applied human anatomy and biomechanics
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Applied Human Anatomy and Biomechanics. Course Content. Introduction to the Course Biomechanical Concepts Related to Human Movement Anatomical Concepts & Principles Related to the Analysis of Human Movement Applications in Human Movement Properties of Biological Materials - PowerPoint PPT PresentationTRANSCRIPT
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Applied Human Anatomy and
Biomechanics
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Course Content
I. Introduction to the CourseII. Biomechanical Concepts Related to
Human MovementIII. Anatomical Concepts & Principles Related
to the Analysis of Human MovementIV. Applications in Human MovementV. Properties of Biological MaterialsVI. Functional Anatomy of Selected Joint
Complexes
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Why study?
Design structures that are safe against the combined effects of applied forces and moments
1. Selection of proper material
2. Determine safe & efficient loading conditions
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ApplicationInjury occurs when an imposed
load exceeds the tolerance (load-carrying ability) of a tissue Training effects Drug effects Equipment Design effects
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Properties of Biological Materials
A. Basic Concepts
B. Properties of Selected Biological MaterialsA. Bone
B. Articular Cartilage
C. Ligaments & Muscle-Tendon Units
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Structural vs. Material Properties
Structural Properties Load-deformation
relationships of like tissues
Material Properties Stress-strain
relationships of different tissues
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Terminology
load – the sum of all the external forces and moments acting on the body or system
deformation – local changes of shape within a body
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Load-deformation relationship
Changes in shape (deformation) experienced by a tissue or structure when it is subjected to various loads
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Extent of deformation dependent on:
Size and shape (geometry) Material
Structure Environmental factors (temperature, humidity) Nutrition
Load application Magnitude, direction, and duration of applied force Point of application (location) Rate of force application Frequency of load application Variability of magnitude of force
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Types of Loads
Uniaxial Loads
Axial Compression Tension
Shear
Multiaxial Loads
Biaxial loading responses
Triaxial loading responses
Bending Torsion
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Types of Loads
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Axial Loads
Whiting & Zernicke (1998)
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Shear Loads
Whiting & Zernicke (1998)
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Axial Loads
Create shear load as well
Whiting & Zernicke (1998)
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Biaxial & Triaxial Loads
Whiting & Zernicke (1998)
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Structural vs. Material Properties
Structural Properties Load-deformation
relationships of like tissues
Material Properties Stress-strain
relationships of different tissues
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Terminology – Stress ()
= F/A (N/m2 or Pa)
normalized load force applied per unit
area, where area is measured in the plane that is perpendicular to force vector (CSA)
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Terminology – Strain ()
= dimension/original dimension
normalized deformation
change in shape of a tissue relative to its initial shape
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How are Stress () and Strain () related?
“Stress is what is done to an object, strain is how the object responds”.
Stress and Strain are proportional to each other.
Modulus of elasticity = stress/strain
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Typical Stress-Strain Curve
kxFe
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Elastic region & Plastic region
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Stiffness
Fig. 3.26a, Whiting & Zernicke, 1998
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Stiffness (Elastic Modulus)
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Lo
ad (
N)
Deformation (cm)
1
5
10
15
20
25
A
B C
1 2 3 4 5 6 7
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Strength stiffness ≠ strength
•Yield•Ultimate Strength•Failure
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Apparent vs. Actual Strain
1. Ultimate Strength2. Yield Strength3. Rupture4. Strain hardening region5. Necking regionA: Apparent stress B: Actual stress
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Tissue PropertiesL
oad
(N
)
Deformation (cm)
1
5
10
15
20
25
A
B C
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Extensibility & Elasticity
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ExtensibilityL
oad
(N
)
Deformation (cm)
1
5
10
15
20
25
A
B C
1 2 3 4 5 6 7
ligament tendon
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Rate of Loading
Bone is stiffer, sustains a higher load to failure, and stores more energy when it is loaded with a high strain rate.
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Bulk mechanical properties
Stiffness Strength Elasticity Ductility Brittleness
Malleability Toughness Resilience Hardness
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Ductility
Characteristic of a material that undergoes considerable plastic deformation under tensile load before rupture
Can you draw???
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Brittleness
Absence of any plastic deformation prior to failure
Can you draw???
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Malleability
Characteristic of a material that undergoes considerable plastic deformation under compressive load before rupture
Can you draw???
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Resilience
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Toughness
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Hardness
Resistance of a material to scratching, wear, or penetration
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Uniqueness of Biological Materials
Anisotropic Viscoelastic
Time-dependent behavior Organic
Self-repair Adaptation to changes in mechanical demands
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General Structure of Connective Tissue
Cellular Component Extracellular Matrix
Protein Fibers
collagen, elastin
Ground Substance
(Fluid)
Resident Cells
fibroblasts, osteocytes,
chondroblasts, etc.
Circulating Cells
lymphocytes, macrophages, etc.
synthesis &maintenance
defense &clean up
determines the functional
characteristics of the connective tissue
Distinguishes CT from other tissues
…blast – produce matrix…clast – resorb matrix…cyte – mature cell
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Collagen vs. Elastin
Collagen Great tensile strength 1 mm2 cross-section
withstand 980 N tension Cross-linked structure
stiffness Tensile strain ~ 8-10% Weak in torsion and
bending
Elastin Great extensibility
Strain ~ 200% Lack of creep
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Types of Connective Tissue
Types of Connective Tissue
OrdinaryOrdinary SpecialSpecial
Irregular OrdinaryIrregular Ordinary Regular OrdinaryRegular Ordinary CartilageCartilage BoneBone
Regular CollagenousRegular Collagenous
Regular ElasticRegular Elastic
LooseLoose
AdiposeAdipose
Irregular CollagenousIrregular Collagenous
Irregular ElasticIrregular Elastic
•Number & type of cells•Proportion of collagen, elastin, & ground substance•Arrangement of protein fibers
•Bind cells•Mechanical links•Resist tensile loads
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Why study?
Design structures that are safe against the combined effects of applied forces and moments
1. Selection of proper material
2. Determine safe & efficient loading conditions
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ApplicationInjury occurs when an imposed
load exceeds the tolerance (load-carrying ability) of a tissue Training effects Drug effects Equipment Design effects
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Properties of Biological Materials
A. Basic Concepts
B. Properties of Selected Biological MaterialsA. Bone
B. Articular Cartilage
C. Ligaments & Muscle-Tendon Units
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Mechanical Properties of Bone
General Nonhomogenous Anisotropic
Strongest Stiffest Tough Little elasticity
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Material Properties: Bone Tissue
Cortical: Stiffer, stronger, less elastic (~2% vs. 50%), low energy storage
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Mechanical Properties of Bone
Ductile vs. Brittle Depends on age and rate at which it is loaded Younger bone is more ductile Bone is more brittle at high speeds
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Glass
Bone
Metal
•Stiffest?•Strongest?•Brittle?•Ductile?
old
young
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Tensile Properties: Bone
Ultimate stress (MPa)
Modulus of elasticity (GPa)
Strain to Fracture (%)
Collagen 50 1.2 -
Osteons 38.8-116.6 - -
Axial
Femur (slow)
(fast)
78.8-144 6.0-17.6 1.4-4.0
Tibia (slow) 140-174 18.4 1.5
Fibula (slow) 146-165.6 - -
Transverse
Femur (fast) 52 11.5 -
Stiffness
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Compressive Properties: Bone
Ultimate stress (MPa)
Modulus of elasticity (GPa)
Strain to Fracture (%)
Osteons 48-93 - -
Axial
Mixed 100-280 - 1-2.4
Femur 170-209 8.7-18.6 1.85
Tibia 213 15.2-35.3 -
Fibula 115 16.6 -
Transverse
Mixed 106-133 4.2 -
140-174
146-165.6
78.8-144 1.4-4.06.0-17.6
18.4
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Other: Bone
Ultimate stress (MPa)
Modulus of elasticity
(GPa)
Strain to Fracture
(%)
Shear 50-100 3.58 -
Bending 132-181 10.6-15.8 -
Torsion 54.1 3.2-4.5 0.4-1.2
Tension 78.8-174 6.0-18.4 1.4-4.0
Compression 100-280 8.7-35.3 1-2.4
From LeVeau (1992). Biomechanics of human motion (3rd ed.). Philadelphia: W.B. Saunders.
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Ultimate stress (MPa)
Modulus of elasticity (GPa)
Strain to Fracture (%)
Polymers (bone cement)
20 2.0 2-4
Ceramic (Alumina) 300 350 <2
Titanium 900 110 15
Metals (Co-Cr alloy)
Cast
Forged
Stainless steel
600
950
850
220
220
210
8
15
10
Cortical bone 100-150 10-15 1-3
Trabecular bone 8-50 - 2-4
Bones (mixed) 100-280 8.7-35.3 1-2.4
Mechanical Properties of Selected Biomaterials
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Viscoelastic Properties :Rate Dependency of Cortical Bone
Fig 2-34, Nordin & Frankel, (2001)
•With loading rate:
brittleness Energy storage 2X (
toughness) Rupture strength 3X Rupture strain 100% Stiffness 2X
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Viscoelastic Properties :Rate Dependency of Cortical Bone
Fig 2-34, Nordin & Frankel, (2001)
•With loading rate:
More energy to be absorbed, so fx pattern changes & amt of soft tissue damage
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Effect of Structure
Larger CSA distributes force over larger area, stress
Tubular structure (vs. solid) More evenly distributes bending & torsional stresses
because the structural material is distributed away from the central axis
bending stiffness without adding large amounts of bone mass
Narrower middle section (long bones) bending stresses & minimizes chance of fracture
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Effects of Acute Physical Activity
Fig 2-32a, Nordin & Frankel (2001)
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Acute Physical Activity
Fig 2-32b, Nordin & Frankel (2001)
•Tensile strength: 140-174 MPa•Comp strength: 213 MPa•Shear strength: 50-100 MPa
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Acute Physical Activity
Fig 2-32b, Nordin & Frankel (2001)
•As speed , and •5X in with speedwalk = 0.001/s
slow jog = 0.03/s
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Acute Physical Activity
Fig 2-33, Nordin & Frankel (2001)
•In vivo, muscle contraction can exaggerate or mitigate the effect of external forces
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Chronic Physical Activity
bone density, compressive strength stiffness (to a certain threshold)
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Chronic Disuse
bone density (1%/wk for bed rest) strength stiffness
Fig 2-47, Nordin & Frankel (2001)
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Repetitive Physical Activity
Injury cycle
Muscle Fatigue
Ability to Neutralize Stresses on Bone
Load on Bone
Tolerance for Repetitions
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Repetitive Physical Activity
Fig 2-38, Nordin & Frankel (2001)
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Applications for Bone Injury
Crack propagation occurs more easily in the transverse than in the longitudinal direction
Bending For adults, failure begins on tension side, since
tension strength < compression strength For youth, failure begins on compression side,
since immature bone more ductile Torsion
Failure begins in shear, then tension direction
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Effects of Age
brittleness strength
( cancellous bone & thickness of cortical bone) ultimate strain energy storage
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Effects of Age on Yield & Ultimate Stresses (Tension)
100
110
120
130
140
150
160
170
180
20-29 30-39 40-49 50-59 60-69 70-79 80-89
Age (yrs)
Str
es
s (
MP
a)
Femur - Yield Tibia - Yield Femur - Ultimate Tibia - Ultimate
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Effects of Age on Eelastic (Tension)
10.0
15.0
20.0
25.0
30.0
35.0
20-29 30-39 40-49 50-59 60-69 70-79 80-89
Age (yrs)
Elas
tic
Mo
du
lus
(G
Pa)
Femur Tibia
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0.000
0.005
0.010
0.015
0.020
0.025
0.030
0.035
0.040
0.045
20-29 30-39 40-49 50-59 60-69 70-79 80-89
Age (yrs)
Ult
imat
e S
trai
n
Femur Tibia
Effects of Age on Ultimate Strain (Tension)
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2
2.5
3
3.5
4
4.5
5
5.5
6
20-29 30-39 40-49 50-59 60-69 70-79 80-89
Age (yrs)
Ene
rgy
(MP
a)
Femur Tibia
Effects of Age on Energy (Tension)
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Properties of Biological Materials
A. Basic Concepts
B. Properties of Selected Biological MaterialsA. Bone
B. Articular Cartilage
C. Ligaments & Muscle-Tendon Units
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Deforms more than bone since is 20X less stiff than bone congruency High water content causes even distribution of stress
High elasticity in the direction of joint motion and where joint pressure is greatest
Compressibility is 50-60%
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Tensile Properties: Cartilage
Ultimate stress (MPa)
Modulus of elasticity (GPa)
Strain to Fracture (%)
Tension 4.41 - 10-100
Superficial 10-40 0.15-0.5 -
Deep 0-30 0-0.2 -
Costal 44 - 25.9
Disc 2.7 - -
Annulus 15.68 - -
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Compressive Properties: Cartilage
Ultimate stress (MPa)
Modulus of elasticity (GPa)
Strain to Fracture (%)
Compression 7-23 0.012-0.047 3-17
Patella - 0.00228 -
Femoral head - 0.0084-0.0153 -
Costal - - 15.0
Disc 11 - -
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Other Loading Properties: Cartilage
Ultimate stress(MPa)
Modulus of elasticity (GPa)
Strain to Fracture (%)
Shear
Normal - 0.00557-0.01022 -
Degenerated - 0.00137-0.00933 -
Torsion
Femoral - 0.01163 -
Disc 4.5-5.1 - -
Tension
From LeVeau (1992). Biomechanics of human motion (3rd ed.). Philadelphia: W.B. Saunders.
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Properties of Biological Materials
A. Basic Concepts
B. Properties of Selected Biological MaterialsA. Bone
B. Articular Cartilage
C. Ligaments & Muscle-Tendon Units
D. Skeletal Muscle
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Structure and Function: Architecture
The arrangement of collagen fibers differs between ligaments and tendons. What is the functional significance?
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Biomechanical Properties and Behavior
Tendons: withstand unidirectional loads
Ligaments: resist tensile stress in one direction and smaller stresses in other directions.
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Viscoelastic Properties :Rate Dependent Behavior
Moderate strain-rate sensitivity With loading rate:
Energy storage ( toughness) Rupture strength Rupture strain Stiffness
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Viscoelastic Properties: Repetitive Loading Effects
Enoka (2002), Figure 5.3, p. 219, From Butler et al. (1978)
stiffness
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Enoka (2002), Figure 5.3, p. 219, From Butler et al. (1978)
Idealized Stress-Strain
for Collagenous
Tissue
Very small plastic region
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Ligamentum flavum
Nordin & Frankel (2001), Figure 4-10, p. 110, From Nachemson & Evans (1968)
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Tensile Properties: Ligaments
Ultimate stress (MPa)
Modulus of elasticity (GPa)
Strain to Fracture (%)
Nonelastic 60-100 0.111 5-14
ACL 37.8 - 23-35.8
Anterior
Longitudinal
.0123
Collagen 50 1.2 -
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Viscoelastic Behavior of Bone-Ligament-Bone Complex
Fast loading rate: Ligament weakest
Slow loading rate: Bony insertion of ligament weakest Load to failure 20% Energy storage 30% Stiffness similar
As loading rate , bone strength more than ligament strength.
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Ligament-capsule injuries
Sprains1st degree – 25% tissue failure; no clinical
instability2nd degree – 50% tissue failure; 50% in
strength & stiffness3rd degree – 75% tissue failure; easily
detectable instabilty Bony avulsion failure (young people –
more likely if tensile load applied slowly)
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Tensile Properties: Muscles & Tendons
Ultimate stress (MPa)
Modulus of elasticity (GPa)
Strain to Fracture (%)
Muscle 0.147-3.50 - 58-65
Fascia 15 - -
Tendon
Various 45-125 0.8-2.0 8-10
Various 50-150 - 9.4-9.9
Various 19.1-88.5 - -
Mammalian 0.8-2
Achilles 34-55 - -
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Enoka (2002), Figure 5.12, p. 227, From Noyes (1977); Noyes et al. (1984)
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Enoka (2002), Figure 3.9, p. 134, From Schechtman & Bader (1997)
EDL Tendon
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ECRB Achilles
Max muscle force (N) 58.00 5000.0
Tendon length (mm) 204.00 350.0
Tendon thickness (mm2) 14.60 65.0
Elastic modulus (MPa) 726.00 1500.0
Stress (MPa) 4.06 76.9
Strain (%) 2.70 5.0
Stiffness (N/cm) 105.00 2875.0
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Muscle – Mechanical Stiffness
Instantaneous rate of change of force with length Unstimulated muscles are very compliant Stiffness increases with tension High rates of change of force have high muscle
stiffness, particularly during eccentric actions Stiffness controlled by stretch and tendon reflexes
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Effects of Disuse
Nordin & Frankel (2001), Figure 4-15a, p. 110, From Noyes (1977)
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Effects of Disuse
Nordin & Frankel (2001), Figure 4-15b, p. 110, From Noyes (1977)
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Effects of corticosteroids
stiffness rupture strength energy absorption
Time & dosage dependent
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Effect of Structure
Whiting & Zernicke (1998), Figure 4.8a,b, p. 104, From Butler et al. (1978).
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Miscellaneous Effects
Age effects More compliant / less strong before maturity Insertion site becomes weak link in middle age
stiffness & strength in pregnancy in rabbits Hormonal?
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Summary
Mechanical properties of biological materials vary across tissues and structures due to material and geometry differences.
Understanding how age, physical activity, nutrition, and disease alter mechanical properties enables us to design appropriate interventions and rehabilitations.
Understanding these mechanical properties allows us to design appropriate prosthetic devices to for joint replacement and repair.