Overarm Throwing and Striking an overhead pattern common to many different sports

Pitching 3 phases cocking (wind-up) acceleration deceleration

Cocking Phase front leg strides forward trunk rotation shoulder abducted to 90, shoulder ext rotation, scapular retraction, and elbow flexion end cocking phase

Cocking Phase early stage deltoid and supraspinatus produce abduction (scapulo-humeral rhythm) infraspinatus and teres minor initiate external rotation and assist abduction trapezius and rhomboids retract the scapula end early stage

Cocking Phase late stage (striding leg hits ground) latissimus dorsi and pectoralis major slow the backward movement and initiate forward motion in shoulder (alot of activity) triceps brachii activates to slow elbow flexion serratus anterior controls scapular movement end late stage

Cocking Phase late stage (cont.) teres minor and infraspinatus increase activity to complete external rotation supraspinatus increases activity to maintain abduction end late stage

Cocking Phase external rotation - EXTREME external rotation terminated by forces from anterior joint capsule & ligaments subscapularis pectoralis major triceps brachii teres major latissimus dorsi

Cocking Phase common injuries resulting from EXTREME external rotation tendinitis of supraspinatus tendon muscle strain of pectoralis major, teres major, or latissimus dorsi

Acceleration Phase explosive phase characterized by initiation of elbow extension shoulder internal rotation maintenance of shoulder abduction at 90 shoulder transverse abduction scapular protraction

Acceleration Phase transverse abduction and internal rotation subscapularis, latissimus dorsi teres major pectoralis major scapular protraction serratus anterior elbow extension triceps brachii

Acceleration Phase injury localized to subacromial area subjected to compression during abduction and internal rotation

Deceleration Phase begins after ball release and after maximal internal rotation in shoulder early stages characterized by rapid shoulder external rotation transverse abduction

Deceleration Phase late stages characterized by muscles active trunk rotation internal shoulder rotation maintenance of shoulder abduction the tendency to transversely abduct shoulder muscles active deltoid latissimus dorsi trapezius supraspinatus

Shoulder Girdle Muscles as Movers often the initiator for movement elevation lifting depression push downward protraction reaching, throwing, push fwd retraction pulling backward upward rotation ROM overhead reaching downward rotation force shoulder adduction

Shoulder Girdle Muscles as Stabilizers shoulder girdle often used to provide a stable base on which muscles of shoulder joint may pull SHOULDER ABDUCTION agonist = deltoid antagonist = latissimus dorsi stabilizer(s) = trapezius to hold shoulder girdle in place so the deltoid can pull the humerus up neutralizer = teres minor if latissimus dorsi is active then the shoulder will tend to internally rotate so the teres minor can be used to counteract this via its ability to externally rotate the shoulder

Shoulder Girdle Muscles levator scapulae trapezius rhomboids serratus anterior pectoralis major pectoralis minor subclavius

Actions of the Scapula Rhomboids Rhomboids Trapezius Trapezius Levator Scapulae Rhomboids Trapezius Levator Scapulae Trapezius Pectoralis Minor Serratus Anterior Pectoralis Minor Trapezius Serratus Anterior Rhomboids Pectoralis Minor Levator Scapulae

Movements of shoulder flexion - extension abduction - adduction medial and lateral rotation aka internal and external rotation transverse abduction - adduction

Shoulder Flexion coracobrachialis Anterior Deltoid Pectoralis Major Clavicular Head

Shoulder Extension NOTE: If no external resistance -- gravity acts as primary mover and flexors antagonistically control movement

Shoulder Extension NOTE: If no external resistance -- gravity acts as primary mover and flexors antagonistically control movement

Shoulder Abduction supraspinatus middle deltoid

Shoulder Adduction teres major latissimus dorsi NOTE: If no resistance -- then gravity acts as primary mover with shoulder abductors antagonistically controlling movement

Shoulder Adduction pectoralis major -- sternal portion NOTE: If no resistance -- then gravity acts as primary mover with shoulder abductors antagonistically controlling movement

Shoulder Girdle Muscles Trapezius

Shoulder Girdle Muscles Serratus Anterior

Shoulder Girdle Muscles Levator Scapulae Rhomboid Minor Rhomboid Major

Shoulder Girdle Muscles Subclavius Pectoralis Minor

Medial Rotation of the Shoulder teres major subscapularis primary muscles -- although on posterior side insert anteriorly on humerus subscapularis

Lateral Rotation of Shoulder infraspinatus teres minor primary muscles on posterior side insert posteriorly on humerus

Horizontal Adduction of the Shoulder coracobrachialis anterior deltoid pectoralis major (both heads)

Horizontal Shoulder Abduction middle deltoid infraspinatus teres minor posterior deltoid

Loads on Shoulder Complex majority of loads supported through shoulder (glenohumeral) joint loads from outstretched arm segmental weight acts through segmental center of mass moment arm of segmental weight is the perpendicular distance b/w weight’s line of action and a

Loads on Outstretched Arms segmental weight acts thru segmental center of mass moment arms a = 0 cm b = 20 cm c = 30 cm shoulder torque A. 0 N cm B. 700 N cm C. 1050 N cm C moment arm is perpendicular distance b/w line of action of weight and line parallel through axis of rotation B A if segment weight = 35 N c b

upper arm weight = 20 N forearm weight = 15 N B A Position A torque = 20 N * 15 cm + 15 N * 30 cm = 750 N cm Position B + 15 N * 15 cm = 525 N cm 15 cm 30 cm

if : arm weighs 33 N : arm CM is 30 cm from shoulder axis : deltoid pulls along a line 3 cm away from shoulder axis dm Fm wt to hold arm steady must balance the torques so the sum of the torques = 0 0 = (Fm)(3 cm) - (33 N)(30 cm) Fm = (33 N) ( 30 cm)/(3 cm) = 330 N

joint reaction force will equal the muscular force pulling on bone so 330 N of compressive force acting on shoulder if a person has a mass of 70 kg then their weight = 686 N so compressive force is about 48% of body weight dm Fm wt