(1) Biomechanics-- Tissue Biomechanics Cont., Bones, Cartilage

Question 1

What is the ability to return to the original shape when the load is removed?

Answer 1

Elasticity

Question 2

What is the point at which the applied stress can lead to permanent deformation?

Answer 2

yield point

Question 3

What is the nonlinear response of material after the yield point, where some degree of deformation will persist after removal of the stress?

Answer 3

Plastic region

will NOT go back to normal shape

Question 4

What is the term for the property of materials to resist load that produce shear or tensile forces?

Answer 4

viscosity

Question 5

Describe what Viscous (plastic) stretch refers to.

Answer 5

the putty-like behavior–> the linear deformation produced by tensile stress remains even after the stress it removed

Question 6

What is Viscoelasticity?

Answer 6

When a material shoes BOTH properties of viscosity AND elasticity

Question 7

What are most biologic tissues, especially tendons and ligaments?
A. Elastic
B. Viscous
C. Viscoelasticity

Answer 7

C. Viscoelasticity

Question 8

What are the two things that affect the Viscoelasticity of a tissue?

Answer 8

rate of loading AND length of time

Question 9

What are the 3 time dependent loading characteristics Viscoelastic structures will show?

Answer 9

1. Creep
2. Relaxation
3. Hysteresis

(creep and relaxation are more related)

Question 10

What is the term for what occurs to tissues due to the expulsion of water?

Answer 10

Creep

Question 11

What will occur with continued deformation over time when constantly loaded?

Answer 11

Creep

Question 12

What is the corresponding eventual decrease in stress that occurs as fluid is no longer exuded?

Answer 12

Relaxation

as force no longer goes through

Question 13

What is the term for the energy loss as heat exhibited by viscoelastic materials when they are subjected to loading and unloading cycles?

Answer 13

Hysteresis

Ex: need energy to go out of tendon before can jump again

Question 14

What is Hysteresis Energy a measure of?

Answer 14

how efficient the tissue is at letting the load out

Question 15

If we have a lower/decrease Hysteresis, what does this tell us about the tissues ability to absorb force?

Answer 15

it have a better ability to absorb force = good

Question 16

How will a longer load affect Hysteresis?

Answer 16

longer the load, the greater the hysteresis

Question 17

What type of Hysteresis will tendons and have? How does this relate to injury?

Answer 17

due to be compliant (pliable/ductile)–> tendons can absorb elastic energy more easily = tend to have a decrease Hysteresis

could be related to decrease injury risk

Question 18

What would we want to warm-up before we exercise?

Answer 18

tendons are Viscoelastic–> and an increase in temperature lessens the viscosity, improving the efficiency of the tendon’s response to stretch and recoil (less Hysteresis)

Question 19

Resistance Training will strength our muscles, but will stiffen the muscle-tendon complex, so what do we do?

Answer 19

must strike right balance b/w tendon pliability and sitffness

heavy weight training will increase stiffness

flexibility exercises will increase compliance

Question 20

Is low or high Hysteresis advantageous? Why?

Answer 20

Low hysteresis–> because hysteresis is dependent on the RATE of loading and unloading

Question 21

What may dynamic exercises be beneficial fro us, like plyometrics or ballistics?

Answer 21

they may increase pliability of muscle-tendon complex –> therefore decrease hysteresis and –> decrease injury risk

Question 22

Overall, what is the bottom line when it comes to Hysteresis?

Answer 22

no ONE answer–> rate of loading/unloading is important

Question 23

In general, who is most likely to get injured?

Answer 23

• workout in cold
• no warm up
• only weight lift and no stretching

Question 24

What is the Toe Region? What occurs after this is “taken away”?

Answer 24

normal range of motion

little force required to remove the “crimping” or “slack” in the tissue

after this, tissue resists elongation much more strongly

Question 25

What occurs during the Micro-Failure region of a Stress/Strain graph?

Answer 25

after slack is taken out of the soft tissue--> still ELASTIC in this region--> small amount of damage to the tissue (Grade One Sprain)

Question 26

What point of the Stress/Strain graph contains a Grade One Sprain?

Answer 26

Micro-Failure region | aka sore muscles after a workout

Question 27

What occurs during the Macro-Failure region of the Stress/Strain graph?

Answer 27

the tissue undergoes PLASTIC deformation (Grade 2 sprain) and eventually tissue ruptures (Grade 3 sprain)

Question 28

When does a Grade Three Sprain occur?

Answer 28

when tissues ruptures (in Macro-Failure region)

Question 29

When does a Grade Two Sprain occur?

Answer 29

when the tissue undergoes PLASTIC deformation (Macro-Failure Region)

Question 30

What does bone consist of? What does it provide?

Answer 30

collagen, ground substance, and minerals-- in a matrix---> provides strength and support

Question 31

Describe the metabolic activity of bone.

Answer 31

one of the most dynamic and metabolically active tissues in body and remains active throughout life

Question 32

Is bone highly vascular or not? What does this allow for?

Answer 32

highly vascular --> allows for excellent capacity for self-repair

Question 33

Compare the mechanical properties of cortical bone and trabecular bone.

Answer 33

Cortical bone = stiffer/brittle Trabecular bone = tougher

Question 34

Describe Anisotropic and its relation to bone.

Answer 34

exhibits distinct mechanical properties when loaded along various axes b/c its structure differs in the transverse and longitudinal directions when load bone longitudinally = toughest

Question 35

Out of longitudinal loads and transverse loads, which can cortical bone tolerate the better?

Answer 35

longitudinal loads > transverse loads

Question 36

Out of tension, shear, compression, list from greatest to least of what cortical bone can withstand greater stress.

Answer 36

compression > tension > shear

Question 37

What are the two ways that bone fractures can be produced in bone?

Answer 37

1. single load that exceeds the ultimate strength of the bone OR 2. repeated applications of a lower-magnitude load (fatigue and stress Fx)

Question 38

Can bone remodel?

Answer 38

yes! it have the ability to remodel-- by altering its size, shape, and structure--> to meet the mechanical demands placed on it

Question 39

What is the term for bones ability to remodel by altering its size, shape, and structure to meet the mechanical demands placed on it?

Answer 39

Wolff's Law | NOT a degenerative response

Question 40

How is load and demand placed on bone? What does this lead to?

Answer 40

muscle activity or gravity--> leading to bone deposition

Question 41

What happens to bone when it is not needed or there is disuse or aging?

Answer 41

bone is resorbed

Question 42

What is cartilage composed of and is it vascular or avascular?

Answer 42

collagen, chondrocytes, and ground substance avascular

Question 43

What are the three types of cartilage?

Answer 43

1. articular cartilage (our focus) 2. hyaline cartilage 3. fibrocartilage

Question 44

Why is cartilage unlike any man-made material?

Answer 44

with respect to its near frictionless properties

Question 45

What type of material describes articular cartilage? What two things is it subject to?

Answer 45

it is viscoelastic creep and relaxation

Question 46

During joint articulation, what do the forces at the joint surface vary from?

Answer 46

almost 0 to greater than 10x body weight

Question 47

What normally allows cartilage to experience minimal wear under varied load?

Answer 47

synovial lubrication

Question 48

What are two types of wear that occur to articular cartilage?

Answer 48

1. Interfacial water | 2. Fatigue water

Question 49

What will cause interfacial wear on articular cartilage?

Answer 49

adhesion or abrasion

Question 50

What type of wear of articular cartilage is the interaction of bearing surfaces?

Answer 50

Interfacial wear

Question 51

What type of wear of articular cartilage is bearing deformation under load?

Answer 51

Fatigue wear

Question 52

What causes Fatigue wear of articular cartilage?

Answer 52

repetition or high loads over a relatively short period OR with repetition of low loads over an extended period

Question 53

Describe the ability for articular cartilage to repair and regenerate.

Answer 53

it has LIMITED ability

Question 54

What determines the magnitude of stress sustained by articular cartilage?

Answer 54

1. Total load on the joint | 2. How that load is distributed over the articular surface contact area

Question 55

What will play a primary role in tissue degeneration of articular cartilage?

Answer 55

any intense stress concentration