Chapter 8 Flashcards
What percentage of body weight do compressive forces on the glenohumeral joint reach?
50% of body weight
What is the recommended shoulder position when sitting at a desk?
20° or less abduction and 25° of flexion
What two bones make up the pectoral girdle?
Clavicle & Scapula
What are the primary functions of the shoulder girdle?
- Increase range of motion (ROM)
- Stabilize scapulae and clavicle during movements
What is the first anterior muscle of the shoulder girdle?
Serratus Anterior
Where does the serratus anterior insert?
Medial border of the scapula
What is the primary role of the serratus anterior?
Stabilization of the shoulder girdle
What is a common condition associated with dysfunction of the serratus anterior?
Winged Scapula
What is the second anterior muscle of the shoulder girdle?
Pectoralis Minor
What does the pectoralis minor do?
Depresses the shoulder
What are the four parts of the trapezius muscle?
Upper, Middle, Lower, and Transverse
What is a force couple in the context of shoulder girdle movement?
Trapezius and Serratus Anterior for upward rotation
What is the function of the rhomboids?
- Downward rotation of the scapula
- Retraction of the scapula
What muscles assist with downward rotation of the scapula?
Levator Scapulae and Rhomboids
What is the significance of neutralization in biomechanics?
Eliminating unwanted movements in other planes to perform a specific motion
What primary plane of motion is associated with upward rotation?
Frontal Plane
What are the four rotator cuff muscles?
- Supraspinatus
- Infraspinatus
- Teres Minor
- Subscapularis
What role do the rotator cuff muscles play?
Stabilize the head of the humerus
What muscles act as agonists in elbow flexion?
- Biceps Brachii
- Brachialis
- Brachioradialis
What is internal torque defined as?
Internal Force x Internal Moment Arm
What is the common classification of the elbow joint?
Hinge joint
What is lateral epicondylitis commonly known as?
Tennis elbow
What is medial epicondylitis also referred to as?
Little-leaguer’s elbow
What is the action of the wrist during flexion?
Simultaneous contraction of FCR & FCU
What are the types of articulations in the hand?
- Intercarpal
- Carpo-metacarpal
- Metacarpo-phalangeal
- Inter-phalangeal
What are the common injuries associated with the elbow?
- Dislocations
- Overuse injuries
- Stress injuries to soft tissue
What is the significance of the moment arm in torque production?
It affects the amount of torque generated by a muscle
What is the effect of slight hyperextension of the glenohumeral joint on biceps force output?
Lengthens the biceps and increases force output
What is the purpose of the neutralization chart?
To identify and eliminate unwanted movements for specific actions
What happens during a ‘pull-up’ regarding muscle function?
Adduction of the shoulder girdle with stabilization needed
What percentage of the body’s weight does the arm make up?
5% of the body weight.
What is the estimated compressive force on the glenohumeral joint?
The compressive forces are estimated to reach 50% of body weight.
What abduction angle do ergonomists recommend when seated at a desk?
20° or less.
What flexion angle do ergonomists recommend when seated at a desk?
25° of flexion.
What are the two bones that constitute the pectoral girdle?
Clavicle & Scapula.
What movements primarily involve the shoulder girdle?
Shoulder girdle movements occur primarily in conjunction with movements of the glenohumeral joint.
What are the functions of the shoulder girdle?
To accompany glenohumeral joint movement to increase Range of Motion (ROM) and to stabilize the scapulae and clavicle during glenohumeral joint movements.
How many primary muscles make up the shoulder girdle?
Five (5) primary muscles.
What is the first anterior muscle of the shoulder girdle?
Serratus Anterior.
Where does the serratus anterior insert?
Medial border of the scapula.
What is the primary role of the serratus anterior?
Stabilization of the shoulder girdle.
Why is the stabilizing effect of the serratus anterior necessary?
To allow muscles of the glenohumeral joint to pull from a stabilized base.
What is the second anterior muscle of the shoulder girdle?
Pectoralis Minor.
What does the pectoralis minor do for the shoulder?
It depresses the shoulder to counteract the upward thrust.
What is the first posterior muscle of the shoulder girdle?
The Trapezius.
How many parts does the trapezius muscle have?
Four parts.
What force coupling is formed by the trapezius and serratus anterior?
Force Couple for upward rotation of the shoulder girdle.
What is the contribution of the lower trapezius?
It contributes to the upward rotation of the scapula.
In what plane do all parts of the trapezius contribute to shoulder girdle retraction?
Transverse Plane.
What are the two movements associated with upper trapezius activity?
Extension & Hyperextension of the cervical vertebrae.
What muscles comprise the second posterior muscle group?
The Rhomboids.
What shape is the rhomboid muscle?
Rhomboid in shape.
What is the function of the rhomboids in the frontal plane?
Force couple with Pectoralis minor and Serratus Anterior to control ‘downward rotation’.
How do the rhomboids stabilize the scapula?
They stabilize the scapula during glenohumeral adduction.
What is a common example of the need for stabilization during a pull-up?
The muscles used must stabilize the scapula for the movement to occur.
What is the role of the levator scapulae?
Assist with downward rotation.
What is necessary to perform movements in any planes of motion?
It is necessary to eliminate or reduce movements in the remaining planes of motion.
What primary plane of motion is implied in bowing to someone?
Sagittal.
What two planes of motion are being neutralized when bowing?
Frontal & Transverse.
What is the significance of constructing neutralization charts?
To understand the reason for eliminating unwanted movements and to be able to construct charts yourself.
What muscles comprise the rotator cuff?
Four muscles: Supraspinatus, Infraspinatus, Teres Minor, and Subscapularis.
What is the primary role of the rotator cuff muscles?
Stabilize the head of the humerus.
Which muscles act as agonists at the elbow joint?
Biceps Brachii, Brachialis, and Brachioradialis.
What is the role of the biceps brachii in flexion?
It acts as a third-class lever for leverage.
What impact does slight hyperextension of the glenohumeral joint have?
It lengthens the biceps and increases force output.
What is a common elbow joint dislocation mechanism?
Most elbow dislocations are hyperextension injuries.
What injuries are progressively common in the elbow?
Stress injuries leading to inflammation, scarring, and calcium deposits.
What is ‘Tennis elbow’?
Lateral Epicondylitis, inflammation or micro-damage to the lateral side of the humerus.
What is ‘Little-leaguer’s elbow’?
Medial Epicondylitis, the equivalent injury on the medial side of the humerus.
What are the articulations in the wrist and hand?
Intercarpal, Carpo-metacarpal, Metacarpo-phalangeal, and Inter-phalangeal joints.
What muscles participate in wrist flexion?
Flexor Carpi Radialis (FCR) & Flexor Carpi Ulnaris (FCU).
What type of force is counteracted during gripping?
Large downward ‘distracting’ forces.
What is the natural tendency during a fall that can cause wrist injuries?
To sustain the force of a fall or excessive ‘hand plant.’
What percentage of body weight does the arm represent?
0.05
What proportion of body weight can compressive forces on the glenohumeral joint reach?
Estimated to reach 50%.
What do ergonomists recommend for shoulder position when seated at a desk?
20° or less abduction and 25° of flexion.
What are the two bones that make up the pectoral girdle?
Clavicle and Scapula.
What joint movements primarily occur in conjunction with glenohumeral joint movements?
Shoulder girdle movements.
What is the primary role of the serratus anterior muscle?
Stabilization of the shoulder girdle.
What is the insertion point of the serratus anterior?
Medial border of the scapula.
What is the function of the rhomboids?
Control ‘downward rotation’ of the scapula.
What is the primary action of the pectoralis minor?
Depresses the shoulder to counteract upward thrust.
What type of joint is the elbow classified as?
Hinge joint.
What common injuries are associated with the shoulder?
Involves 8 to 13% of all sport-related injuries.
What are the anterior muscles of the glenohumeral joint?
Pectoralis Major, Anterior Deltoid, Biceps Brachii, Coraco-brachialis.
What causes lateral epicondylitis?
Inflammation or micro-damage to the tissue on the lateral side of the distal humerus.
What is a common term for medial epicondylitis?
Little-leaguer’s elbow.
What muscles are involved in wrist flexion?
Simultaneous contraction of FCR (Flexor Carpi Radialis) and FCU (Flexor Carpi Ulnaris).
What must be neutralized during upward rotation to ensure pure motion?
Unwanted movements in any other planes.
What follows inflammation and swelling in stress injuries to the soft tissues?
Scarring of the soft tissue.
What happens when the position of crutches is set too high?
It requires more effort due to differences in moment arms.
What are the two primary posterior muscle groups of the shoulder?
The Trapezius and the Rhomboids.
What is the effect of slight hyperextension of the glenohumeral joint?
Lengthens the biceps and increases force output.
What anatomical structure stabilizes the head of the humerus?
Rotator cuff muscles.
What are the five primary muscles of the shoulder girdle?
Serratus Anterior, Pectoralis Minor, Trapezius, Rhomboids, Levator Scapulae.
What is necessary for movements in any plane of motion?
To eliminate or reduce movements in the remaining planes.
What causes upward rotation of the scapula?
Action of the trapezius together with the serratus anterior.
Name two posterior muscles of the glenohumeral joint.
Latissimus Dorsi, Teres Major.
What is the primary role of the rotator cuff?
Stabilize the head of the humerus during movement.
What is the common effect of stress injuries to soft tissue?
Progressive scarring and accumulation of calcium deposits.
How does the force exerted differ when crutches are set at a high position?
It creates greater external torque, requiring more internal torque.
How much range of motion do common elbow injuries typically go through?
30 to 130 degrees of flexion.
What are the classifications of muscle actions at the elbow joint?
Agonists: Biceps Brachii, Brachialis, Brachioradialis.
What stabilizes the scapula during glenohumeral adduction?
Rhomboids and Serratus Anterior.
Name the structure involved in creating a force couple for scapular movement.
Serratus Anterior and Trapezius.
What does the serratus anterior allow other muscles of the G.H. joint to do?
Pull from a stabilized base.
What plane is specifically addressed when discussing upward rotation of the scapula?
Frontal plane.
What is a potential outcome of anterior muscles of the elbow working together?
Contribute to flexion and movement mechanics.
What condition results from chronic inflammation in elbow soft tissues?
Tennis elbow or Golfer’s elbow.
