(1) Biomechanics-- Tissue Biomechanics Cont., Bones, Cartilage Flashcards
What is the ability to return to the original shape when the load is removed?
Elasticity
What is the point at which the applied stress can lead to permanent deformation?
yield point
What is the nonlinear response of material after the yield point, where some degree of deformation will persist after removal of the stress?
Plastic region
will NOT go back to normal shape
What is the term for the property of materials to resist load that produce shear or tensile forces?
viscosity
Describe what Viscous (plastic) stretch refers to.
the putty-like behavior–> the linear deformation produced by tensile stress remains even after the stress it removed
What is Viscoelasticity?
When a material shoes BOTH properties of viscosity AND elasticity
What are most biologic tissues, especially tendons and ligaments?
A. Elastic
B. Viscous
C. Viscoelasticity
C. Viscoelasticity
What are the two things that affect the Viscoelasticity of a tissue?
rate of loading AND length of time
What are the 3 time dependent loading characteristics Viscoelastic structures will show?
- Creep
- Relaxation
- Hysteresis
(creep and relaxation are more related)
What is the term for what occurs to tissues due to the expulsion of water?
Creep
What will occur with continued deformation over time when constantly loaded?
Creep
What is the corresponding eventual decrease in stress that occurs as fluid is no longer exuded?
Relaxation
as force no longer goes through
What is the term for the energy loss as heat exhibited by viscoelastic materials when they are subjected to loading and unloading cycles?
Hysteresis
Ex: need energy to go out of tendon before can jump again
What is Hysteresis Energy a measure of?
how efficient the tissue is at letting the load out
If we have a lower/decrease Hysteresis, what does this tell us about the tissues ability to absorb force?
it have a better ability to absorb force = good
How will a longer load affect Hysteresis?
longer the load, the greater the hysteresis
What type of Hysteresis will tendons and have? How does this relate to injury?
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
What would we want to warm-up before we exercise?
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)
Resistance Training will strength our muscles, but will stiffen the muscle-tendon complex, so what do we do?
must strike right balance b/w tendon pliability and sitffness
heavy weight training will increase stiffness
flexibility exercises will increase compliance
Is low or high Hysteresis advantageous? Why?
Low hysteresis–> because hysteresis is dependent on the RATE of loading and unloading
What may dynamic exercises be beneficial fro us, like plyometrics or ballistics?
they may increase pliability of muscle-tendon complex –> therefore decrease hysteresis and –> decrease injury risk
Overall, what is the bottom line when it comes to Hysteresis?
no ONE answer–> rate of loading/unloading is important
In general, who is most likely to get injured?
- workout in cold
- no warm up
- only weight lift and no stretching
What is the Toe Region? What occurs after this is “taken away”?
normal range of motion
little force required to remove the “crimping” or “slack” in the tissue
after this, tissue resists elongation much more strongly
What occurs during the Micro-Failure region of a Stress/Strain graph?
after slack is taken out of the soft tissue–> still ELASTIC in this region–> small amount of damage to the tissue (Grade One Sprain)
What point of the Stress/Strain graph contains a Grade One Sprain?
Micro-Failure region
aka sore muscles after a workout
What occurs during the Macro-Failure region of the Stress/Strain graph?
the tissue undergoes PLASTIC deformation (Grade 2 sprain) and eventually tissue ruptures (Grade 3 sprain)
When does a Grade Three Sprain occur?
when tissues ruptures (in Macro-Failure region)
When does a Grade Two Sprain occur?
when the tissue undergoes PLASTIC deformation (Macro-Failure Region)
What does bone consist of? What does it provide?
collagen, ground substance, and minerals– in a matrix—> provides strength and support
Describe the metabolic activity of bone.
one of the most dynamic and metabolically active tissues in body and remains active throughout life
Is bone highly vascular or not? What does this allow for?
highly vascular –> allows for excellent capacity for self-repair
Compare the mechanical properties of cortical bone and trabecular bone.
Cortical bone = stiffer/brittle
Trabecular bone = tougher
Describe Anisotropic and its relation to bone.
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
Out of longitudinal loads and transverse loads, which can cortical bone tolerate the better?
longitudinal loads > transverse loads
Out of tension, shear, compression, list from greatest to least of what cortical bone can withstand greater stress.
compression > tension > shear
What are the two ways that bone fractures can be produced in bone?
- single load that exceeds the ultimate strength of the bone
OR - repeated applications of a lower-magnitude load (fatigue and stress Fx)
Can bone remodel?
yes! it have the ability to remodel– by altering its size, shape, and structure–> to meet the mechanical demands placed on it
What is the term for bones ability to remodel by altering its size, shape, and structure to meet the mechanical demands placed on it?
Wolff’s Law
NOT a degenerative response
How is load and demand placed on bone? What does this lead to?
muscle activity or gravity–> leading to bone deposition
What happens to bone when it is not needed or there is disuse or aging?
bone is resorbed
What is cartilage composed of and is it vascular or avascular?
collagen, chondrocytes, and ground substance
avascular
What are the three types of cartilage?
- articular cartilage (our focus)
- hyaline cartilage
- fibrocartilage
Why is cartilage unlike any man-made material?
with respect to its near frictionless properties
What type of material describes articular cartilage? What two things is it subject to?
it is viscoelastic
creep and relaxation
During joint articulation, what do the forces at the joint surface vary from?
almost 0 to greater than 10x body weight
What normally allows cartilage to experience minimal wear under varied load?
synovial lubrication
What are two types of wear that occur to articular cartilage?
- Interfacial water
2. Fatigue water
What will cause interfacial wear on articular cartilage?
adhesion or abrasion
What type of wear of articular cartilage is the interaction of bearing surfaces?
Interfacial wear
What type of wear of articular cartilage is bearing deformation under load?
Fatigue wear
What causes Fatigue wear of articular cartilage?
repetition or high loads over a relatively short period OR with repetition of low loads over an extended period
Describe the ability for articular cartilage to repair and regenerate.
it has LIMITED ability
What determines the magnitude of stress sustained by articular cartilage?
- Total load on the joint
2. How that load is distributed over the articular surface contact area
What will play a primary role in tissue degeneration of articular cartilage?
any intense stress concentration
