Quiz 2.1

Question 1

Line of action

Answer 1

The line between the origin and insertion (tendon to tendon)

Question 2

Muscle function

Answer 2

Generate force

Question 3

How do you get a torque to be produced

Answer 3

The line of action does not intersect directly with the axis of rotation –> torque produced about joint it crosses
Force applied directly through AOR does NOT produce torque.

Question 4

Torque

Answer 4

Tendency of a force to rotate an object about an axis
Units: Nm
T = F*(Perp. distance from axis)

Question 5

Moment arm

Answer 5

Perp. distance from the LOA of muscle force to the center of the rotation of the joint
Depends on: origin/insertion and joint angle
As joint angle changes during movement, the moment arm length changes
T = F*(distance perp to force)

Question 6

Lever arm

Answer 6

Distance from axis to perp. component of force
T = perp force*(distance)

Question 7

Net joint torque

Answer 7

Summation of torques produced by all muscles acting simultaneously at a joint

Question 8

Torque when concentric muscle action

Answer 8

Net joint torque is in the same direction as joint motion
ex: arm flexion

Question 9

Torque when eccentric muscle action

Answer 9

Net joint torque is in the opposite direction as joint motion
ex: arm extension

Question 10

Concentric internal/external torque

Answer 10

Internal T greater than external T
ex: Bicep torque greater than the dumbbell, you can lift it

Question 11

Eccentric internal/external torque

Answer 11

External torque greater than internal torque –> lengthening

Question 12

Isometric internal/external torque

Answer 12

Internal and external torques are equal, object remains stationary

Question 13

Why is more muscle force necessary when muscle inserts at an angle instead of perp.

Answer 13

The moment arm becomes smaller due to the angle. See diagram

Question 14

Lever

Answer 14

A simple machine consisting of a rigid body that rotates about an axis

Question 15

Fulcrum

Answer 15

Point about a lever rotates (axis)

Question 16

How are levers classified

Answer 16

By Axis, motive force, and resistive force
ARM

Question 17

Mechanical advantage

Answer 17

MA = (Moment arm of motive force)/(moment arm of resistance)

Question 18

Force moment arm > resistance moment arm

Answer 18

MA > 1.0
Not likely in body
Low force necessary to overcome resistance but resistance moved through limited ROM

Question 19

Resistance M.arm > Force M.arm

Answer 19

MA <1.0
Most similar to body
Large force necessary to overcome resistance but moved through larger ROM

Question 20

1st class lever

Answer 20

Axis between the motive force and resistive force (RAM)
Ex: elbow extension (Tricep-elbow joint- arm)
Plantar flexion

Question 21

2nd class lever

Answer 21

ARM
Torque advantage (MA) usually exists for motive force (limited ROM)
Ex: Push-up

Question 22

3rd class lever

Answer 22

AMR
most joints
Advantage in ROM and speed but disadvantage in force
ex: arm flexion, hip flexion, knee extension (quad inserts below knee)

Question 23

Uniarticular

Answer 23

Muscles crossing one joint

Question 24

Biarticular

Answer 24

Muscles crossing two joints

Question 25

Multiarticualr

Answer 25

Muscles crossing multiple joints

Question 26

Biarticulate muscles

Answer 26

Contribute to two joint torques simultaneously Torque produced by muscle on one joint is dependent on angle of the other joint

Question 27

Lombard's Paradox

Answer 27

See slide 2 antagonistic muscles active in one movement but each muscle ends up being more active at a different joint therefore enhancing each other to complete the total movement Biarticulate muscles can act like tendon

Question 28

Shoulder ligaments

Answer 28

Superior acromioclavicular Coracoacromial Coracoclavicular Coracohumeral Capsular ligament

Question 29

general function of ligaments

Answer 29

provide stability for the joints

Question 30

Other shoulder structures

Answer 30

Articular cartilage Glenoid labrum Bursae

Question 31

SLAP (Superior Labrum Anterior and Posterior) tear

Answer 31

Where the bicep tendon attaches to labrum Causes: Heavy lifting, repetitive overhead movement like throwing, falling onto outstretched hand

Question 32

Muscles of shoulder

Answer 32

Know functional relevance, go through slide tables of movement

Question 33

Why do so many muscles cross the shoulder (structural and functional reasons)

Answer 33

Structural: Stability for the inherently unstable joint Functional: The triaxial joint needs many muscles to perform all the movements of the shoulder. Many smaller muscles allow for greater DOF

Question 34

Why does anterior and middle deltoid produce max force of muscles crossing the shoulder

Answer 34

Because arm's function is to lift and carry which is primarily a movement in the front/middle of body. ** see table

Question 35

Rotator cuff muscles

Answer 35

Supraspinatus, infraspinatus subscapularis, teres minor ** see table

Question 36

4 joints of the shoulder

Answer 36

Sternoclavicular, acromioclavicular, scapulothoracic, glenohumeral

Question 37

Sternoclavicular joint

Answer 37

Condylar non-axial joint articular disc A/P sternoclavicular ligament and costoclavicular ligament 3 DOF (Elev/depress, protrac/retract, post rotation(Closed))

Question 38

Acromioclavicular joint

Answer 38

Plane, non-axial joint Articular disc S/I acromioclavicular ligament, coracoclavicular lig. Sloping interface leads to possible dislocation from lateral, superior force 3 DOF (Up (Closed)/down rotation, int/ext rotation, A/P tilting) **See images for movements

Question 39

Close packed

Answer 39

Maximum articulation between 2 bones in joint

Question 40

Open packed

Answer 40

Minimal articulation between bones in a joint

Question 41

Scapulothoracic joint

Answer 41

Not a true joint Elevation/depress Protract/retract Up/down rotation

Question 42

When is Sternoclavicular the axis for scapulothoracic

Answer 42

Elevation, protraction

Question 43

When is acromioclavicular the axis for scapulothoracic

Answer 43

Downward rotation, internal rotation, upward rotation

Question 44

Glenohumeral joint

Answer 44

Ball and socket, triaxial G. Fossa points up and humeral head points up and back