Function of Human Tissue / Applied Tissue Biomechanics / Muscle Structure & Function

Question 1

What is the formula for extrinsic stiffness?

Answer 1

Change in force / change in length

Question 2

What does extrinsic stiffness depend on?

Answer 2

Material composition and shape or size

Question 3

What is the formula for stress?

Answer 3

Force / area

Question 4

What is the formula for strain?

Answer 4

Change in length / original length

Question 5

What is the formula for Young’s Modulus?

Answer 5

Change in stress / change in strain

Question 6

What is intrinsic stiffness dependent on ?

Answer 6

Material composition, not shape or size

Question 7

The phenomenon of the tissue being longer as it recoils or unloads in comparison to when it was first loaded is called what?

Answer 7

Hysteresis

Question 8

The idea of using multiple cycles to take advantage of hysteresis is called what ?

Answer 8

Preconditioning

Question 9

Let’s say some tissue is deformed to a specific length and it is held there for a period of time, at the beginning at the early stages of time, the stress that leads to the deformation has to be much higher (the change in force). However as the length remains constant, the measured force to maintain the specific length decreases. So the internal resistance of the tissue is actually decreasing and the force needed to maintain that change in length is decreasing.

What is this called?

Answer 9

Stress relaxation

Question 10

In stress relaxation, is the length of the tissue being held constant ?

Answer 10

Yes

Question 11

Let’s say that there is a constant 2N load that is pulling a rat tail apart. As the time increases, that 2N load will slowly start to increase the length of that rat tail but at a certain point equilibrium is reached and it no longer changes the length.

What is this phenomena?

Answer 11

Creep

Question 12

In Creep, is the load held constant?

Answer 12

Yes

Question 13

Which phenomena(s) discussed in class is rate dependent (how fast something is being loaded)?

Answer 13

Preconditioning

Question 14

Which phenomena(s) discussed in class are time dependent?

Answer 14

Stress relaxation & Creep

Question 15

A knee having a bigger contact area would be able to handle (larger/smaller) load rates rather than a smaller joint in your body

Answer 15

Larger

Question 16

What are some of the physiological effects of disuse (inactivity or immobilization)?

Answer 16

Collagen fibers atrophy (smaller cross sectional area and lower number), the collagen fibers are shortened and disorganized, overall increase in the quantity of collagen cross-links of lower quality, loss of Proteoglycans (GAGS) (Proteoglycans are proteins that are necessary for healthy tissue), and loss of H2O (Water is essential for our cells to go through its’ normal cellular functioning).

Question 17

What is resistance to tensile forces called?

Answer 17

Stiffness

Question 18

The clinical significance of immobilization is decreased ____ and ____

Answer 18

Stiffness and reduced load to failure

Question 19

What are the physiological effects of activity on tissue?

Answer 19

Increased size of collagen fibers, increased amount of collagen fibers, reorients the collagen fibers along lines of tensile stress, and promotes fluid movement (blood flow is a good thing, it’s what’s clearing out waste product, it is also what is bringing in nutrition. We’re moving water around and we’re getting nutrients to where they need to be).

Question 20

What is the clinical significance of stress deprivation of articular cartilage?

Answer 20

Decreased ability to handle compressive forces (if the cartilage is having a hard time absorbing shock you might see some swelling in the knee)

Question 21

Articular cartilage acts as a single phase (solid/liquid) during impact loading because the force is applied quickly instead of slowly over a period of time (rate dependence).

Answer 21

Solid

It is viscoelastic and the articular cartilage acts more like a solid in that situation.

Question 22

Are muscles shock absorbers?

Answer 22

Muscles are shock absorbers, the stronger they are the more shock you’re absorbing through your muscles and not through your joint surfaces. That is why it is important to improve muscle strength.

Question 23

What is considered the force generator of muscle contraction?

Answer 23

Sarcomeres

Question 24

Sarcomeres are broken down into proteins. What were the two contractile proteins we learned about in class?

Answer 24

Actin & Myosin

Question 25

Sarcomeres are broken down into proteins. What were the two non contractile (structural) proteins we learned about in class?

Answer 25

Titin & Desmin

Question 26

What are the things that have a strong influence on the amount of force transmitted through the muscle and its tendon (eventually to the skeleton) ?

Answer 26

Physiologic Cross-Sectional Area- area of the whole muscle represents the number of active proteins available to generate active force

Pennation Angle - angle of orientation between the muscle fibers and the tendon

Question 27

What two components are most responsible for the passive length tension curve?

Answer 27

Series elastic components and parallel elastic components

When parallel and series components are stretched passive length-tension curve is generated

Question 28

Which component that is responsible for the passive length tension curve is attached in series (end to end) with active proteins?

Answer 28

Series elastic components

Question 29

What component that is responsible for the passive length tension curve is attached in parallel (surround) with active proteins?

Answer 29

Parallel elastic components

Question 30

The graph of the passive length tension curves shows:

(Increasing/Decreasing) muscle length and with increasing muscle length is (Increasing/Decreasing) muscle tension

Answer 30

Increasing; Increasing

Question 31

What is this an example of?

I am walking and my right foot hits the ground. If I hit with my heel and then I move my body forward, my ankle is in dorsi flexion, which would put my plantar flexions under tension. We know that at the end range from all the testing you did in lab it’s kind of difficult to make a muscle in that position. When you have that elastic recoil it can kind of aid your muscle where it’s the weakest. In this example it will help propel me forward because my calf is in an optimal position to work in that situation.

Answer 31

Passive tension

Question 32

Myosin “heads” form cross bridges with actin filaments, greater number of cross bridges the (greater/lesser) the force generated within the sarcomere

Answer 32

Greater

Question 33

Amount of active force depends partly on the length of the muscle fiber. The Ideal length of the muscle fiber/sarcomere is the length that allows the greatest number of ____ throughout its overall length.

Answer 33

Cross bridges

Question 34

What is this an example of?

If my bicep is at a certain length, I can only generate a certain amount of force, if my muscle is here in the mid range I can generate more force and then, if it’s here and shorten I can’t generate as much force. The amount of force that you generate changes with the length of the muscles.

Answer 34

Active length tension curve (length force is probably more of an appropriate name)

Question 35

In the active length tension curve graph, you can see that In the graph, as you increase the length of the sarcomere you get to a plateau and then when you stretch too far it is much less. You can see that the crossbridges are really working well in (midrange / end range). In lengths before and after mid range the crossbridges are working (poorly/well).

Answer 35

Mid range; Poorly

Question 36

Total length tension curve:

Start at the most shortened position:
Active force generation continues to rise as the muscle is lengthened to its resting length. Beyond resting length (passive tension/active tension) starts to contribute to total muscle force, making up for decreased active force generation. At most lengthened state, (passive tension/active tension) dominates the curve, tissues are under maximal stress

Answer 36

Passive tension; passive tension

Question 37

What is this an example of?

When you have a barbell and it is falling down and you see the guy doing that rocking motion with his back when the weight is too heavy. That quick extension that lengthens the tissue that helps to pull the weight back up is what phenomena at work?

Answer 37

Passive tension

Question 38

When we have no load in the concentric phase we have the (fastest / slowest) velocity (I can flex my arm as quick as I can when there is no load) because nothing is resisting against me so my muscle is free to work in a quick manner.
If you progressively add load, that will (slow/increase) down the velocity at which you can contract the muscle. Eventually, you’ll get to a large load where there will be 0 velocity (think of a weight that is too heavy to lift) which is an (isometric/concentric) contraction. Let’s say the weight which is too heavy for me where I was doing an isometric contraction at 50 pounds. If I try and lift 50.5 pounds, I am trying to overcome gravity but I can’t and that transitions me into the (eccentric/isometric) phase.

What kind of curve was illustrated in this example?

Answer 38

Fastest; slow; isometric; eccentric

Force velocity curve

Question 39

At (slower/higher) speeds more cross bridges are formed which equates to more force. At ____ velocity the max number of cross bridges are formed so at that isometric contraction you are really trying to form all of those cross bridges that you can.

Answer 39

Slower; zero

The slower I go the more force i’m generating which also makes sense, you don’t have to generate as much force for lifting the one pound dumbbell quickly, as you do for lifting a 10 pound dumbbell slowly.

Question 40

The greatest force is produced during what phase of activation?

Answer 40

Eccentric

Question 41

What is this called?

In a stretching exercise on the first trial may lead to an end point at a much quicker distance than the fifth rep. One of the theories on why this happens is because you are performing multiple cycles in a row of the same tendon loading or stretch and it has never actually returned back to its original length and it takes less force to increase from there as it did previously and in the end you have now increased the length of your tissue after doing two, three, or four reps of a particular stretch.

Answer 41

Preconditioning

Question 42

What is this called?

Where the rat tail is being pulled apart and you get to a certain force, and the force to pull the tendon apart stops at a certain force and what happens is, it’s gonna hold that length and it’s gonna hold for an extended period of time, and then all of a sudden the force needed to hold the tendon at that amount of length is less than when the experiment started.

Answer 42

Stress relaxation

Question 43

A constant load on top of a branch that is slowly sagging it down. Deformation will continue until a state of equilibrium is reached.

What is this called?

Answer 43

CREEP

Question 44

What is this called?

In terms of length, think of the first time you do a stretch compared to the fifth rep and how much deeper you can get in that stretch. This is taking advantage of the tissue not returning to its’ original length when it recoils (hysteresis).

Answer 44

Preconditioning

Question 45

If you (increase/decrease) the loading rate (how quickly something is being loaded) it takes a lot more force to achieve the same change in length than if the rate is much slower

Answer 45

Increase

Question 46

A tendon or ligament can become stiffer if the rate of loading is (increased/decreased) which is protective to itself and its’ surrounding structures. Think about running and landing at a fast rate, you land and lift off quickly so a tendons stiffness is (greater/lesser) than walking where the load is much slower doing the impact stages. This allows our structures (tendon and ligaments) to return to our original state after the force is gone. This is beneficial because you want to have a large elastic region. If every time you had a force it moved into the plastic region it wouldn’t be too long until you entered the ultimate yield point.

Answer 46

Increased; greater

Question 47

When tendons and ligaments are loaded rapidly they exhibit (greater/less) resistance to deformation than when loaded slowly. Generally, the (lower/greater) the rate and longer the duration of applied force, the greater the deformation

Answer 47

Greater; lower

Question 48

If you increase the loading rate (how quickly something is being loaded) it takes a lot (more/less) force to achieve the same change in length than if the rate is much slower (another property of viscoelastic tissue).

Answer 48

More

Question 49

For the sake of the test, if you see a static splint and the question asks about which phenomenon it is, the answer is _________

Answer 49

Stress relaxation

Question 50

For the sake of the test, if you see a dynamic splint for around 15 minutes and the question asks about which phenomenon it is, the answer is _______

Answer 50

CREEP

Question 51

The (quicker/slower) the loading rate is, It could have articular cartilage behaving like an incompressible material. A quick high load being dispersed through the knee joint would behave differently than a slow gradual build up of load during a leg press.

Answer 51

Quicker

Question 52

What law is this an example of?

In areas where load is required, the bone will slowly adapt to that need. If it is not needed somewhere it is reabsorbed. Think of astronauts that go to space with a low gravity associated and when they come back they have osteoporosis of their bones because their bones started resorbing itself because they haven’t been needing it. Similar things happen to patients who have been immobilized.

Answer 52

Wolf’s Law

Question 53

External forces cause osteoblast activity to (increase/decrease) and bone mass (increases/decreases)

Without these forces, osteoclast activity predominates and bone mass (decreases/increases) – bone is sensitive to disuse

If osteoclasts break down or absorb bone faster than osteoblasts can remodel, osteoporosis will result – bones (decreases/increases) in density and weakens

Answer 53

Increase; increases;
decreases
decreases

Question 54

The amount of stress that normal tissue can feel before it gets to the plastic zone is much (greater/less) than its immobilized counterpart.

Answer 54

Greater

Question 55

If you have some tension placed in the immobilized joint, you’ll get (less/more) collagen disorganization and (less/more) deterioration of those tensile properties. If I were to take an ankle and I was to immobilize it in full dorsiflexion, what structures would be under tension? Immobilizing an ankle in full dorsiflexion your (plantar/dorsi) flexors would be under tension. That reduces some of the effects of immobilization.

Answer 55

Less; less; plantar

Question 56

If someone is coming out of something that’s like a splint, things like (active/passive) range of motion are good for the patient.

Answer 56

Active

If i’m the injured person and I just came out of a splint, if I push on myself with outside force or the therapist pushes on me, I might injure something. Just start with active range of motion and see where you get to. You want the person who just got out of splint to start moving.

Question 57

Stretching is (passive/active) range of motion and something that you do a little (later/earlier) in the rehab process because you are putting a lot of tension through the tissue.

Answer 57

Passive; later

Question 58

If we did the stretch where you have one leg extended on a chair with weight placed over the knee to get it into full extension and 15 minutes later the knee was fully straight and the individual left the clinic saying oh my God, I feel so much better, and they came back and their knee was still straight and they were oh my God, I feel so much better, since I got my knee straight. Providing a gentle stretch, for a short amount of time and the body’s like oh wait this isn’t so bad, I can relax and let things settle down down and that person gets better and they’re walking and they’re doing everything right after that, that is one of those clinical situations where all you did was perform (CREEP/Stress relaxation) (Same force over a somewhat defined time). But you know, and I know that you didn’t change the cellular makeup and remodel the tissue right, it’s still the same tissue it was people.

If that same individual came back and said that by the time I left, drove in my car to go home and my knee was bent again. So we know that (Creep/stress relaxation) was not good enough to cause a long lasting change. In this situation a (LLPS/HLBS) stretch would be a better option so that individual can remodel the tissue.

Answer 58

Creep; Creep; LLPS

Question 59

In regard to altering a TERT prescription for a patient, what is the first factor you want to change between intensity, duration, & frequency?

Answer 59

Duration

You do not want to change the intensity of the stretch first because that might be too much for the tissue to handle. Immobilized tissue has less stiffness (less resistance to tensile forces).

Question 60

What are the indications for using TERT?

Answer 60

A history of trauma followed by immobilization

A history of restricted motion greater than three weeks

Loss of passive range of motion in a capsular pattern

A firm end feel (a firm end feel goes along with that loss of passive range of motion)

Question 61

What happens to the contact area of articular cartilage during stress deprivation (a situation where the individual was immobilized)?

Answer 61

Decreased proteoglycans (GAGs)
Decreased chondrocytes (the cells that makeup the cartilage)
Degeneration into deeper layers of the cartilage

Question 62

What happens to the non contact area of articular cartilage during stress deprivation (a situation where the individual was immobilized)?

Answer 62

There are no significant changes

Question 63

When articular cartilage goes through stress deprivation, does the cartilage become softer or harder?
Is this reversible?

What is the clinical significance of this?

Answer 63

Softer
Consensus is that it is probably not reversible, just a matter of how much has it been softened

Decreased ability to handle compressive forces

Question 64

How does articular cartilage get their health?

Answer 64

The flow of synovial fluid in and out, waste products out, nutrients in.

Question 65

Contraction of (individual/multiple) fibers are responsible for an overall muscle contraction

Answer 65

Individual

Question 66

When you’re thinking about each fiber contracting, if you really think to a smaller level it is each _____ contracting. And because they are contracting and they are in the line with each other, each one contracts a little bit and then the whole fiber contracts.

Answer 66

Sarcomere

Question 67

Pennate muscles produce (more/less) force than fusiform muscles of similar volume.
Why?

Answer 67

More;

They can fit more fibers into a given area

Question 68

What is most responsible for the initial tension in the passive length tension curve?

Answer 68

Structural protein (especially Titin)

Question 69

What is most responsible for the later tension in the passive length tension curve?

Answer 69

The parallel proteins (Extracellular connective tissues (especially the tendon that it inserts to bone with))

Question 70

Muscle is also viscoelastic, so an (increase/decrease) of the velocity of the stretch can (increase/decrease) its stiffness (think plyometric exercise)

Answer 70

Increase; increase

Question 71

This (passive/active) tension can also serve a protective feature protecting the structure of the muscle and tendon during maximal elongation

Answer 71

Passive

Question 72

The two most important myofilaments are the proteins ____ and ____ (they are contractile proteins).

Answer 72

actin and myosin

Question 73

Definition:

Dark bands cause by the presence of thick myosin

Answer 73

A bands

Question 74

Definition:

Light bands cause by the presence of thin actin myofilaments

Answer 74

I bands

Question 75

Definition:

Region within the A band where actin and myosin do not overlap

Answer 75

H bands

Question 76

Definition:

Midregion thickening of myosin myofilaments in the center of the H band

Answer 76

M line

Question 77

Definition:

Connecting points between successive sarcomeres; these discs help anchor the thin actin myofilaments

Answer 77

Z discs

Question 78

Definition:

Active force is generated as actin myofilaments are sliding past myosin filaments, pulling Z discs closer narrowing the H band

Answer 78

Sliding filament theory

Question 79

There is a progressive overlap of actin and myosin, however actin and myosin don’t actually shorten themselves. One filament is pulling the other filament over itself. It does not change the length of the filaments.

True or false?

Answer 79

True

Question 80

It makes sense that we are the strongest in the region where the (external/internal) torque has the highest demand.

The hip abductors in real life keep the pelvis stable and from rotating. So if I am standing on my right leg, the pelvis (the external torque) is dropping me into hip abduction. So if I drop into hip abduction, the hip abductor is controlling that to keep my pelvis level.
So it makes sense that we are in this minus 10 to 10 degree range, where we are the strongest in hip abduction. My hip abductor doesn’t need to be strong in 40 degrees of hip abduction, i’m like never, never there right, so it doesn’t need to be strong. It needs to be strong when i’m walking and going up and down steps.

Answer 80

External

Question 81

Concentric activation:
(increasing/decreasing) load slows down velocity of contraction

As the force (increases/decreases) the speed of eccentric activation also increases

Answer 81

Increasing

Increases

Question 82

Maximal Eccentric Activation is directly proportional to the velocity of muscle lengthening (up to a certain point) . What that means is, as that force generates and goes (quicker/slower) and (quicker/slower) and (quicker/slower) the force velocity generated in my muscle is the highest. The force keeps getting higher as the speed increases in an eccentric contraction.
Thought to be protective against large forces causing muscle damage. If you have the MOST amount of force during this eccentric phase, we think that it is trying to make it more protective so you do not injure your muscle tissue.

Answer 82

Quicker; quicker; quicker

Question 83

The greatest force is produced during (eccentric/isometric) activation.

Answer 83

Eccentric

Question 84

Reasons for increased forces during (eccentric/concentric) Activation

1) greater force produced by crossbridges being pulled apart
2) a more rapid reattachment phase of crossbridge formation
3) passive tension formed by series and parallel elastic components

Answer 84

Eccentric

Question 85

Overall (eccentric/concentric) contraction is viewed as more efficient (less metabolic cost and total muscle fiber activation) than the same overall workload when compared to (concentric/eccentric) activation

Answer 85

Eccentric; concentric

Question 86

If you were to do a bicep curl and it took you 10 motor units to do this bicep curl on the concentric phase, it would take (less/more) motor units to do this bicep curl (eccentrically/concentrically) because this phase is more efficient

Answer 86

less; eccentrically

Question 87

Through recruitment of (more/less) alpha motor neurons (more muscle fibers) (more/less) force is generated within that particular muscle
The type of muscle and its requirements dictate the size of motor units. Smaller more precise muscles have (less/more), larger more forceful muscles have (more/less).

Answer 87

more; more; less; more

Question 88

Size of motor neurons is important in the order of recruitment. (Smaller/larger) motor neurons are recruited before (larger/smaller) motor neurons (Henneman Size Principle). This allows for smooth, controlled and orderly recruitment of force development.

Answer 88

Smaller; larger

It doesn’t make sense to try and lift a cup of coffee off of the counter, with a ton of motor units first. We start with the small one. And then you slowly lift and try to recruit what you can, and then, if it’s harder than you lift with more, you recruit more of the bigger ones as you need them, you don’t do it in reverse.

Question 89

Are Slow Oxidative fibers fatigue resistant?

Answer 89

Yes

Question 90

Generally (slow oxidative/fast twitch) resistant fibers, these fibers dominate “postural” muscles because they have to be on 10% on 100% of the time if you are up and about. So those type of fibers are more beneficial in your postural muscles because they are fatigue resistant.

Answer 90

Slow oxidative

Question 91

What are the two types of fast twitch motor unit types?

Answer 91

1) Fast Fatigable (FF)

2) Fast Fatigue Resistant (FR)

Question 92

Muscle fibers associated with larger motor neurons have (short/long) duration twitch responses (Fast twitch). These motor units tend to have a (higher/lower) amplitude which equates to more force.

Answer 92

Short; higher

Question 93

Muscle fibers that are recruited after smaller motor units (Slow Oxidative) have been recruited, occurs when very (large/small) forces are required.

Answer 93

Large

Question 94

Because the muscle twitch can last (longer/shorter) than it takes another action potential to occur, the subsequent twitch gets ”added” to what is left of the previous twitch and creates greater peak force.

Answer 94

longer

Question 95

Definition:

Set of repeating action potentials that summate

Answer 95

Unfused tetanus

Question 96

Definition:

The greatest possible force of a muscle fiber that contracts to the point where there are no twitches

Answer 96

Fused tetanus

Question 97

Definition:

Results in sarcomeres being added in parallel within muscle fiber, increase in fiber hypertrophy not in the number of fibers

Answer 97

Protein synthesis

Question 98

Definition:

Increase in the physiologic cross sectional area of the whole muscle (secondary to increased protein synthesis)

Answer 98

Hypertrophy

Question 99

(Type II/Type I) fibers has the greatest potential for hypertrophy of all

Answer 99

Type II

Question 100

Strength gains, especially during first few training sessions have a great (neural/physiological) influence.

If someone can do a knee extension with 30 pounds and then they come back and they’ve done it a couple times, and then they can do 50. That 20 pound difference wasn’t because sarcomeres were added in parallel and they’ve gone beyond. It’s probably due to that nerve coming down to the motor units and being able to recruit fibers more efficiently.

Answer 100

Neural

Question 101

We generally think in order for hypertrophy to happen there has to be a minimum of ___ weeks that have gone by.

Answer 101

6

Question 102

After immobilization, reduction in strength can be (double/triple) that of muscle atrophy (20% atrophy can lead to ___% reduction in strength)

Answer 102

double; 40

Question 103

Relatively early changes in muscle with reduced use/immobilization suggest a strong (neurologic/physiological) basis on top of loss of contractile proteins

Answer 103

Neurologic

Question 104

Protein synthesis is reduced in immobilized limb, especially (slow/fast) twitch fibers (shift towards (faster/slower) twitch muscle fibers)

Answer 104

slow; faster

There is a shift towards faster twitch muscle fibers, but the fast twitch muscle fibers are not actually increasing during immobilization. What is happening is that the slow twitch fibers are more affected by immobilization which is why there is a shift towards faster twitch muscle fibers.

Question 105

Loss of strength is greatest when muscle is placed in its (shortened/lengthened) position (think of the example of immobilizing a joint in dorsiflexion and the plantar flexors would get stronger because they are in a tensioned position)

Answer 105

Shortened

Question 106

(Single/multi) joint muscles have greater atrophy than (multi/single) joint muscles because if you have a (single/multi) joint muscle and that muscle is immobilized then there is no movement that can occur. That muscle is not able to move normally at all so they are going to have a greater amount of atrophy.

Answer 106

Single; multi; single

Question 107

Changes in muscle with advanced age is (more/less) pronounced in the muscles of the lower limb like the quadriceps

Answer 107

More

Question 108

Definition:

The loss in muscle tissue with advanced age

Answer 108

Sarcopenia

Question 109

Changes in muscle with advanced age:

Loss in the ___ of fibers as well as the ____ of the existing fibers

Answer 109

Number; size

Question 110

Changes in muscle with advanced age:

Loss in the total number of fibers caused by gradual demise of ____ neurons because they do not work, the signal is not getting to them and it becomes a nervous system issue.

Answer 110

alpha motor

Question 111

Changes in muscle with advanced age:

Proportion of fibers remains the same. The Type (II/I) fibers have greater atrophy.
Greater proportional volume of type (I/II) fibers (less forceful and powerful contractions) .

Answer 111

II; I