculature is very
important.
• Poor position and movement of the scapula can
increase the risk of impingement and other related
injuries, as well as reducing the optimal length tension
relationship of both scapular and glenohumeral
musculature

Arm-Deceleration Phase
• Posterior shoulder musculature, such as the infraspinatus, teres minor
and major posterior deltoid and latissimus dorsi, contract
eccentrically not only to decelerate horizontal adduction and internal
rotation of the UE but also help resist shoulder distraction and
anterior subluxation forces.
• A shoulder compressive force slightly greater than body weight is
needed to resist shoulder distraction, and a posterior shear force
between 40% and 50% of body weight is generated to resist shoulder
anterior subluxation.
• Scapular muscles also exhibit high activity to control scapular
elevation, protraction, and rotation during this phase.

• High EMG activity from glenohumeral and scapular
musculature illustrates the importance of strength and
endurance training of the posterior musculature in the
overhead-throwing athlete.
• Weak or fatigued posterior musculature can lead to
multiple injuries, such as tensile overload undersurface
cuff tears, labral and biceps pathology, capsule injuries,
and internal impingement of the infraspinatus and
supraspinatus tendons on the posterosuperior glenoid
labrum.

• The biceps brachii generate their highest activity during arm
deceleration. The function of this muscle during this phase
to twofold.
• First, it must contract eccentrically along with other elbow
flexors to help decelerate the rapid elbow extension that
peaks during arm acceleration. This is an important function
because weakness or fatigue in the elbow flexors can result
in elbow extension being decelerated by impingement of the
olecranon in the olecranon fossa, which can lead to bone
spurs and subsequent loose bodies within the elbow.
• Second, the biceps brachii works synergistically with the
rotator cuff muscles to resist distraction and anterior
subluxation at the glenohumeral joint.

Follow through
• Maximum shoulder internal rotation arm completes its
movement across the body and balance position is achieved.
• A long arc of deceleration from throwing arm as well as
sufficient forward tilting of trunk allows energy to be
absorbed by large musulature of trunk.
• Posterior shoulder muscles contract eccentrically to
decelerate the arm
• Serratus anterior highest active of all scapular rotators.
• Middle trapezius and romboidus eccentrically contract to
decelerate shoulder protraction.
• Wrist and finger extensors moderately active.

Shoulder Injuries in Baseball
Primary Rotator Cuff Injuries
• Compression cuff disease
• Internal impingement
• Overuse tendinitis
• Primary lesions
• Rotator cuff tears
• Tensile failure
Secondary Rotator Cuff Lesions
• Anterior instability
• Compressive cuff disease secondary to laxity
• Multidirectional instability
• Posterior instability
• Primary instability (nontraumatic)
• Tensile failure secondary to laxity

Glenoid Labrum Tears
• Peel-back lesions
• SLAP lesions
• Thrower’s exostosis
Biceps Tendon Pathology
• Bicipital tendinitis
• Ruptures and tears
Other
• Acromioclavicular joint degenerative changes
• Neurovascular syndromes
• Scapula disorders
• Suprascapular nerve entrapment

Internal Impingement
• Internal impingement is one of the most common
shoulder lesions seen in baseball pitchers.
• This lesion occurs when the athlete abducts the arm to 90
to 100 degrees and maximally externally rotates.
• During this motion, the undersurface of the
supraspinatus or infraspinatus tendon (or both) contacts
the posterior superior glenoid rim and glenoid labrum.
• This results in undersurface rotator cuff wear and
glenoid labrum fraying and possible detachment.
• This lesion develops because of the repetitive nature of
throwing.
• Causes may be anterior capsule laxity, posterior capsule
tightness,and over-rotation.

• The diagnosis of internal impingement is established based on
subjective history, imaging studies, and physical examination.
• Internal impingement is most often managed nonoperatively with
rest, stretching, and strengthening.
• Usually, nonoperative treatment is successful in these athletes.

ROTATOR CUFF INJURIES
• The rotator cuff is vital for normal shoulder function, especially in the
throwing athlete.
• High demands placed on the shoulder musculature during throwing
can result in subsequent muscle fatigue, eccentric overload,
inflammation, and eventual tendon failure.
• Once the rotator cuff musculature has been injured, the dynamic
stabilizing ability iscompromised, and additional injuries such as
labrum tears, capsular lesions, and osseous changes can ensue.
• Poor mechanics often results from this type of chronic inflammation,
producing a compensatory mechanism in the throwing act that can
contribute to the injury producing scenario.
• These repetitive muscle strains can result in overuse tendinitis of the
rotator cuff.

Overuse Tendinitis
• Overuse tendinitis is commonly seen in the posterior rotator cuff
muscles, the infraspinatus, and the teres minor.
• These occur due to the large stress placed on the shoulder joint
during the deceleration phase of throwing.
• The stresses applied to the posterior rotator cuff musculature
effectively exceed the body weight during the deceleration phase.
• Weakness or fatigue of the external rotators decreases the muscular
effi ciency required to decelerate the throwing shoulder properly and
can result in tissue damage.
• A decrease in the power of the infraspinatus and teres minor
muscles alters the effectiveness of the subscapular, teres minor, and
infraspinatus force couple, and humeral head translation increases .
• Before musculotendinous infl ammation, the posterior glenohumeral
capsule often becomes inflamed, which appears to act as a precursor
to posterior rotator cuff tendinitis. This inflamed capsule is referred
to as posterior capsulitis.

Tensile Lesions
• A common rotator cuff pathology seen in the thrower is a tensile lesion of
the undersurface of the rotator cuff.
• The mechanism of injury in this instance is deceleration of the arm as the
rotator cuff attempts to resist the horizontal adduction, internal rotation, and
glenohumeral distraction forces placed on it.
• Combined, these forces result in an eccentric tensile overload failure and a
partial undersurface tear of the rotator cuff caused by repetitive
microtrauma.
• Most commonly, these lesions are found in the region of the supraspinatus
tendon .
• On physical examination, tenderness can be elicited over the supraspinatus
or infraspinatus tendon.
• Obvious gross weakness of the rotator cuff usually is not present, especially
in the highly skilled thrower.
• Palpation of the infraspinatus, teres minor, and posterior capsule can be
helpful.
• Computed tomography (CT) or magnetic resonance imaging (MRI) can
reveal a partial undersurface tear of the rotator cuff.

• Initially, the athlete should begin a rehabilitation program with
emphasis on rotator cuff strengthening.
• If no improvement is made over a period of 3 to 6 months, an
arthroscopy may be performed to débride the injured tissue and to
attempt to promote a healing response.
• After this procedure, an aggressive rotator cuff strengthening
program must be used to minimize the risk of recurrence and
maximize a return to symptom-free function.
• This program should emphasize eccentric strengthening of the
posterior rotator cuff musculature

Subacromial Impingement
• The throwing motion requires the arm to be abducted to 90 degrees while
being repetitively submitted to horizontal adduction and internal rotation
motions.
• This motion can produce subacromial impingement symptoms.
• Often the thrower complains of shoulder pain during activity and especially
after prolonged throwing.
• Once the lesion becomes more severe, pain may be present during all
throwing activities.
• Most athletes respond successfully to a conservative program of active rest,
nonsteroidal anti-inflammatory medication, and a progressive rotator cuff
strengthening and stretching exercise program.
• In the thrower, external rotation is often excessive and internal rotation is
significantly limited. This limitation of internal rotation results in posterior
capsular tightness, which causes the humeral head to migrate anteriorly
during overhead motion.
• Any conservative rehabilitation program should include stretching of the
posterior capsule, re-establishing normal internal rotation, and gradual
aggressive strengthening of the rotator cuff musculature.

• Significant weakness of the shoulder’s abductors and
external rotators can be seen. Often a repair of the
rotator cuff is necessary to allow symptom-free return
to normal daily activities.
• The surgical procedure of choice to repair a rotator
cuff tear in a thrower uses an arthroscopic technique
that minimizes scarring of the capsule and soft tissue.

SHOULDER INSTABILITY
• The throwing motion requires excessive glenohumeral external
rotation, which places extreme tension on the anterior stabilizing
structures of the glenohumeral joint and especially the anterior
capsule and the rotator cuff musculature.
• The throwing athlete must exhibit laxity to perform high-
performance throwing activities. However, the rotator cuff
musculature must control this laxity dynamically for symptom-
free throwing.
• Instability ensues when the dynamic stability is altered and the
rotator cuff muscles are unable to control humeral head motion
within the glenoid during activities.
• In the thrower, hyperlaxity is a common problem. The shoulder
must be loose enough to allow the tremendous motion necessary
to throw a baseball but must be tight enough to provide inherent
stability

• Shoulder instability is restricted by the static stabilizers, the
geometry of the joint, and the ligamentous system and labrum.
• Repetitive overhead throwing often results in stretching of these
capsular restraints and can lead to joint capsule injury.
• As the capsule becomes more lax, the glenohumeral joint
depends on an increase in the dynamic muscular effort to
provide the required functional stability required. If the dynamic
stabilizers fail because of overuse, injury, or pain, underlying
primary instability will result.
• During the cocking and early acceleration phases of throwing,
the anterior and inferior portions of the joint capsule are
significantly stressed in a repeated fashion.
• The anteroinferior glenohumeral ligament (anterior band)
provides the static stabilization for this anterior force applied
with the shoulder abducted to 90 degrees.

• The dynamic stability required to supplement the anteroinferior
glenohumeral ligament is provided through a rotator cuff muscular
contraction on both sides of the glenohumeral joint.
• In time, the thrower can develop a loose shoulder joint. Because of
this ensuing looseness, the thrower must rely on dynamically
controlled stability and thus may be predisposed to musculotendinous
injuries caused by overuse, such as secondary internal impingement,
tensile failure, and rotator cuff failure.
• The thrower might complain of anterior or posterior shoulder pain,
especially during the late cocking and acceleration phases.
• Also, the thrower might notice clicking, popping, or early arm fatigue
with competitive activities.
• Several clinical tests are routinely performed to determine the degree
of anterior humeral head translation on the glenoid.
• Anterior laxity is determined with the use of a drawer test
(Lachmann’s test of the shoulder) , fulcrum test , or a relocation test

• Posterior instability can also be seen in the thrower. This occurs
during the deceleration and follow-through phases of throwing
when the arm horizontally adducts and internally rotates.
• During this motion, the posterior capsule is stressed and
posterior labral injuries can also occur.
• Stretching of the posterior capsule in this fashion irritates and
inflames the capsule, which results in pain and inhibition of the
posterior rotator cuff musculature.
• This muscular inhibition, if unaddressed, eventually results in
tendon fatigue and microfailure in addition to increased
instability.
• Clinically, posterior instability can be determined through a
posterior drawer test and a posterior fulcrum test.

• Most athletes exhibiting glenohumeral laxity without
associated labral detachment can be treated with a
conservative treatment program.
• The program consists of temporarily decreasing the stresses
from throwing, normalizing the motion of the shoulder, and
improving the dynamic stability through muscular
strengthening and neuromuscular control.
• Once the athlete’s shoulder pain has subsided, a gradual return
to throwing may begin.
• If a conservative program is unsuccessful after 2 to 3 months,
a surgical procedure may be warranted.

BICEPS BRACHII TENDON PATHOLOGY
• Biceps activity requires during the cocking and acceleration phases
but a high level of biceps activity requires during the follow-through
phase.
• During this later phase,the role of the biceps is in deceleration of the
elbow joint.
• Because of the eccentric deceleration action of the biceps brachii,
overuse tendinitis of the long head can occur.
• Also, anterosuperior shoulder stability may be enhanced and assisted
by biceps activity especially during the throwing movement.
• Therefore, both activities place considerable stress on the biceps
musculotendinous unit and can lead to inflammation of the biceps.
• Biceps pain has a variety of causes, including biceps instability,
tendinitis, tendinosis, SLAP lesions, rotator cuff failure, capsular
inflammation, and hypermobility of the glenohumeral joint.

• The diagnosis of biceps tendinitis is made on clinical examination
through palpation, resisted muscle testing, and special tests.
• The biceps should be emphasized in an appropriate exercise
program using concentric and eccentric muscle contractions to
control the rapid elbow-extension moment during the follow-
through phase.

GLENOID LABRUM TEARS
• During the throwing motion, the glenohumeral joint receives large
compressive and shear forces, as well as distraction forces, as the
humeral head moves from anterior to posterior during the phases of
throwing.
• These large compressive and shear forces can injure the glenoid
labrum, resulting in degenerative tears, frank tears, or labral
detachments from the glenoid.
• A common location for labrum tears is in the posterosuperior and
superior portion, where the long head of the biceps attaches.
• During the deceleration and follow-through phases of throwing, the
biceps acts at the elbow joint to decelerate the arm, slowing the
extensor movement.

• Because of the large stabilizing muscle activity of the biceps
across the glenohumeral joint, an avulsion tear of the biceps or
of the biceps-labrum insertion can result.
• During the follow-through phase, the humeral head translates
posteriorly and can cause degenerative tearing of the labrum.
Another type of labrum lesion is the superior labrum anterior-
posterior (SLAP) lesion.
• A commonly seen labrum tear in the throwing athlete is the
posterior or posterosuperior labrum tear.
• During the follow-through phase, the humeral head translates
posteriorly and can cause degenerative tearing of the labrum.
• Another type of labrum lesion is the superior labrum anterior-
posterior (SLAP) lesion.

• The elbow undergoes significant stress during the throwing
motion of an overhead athlete. The forces generated in the various
phases of the throwing arc are distributed through the soft tissue
and bone of the elbow joint.
• In baseball players, repetition leads to attritional damage to the
elbow.
• The specific constellation of injuries suffered in baseball .
• These injuries include :
1. medial UCL tears,
2. ulnar neuritis,
3. flexor-pronator injury,
4. medial epicondyle apophysitis or avulsion,
5. valgus extension overload syndrome with olecranon osteophytes,
6. olecranon stress fractures,
7. osteochondritis dissecans (OCD) of the capitellum,
8. loose bodies.

Coronal slice of an MRI demonstrating a
medial UCL tear

PATHOPHYSIOLOGY OF ELBOW INJURIES
• Elbow injuries in baseball pitchers from medial tension overload to
extension overload to lateral compression overload.
• These injury patterns can be explained by one mechanism: valgus
extension overload syndrome.
• During overhead throwing, a large valgus force on the elbow created
by humeral torque is countered by rapid elbow extension creating
significant tensile stress along the medial compartment, shear stress in
the posterior compartment, and compressive stress in the lateral
compartment. Repetitive, near-failure tensile stresses create
microtrauma and attenuation anterior bundle of the UCL, leading to
progressive valgus instability.
• Continued shear stress and impingement in the posterior compartment
lead to olecranon tip osteophytes, loose bodies, and articular damage
to the posteromedial trochlea in the continuum of valgus extension
overload syndrome .

• As the UCL becomes incompetent, the osseous constraints of
the posteromedial elbow become important stabilizers during
throwing.
• Subtle laxity in the UCL also leads to stretch of the other
medial structures, including the flexor-pronator mass and ulnar
nerve.
• Extrinsic valgus stresses and intrinsic muscular contractions of
the flexor-pronator mass lead to tendonitis.
• Ulnar neuropathy is common given the superficial position of
the nerve.
• The nerve is susceptible to injury from traction, compression,
and irritation at the medial aspect of the elbow.
• In any overhead throwing athlete, UCL attenuation or failure
must be ruled out but should not be the only pathology
considered.

Gleno humeral internal-rotation deficit
• Commonly seen in overhead throwers.
• Contracture of posterior capsule or posterior band
of inferior glenohumeral ligament.
Centre of rotation of humerus shifts
posterosuperiorly.
• Leads to increase in length of the anterior aspect of
the capsule.
• Decrease contact point of anteroinferior aspect of
capsule with the proximal part of the humerus.
• Results in excessive external rotation.
• Biceps anchor peeled back results in injury to
posterior superior structures(labrum).
• Further laxity of anterior capsule leads to torsional
failure of rotator cuff which can further leads to
rotator cuff tear and SLAP leasion.

GIRD
• Andrews and Wilk proposed that the repetitive micro trauma
associated with throwing leads to tissue fatigue, inflammation,
decreased muscle performance with resulting instability, and
ultimately tissue damage.10 which can be underlying cause for
posterior capsule thickness and then tightness. The
• Glenohumeral internal rotation loss can be due to two reasons
• a: due to bony remodelling, b: posterior capsular/cuff contracture 1.
Contracted posterior/inferior capsule will not permit full external
rotation of the humerus. In an effort to “find the slot” the thrower
will begin to rotate around a new instant centre of rotation – one
that is more posterior and proximal. In essence, a tightened
posterior inferior capsule will drive the humerus more proximally
and posteriorly. The concomitant posterior shift in humeral head
contact, tightening of the posterior capsule, and anterior laxity can
also result in significant rotator cuff pathology by a mechanism
termed posterior superior glenoid impingement

• Clinical presentations-more than 25 degrees
loss of internal rotation can be upto 50
degrees in throwers.
• Increase in external rotation range-30
degrees.
Rehabilitation-kibler studied that
posteroinferior capsule stretching group
improved more than routine exercise group.
38 % decrease in the occurrence of shoulder
problem was found.

phases Duration Kinematics kinetics Proper
mechanics
Pathomechanic
s
WIND UP
(preparat
ory
phase)
Elevation
of lead
leg to
highest &
pivots
around
stance leg
0.5-1.0
sec
Shoulder
flexed,abd
uct-ed
with
elbow
flexed to
45
degrees.
Mild tension in the
muscles of shoulder
girdle(supraspinatus,ant.
and middle deltoid and
clavicular portion of
pectoralis major) and
elbow-biceps,brachii and
brachioradialis.
Hip- lead leg
flexors(concentric) and
abductors(isometric) and
extensors(eccentric)
Stance leg bend slightly by
eccentric contraction of
quadriceps.
Keeps COG
over the
back leg to
allow
generation
of maximum
momentum
once
forward
motion is
initiated to
upper limb
to the ball.
If momentum
falls
prematurely,kin
etic chain will
be distrupted
leads to greater
force from the
shoulder to
propel ball at
top velocity.

Phases Duration kinematics kinetics Proper
mechanics
Pathomechanics
Stride
phase
Lead leg
begins to
fall and
moves
towards
the target
and 2
arms
separates.
0.5-0.75
sec
Lead foot contacts
the ground.
Increased distance
between legs.
Pelvis achieves
maximum rotational
velocity(400-700
deg/sec).
Lumbar
hyperextension.
Knee and hip stance-
extension.
Stride-hip and knee
flexion(45-55deg)
Shoulder-90 degrees
and external
rotation-60
Elbow-80-100
degrees.
Deltoid is very
active.
Rotator cuff-
supraspinatus
is active
more.
If front foot
open
position-
increase
shoulder
anterior force
to 3N.
Stride
length-70-
80% of
atheletes
height.
Front foot
inwards-5-
25 degrees.
Decrease stride
length-decreases
ball velocity.
Closed-block
rotation of pelvis
& decrease
contribution from
lower extremity
segments.
Open foot angle-
too early pelvic
rotation-early
dissipation of
ground reaction
forces and LE
contributions-
hyperangulation
and arm lag-
increased stress
on medial elbow

mechanics
Pathomechanic
s
Arm
cocking
phase-
lead foot
contact to
maximal
shoulder
external
rotation
0.10-0.15
sec
Upper
body
rotated
towards
the target
Pelvic
maximal
external
rotation
Lead knee
begins to
extends.
10-20 deg
horizontal
abduction.
Scapula
retracts
and
rotates
upwards
Shoulder-Increase activity
of teres minor and
infraspinatus to resist
anterior forces.
Supraspinatus is least
active.provides GH joint
compressive forces of 550-
770 N.
Rhomboids,levator
scapulae and trapezius
activity.
Pelvic
rotation
followed by
upper trunk
rotation,
shoulder
externally
rotates and
trunk
arches.
Poor timing
between pelvic
rotation &
upper trunk
rotation
decreases ball
velocity leads
to decrease
internal
rotation torque.
Abduction and
external
rotation-
posterior band
of inferior GH
ligament-
bowstringing
effect leads to

mechanics
Pathomechanic
s
Arm
cocking
phase-
lead foot
contact to
maximal
shoulder
external
rotation
0.10-0.15
sec
Late
cocking-
elbow-95
deg
flexion.
shoulder
External
rotation-
165-175
degrees.
Abduction-
90-95
degrees.
Horizontal
adduction-
10-20
degrees.
As torso rotates increase
activity of anterior deltoid
& p.major to bring
throwing extremity into
horizontally adducted
position of 15-20 deg.
Late phase-inc. activity of
serratus anterior.
Elbow-max .valgus
torgue(64%) flexors and
pronator counter
torque(64 Nm).
Increase biceps activity.
External
rotation
allows
accelerating
forces to
acts over
the longest
distance,gre
ater
prestretch
will leads to
the greater
elastic
recoiling
effect.
posterior
superior shift of
humeral head-
can leads to
rotator cuff &
labral
pathology.
Excessive
horizontal
adduction,exter
nal rotation and
elbow flexion
increase
shoulder and
elbow kinetics.

mechanics
Pathome
chanics
Accelerati
on phase
Phase
between
maximum
external
rotation
and ball
release
0.03-
0.04sec
Trunk continues to
rotates and tilt.
Scapula protracted
to maintain stable
position of head of
humerus to rotate
internally and
horizontal
adduction.
Arm-175-100 deg
internal rotation in
only 42-58 ms.
Internal rotational
velocities high-
7000-9000 deg/sec
Elbow- from 90-
120 deg flexion to
25 deg extension
at ball release.
Transfer of potential
energy to the upper
extremity.
Maximal activity of
subscapularis at this
phase.
Max.activity of
serratus anterior.
Biceps flexion
torque-61 Nm just
before ball release.
Transfer of
centrifugal force to
elbow helps in
extension and
concentric activity of
triceps.
Decrease time
between
max.shoulder
internal
rotation and
inc.trunk tilt at
ball release
increase ball
velocity.
Elbow
extension
followed by
shoulder
internal
rotation.

phases Durati
on
Kinematics kinetics Proper
mechanics
Pathomechanics
Accelerati
on phase
Phase
between
maximum
external
rotation
and ball
release
0.03-
0.04se
c
Max.extension
angular velocity at
elbow just before ball
release-2251
deg/sec.
Radioulnar-pronation
90 deg in 10 sec.
Lead leg-hip flexion
and knee extension.
Forward movement
of trunk-30-55
degrees.
Max angular velocity-
300-450 deg.
Shoulder abducted
approx-90-110 deg
Ar.-10-15 deg behind.
Inc.activity
of rectus
abdominus,
obliques
and lumbar
paraspinals.
Inc. activity
of rectus
femoris
Lead leg hip
flexion & knee
extension-
inc.angular
momentum of
trunk.
Trunk tilt allows
acceleration to
greater distance-
more forces
transferred to
the ball.
Inc.knee
extension at ball
release-increases
the velocity.
Dec.knee
extension
velocity-dec.ball
velocity.
Dec.shoulder
abduction-
inc.elbow varus
torque.
Decrease forward
tilt-decrease
velocity of ball.
>110 deg
abduction can
leads to rotator
cuff
impingement.

phases Duratio
n
mechanics
Pathomecha
nics
Deceler
ation
Betwee
n ball
release
&
max.hu
meral
internal
rotatio
n and
elbow
extensi
on
0.03-
0.05sec
Ends with shoulder
internal rotation to
0 deg.
Abduction -100
deg
Horizontal arm
adduction-35 deg.
Arms continues to
adduct and
internally rotates.
After ball release
elbow flexion-25
deg and
abduction-93
degrees.
Violent phase,greatest
joint loading,excessive
posterior(400 N)& inferior
shear force(300 N)anterior
compressive forces >1000
N.
Inc.eccentric contractile
loading of teres
minor,infraspinatus &
posterior deltoid)
Increase biceps &
brachialis activity to
decelerate the rapidly
extending elbow &
pronating elbow.
Teres minor activity
highest to resist anterior
humeral head translation
,horizontal adduction &
int.rotation.
Movement
of entire
body helps
in
dessipatio
n of
energy of
arm.
Posterior
capsule and
soft tissues
reaction
leads to
GIRD.

phases Duratio
n
mechanics
Pathomecha
nics
Follow
throug
h phase
<1 sec Horizontal
adduction increase
to 60 degrees.
Rear leg comes
forwards.
Muscle firing decreases
and decrease joint loading
and minimal forces.
Movement
of entire
body helps
to
dissipate
energy.
forward
leg assisst
in coming
to
balanced
position.

Physics of throwing
• The throwing activity starts with large base segments(hip,trunk and pelvis)
& terminates with smaller base segment(shoulder,upper arm forearm and
hand).
• Segments involved in throwing-lower extremity,pelvis,trunk,shoulder
girdle,upper arm,forearm and trunk.These segments moves around joint
at their axis.
• Rotational inertia
A measure of a body's resistance to angular acceleration
angular acceleration for a body segment by applied torque is indirectly
proportional to segment’s rotational inertia.
• Depends on mass and distance between axis of rotation.
• More the rotational inertia less will be the angular acceleration of
segments.

• Throwing body follows the law of
conservation of momentum(product of
angular velocity and rotational inertia of a
system remains constant).
• Two types of forces acts on the throwing
athelete –external-athelete applies force to
the ground,an equal but opposite force is
applied by the ground to the athelete,this
force adds both angular and linear
momentum to the system.
• Internal- deceleration of pelvic segments
accelerates the trunk segment,angular
momentum lost by the pelvis is gained by
the trunk segment,deceleration of trunk
segment accelerates the arm segment.This
process continues angular momentum
finally transferred to the hand segment with
release of ball.

Determining factors for maximal
distance• Release velocity-greater release
velocity produces greater distance.
• Release angle-optimal release angle
produces greater distance.
• Release height-greater release height
produces greater distance.
• Aerodynamics

Aerodynamics
• Aerodynamic forces depends on-ball velocity and surface
roughness .
• Low ball velocity & smooth ball-generates area of positive
pressure in front and negative area in along their surfaces
as the air speeds up and this area of negative pressure
extends to the rear of the ball,generating a significant drag
forces.
• High velocity and rough surface-velocity,values of forces
decreases with surface roughness,the flow of air becomes
turbulent,such flow still generates a positive pressure at
front of the ball.negative pressure at the sides and rear of
the ball reduced,thus drag force is less for a rough ball.

• Fig;showing aerodynamic forces on a ball moving through air.
• A)low velocity balls regardless of surface roughness,pass smoothly through air generating an area of positive
pressure in front of them & an area of negative pressure along their surfaces as the air speeds up to go around
the ball,this area of negative pressure extends to the rear of the ball,generating a significant drag force.
• B)same velocity with increased roughness,flow of air around the ball becomes turbulent.still positive pressure
in front of ball.However,the area of negative pressure at the sides & rear of the ball is
reduced.Thus,counternuitively,the drag force is less for a rough ball than for a smooth ball.

Aerodynamics -Magnus effect
When spinning ball is thrown,it deviates
from its usual path in flight.
Spin in air,air around sets in rotation in the
form of concentric stream lines.
If the ball is spinning as well as moving
linearly,the stream lines set at the top of
the top of the ball due to two types of
motion are opposed to each other.
Velocity of air flow is greater below than
above the ball and pressure up is
more,resultant force F acts upon ball at
right angle to the linear motion is down.
This force provides necessary centripetal
force to move the ball along the curved
path.This effect is called magnus effect.

Types of pitches
• Commonly used slider,changeup and
curveball.
• 1.SLIDER-mimics the appearance of
fast ball in arm speed & motion with
slightly decreased ball velocity & the
addition of horizontal plane ball
movement(break) to fool the hitter.
• Arm position and grip remains same
as fast ball,but the pitcher supinates
the forearm until ball release during
late acceleration,generating rotation
of the ball around the central
axis,which generates horizontal
plane movement from right to left
for right handed pitchers.
• Fingers-3 and 9 o’clock position.

• CHANGE UP-the change up is thrown with
the same arm slot & motion as fast ball.
• The spin generated on the ball is in the
same direction of the
fastball(backspin)with a lower velocity to
distort the hitter’s timing.
• The ball is positioned deeper to palm to
decrease the velocity of pitch.
2.CURVEBALL-is thrown slower,with different
trajectory and spin.
• Pitcher’s fingers are located on top of the
ball at release to generate a forward
rotation(12 to 6o’clock rotation) that
allows vertical plane movement(break or
drop).

Comparision of throwing mechanics in overhead
throwers with respect to the pitch types
• Eschamilla et al studied the throwing
mechanics in overhead atheletes.
• Fastball are thrown with more pelvis and
upper torso angular velocities & stride
length.
• Peak shoulder angular velocities were
significantly greater when throwing fastball
then curveball.
• Curveball was thrown with more knee
flexion,greater forward and lateral trunk
tilt,increased shoulder horizontal adduction
at ball release.
• Shoulder abduction higher during
acceleration in the curveball versus fastball.
• Fastball-lead knee continues to flex
throughout much acceleration & is greater at
ball release.

Research-elite sports medicine & center for motion analysis)
KINEMATICS
• Wrist remains extended more for fastball then in
curveball.
• Highest wrist ulnar angular velocity for curveball(360±47
deg).
• Wrist remains pronated for the fastball as compared to
curveball.
• Elbow angular velocity were slightly higher for fastball
than curveball.
• Overall arc of motion for glenohumeral joint was greater
for fastball.(fastball 124±12 deg vs. curve 117±17 deg).
• Peak velocity of GH internal rotation velocity was higher
for the fastball(3619±656deg/sec) vs.
curveball(3409±722 deg/sec)(p=0.023).

KINETICS
• Elbow peak varus moment-fastball-59.6±16.3 more as compared to
curveball varus moment of 54.1±16.1Nm(p<0.001).
• Shoulder internal rotation moment-fastball=59.8±16.5Nm
curveball=53.9±15.5Nm
These findings are contrary to the long held belief that throwing a
curveball placed the arm at a higher risk of injury than throwing a
fastball.
Stress on elbow & shoulder were directly related on ball velocity-lower
force at joint with the slower curveball & higher force with the
fastball.

References
• Sports physiotherapy -applied science and
practice(zuluaga and christopher briggs)
• Atheletic injuries and rehabilitation(zachazewiski)
• The atheletic shoulder-book
• Sports injuries and rehabilitation-by cars petersons-3rd
edition.
• Post surgical sports rehabilitation(Robert c.mashe).
• The shoulder and the overhead atheletes(sumant
G.krishnan)
• Sports specific rehabilitation(robert donatelli)
• Research articles
• Internet
• You tube

Biomechanics of Throwing

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