exercise science Chapter 4, 5

Pectoralis major

-Clavicular -medial half of clavical -Sternal -Costal portion of first 6ri All fibers insert on lateral portion of the humerus The pectoralis major has four actions which are primarily responsible for movement of the shoulder joint.[5] The first action is flexion of the humerus, as in throwing a ball side-arm, and in lifting a child. Secondly, it adducts the humerus, as when flapping the arms. Thirdly, it rotates the humerus medially, as occurs when arm-wrestling. The pectoralis major is also responsible for keeping the arm attached to the trunk of the body.[5][6] It has two different parts which are responsible for different actions. The clavicular part is close to the deltoid muscle and contributes to flexion, horizontal adduction, and inward rotation of the humerus. When at an approximately 110 degree angle,[citation needed] it contributes to adduction of the humerus. The sternocostal part is antagonistic to the clavicular part contributing to downward and forward movement of the arm and inward rotation when accompanied by adduction. The sternal fibers can also contribute to extension, but not beyond anatomical position.[7]

Functional anatomy of rotator cuff muscles

-Great degree of mobility w/limited stability -Round humeral head that articulates with a flat glenoid-critical to have head in fossa at all times -Supraspinatus compresses the head while the other rotator cuff muscles depress the humeral head during overhead motion.

Shoulder (Glenohumeral) Joint

-Greatest Range of motion of any joint -Shallow socket -reinforced ring of cartilage -Rarely have movement without scapular movement -reffered to as " pairing"

horizontal adduction

-Pectoralis Major -Deltoid (anterior)

Latissimus Dorsi

-Same as Teres major The latissimus dorsi is responsible for extension, adduction, transverse extension also known as horizontal abduction, flexion from an extended position, and (medial) internal rotation of the shoulder joint.[citation needed] It also has a synergistic role in extension (posterior fibers) and lateral flexion (anterior fibers) of the lumbar spine, and assists as a muscle of both forced expiration (anterior fibers) and an accessory muscles of ispiration (posterior fibers).[6] Most latissimus dorsi exercises concurrently recruit the teres major, posterior fibres of the deltoid, long head of the triceps brachii, among numerous other stabilizing muscles. Compound exercises for the 'lats' typically involve elbow flexion and tend to recruit the biceps brachii, brachialis, and brachioradialis for this function. Depending on the line of pull, the trapezius muscles can be recruited as well; horizontal pulling motions such as rows recruit both latissimus dorsi and trapezius heavily. Training The power/size/strength of this muscle can be trained with a variety of different exercises. Some of these include: Vertical pulling movements such as pull-downs and pull-ups (including chin-ups) Horizontal pulling movements such as bent-over row, T-bar row and other rowing exercises pull-overs deadlift

Rotator cuff

-frequently injured -subscapularis -suprasinatus -infraspinatus -teres minor -attach to the front, top, and rear of humeral head -point of insertion enables humeral rotation -vital in maintaining humeral head in correct approximation within glenoid fossa while more powerful muscles move humerus through its wide range of motion.

Horizontal adduction

Abduction (protraction)

Internal rotation

Abduction (protraction)

Scapulohumeral rhythym

Abduction- (0-90 degrees) -deltoid/supraspinatus -Teres major/latissimus dorsi stabilize

levator scapulae

Action strengthen stretch The levator scapulae originates from the dorsal tubercles of the transverse processes of cervical vertebrae one to four. The muscle is inserted into medial border of the scapula extending from superior angle to junction of spine and medial border of scapula [1] The levator scapulae may lie deep to the sternocleidomastoideus at its origin, deep or adjacent to the splenius capitis at its origin and mid-portion, and deep to the trapezius in its lower portion. Actions When the spine is fixed, levator scapulae elevates the scapula and rotates its inferior angle medially.[1] It often works in combination with other muscles like the rhomboids and pectoralis minor to rotate down. Elevating or rotating one shoulder at a time would require muscles to stabilize the cervical spine and keep it immobile so it does not flex or rotate. Elevating both at once with equal amounts of pull on both side of cervical spinal origins would counteract these forces. Downward rotation would be prevented by co-contraction of other muscles that elevate the spine, the upper fibers of the trapezius, which is an upward rotator. When the shoulder is fixed, levator scapula rotates and flexes the cervical spine laterally.[2] When both shoulders are fixed, a simultaneous co-contraction of both levator scapulae muscles in equal amounts would not produce lateral flexion or rotation, and may produce straight flexion or extension of the cervical spine.

External rotation

Adduction (retraction)

Horizontal abduction

Adduction (retraction)

Weak Contributing muscles (to shoulder)

Biceps brachii- weak flexor Triceps Brachii- extension, adduction, horizontal abduction.

Extrinsic (originate on scapula and attach to humerus NO axial attachment)

Deltoid teres major Coracobrachialis rotater cuff bicep/tricep

Downward rotation

Downward and medial movement -Glenoid fossa is rotated downward when downward movement of shoulder joint occurs ex: Lat pulls -agonists Pectoralis minor Rhomboid

Scapulohumeral rhythm

Flexion -Same scapula muslces -deltoid (ant) Pec major(clav) Biceps brachii (short head weak) Scapular -retract/depress/downward rotation -rhomboid, pec minor, trapezius, (mid lower)

movements of glenohumeral joint

Flexion/extension interal/exteral rotation abduction/adduction Horizontal abduction/horizontal adduction Diagonal patterns (adduction abduction) (wood chop)

Glenohumeral joint

Frequently injured due to anatomical design -shallowness of glenoid fossa -laxity of ligamentous structures -lack of strength and endurance in muscles -anterior or anterioinferior glenohumeral subluxations and dislocations common -posterior dislocations- rare -posterior instability problems are somewhat common

Glenohumeral Joint

Glenohumeral ligaments provide stability -especially aneriorly and inferiorlly -inferior glenohumeral ligament

Horizontal abduction

Infraspinatus teres major Deltoid (posterior)

Rotation (shoulder)

Internal -subscapularis -latissimus dorsi -teres major -pectoralis major

Upward rotation

Lateral and upward movement -Agonists: Middle trapezius Lower trapezius Serratus anterior

Intrinsic (originate on axial and attach to humerus, NO scapulae attachment)

Latissimus Dorsi Pectoralis major

Glenohumeral joint

Ligaments are quite lax until extreme ranges of motion reached due to wide range of motion involved - stability is sacraficed to gain mobility

Serratus anterior pectoralis minor

Shoulder protraction

Functions of Rotator cuff

Stabilization -Especially above 90 degrees -abduction -deltoid/supraspinatus displaces superior -Rotator cuff maintain head in scapula -Teres major also opposes deltoid -Must have efficient strength and endurance

Serratus anterior

Strengthening -winging All three parts described above pull the scapula forward around the thorax, which is essential for anteversion of the arm. As such, the muscle is an antagonist to the rhomboids. However, when the inferior and superior parts act together, they keep the scapula pressed against the thorax together with the rhomboids and therefore these parts also act as synergists to the rhomboids. The inferior part can pull the lower end of the scapula laterally and forward and thus rotates the scapula to make elevation of the arm possible. Additionally, all three parts can lift the ribs when the shoulder girdle is fixed, and thus assist in respiration.[1] The serratus anterior is occasionally called the "big swing muscle" or "boxer's muscle" because it is largely responsible for the protraction of the scapula — that is, the pulling of the scapula forward and around the rib cage that occurs when someone throws a punch. The serratus anterior also plays an important role in the upward rotation of the scapula, such as when lifting a weight overhead. It performs this in sync with the upper and lower fibers of the trapezius.[4]

Rotator cuff muscles

Subscapularis Supraspinatus infraspinatus teres minor

Coracobrachialis

The action of the coracobrachialis is to flex and adduct the arm at the glenohumural joint. Also, the coracobrachialis resists deviation of the arm from the frontal plane during abduction.[1] Therefore, the contraction of the coracobrachialis leads to two distinct movements at the shoulder joint. It both draws the humerus forward, causing shoulder flexion, and draws the humerus toward the torso, causing shoulder adduction. To a smaller extent, it also turns the humerus inwards, causing inward rotation.[2] Another important function of the coracobrachialis is the stabilization of the humeral head within the shoulder joint, especially when the arm is hanging freely at a person's side.[3]

Pectoralis minor

The pectoralis minor depresses the point of the shoulder, drawing the scapula inferior, towards the thorax, and throwing its inferior angle posteriorly.

subclavius

The subclavius depresses the shoulder, carrying it downward and forward. It draws the clavicle inferiorly as well as anteriorly.

teres major

The teres major is a medial rotator and adductor of the humerus and assists the latissimus dorsi in drawing the previously raised humerus downward and backward (extension, but not hyper extension). It also helps stabilize the humeral head in the glenoid cavity.

origin on axial skeleton to insertion on scapula (no attachment to humerus

Trapezius upper, middle, lower Strengthening

5 muscles primarily involved in shoulder girdle movements

Trapezius- upper, middle lower Rhomboids- Deep Levator Scapula Serratus anterior pectoralis minor- deep

deltoid

When all its fibers contract simultaneously, the deltoid is the prime mover of arm abduction along the frontal plane. The arm must be medially rotated for the deltoid to have maximum effect{[18]}. This makes the deltoid an antagonist muscle of the pectoralis major and latissimus dorsi during arm adduction. The anterior fibers are involved in shoulder abduction when the shoulder is externally rotated. The anterior deltoid is weak in strict transverse flexion but assists the pectoralis major during shoulder transverse flexion / shoulder flexion (elbow slightly inferior to shoulders). The anterior deltoid also works in tandem with the subscapularis, pecs and lats to internally (medially) rotate the humerus.[19] Deltoid muscle with superior limb in abduction The posterior fibers are strongly involved in transverse extension particularly as the latissimus dorsi is very weak in strict transverse extension. Other transverse extensors, the infraspinatus and teres minor, also work in tandem with the posterior deltoid as external (lateral) rotators, antagonists to strong internal rotators like the pecs and lats. The posterior deltoid is also the primary shoulder hyperextensor, more so than the long head of the triceps which also assists in this function.[20] The lateral fibers perform basic shoulder abduction when the shoulder is internally rotated, and perform shoulder transverse abduction when the shoulder is externally rotated. They are not utilized significantly during strict transverse extension (shoulder internally rotated) such as in rowing movements, which use the posterior fibers.[21]

Scapulohumeral rhythm

above 90 degrees -rotator cuff inferior -Serratus anterior, levator scapla, trapezius rotate

Rhomboids

action strengthen stretch The rhomboid muscles (/ˈrɒmbɔɪd/), often simply called the rhomboids, are rhombus-shaped muscles associated with the scapula and are chiefly responsible for its retraction. They are innervated by the dorsal scapular nerve. There are two rhomboid muscles on each side of the upper back:

extension

depression/downward rotation

adduction shoulder joint

downward rotation

flexion

elevation/upward rotation

rotation (shoulder)

external -infraspinatus -teres minor

Scapular movements

retraction/protraction upward and downward rotation elevation/depression

Trapezius (middle and lower) Serratus anterior

shoulder abduction (lateral raise)

Rhomboids Pectoralis minor

shoulder adduction

Trapezius (lower) Pectoralis minor

shoulder goes downward

Rhomboids, Trapezius (middle and lower)

shoulder goes inward (medial)

Rhomboids/Trapezius (upper and middle) levator scapula

shoulder goes up

The shoulder complex

the shoulder is an exteremely complicated region of the body -joint which has a high degree of mobility, but not without compromising stability -incomplete ring -involved in a variety of overhead activities relative to sport making it susceptible to a number of repetitive and over used type injuries

abduction shoulder

upward rotation