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KIN 316 - Biomechanics of Tissue > Module 11 - Introducing the Tendon > Flashcards

Module 11 - Introducing the Tendon Flashcards

1
Q

Describe the structure of a tendon

A
  • Not Rigid
  • Attach muscle to bone
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2
Q

Why do tendons affect muscle function in a positive way?

A
  • Right amount of compliance
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3
Q

How do tendons form?

A
  • Connective tissue around muscles converge to form the tendon
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4
Q

What do tendons look like?

A
  • White
  • Glossy
  • Smooth
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5
Q

Describe the difference in tendons regarding the structure

A
  • enclosed in a connective tissue sheath
  • some, slide with respect to adjacent tissues and skin
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6
Q

What is the difference in tendons regarding attachment structure?

A
  • some, wrap around pulley
  • some, pull in direct line from muscle to bone
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7
Q

What are tendons mainly composed of?

A
  • Collagen
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8
Q

How are the collagen fibers in a tendon arranged?

A
  • Mainly in a staggered pattern
  • Create collagen fibril
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9
Q

How do Fibrils relate to tendon?

A
  • Fibrils bundled into fascicles
  • Fascicles bundled into tendons
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10
Q

What is a dominant feature of the collagen fibers under a light microscope?

A
  • Wavy appearance
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11
Q

What happens when a tendon is placed under a load?

A
  • Wavy appearance disappears
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12
Q

What is part of tendon compliance?

A
  • Wavy appearance of the collagen fiber
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13
Q

What is the term for the wavy pattern of the collagen?

A
  • Crimp pattern
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14
Q

What other structures contribute to tendon viscoelasticity?

A
  • Glycosaminoglycan
  • Elastin
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15
Q

What is stress?

A
  • Resistance developed by tissue when externally loaded
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16
Q

What is strain?

A
  • Deformation of tissue submitted to external load
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17
Q

Do tendons produce active tension?

A
  • No
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18
Q

How is the stress-strain property of tendons documented?

A
  • Tendon connected to a force transducer and stretched
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19
Q

Describe the stress-strain relationship of a tendon at a low load

A
  • Relatively compliant
  • Toe Region
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20
Q

What happens to the stress-strain relationship of a tendon as load increases?

A
  • Stiffness of tendon increases
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21
Q

Is the stress-strain relationship of a tendon linear?

A
  • No
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22
Q

What is Young’s Modulus useful for?

A
  • Comparing stress-strain properties of tissues
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23
Q

Why does a tendon strain when going through muscle contraction?

A
  • Muscle applies a load to tendon
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24
Q

What determines the elongation of teh tendon?

A
  • Stiffness of the tendon
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25
Q

What, regarding the tendon, must be well adjusted to positively affect muscle function?

A
  • Load deformation
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26
Q

What is the ratio of Young’s Modulus of the tendon to the passive muscle?

A
  • 100:1
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27
Q

What percentage of strain is the tendon at during maximal isometric muscle tension?

A
  • 3%
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28
Q

Fill in the blank: Tendons are relatively _______ & _____ vascular supply

A

Acellular & Poor

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29
Q

What does active muscle force generation depend on?

A

Mainly
- Force-length relationship
- Force-Velocity Relationship

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30
Q

What happens to the tendon when active force develops? What does this mean?

A

Happens
- Tendon Strains
Means
- Muscle shortens further

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31
Q

What does the magnitude of tendon elongation depend on?

A
  • stress-strain properties
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32
Q

What is the consequence of the tendon regarding isometric contractions?

A
  • Muscle activation at fixed joint angle is not true isometric action
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33
Q

What is the difference between long and short tendons?

A
  • Long tendon deform more when same load is applied
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34
Q

What do you need to do to compare b/w tissues?

A
  • normalize elongation (I - I0 / I0)
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35
Q

How is the control of balance predicted to occur?

A
  • Reflexive control
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36
Q

How do reflexes play into control of balance?

A
  • Generate forces to maintain equalibrium in reaction to movement of body
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37
Q

What happens to the calf muscle during swaying forward?

A
  • Stretched while active: eccentric action
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38
Q

What does the stretched calf muscle do during swaying forward motion?

A
  • Elicite reflexes that leads to increased muscle activity
  • Restoration of body position toward a ‘neutral’ position
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39
Q

What did the Loram paper identify about the SOL and Gas muscles during standing balance?

A
  • Paradoxical contraction
  • Concentric action on sway forward
  • Passive lengthen on sway backwards
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40
Q

What did the Loram paper identify about the tendon?

A
  • Stiffness insufficient for static stabilization
  • Contrasts spring-like stiffness regulation of balance
41
Q

What did the Loram paper identify about control of balance?

A
  • controlled through repeated impulses
  • Transient shift in muscle length
42
Q

What should we consider about velocity when a joint is allowed to move?

A

Even if muscle-tendon unit shortens at constant velo
- fiber and tendon may not shorten at constant velo

43
Q

When are the simple biomechanical models to estimate muscle fiber length/velocity during various muscle actions useful?

A
  • to estimate muscle-tendon unit length
44
Q

What is needed to measure muscle fiber length/velocity?

A
  • direct measure
45
Q

Does the development of active muscle tension occur instantly following the activation of the muscle?

A
  • No
46
Q

What is the delay between active muscle tension and the activation of the muscle called?

A
  • Electro-mechanical delay
47
Q

What is the elctro-mechanical delay subdivided into?

A
  • Excitation dynamics
  • Contraction dynamics
48
Q

What is excitation dynamics?

A
  • Delay associated with muscle stimulation
49
Q

Where does the excitation dynamics occur?

A
  • Conduction delay in T-tubules
  • Release of Ca2+
  • Cross-bridge formation
50
Q

What is contraction dynamics?

A
  • Delay associated with the actual build-up of muscle tension
51
Q

What will the stretching SEC by contractile elements be affected by?

A
  • Type of muscle action and contraction history
52
Q

What is the tension development in the contractile element ?

A
  • Type of motor unit recruited (FF: 20ms; S: 100ms)
53
Q

What is the electro-mechanical delay determined by?

A
  • type of muscle action
54
Q

How might the emg signal differ from the force signal?

A
  • EMG before Force
55
Q

What does the delay between emg and force signals depend on?

A
  • Type of muscle action
56
Q

What avoids the dissociation between msucle activity and force?

A
  • Maintaining isometric action
57
Q

What leads to a temporal dissociation between muscle activity and force?

A
  • electromechanical delay
  • emg and force signal delay
58
Q

What does the timing of the force delay affect?

A
  • Movement coordination
59
Q

What does the force-time relationship say about EMG and muscle force?

A
  • EMG not good indicator of muscle force
60
Q

What amplifies the force-time delay?

A
  • faster movements
  • rapid changes in force
61
Q

When is the electromechanical delay a problem during constant force being applied at static joint angles?

A
  • Onset action
  • Offset Action
62
Q

How is muscle force expressed through the musculoskeletal system?

A
  • As a joint moment
  • Causes angular acceleration
63
Q

What will be detected before velocity and displacement?

A
  • Acceleration
64
Q

What does tendon compliance do to the force-length relationship?

A
  • Systematic change
65
Q

What happens when the tendon is perfectly stiff?

A
  • Acts as a rigid linkage between muscle and bone
66
Q

What does a perfectly stiff tendon do to the force-length relationship?

A
  • offsets it
67
Q

What does tendon compliance result in regarding the force-length relationship?

A
  • rightward shift
68
Q

Why does tendon compliance result in a rightward shift of the force-length relationship?

A
  • Added elasticity in series
  • Sarcomeres can shorten at expense of tendon elongation
69
Q

What does a longer tendon in series result in regarding the force-length relationship?

A
  • Greater rightward shift
70
Q

What causes a differential degree of sarcomere shortening?

A
  • Initial length of tendon
71
Q

What is the tendon strain at max isometric contraction?

A
  • 3%
72
Q

What increases the range over which the muscle-tendon unit curve operates? by how much?

A

Tendon compliance
- 50%

73
Q

What causes a shift of the muscle’s optimal length?

A
  • Shift in optimal sarcomere length
  • Tendon compliance
74
Q

What do modest changes at the sarcomere force-length relationship lead to?

A
  • changes at whole muscle level
75
Q

What whole muscle level changes does the sarcomere force-length relationship change that occurs due to tendon compliance cause?

A
  • Operating range increase: 50%
  • Shift in optimal length
76
Q

What is an increase in operating range and shift in the optimal length of a whole muscle a result of?

A
  • sarcomere shortening at expense of tendon lengthening
77
Q

What would happen if the tendon was too stiff?

A
  • No benefit to muscle
78
Q

What happens if the tendon is too compliant?

A
  • Muscle would shorten to nothing
79
Q

What is an important design parameter of muscle-tendon unit?

A
  • Muscle fiber length ratio
80
Q

What does the length of the tendon determine?

A
  • The influence of the tendon (operating range & shift in P0)
81
Q

What is the limit to the benefit of increasing tendon length?

A
  • sarcomere shortens to length with no active force production
82
Q

What do the flexor digitorum profundus and superficialis have in common?

A
  • long tendons
  • located in forearm
83
Q

What does a long tendon suggest?

A
  • compliant tendon
84
Q

Why might the Flexor digitorum profundus and superficialis muscle receptors not be able to properly code for the joint position?

A

Tendon acts like spring
- Lower inertia on fingers

85
Q

What is the tendon strain at P0 of the Flexor digitorum profundus and superficials? What is this an example of?

A
  • 1.2%
  • Specialization of tendon
86
Q

What is a common pattern of muscle activation?

A
  • Lengthening-shortening muscle action
87
Q

Describe the lengthening-shortening muscle action

A
  • counter-movement away from the intended direction
  • motion slowed by eccentric muscle-tendon unit action
  • Followed by concentric action in intended direction
88
Q

What is an example of a lengthening-shortening muscle action?

A
  • Knee extensor muscle during kicking
  • hip,knee, and ankle extension during counter-movement jump
89
Q

What is the lengthening-shortening muscle action known as?

A
  • Stretch-shortening cycle
90
Q

What can a muscle do when it is actively stretched before it is allowed to shorten?

A
  • Perform more positive work
91
Q

What are the performance benefits of stretch-shortening cycle?

A

10-20%

92
Q

What mechanisms have been proposed to explain the greater positive work a muscle can do with a stretch-shortening cycle?

A
  • Increases time to full muscle activation
  • Stores elastic energy
  • Force enhancement: role of titin
  • Stretch reflexes: evoked by muscle lengthening
93
Q

When is the elastic energy storage during a stretch-shortening cycle best able to explain the increase in positive work?

A
  • During Rapid Stretch-Shortening
94
Q

What best explains the increase in height of a slow countermovement jump (stretch-shortening cycle)?

A
  • Extra time of muscle to develop tension
95
Q

Where is the elastic energy stored during the lengthening action of the stretch-shortening cycle?

A
  • Elastic components
96
Q

How does the elastic energy storage of the stretch-shortening cycle influence metabolic cost?

A

Reduces it
- Elastic energy stored in connective tissues

97
Q

Describe the energy storage and usage of the Triceps Surae during slow running

A

Stance Phase
- 45J absorbed
Second phase
- 60J used

98
Q

What are the advantages of the stretch-shortening cycle?

A
  • Increase in positive work: power production
  • Lower metabolic cost
99
Q

For the same force output, what consumes more energy: Isometric or Eccentric? (how is the tendon involved)

A
  • Isometric: tendon can store energy and restore it

KIN 316 - Biomechanics of Tissue (11 decks)

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