Overarm Throwing and Striking

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

3. Pitching • 3 phases • cocking (wind-up) • acceleration • deceleration

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

5. 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

6. 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

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

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

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

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

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

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

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

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

15. Shoulder Girdle Musclesas 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

16. Shoulder Girdle Musclesas Stabilizers • shoulder girdle often used to provide a stable base on which muscles of shoulder joint may pull 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 ABDUCTION

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

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

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

20. coracobrachialis Shoulder Flexion Anterior Deltoid Pectoralis Major Clavicular Head

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

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

23. Shoulder Abduction supraspinatus middle deltoid

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

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

26. Shoulder Girdle Muscles Trapezius

27. Shoulder Girdle Muscles Serratus Anterior

28. Shoulder Girdle Muscles Levator Scapulae Rhomboid Minor Rhomboid Major

29. Shoulder Girdle Muscles Subclavius Pectoralis Minor

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

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

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

33. Horizontal Shoulder Abduction middle deltoid infraspinatus teres minor posterior deltoid

34. 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

35. 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

36. 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 torque = 20 N * 15 cm + 15 N * 15 cm = 525 N cm 15 cm 30 cm

37. Fm wt dm if : arm weighs 33 N : arm CM is 30 cm from shoulder axis : deltoid pulls along a line 3 cm away from shoulder axis 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

38. Fm wt dm 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