What is the sarcomere?
The fundamental unit within muscle fiber.
What are the contractile proteins of a muscle? What is there function?
- Actin
- Myosin
Shorten muscle fiber and generate active force.
What are the non-contractile proteins of a muscle? What do they do?
- Titin
- Desmin
Support the structure of the muscle fiber.
What is the components of extracellular connective tissue in muscle?
Collagen and elastin
What is the difference between a muscle belly, a muscle fascicle, and a muscle fiber?
Muscle belly = a bunch of fascicles put together.
Fascicles = a bunch of fibers put together
Muscle fiber = a bunch of myofibrils
Describe a fusiform muscle.
- Have parallel fibers attach to central tendon
- Typically longer
- Have a greater ROM potential
Describe a pennate muscle.
- Has oblique fibers that approach central tendon
- Typically are shorter
- Have more numerous fibers per given area = greater strength/greater force production
- Smallar ROM
What is force coupling?
- Another example of a synergist
- Formed when 2 or more muscles simultaneously produce force in different linear directions but produce torque in the same direction.
Example: Anterior tilt of pelvis
Describe the qualities of a concentric contraction.
- Typically a “shortening” muscle contraction.
- The movement usually occurs against gravity.
- Typically an acceleration activity.
Describe the qualities of a eccentric contraction.
- Typically a “lengthening” muscle contraction.
- Movement usually occurs with gravity.
- Typically a deceleration activity.
Describe an isometric contraction.
- Allows contraction of the muscle without movement through full ROM.
- Usually for post-op rehabilitation.
Describe an isokinetic contraction.
- Allows the ability to adjust resistance throughout ROM of the muscle to account for stronger/weaker areas.
What type of contraction causes more overall muscle damage?
Eccentric Contractions
What is tension? Where does active tension come from? And what builds passive tension?
Tension = force built up within a muscle
- Active tension comes from contractile units
- Passive tension is built by stretching
What is total tension?
Combination of active and passive tension.
What is tone?
Slight tension in muscle at all times; state of readiness.
Describe passive length tension.
- When a muscle is stretched, spring-like resistance (stiffness) is generated within the muscle.
- Passive tension is attributed to elastic forces produced by non-contractile elements.
What does the passive length tension curve tell you?
- Passive tension is created after the critical length is reached.
- The tension is increased as the tissue is stretched.
- High tension results in rupture or failure.
Describe active-length tension.
- Muscle is generating active force.
- Ideal resting length = length that allows the greatest number of crossbridges
- Potential crossbridges decrease as the muscle is stretched or shortened from resting length. So less active force can be generated.
- Peak of curve = ideal resting length. Place where the most force can be produced.
What does the length-tension relationship tell you?
- Muscle length is a factor that determines the amount of tension present.
- Muscle can produce greater force if put on stretch prior to contracting.
In the length tension relationship, what is the difference for muscles that span 1 or 2 or more joints?
Muscles spanning 1 joint = usually have sufficient excursion to allow joint to move through the entire ROM.
Muscles spanning 2 or more joints = may not have sufficient excursion to allow joint to move through combined range of all joints it crosses.
In the length tension relationship, what is the amount of passive tension dependent on?
- Dependent on stiffness of the muscle.
**High levels of passive tension in muscles that cross multiple joints.
Example = during wrist extension, fingers flex
What is passive insufficiency?
When a multi-joint muscle is of insufficient length to permit full ROM.
What is tenodesis grasp?
Passive movement of tendons in response to passive insufficiency.
