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 muscles active
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 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

16. 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

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

18. 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

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

20. Shoulder Flexion coracobrachialis 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 subscapularis
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 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
+ 15 N * 15 cm
= 525 N cm
15 cm
30 cm

37. 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

38. 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