Midterm

Question 1

How do collagen fibers change with age?

Answer 1

Collagen fibers get thinner and smaller as we age

Question 2

What do proteoglycans do?

Answer 2

Basically act as little brushes connected to link proteins, they respond really well to compression, little bristles in the brush push back against compressive forces

Question 3

What forces do GaGs resist?

What is their charge and therefore their affinity for water?

How are they complementary to collagen?

How do they affect the flow of water in and out of cartilage?

Answer 3

Also resist compressive forces, have a negative charge and are hydrophilic so they have the ability to push back against compression and absorb all the water into the proteoglycan brushes, complementary to the collagen which is better at resisting tension forces, water flow in and out of the cartilage ensures that the cartilage stays healthy

Question 4

What does movement bring into the cartilage?

How fast is the metabolism of cartilage?

What is immobility’s effect on cartilage?

Answer 4

Movement causes water and nutrients to flow in and out of the cartilage

Cartilage has a very slow metabolism

Cartilage becomes more porous and pliable, may eventually lead to bones touching each other which causes shearing forces

Question 5

What are the 2 most common causes of damage to the cartilage?

Answer 5

1. Immobility
2. Excessive loading

Question 6

How do mogul skiiers minimize the load on the structures of the knee?

Answer 6

Large eccentric contraction in quads to “brake” against gravity and avoid going into full knee flexion at any point

Question 7

Where is most of the fluid in articular cartliage found?

How does the concentration change with depth?

Answer 7

Fluid is concentrated at the joint’s surface, decreased concentration with depth

Question 8

What is an aggregan?

Answer 8

Combination of GaGs and link protein

Question 9

How is the cartilage closest to the bone organized?

Answer 9

Cartilage nearest to the bones in perpendicular to the bone in order to absorb compression and to be able to directly attach to the bone

Question 10

What does viscoelastic mean in the context of cartilage?

Answer 10

Visco refers to water
Elastic refers to cartilage

Question 11

How can we describe creep and relaxation of our cartilage?

Answer 11

Creep-liquid goes out of the cartilage quickly when the structure is pressed and then it stabilizes over time

Relaxation-characterized by initial compression and then a relaxation phase
(ex. trying to touch your toes for a few minutes, there will be initial resistance and you will feel tight but as you give your body enough time and ease into the stretch gradually you will be able to go deeper and deeper because the fluid in the structure moves and the collagen repositions itself to accommodate the stretch, do not try to stretch ballistically)

Question 12

What is the relationship between permeability and resistance to fluid?

Answer 12

High permeability = low resistance to fluid

Low permeability = high permeability to fluid

Question 13

How porous is cartilage?

How permeable is cartilage?

What causes this level of permeability in the cartilage?

Answer 13

Articular cartilage is very porous

Articular cartilage has very low permeability, lets fluid come in and go out at a very slow rate

This is because of the large generation of friction from the collagen and the proteoglycans within the articular cartilage

Question 14

Why is it important to retain water in the articular cartilage?

Answer 14

Water in the cartilage helps to absorb the compressive forces and acts as a cushion

Question 15

How will fluid in the carilage react to load?

Answer 15

If you have a compressive force straight down, fluids will move to the sides to try and avoid the compressive force.

Question 16

What structure brings water back into the cartilage once unloading takes place?

Answer 16

Proteoglycans bring water back into the cartilage

Question 17

How does a high outside pressure applied by a load to the cartilage affect the permeability of the cartilage?

Answer 17

P1=pressure applied by the load to the cartilage
P2=pressure within the cartilage

When there’s a big difference between P1 and P2, there’s more compression so there will be much less permeability in the cartilage.

When theres a small difference between P1 and P2, there’s less compression so there will be much more permeability

Question 18

What is the last resort protection of the cartilage?

Answer 18

Lubrication models,
mix of models 1 & 2, not one or the other
(liquid lubricating film and surface lubrication)

Question 19

Why is osteoarthitis so prevalent?

Answer 19

We don’t move enough as a society, and when we do try to move we overcompensate and do big bursts of physical activity at one time and put excessive loading on the structures

Question 20

how does the body receive most loads?

how long does it take for the body to receive a steady state response to the cyclical loading?

What is the ideal oscillation or variability between cycles?

When is it good to see more variability in cycles, in running for example?

Answer 20

Cyclical, such as walking or cycling

30 cycles

We want as small an oscillation, or variation, as possible when doing cyclical activities like walking or cycling

Trail running, don’t have a choice and need to be able to adapt to the outside environment and change variability due to instability

Question 21

What property makes cartilage have a non-elastic response as opposed to an elastic response?

What is lost energy between loading and unloading cycle?

What kind of training uses this method?

What is important in plyometric training?

Answer 21

No, it has a non-elastic response because it is viscoelastic

Energy lost to heat when structure is deforming and forming back during loading and unloading cycles

Plyometrics, being able to absorb energy and use it again

You need to tell the client to jump up and down and jump back up again as quick as possible, faster than 1 second within touching the ground, this makes sure that energy used is hystesis energy that is stored in the muscles and that this energy is not lost to heat.
(ex. do a box jump, get down off the box, jump back down as fast as possible)

Question 22

What kind of force is required to elicit an elastic response from the cartilage?

What kind of force is required to elicit a viscoelastic response from the cartilage?

Answer 22

Very fast force
(intracellular fluid doesn’t have time to move around)

Normal force
(intracellular fluid does have time to move around)

Question 23

What does collagen look like in normal situations compared to when it is under stress/strain

Answer 23

collagen spread out in all different directions, changes it shape and becomes more parralel to increase the rigidity of the fibers as it reacts to the stress/strain
(moves from toe region to linear region to eventually failure)

Question 24

how does collagen react to shear forces and are pure shear forces common?

What combination of forces does it not react well to?

Answer 24

Reacts well to pure shear forces such as translation between the bottom and top layer but the body NEVER has pure shear forces
(minimal deformation, no volume changes, no fluid movement)

Doesn’t react well to compression/
tension forces being combined with shear forces

Question 25

What causes wear and tear?

Answer 25

repetitive movements that cause stress and strain on the same structure

Question 26

How does elastic/viscoelastic response change with cyclic movements?

Answer 26

Response because more elastic because intracellular fluid doesn’t have time to move around

Question 27

What is important to prevent cartilage damage?

How is this impacted by age?

Answer 27

Loading-unloading through physical activity

Young people on bedrest can recover their cartilage through physical activity after deconditioning
Older people on bedrest may not be able to fully recover their cartilage after deconditioning, may need to start physical activity in the water and progress from there

Question 28

What activities lead to acute cartilage damage?

What activities lead to chronic cartilage damage?

Answer 28

High stress events such as bike accidents, car crashes, etc.

Daily activities performed with repeated asymmetrical loading through faulty biomechanics

Question 29

Why is too much static stretching bad before a workout?

Answer 29

Elastic response of the muscle will be dampened and viscoelastic response will be prioritized which will change the way the structures react to high force movements like sprinting, lifting, etc.

Question 30

How fast can chondrocytes replace collagen matrix in the cartilage?

Answer 30

Cartilage is very slow to regenerate and the chondocytes have a poor ability to synthesize new collagen matrix within the cartilage

Question 31

What are 2 factors that can increase the breakdown of cartilage if they are not optimal?

Answer 31

1.Alignment of the structures at rest and during dynamic movements, as well as imbalances between the muscles

2.Strength of the ligaments

Question 32

What is the only way to fully recover a ligament after injury?

Answer 32

Surgery
(surgeon needs to go in and tighten the ligament again)

Question 33

What lifestyle factor is the main cause of wear and tear on the cartilage?

What is a biomechanical factor in the case of wear and tear?

Answer 33

Lack of physical activity

misalignment is a close second

Question 34

How does the ratio between proteoglycan and synovial fluid change with age?

Answer 34

ratio of proteoglycan and fluid will change, less synovial fluid and more proteoglycan

Question 35

What is there a lack of in the case of arthrosis and what does this lack cause a decrease in? what does this lead to?

Answer 35

Lack of joint space causes large decrease in range of motion and leads to two ends pinching and rubbing together

Question 36

Where do knee valgus and varus cause damage?

Answer 36

Knee varus causes damage to inside of the knee
Knee valgus causes damage to the outside of the knee

Question 37

What 2 things should be your priority if your clients wants to transition to barefoot running?

Answer 37

1. Work on perfecting their form
2. switch to barefoot running slowly and increase over time, do not go for a long barefoot run right away

Question 38

How much variability should you have in joint positions?

Answer 38

A moderate amount

Not too much so there is not any standardization but not too little so there is too much rigidity and no flexibility

Question 39

What is hysteris energy and which mechanical property is responsible for it?

Answer 39

Viscoelastic component creates hysteris or energy lost to heat

Question 40

What is the pre-conditioned state?

What will the same load cause more of over time and how will this effect the loading/unloading curve and how does it make us more efficient?

Answer 40

Doing warm up before physical activity to reach the pre-conditioned state, muscle fibers/tendons/
ligaments are ready to perform task

Same load will cause more deformation over time, the difference between the loading and unloading curve will get smaller with time because we become more efficient (more elastic and less viscoelastic)

(slide 22 of lecture 4)

Question 41

What type of warm-up is best for pre-conditioning?

Answer 41

Dynamic warm-up movements are specific to the task
(ex.high knees before you go running)

Question 42

What is the issue with 30 reps of plyometrics at a time?

What is the better way to do it?

Answer 42

Fatigue will build up and show in the results

3-5 trials of a couple reps each and then find the average
(always do an uneven number)

Question 43

How to prepare for a 1RM test?

Answer 43

Condition muscle to do the movement and make sure my joints are ready to perform the task, build up slowly

Question 44

Why is warm-up important?

Answer 44

Prevent injuries and get optimal performance, injuries in your 20s from not warming up will follow you for the rest of your life

Question 45

How does immobility affect tendon/ligament recovery?

Answer 45

1,2,3 weeks in the hospital will rapidly decrease the mechanical structures of the muscles, tendon/ligament recovery from immobility is better the younger you are.

Question 46

Why does the middle part of the ligament recover faster than the part connected to the bone from immobility?

How is the structure of the ligament in the middle and at the meeting point of bone and bone different?

Answer 46

The middle part of the ligament has all the same structures(collagen), the structures of the ligament change when you get closer to the insertion site on the bone and take longer to recover(mix of collagen from the ligament and calcium from the bone)

(slide 23 of lecture 4)

Question 47

Can ligaments go back to 100% after injury?

What is the best way to recover a ligament?

Answer 47

Very hard for a ligament to regain 100% of function and you never recover completely, especially near the insertion site of the ligament

Regular exercise/movement with progression and warm-ups is #1 to make the baseline strength of ligaments higher, starting with above average strength of ligaments will allow the ligaments to go back to average strength of gen pop after recovering from injury

Question 48

What happens when most people get immobilized?

What are the 4 best dietary guidelines to recover from injury?

How does creatine affect injury recovery?

Answer 48

They gain weight and their nutrition/hydration is not optimal to recover from their injury

1.Drink a lot of water to increase the intracellular water
2.Eat a high amount of calcium to support the bones
3.Eat a high amount of protein because they support muscle tissue
4.Eat a high amount of carbs because they carry alot of water with them

Creatine was mixed with a lot of different things in the early 90’s which gave it bad press, now it can be 99% pure and it is beneficial because it will increase intracellular water

Question 49

What type of activity does bone need to grow and to be healthy?

Answer 49

Mechanical loading of the bone through weight-bearing activity

Question 50

What decreases in the ligaments as we age?

When does this decline start?

What is the most common injury in an active population?

Answer 50

Intracellular water

Starts in early 20s, best course of action is to start healthy habits in your 20s to start the decline at a higher point

ACL injury

Question 51

Why do ACLs get injured so much?

Answer 51

We use them all the time, makes sure the knee doesn’t go forward and there is no anterior translation

ACL is always in tension even when your not moving around so it is always active, problem is ACL affects many other components of your knee

Question 52

Why are steroids bad for the tendons?

Answer 52

The growth of the muscle outpaces the adaptations of the tendons and the muscle applies massive forces to the tendons

Question 53

How many bones do babies have and how many bones do adults have?

What do giraffe’s necks and human’s necks have in common?

What is the smallest bone in the human body and where is it found?

Answer 53

Babies = 300 bones
Adults = 206 bones

A giraffe’s neck contains the same number of vertebrae as a human neck.

The smallest bone in the human body is found in the inner ear and is about 0.28 cm long (Stirrup)

Question 54

What are the 3 mechanical functions of bone?

Answer 54

1. Support
2. Protection
3. Levers for locomotion

Question 55

What are the 2 physiological functions of bone?

Answer 55

1. Mineral Homeostasis: storage of minerals
2. Hematopoiesis: Formation of red blood cells

Question 56

What 2 places can hematopoietic tissue(red bone marrow) be found in newborns?

Answer 56

In newborns:
* Medullary canal/cavity of long bones
* Cancellous bone (aka spongy bone)

Question 57

What 4 places can hematopoetic tissue be found in adults?

Answer 57

In adults:
* Axial skeleton
* Heads of long bones (femur & humerus)
* Flat bones (cancellous layer)
* Some irregular bones

Question 58

How does bone marrow composition change from childhood to adulthood?

Answer 58

Child: marrow is almost exclusively red (40% water, 40% fat, and 20% proteins)

Adult: gradual transition to yellow marrow (85% fat, 15% water and 5% protein)

Question 59

What are the 2 systems of the human skeleton and how many bones total across the 2 systems?

Answer 59

Axial and appendicular, there are 206 bones

Question 60

What are the 3 components of the axial skeleton?

Answer 60

i. Bones in skull/head
ii. Spine
iii. Rib cage

Question 61

What are the 4 components of the appendicular skeleton?

Answer 61

i. Upper limb bones
ii. Lower limb bones
iii. Shoulder complex
iv. Pelvis

Question 62

What is the diaphysis?

What type of bone is in the diaphysis?

What is the endosteum?

Answer 62

the shaft or central part of a long bone.

periosteum on the outside, compact bone in the middle and the medullary canal(containing bone marrow) on the inside

A membrane lining the inner surface of the bony wall also identified as the lining membrane of the Bone marrow cavity

Question 63

What is the metaphysis?

What type of bone is in the metaphysis?

Answer 63

the region where the epiphysis joins the diaphysis

cancellous (or spongy) bone

Question 64

What is the epiphysis?

What type of bone is in the epiphysis?

Answer 64

the enlarged wide end of a long bone that articulates with other bones at joints

physis (growth plate)

Question 65

What type of bone is in the proximal epiphysis?

Where is the epiphyseal line?

Answer 65

Spongy bone

Between the proximal epiphysis and the diaphysis

Question 66

What is compact bone made of?

What kind of system is a compact bone?

What is the difference between haversian canal’s and volkmann canals?

What is cancellous (or spongy) bone made of?

Answer 66

made up of osteons

Harvesian system

Both are found in bones: Haversian canals are located in the center of compact bones, while Volkmann’s canals are located at the edges of bones.

consist of trabeculae, arranged to optimize stress resistance

Question 67

What are osteoblasts?

Answer 67

Osteoblasts : cells that produce and
coordinate mineralization of bone
-Synthesize and secrete collagen
fibers and initiate calcification

Question 68

What are osteoclasts and what are they responsible for?

Where are they concentrated?

Answer 68

Osteoclasts:
cells that breakdown bone
-Concentrated in the endosteum

Question 69

What are osteocytes?

Answer 69

Osteocytes: mature osteoblasts
surrounded in bone matrix

Question 70

What are the 2 mechanisms of bone maintenance?

Answer 70

Deposit and resorption of minerals in the bone

Question 71

What are the 2 types of bone growth and what dimension do they grow?

How are osteoblasts involved in the process of the second type and where are they located?

Answer 71

Interstitial Growth leads to increase in bone length
Appositional Growth leads to increase in bone thickness

Osteoblasts below the periosteum form new osteons on the external bone surface.

Question 72

How does the use of a bone change it’s bone density?

What is an example of this in sports?

Answer 72

• Change in use = change in bone
  density
  – Mechanical Loading
• Different bone modification depending
  on location

Study on tennis players:
cortical bone density
~35% higher in active arm.

Question 73

What are 7 factors that affect bones?

Answer 73

Disease
Genetics
Local tissue
Mechanical loading
Metabolism
Hormones
Medications

Question 74

What are the 3 major contributors to bone composition and what are the percentages of each?

Answer 74

Bone Composition:
Minerals: 40%,
Collagen: 35%,
Water: 25%

Question 75

What cells are found in bones?

What is in the extracellular matrix of bones?

What is the main type of inorganic material found in bones?

Answer 75

Organic Material
– Cells
* Osteoblasts, Osteoclastes & Osteocytes

– Extracellular matrix
* Collagen (type I) (~90%)
* Proteoglycanes (~5%)
* Polysaccharides/glycosaminoglycans act as cement

Inorganic Material
– Minerals: mainly calcium and phosphate

Question 76

What is the distribution of weight in the extracellular matrix of bones?

What does it mean that bone is bi-phasic and which materials give that property?

Answer 76

1. Organic material: ~ 1/3
   Flexible & resilient
2. Inorganic material (minerals): ~ 2/3
   Hardness, rigidity & strength

Mechanical property of bone = bi-phasic composite materials, with organic components being flexible & resilient/inorganic components being hard & rigid

Question 77

What are 2 mechanical properties of bone tissue?

How do these 2 mechanical properties refect on the damage they sustain?

Answer 77

Ductile: implies large deformations
Fragile: reduced or inconsistent plasticity

Ductile = slow rupture
Fragile = brutal breaks

Question 78

What are the properties of bone?

What is the material of each property of bone and what do these materials resist changes in?

What forces does ductility resist and what forces does fragility resist?

Answer 78

Bone is semiductile & viscoelastic

Ductile:
made up of collagen
resists changes in tension

Fragile:
made up of minerals
resists changes in compression

Viscoelastic:
made up of water

Question 79

What is the definition of stress?

What is the definition of strain?

What is another name for stress-strain curve?

What are the 3 parameters of the stress-strain curve?

Answer 79

Stress – intensity or magnitude of
the load

Strain – deformation (change in
dimension) that occurs in a structure
in response to applied loads.

Load-deformation curve

1. Maximum stress supported by bone or material
2. Maximum deformation before
   rupture/failure
3. Energy stored before rupture/failure

Question 80

What are the 2 regions on the load deformation curve?

Answer 80

Elastic region up to the breaking point

Plastic region up to the irreversible breaking point

Question 81

What is the definition of elasticity?

What is the end of the elastic region?

Answer 81

Capacity of a tissue to return to its initial form when load is no longer applied

Elastic region ends at the breaking point on the load-deformation curve where elastic strain can no longer be taken

Question 82

What is the definition of permanent deformation?

Answer 82

resulting from micro ruptures and lesions in the plastic region up until the point of the irreversible breaking point

Question 83

How is rigidity calculated on the load-deformation curve?

Answer 83

Rigidity or Modulus of elasticity
(young’s modulus):

Equation:
stress(load)
divided by
strain(deformation)

Question 84

What does the area under the curve represent on the load-deformation curve?

Answer 84

Area Under Curve
= Force of Material

Question 85

What is the equation for hooke’s law?

Answer 85

Fs = k * x

Fs = force exerted by material to return to original shape
k = stiffness (constant to material being
tested)
x = change in distance (deformation).

Question 86

Give an example of applying hooke’s law

Answer 86

*Situation: we hook a mass on a spring whose spring constant (k) is 15 N/m. The spring, which had an initial length of 10 cm, is now 25 cm long.
*What will be the final length (xf) of the spring if we hook an object that has a weight of 2.0 N?
In this case, we will not take into account the orientation of the forces and the elongation. This is why we will not include the negative sign in the equation of Hooke’s law.

Fs = (0.15m * 15 N/m) + 2.0 N
k = 15 N/m
xi = 10 cm = 0.10 m
xf = ?

Fs = k * x
↕
Δx = Fs / k
Δx = 4.25 N / 15 N/m
Δx = 0.28 m
Δx = xf – xi
xf = xi + Δx
xf = 0.1 m + 0.28 m
xf = 0.38 m

Question 87

What is the max deformation in the elastic response?

How does the deformation in elastic response vary?

Can bone return to original shape in this response?

Answer 87

When loaded…
* Deformation: max length = 3%
* Deformation graph varies linearly
* Yes, Bone still returns to its original shape/length

Question 88

Which fibers give way in the plastic region?

What is the end point of the plastic region?

Can the bone return to original shape?

Answer 88

When loaded…
* External fibers begin to give way
(Micro-tears)
* Can go as far as fracture
* Bone cannot return to original shape/length
(permanent change)

Question 89

Which type of bone resists either stress or strain?

What is the max stretching for either compact or spongy bone/

Answer 89

Compact Bone:
* Resistor of stress
* Max stretching: 1.5-2%

Spongy Bone:
* Resistor of strain
* Stores more energy
* Max stretching: 50%

Question 90

What does the behaviour of the bone depend on?

Is bone homogenous or non-homogenous?

In which direction can bone accept more force?

Answer 90

• Behaviour of the bone depends on the orientation of the load being applied.
• Bone is a non-homogenous material
• Can accept more force longitudinally & less force perpendicularly

Question 91

What are the 6 types of loading that the skeleton withstands?

Answer 91

Compression pushes inward
Tension pulls outward
Bending moves side to side
Shear creates friction
Torsion twists
Combined loading is a combination

Question 92

What do compressive forces do and what effect do they have on the bone and what are they necessary for?

What joint requires special considerations when it comes to compressive forces?

Answer 92

-Forces that compress the ends of the bones in the direction of the length of the bone
-Shortening and widening
-Necessary for bone growth and
deposition!

Hip joint

Question 93

How do vertical compression forces change moving downward along the spine?

Answer 93

Low at cervical vertebrae
Moderate at thoracic vertebrae
High at lumbar vertebrae

Question 94

What is often the source of tensile forces on bones and what effect do they have on the bone and what do they help develop?

Answer 94

-Often muscle is the source
-Lengthening/narrowing
-Development of bone growth

Question 95

Where do shear forces occur, what kind of deformation do they cause and which other forces do they usually come at the same time as?

What is spondylolisthesis and what type of posture does it cause and which section of the spine has increased shear forces?

Answer 95

Shear Forces:
– On the surface
– Angular deformation
– Present during compression & tension
loading

Spondylolisthesis:
– Vertebra slide anterior on one another
– Hyperlordosis posture
– Increased shear forces (L4/L5)

Question 96

In which 2 ways do materials deform from flexion forces?

What are the 2 types of flexion forces in regards to the number of points of application?

Which type of deformation causes more injury?

Answer 96

– Material deforms convexly from tension and concavely from compression

– Two Types of Flexion Forces
* 3 points of application (A)
* 4 points of application deformation (B)

– Risk of injury on convex part of the bone from tension (i.e. ‘boot top’ fracture in skiers)

Question 97

What axis do torsion forces occur on, what are the 2 opposing forces around this axis, what kind of deformation do they cause and what is a common injury with torsion forces?

Answer 97

Torsion Forces:
– Twisting about the longitudinal axis
* 2 opposing forces around the axis (Material deforms convexly from tension and concavely from compression
– Angular deformation, especially on the periphery
– Common injury, spiral fractures

Question 98

What are 2 factors that affect the deformation rate and what is the important of these 2 factors?

Which one is bone failure dependent on?

Do bones have better resistance to loads applied quickly or slowly?

Answer 98

The bone responds differently depending on:
- Loading rate
- Loading time

-Bone failure is dependent on the loading rate

-Better resistance to loads applied quickly

Question 99

How does lower or higher loading rate affect fractures?

Answer 99

-Lower loading rate: energy has time to
dissipate = single fracture

-Bigger loading rate: energy does not have time to dissipate = bone fragments

Question 100

What are 2 factors that influence injury rate and fracture rate?

Answer 100

1. Bone Strength Limit
   * Depends on: Physical Exercise,
   Conditioning, Immobilization, Skeletal
   Maturation, Fatigue, Loading Rate, etc.
2. History of Loading
   * Repetition and Load
   * Microtraumas: frequency is greater than the bone repair process.

Example(During fatigue, reduced shock
absorption leads to a change in distribution of the forces in the body

Question 101

What is the difference in how oblique fractures and transverse fractures occur?

Answer 101

Refer to slide 45 of bones lecture

Question 102

What are 5 common types of fractures?

When do these fractures most commonly occur?

Answer 102

• Tibia
• Fibula
• Femur
• Metatarsal
• Calcaneum

Especially when walking or running long distances!

Question 103

Why is physical activity important in bone remodelling? What 2 things is bone density influenced by?

Give 2 examples of people who face the repercussions of not having enough physical activity?

Answer 103

Physical Activity & Bone Remodeling:

• Daily stimulation is needed: bone requires mechanical stresses to grow and strengthen.
• Density is influenced by the number of
  cycles and the magnitude of loading

Examples:
* Astronauts
* Persons with different mobility capacities

Question 104

What is the rate of bone mass loss during immobilization?

Answer 104

Bone mass loss is ~1% per week during
immobilization

Question 105

What is the effect of bone geometry on the ability to resist rotational forces?

What do tension & compression depend on in the case of bone geometry?

What does flexion depend on in the case of bone geometry? How does the length of bone effect flexion?

What does bending depend on in the case of bone geometry?

What 3 greater forces are long bones subject to?

What type of bone shape resists bending?

Answer 105

Bone geometry will affect the moment of inertia (ability to resist rotational forces)

Tension and compression: depends on the cross-section of the area of bone

Flexion: depending on the moment of inertia of the area

The length of the bone influences its strength and rigidity. The longer the bone = greater the flexion moment and less ability to resist flexion

The magnitude of the stress at the point of application of the bending moment is proportional to the length of the structure.

Long bones are subject to greater flexion
moments …therefore greater tension and compression force!

Tubular shape: resist bending moments

Question 106

Which property of bone increases with age? What property decrease?

Answer 106

– Bone porosity increases
– Bone density decreases

Question 107

When does the cortical diameter of bone max out?

What percent does bone mass decrease for men and women per year after 40?

Answer 107

Cortical Diameter: max at ~30-40 yrs
After 40 yrs, bone mass begins to decrease
* Less Mass = Reduced mechanics
* Women: 1.5 - 2% of mass/year
* Men: 0.5 – 0.75% of mass/year

Question 108

How does menopause affect bone mass loss?

Answer 108

Post-menopause: bone mass loss accelerates

Ultimate compressive force decreases by 15-20% between 20-39 yrs and 60-89 yrs

Bone fails more easily to weaker forces in women

Constant difference of 17% between men and women

Higher rate of fractures in women

Refer to slide 52 of bone lecture

Question 109

Which bone maintenance mechanism is dominant in the case of osteoporosis?

What happens when there is loss of trabecular or spongy bone?

Answer 109

Bone resorption exceeds bone deposition

Loss of rigidity in the lower area of the bone leads to higher fracture rates

Question 110

What percent of men and women have osteoporosis over 50?

What are 4 risk factors for the development of osteoporosis?

Answer 110

Women:
50% of population over 50 years old
90% …over 75 years old
Men:
30% of population over 50 years old

Risk Factors
* Low body weight (BMI < 19)
* Low muscle mass
* Inadequate or excessive exercise
* Early menopause

Question 111

What are the 4 functions of skeletal muscles?

Answer 111

Functions:
* Produce body movements
* Stabilize posture
* Move substances/fluids throughout the body
* Produce heat

Question 112

What are the 3 methods of structure/organization of skeletal muscles?

Answer 112

1. Arrangement
   * Macroscopic
   * Microscopic
2. Fiber organization/direction
3. Muscle attachments

Question 113

What is the definition of fascia?

What is the difference between superficial & deep fascia?

What are the 2 types of tissues in superficial fascia?

What are 4 roles of fascia?

Answer 113

Fascia: Fibrous connective tissue that envelops muscles (and other organs).

Superficial fascia:
Separates muscles from skin

Deep fascia:
Lines the muscles

1. Areolar Connective
2. Adipose Tissue

Roles of Fascia:
-Reduce friction
-provide blood flow and nerve supply
-coordinate muscles
-Fills gaps between muscles and provides structure

Question 114

How do the epimysium, perimisyum and endomisyum stratify the muscle?

Answer 114

Epimysium:
Outer layer enveloping the entire muscle

Perimisyum :
Surrounds and separates muscle fibers in packs of 10-100 fibers called Fasicles

Endomisyum:
Membrane that envelops each muscle fiber

Question 115

What is the sarcolemma?

What is it’s function

Where is it located?

Answer 115

Sarcolemma : the membrane inside the endomysium, the tissue that completely surrounds each muscle fiber and defines the limits of the muscle cell.

• Allows chemical neurotransmitters to reach contractile unit of muscle
• Directly under endomysium

Question 116

Where are t-tubules located?

What is it’s function?

Answer 116

T-Tubules :

Run along the surface to the center of each muscle fiber

propogates the action potential across the sarcolemma

Question 117

What is sarcoplasm inside of?

What 2 things is the sarcoplasm made of?

Answer 117

Sarcoplasm :

Fluid inside sarcolemma

(glycogen, myoglobin)

Question 118

What are myofibrils and what are they inside?

What is their function within the muscle?

Answer 118

Thin filaments inside the sarcoplasm

contractile elements of the muscle!

Question 119

What is sarcoplasmic reticulum filled with and what does it surround?

What is it’s function?

Answer 119

Sarcoplasmic reticulum (SR):

membranous sac filled with fluid surrounding each myofibril.

Storage of calcium to trigger action potentials

Question 120

What is the terminal cistae?

What is the triad?

What is the sarcomere?

What are the 2 contractile proteins?

Answer 120

Terminal cisternae: ends of the sarcoplasmic reticulum that surround the T-tubules

Triad: combination of 2 terminal cisternae and a T-tubule

Sarcomere: functional unit of the contractile system of muscle

• Contractile Proteins: Actin (thin) and Myosin (thick)

Question 121

What is Huxley’s ‘Sliding Filament Theory’?

Answer 121

During muscle contraction, actin filaments slide between the filaments of myosin

Question 122

What are 3 characteristics of fusiform muscles?

What are 3 examples?

Answer 122

A) Fusiform Muscles
Characteristics:
* Fibers run in parrallel
* Muscle fibers shorten
* They promote speed

Ex: sartorius, biceps brachii, brachialis

Question 123

What are 3 characteristics of pennate muscles?

What are 3 examples?

Answer 123

B) Pennate Muscles
Characteristics:
* Fibers arranged on an angle towards tendon
* High amount of fibers for a given area(dense)
* They promote strength

Ex: semimembranosus of hamstring, gastrocnemius, deltoid

Question 124

What is the performance of a muscle determined by(E.C.E.E)?

Which 2 of these are protective mechanisms?

Answer 124

E.C.E.E

Excitability - The ability to respond to a simulation by
a neurotransmitter (action potentials)
Contractility - The ability of a muscle to shorten (50-70% of their length at rest)
Extensibility - The ability of a muscle to elongate beyond its length at rest (stretch without rupture)
Elasticity - The ability of a muscle fiber to return to its initial length

Extensibility & Elasticity

Question 125

What is the contractile element of a muscle contraction and what do they cause?

What 3 things do the elastic/passive components of muscle contraction do with mechanical energy?

What are the 2 things that are apart of the elastic component in series?

What are the 2 things that are apart of the elastic component in parallel?

Answer 125

Contractile Element (CE)
* Myofibrils with bridges binding actin/myosin filaments
* Shortening of the muscles during contraction

Elastic and passive components
Functions: absorb, transmit, store mechanical energy

Elastic component in series (SE)
* Tendon (85%)
* Actin-myosin bridge (15%)

Elastic component in parallel (PE)
* Sarcolemma
* The connective tissue that surrounds the muscle(epi/peri/endomysium)

Question 126

What are the 3 types of muscle actions?

How does each change the length of the muscle?

Answer 126

Types of Muscle Actions
A. Isometric - The muscle is active, No changes in length

B. Concentric - The muscle is active, Shortening of muscle

C. Eccentric - External moment > internal moment, Lengthening under the effects of gravity or antagonistic muscles

Question 127

What is the benefit of eccentric contractions?

How efficient are eccentric contractions? how energy intensive are they?

Answer 127

Eccentric: develops same muscle strength with use of less muscle fibers when compared to Isometrics and concentrics

More efficient and consumes less energy!

Question 128

What are 4 reasons that concentric contractions are less efficient?

Answer 128

Energy expenditure: During a concentric contraction, the muscle has to generate force to overcome resistance (e.g., lifting a weight). This requires energy in the form of ATP (adenosine triphosphate) to be used for muscle contraction. This energy expenditure can be significant, especially when lifting heavy loads.

Requires energy to overcome gravity, break inertia as well as lift the load

The muscle is at a joint angle that places it at a mechanical disadvantage so it has to generate more force

Concentric contractions can lead to muscle fatigue more quickly than eccentric contractions because of the shortening of the muscle.

Concentric contractions generate more heat within the muscle tissue compared to eccentric contractions.

Question 129

What is the purpose of isometric contractions?

How are concentrics/eccentrics used together and how do they maximize energy storage/muscle performance?

Answer 129

Isometrics:
stabilize a part of the body

Concentrics/Eccentrics:
Used sequentially
Maximize energy storage and muscle performance through stretch/shortening cycles

Question 130

What is a muscle twitch?

What is the latent period?

What is the contraction period?

What is the relaxation period?

Answer 130

Muscle Twitch:
Mechanical response to a single stimulation
-fundamental unit of muscle activity

Latent Period:
Short delay from when action potential reaches muscle until tension starts (~2ms)

Contraction Period:
From beginning of the action potential to the maximum tension

Relaxation Period:
From maximum tension until resting length

Question 131

What is tetanus?

What happens the muscle is at max frequency?

How do the muscle twitches fuse?

Answer 131

Tetanus:
Prolonged contraction of a striated muscle, produced by continued stimulation at a fairly high frequency
* Max frequency, at which the force no longer increases
* Fusion of muscle twitches by increasing frequency

Question 132

What are 2 influential relationships on force generation in muscles?

What is an important cycle in force generation of muscles?

What is an important angle in force generation of muscles?

Answer 132

• Muscle Attachment Angle
• Force-Length Relationship
• Force-Velocity Relationship
• Stretch-Shortening Cycle

Question 133

At what angle is the muscle at a mechanical advantage?

What is the purpose of higher forces when the muscle is either at an obtuse angle or an acute angle?

Answer 133

Right angle (90 degrees)

Obtuse angle (greater than 90 degrees):
Mostly force to stabilize the joint

Acute angle (less than 90 degrees):
Mostly force to rotate the joint

Question 134

What are the functional biomechanical characteristics of muscle?

Answer 134

Refer to slides 4-17 of lecture 6

Question 135

What are the 3 types of articulations?

Answer 135

1. Fibrous:
   ex. sutures in the skull
2. Cartilaginous
   ex. vertebral discs in the spine
3. Synovial
   ex. synovial joints like elbow and knee

Question 136

What bones have fibrous articulations?

What 2 things do these joints require?

Answer 136

• Bones bound by tough fibrous tissue
• In joints that require strength & stability

Question 137

What is responsible for connecting bones in cartilaginous articulations?

What are 2 types?

What type of cartilage is each connected by and how movable are they?

Answer 137

Bones are connected by cartilage

1. Synchondroses (ex. ribs)
   * Connected by hyaline cartilage
   * Immovable
2. Symphyses (ex. pubic symphysis)
   * Connected by fibrocartilage
   * Slightly movable

Question 138

What are synovial articulations filled with? what surrounds the joint?

How common are synovial joints?

How large is their range of motion?

Answer 138

Fluid-filled joint within a thin fibrous capsule

Most common joint in human body

Large ranges of motion compared to other types of joints

Question 139

What are the 6 types of synovial joints and where can each be found?

Answer 139

1. Ball and socket joint (hip joint)
2. Pivot joint (between cervical vertebrae)
3. Hinge joint (elbow)
4. Saddle joint (between carpal and
   metacarpal bones in hands)
5. Plane joint (between tarsal bones in feet)
6. Condyloid joint (between radius and carpal bones in wrist)

Question 140

What are the 3 dynamic functions of cartilage?

Answer 140

1. Transfers forces between bones
2. Distribute and dissipate forces over a larger surface area to reduce stress on bone
3. Minimizes friction and wear during movement of joint

• Coefficient of friction: ~ 0.0025

Question 141

What is the static function of cartilage?

Where in the body is there constant tension?

Answer 141

1. Dissipate loading
2. Vertebral discs of spine (constant tension is present)

Question 142

What are the planes of the human body?

Answer 142

Transverse plane-at the waist, dividing top half and bottom half

Frontal plane-through the body, dividing the body into front half and back half

Sagittal plane-through the body, dividing the body into left half and right half

Question 143

Does cartilage have a strong blood supply?

Answer 143

No, Cartilage is an isolated tissue with a very slow metabolism

Question 144

What are the axis’ of movement and give an example of each?

Answer 144

Sagittal plane about the frontal axis
(flexion/extension of the shoulder,hip)

Frontal plane about the sagittal axis
(abduction/adduction of the shoulder,
hip)

Transverse plane about the longitudinal axis
(internal/external rotation of the shoulder,hip)

Question 146

What kind of cells is cartilage made of and what are it’s two functions?

What is found in the organic matrix of articular cartilage?

Which forces do Type 2 collagen and proteoglycans resist within the organic matrix of the articular cartilage?

What is the last component of articular cartilage?

What do these components of articular cartilage determine?

Answer 146

• Cells: Chondrocytes
  – organize the extracellular matrix
  – Produce proteoglycans and collagen
• Organic Matrix
  – Dense network of collagen fibers and proteoglycans
• Collagen (Type II*) resists tension
• Proteoglycans resists compression
• Interstitial fluids

Matrix components determine the biomechanical behavior of cartilage tissue

Question 147

Is cartilage stratified heterogenously or homeogenously?

What are the 2 biomechanical functions of this stratification?

Answer 147

Stratification: Cartilage is heterogenous = different layers or ‘zones’ in tissue

1. Improves support of interstitial fluids
2. Improves resistance to friction

Question 148

How could the arrangement of chondrocytes and collagen in articular cartilage be described?

Answer 148

Anisotropic arrangement of chondrocytes and collagen

Question 149

What is the meaning of articular cartilage being anisotropic? Is the cartilage uniform or varied?

Answer 149

behaviour of cartilage changes depending on the direction of the loading

1. Varying arrangements of collagen fibers with respect to articular surface.

Question 150

What percent of the articular cartilage does the superficial zone represent?

What percent of the superficial zone is made up of water?

Answer 150

1. Superficial Zone (represents ~10-20% of the total cartilage thickness)

It is in this area that there is the most water (~80%)!

Question 151

What percent of the articular cartilage does the transition/middle zone represent

How is collagen dispersed in the transition/middle zone?

Answer 151

2. Transitional/Middle Zone (~40-60%)

Collagen fibers
* Random orientation
* More dispersed
* More homogeneous dispersion

Question 152

Is there a high or low density of collagen in the superficial zone?

What force does this help resist?

Answer 152

Collagen fibers
* High density on the articular surface within the superficial zone
* Resists shear loading

Question 153

What percent of the articular cartilage does the deep zone represent?

What component is high in this zone and which component is lower?

What area do the collagen fibers penetrate?

Answer 153

Deep Zone (~30%)

Proteoglycan content is high and water content is lower (~65%)

• Broad grouping of fibers in the plane of movement
• Penetrates calcified area

Question 154

What percent of the articular cartilage does the calcified zone represent?

What does the tide mark within the calcified zone represent?

What do the collagen fibers attach to in this zone?

Answer 154

Calcified Zone (~2%)

Tide mark=transitional interface between soft cartilage and stiffer subchondral bone

Collagen fibers attach to the subchondral bone: anchoring cartilage to the cortical bone

Question 155

What percent of the articular cartilage does chondrocyte cells represent?

What does the variance of their size, shape and density depend on?

What 2 things do they specialize in producing?

What do they keep organized?

How do they receive nutrients?

Answer 155

Cells: Chondrocytes ( 5% )

• Vary in size, shape and density according to their location
• Specialize in producing/secreting proteoglycans and collagen
• Organize and maintain the components of the extracellular matrix
• Receive nutrients through matrix diffusion

Question 156

What percent of the articular cartilage does the extracellular matrix represent?

What are the 3 components of the extracellular matrix within the articular cartilage?

Answer 156

Extracellular Matrix ( 95% )

• Collagen
• Proteoglycans
• Interstitial fluid

Question 157

What type of protein is collagen?

Is it flexible or rigid?

What type of forces is it strong at resisting?

What type of forces can it not resist?

Answer 157

Collagen

• Fibrous protein
• Very rigid
• Resists tension forces
• Little resistance to compressive & shear
  strength

Question 158

What type of proteins are proteoglycans and what do they help attach?

Are they large or small? and what shape do they resemble?

What is their affinity to water?

What type of forces is it strong at resisting?

Answer 158

Proteoglycans (PGs)

*‘Link protein’ for glycosaminoglycan (GaG) sugar chains to attach

• Large molecules (brush-like from chains of GaGs).
• Negative charge = affinity for water.
• Resists compressive forces

Question 159

What is the main type of Glycosaminoglycans and what do they bind to?

What type of charge do they have?

Do they have an affinity for water? and what type of bond do they have?

Answer 159

Glycosaminoglycans (GaGs)

• Mainly aggrecan (aggregates of large proteoglycans - sugars) that bind to hyaluronic acid (protein)
• Strong negative charge
• Affinity with water (hydrophilia)
• Non-covalent bond

Question 160

What does the metabolism of PGs in the articular cartilage depend on?

What 3 things does immobility lead to?

What 2 things does excessive loading lead to?

Answer 160

Proteoglycans

• Metabolism of PGs in articular cartilage depends on loading history
• Immobility leads to…
  1. Decreased synthesis
  2. Thinning of cartilage
  3. Tissue water leakage
• Excessive loading leads to…
  1. Decreased size
  2. Disorganization of
  collagen fibers

Question 161

What is interstitial fluid mainly made of?

What percent of the extracellular matrix do they represent?

Where are they mainly concentrated and how does their concentration change with depth?

What does the movement of fluid in and out of the cartilage depend on? and what characteristic does this give the cartilage?

What are the 2 main roles of the interstitial fluid?

Answer 161

Interstitial fluids

• Mostly water (gel-like substance) and
  minerals (Na+, K+, Ca2+)
• Represents ~ 65-80% of extracellular matrix
• Concentrated at the joint’s surface (~80%)
• Decreased concentration with
  depth (Deep Zone = ~ 65%)
• Fluid has the ability to freely move into/out of cartilage (depending on loading)
• Gives cartilage its sponge-like characteristic
  (fills in around PGs & collagen)
• Main roles:
  1. maintain mechanical integrity of tissue 2. lubricate the joint

Question 162

What are the 4 mechanical properties of articular cartilage?

Answer 162

• Viscoelasticity
• Permeability
• Dependance on Load (Loading
  Profile)
• ‘Wear and Tear’ of Cartilage

Question 163

When does the viscoelasticity of the articular cartilage become relevant?

What are the 2 ways to describe the viscoelasticity of articular cartilage?

When does creep behaviour happen and what is an example of creep behaviour?

What does relaxation behaviour result from?

Answer 163

Viscoelasticity
-When stress/deformation are constant and the response varies with time

Creep & Relaxation

This behavior can be described by:
1. Creep: constant stress with deformation as a function of time= permanently deforms!
* Example: A person standing

2. Relaxation: constant deformation with stress release, results from flow of interstiatial fluids in cartilage

Question 164

What type of stress is present in the creep viscoelastic response and what type of response is seen?

What are the 3 steps of the creep response?

Where does the point of equilibrium occur and what is it caused by?

Answer 164

Viscoelasticity: Creep

• Constant stress, bi-phasic response

1. Rapid initial deformation
2. Slow and progressive deformation
   to the point of equilibrium.
3. Point of Equilibrium: when the
   compression stress in the matrix*
   balances the external stress

*compressive stress developed in the collagen-PG matrix and friction forces due to the flow created by the output of fluids

Question 165

What type of stress is present in the creep viscoelastic response and what type of response is seen?

What are the 2 phases of the relaxation response? What is the amount of stress in each phase and what is it due to?

Answer 165

• Constant stress, bi-phasic response

1. Compression Phase (0-A):
   * Stress continuously increases to the
   max
   * Due to dispersion of fluids
2. Relaxation Phase (B-E):
   * Stress decreases slowly and
   gradually to maintain deformation
   * Due to the redistribution of the fluids
   in the matrix.

Question 166

What does the permeability of articular cartilage measure?

What is it inversely proportional to?

Answer 166

Permeability

• The measurement of the ease of a fluid passing through a porous material
• Is inversely proportional to the friction created by the liquid passing through the material

Question 167

What is the relationship between permeability and resistance?

What is the equation for porosity?

How porous is articular cartilage?

Answer 167

High permeability = low resistance
Low permeability = high resistance

Porosity = ratio of fluid volume to total volume
(β) = Vf /Vt

Articular cartilage is very porous ~80%

Question 168

What is another way to define permeability of articular cartilage?

What is this dependent on?

What is the equation for permeability?

How permeable is articular cartilage and why is it that way?

Answer 168

A measurement of the resistance force required to penetrate a liquid into a membrane at a given speed.

This friction resistance force is dependent on the interaction between
the fluid and the porosity of the material.

Coefficient of permeability (k) is related
to the coefficient of friction (K) & porosity (β)
k = β2 / K

Articular cartilage has very low permeability
– Large generation of friction resistance force when the fluids pass
through the matrix

Question 169

What are the 2 ways to directly measure permeability?

Answer 169

• Ways to directly measure permeability:
  – Two mechanical means
  1. Effect of a load on the material/tissue
  2. Pressure gradient

Question 170

What are the 2 things that will happen using the “effect of a load” method of testing permeability?

Answer 170

Effect of a Load
If cartilage is saturated with fluids and
placed under load…
1. Fluids will escape due to compressive deformation
2. Increase in local pressure (from fluid dispersion)

Question 171

What is the equation for the pressure gradient test of permeability?

What 2 things does permeability decrease exponentially with?

Answer 171

Pressure gradient:

(P1-P2) / h
* Coefficient of permeability (k);
volumetric discharge per unit of
time (Q); permeability area (A).
k = Qh / A(P1-P2)

• Permeability decreases
  exponentially with….
  – Increase in pressure gradient
  – Increase in deformation

Question 172

What 2 loads can occur in the pressure gradient test of permeability?

What are the 2 stages of transmission/dampening of stresses?

What 2 things does this lead to?

Answer 172

1. Dynamic Loads
   – Ensures sliding between joint
   surfaces and minimizes friction
2. Static Loads

Transmission / damping of stresses are carried out in two stages:
1. Sudden rise in intracellular pressure (little deformation due to fibrous network)
2. Water and electrolytes migrate to lower pressure areas via pores in cartilage

Leads to…
– Increase concentration in proteoglycans
– Increase in the osmotic pressure
This 2-step process makes it possible to effectively distribute loading.

Question 173

What are the 2 lubrication models of permeability and what are the key features of each?

What is the 3rd lubrication model of permeability and what 2 things is it dependent on?

Answer 173

1. Liquid lubricating film:
   -Thin lubricant film between each articular surface.
   -Additional load support from pressure developed in film
   If model 1 is not sufficient to reduce friction, model 2!
2. Surface lubrication:
   -A single layer of lubricating molecules incorporated into each joint surface.
   -Not effected by physical properties (i.e. lubricant’s viscosity)
   -Effected by chemical properties (i.e. proteoglycans)
   -Limits surface wear of cartilage
3. Mixed lubrication: (Combining of 1 + 2)
   The lubrication mode is dependent on the load applied and the relative speed and direction of loading.

Question 174

What is the definition of the “dependence on the rate and application of forces” mechanical property of articular cartilage?

How many cyclical cycles are needed for soft tissue to reach a steady state response?

What is the definition of a non-elastic response in this case?

What is hysteresis energy?

Answer 174

3. Dependence on the rate of application of forces

• Most body loads are not constant and are cyclical in nature
• The influence of cyclic loading, most soft tissues achieve a steady state response ( ~ 30 cycles )
• NON-ELASTIC RESPONSE
• Strain during loading ≠ strain during unloading
• Hysteresis energy: energy
  stored by tissues during each
  cycle

Question 175

In the case of the mechanical property of “dependence on the rate and application of forces”, what does the response depend on and what is the behaviour of material dependent on?

What are the 2 possible responses in cartilage and how is the fluid different in each?

Answer 175

• Remember…response depends on loading profile
  – Behavior of material is very dependent on the rate at which a load is applied and then removed.
• Two possible responses in cartilage
  1. Elastic Response (independent of time: rapid loading/unloading)
  – Fluid does not have time to be expelled
  2. Viscoelastic Response (dependent on time: slow loading/unloading)
  – During unloading, the cartilage will recover its original dimensions if it
  receives enough fluid for enough time

Question 176

What is the response to tension forces in articular cartilage?

Answer 176

Highly complex mechanical behavior leads to Highly anisotropic/
heterogeneous composition

Question 177

Can interstitial fluid be tested in compression and tension?

Answer 177

in tension, only the collagen-PG matrix can be tested, since this test does not allow to test viscoelasticity.

Therefore, interstitial fluid can only be tested in compression

Question 178

Can articular cartilage resist shear forces?

What are 3 ways that cartilage responds to shear forces?

Answer 178

• Unlike during compression and tension, collagen fibers have good resistance under pure shear forces.
• With minimal deformation
• No volume changes
• No fluid movement

Question 179

What is wear and tear of articular cartilage due to?

What is the difference between interface wear and fatigue wear?

How is the surface layer affected by wear and what is a result of this?

Answer 179

After wear, the surface layer becomes softer and permeable

Wear and tear due to mechanical action: part of the material is removed from a solid surface (i.e. injury)

Interface wear: due to the interaction between the support surfaces (soft versus hard material)
Fatigue wear: due to the deformation of the bodies in contact (cyclic deformations)

↑ fluid output, ↑ surface abrasion

Question 180

What is the key principle in the prevention of the “breakdown in cartilage” mechanical property?

What are 3 ways that this principle keeps articular cartilage healthy?

What is the lack of this principle associated with?

Answer 180

Loading – unloading is key!

This principle keeps tissues healthy by allowing…
- Entry of nutrients
- Expulsion of waste
- Lubrication of the joint

Lack of use is associated with tissue degeneration

Question 181

What are the 2 different kinds of breakdown in cartilage?

In the case of chronic cartilage damage, what type of damage does each kind of wear cause?

Answer 181

Acute Cartilage Damage
* Local stress greater than strength of material
-High external forces (impact or active) with a small contact area

Chronic Cartilage Damage
* Following interface issues (abnormal loading/growths) and/or fatigue phenomena

-Wear at the interface = lack of lubrication
-Wear from fatigue (repeated loading) = structural damage in matrix

Question 182

What is the role of chondrocytes in the prevention of “breakdown in cartilage” and what is their ability to regenerate?

Answer 182

Responsible for the synthesis and degradation of the matrix…

Have a very poor ability to regenerate!!

Question 183

What are 6 factors that influence contact in synovial joints and ROM that are involved in the breakdown of cartilage?

Answer 183

Factors that influence contact in synovial
joints and range of motion:

1. structure/shape of bones that articulate
2. Strength and tension of ligaments
3. Muscle arrangement and tension
4. Soft tissues
5. Hormones
   -Relaxin during childbirth
6. Inactivity
   -short- vs. long-term

Question 184

What are 3 ways that aging affect the breakdown of cartilage?

What are 2 ways that articular cartilage is affected by aging and what are 2 results of that?

Answer 184

1. Decreased production of synovial fluid
2. Thinning of articular cartilage
3. Shortening and loss of flexibility of soft tissues

Articular Cartilage:
1. ↓ water content & ↓ the number of chondrocytes
2. Cartilage tends to calcify/ossify

What happens to the articular cartilage now?
* Reduced mechanical function
* Increased risk for damage…and injury!

Question 185

What is the biomechanical model of the breakdown of cartilage?

Answer 185

Refer to slide 41 of lecture 3

Question 186

What is arthrosis and why is aging relevant in the process?

Answer 186

• Wear of the cartilage that covers the bony ends at a joint
• Aging = > decrease in the number of chondrocytes

Question 187

What is the difference between incomplete and complete wear in arthrosis?

What are the 4 stages of arthrosis?

Answer 187

Incomplete wear
Decreased cartilage thickness =
surface becomes irregular and
hinders movement / causes pain

Complete wear
Disappearance of cartilage leads to bone
against bone = Importance of pain!

1. start of erosion
2. progressive pinch
3. of the articular line
4. complete destruction

Question 188

What are 4 influential factors in arthrosis?

Answer 188

Influential Factors
1. Axis orientation of the lower limbs (i.e. knee valgus)
2. Excess weight
3. History of trauma (previous injury)
4. Certain sicknesses (infections, auto-immune disease)

Question 189

How are cartilage grafts used in arthrosis?

Answer 189

Cartilage Grafts
* Take donor tissue from area of little wear/loading
* Affected area is small and surrounded by healthy tissue
* Lesion - femoral condyles

Question 190

What is the difference between tendons and ligaments?

Answer 190

Tendons connect muscles to bone
Ligaments connect bone to bone(joints)

Question 191

What are the 4 functions of tendons?

Answer 191

Functions:
1. Attaches muscle to the bone (myotendinous junction)
2. Transfer of forces between muscle and bone
3. Joint stability
4. Elastic energy storage

Question 192

What is tropocollagen in tendons?

Answer 192

Tropocollagen - fundamental unit

Question 193

What is the function of paratenon in tendons?

Answer 193

Paratenon: facilitates sliding of tendons

Question 194

What is the circuit model of muscular contraction?

Answer 194

-Tendons are the series element and they stretch the muscle fiber to create force
-Connective tissues are the parallel element and they work to protect the muscle fiber and absorb force
-Actin & Myosin cross bridges are the contractile element and they provide the muscle contraction in the fiber

Connective tissue works in parallel with the tendon and the actin/myosin cross-bridges

Tendon works in series with the actin/myosin cross-bridges

Question 195

What is the function of epitenon in tendons?

Answer 195

Epitenon: helps with structural integrity and provides microvasculature

Question 196

What is the function of Endotenon in tendons?

Answer 196

Endotenon: extends from the perimysium (musculo-tendon junction) to the periosteum (osteotendinous junction.)

Question 197

What are 2 types of connective tissue?

Answer 197

Fascia
Protective components of muscle
(perimyseum,epimyseum,endomyseum)

Question 198

How do active and passive contractions change with resting length?

Answer 198

Active = actin & myosin crossbridges as you get close to resting length and then it will go down as the cross bridges separate

Passive = goes up as you go past the resting length on the eccentric contraction

Passive strength passes active strength once past the resting length and the total torque goes higher

Question 199

When is the bicep at it’s highest tension?

Answer 199

At 90 degrees is where all the actin-myosin cross bridges form and where there is the highest force

Question 200

Why is it important to know the length of the tendon when re-attaching it?

Answer 200

Need to know how long the tendon will be so you can create the right moment arm at the connection for the certain muscles

Question 201

What is the significance of the internal moment for muscle contraction?

Answer 201

Internal moment is the force needed from the muscle on the concentric contraction to fight against gravity

Concentric creates energy,
Eccentric absorbs energy

Question 202

Is there an advantage to doing isometric over concentric/eccentric?

Answer 202

Isometric is good for rehab because you can work the muscle and improve joint stability without shortening/lengthening the muscle

Question 203

Why is there more injuries on the eccentric?

Answer 203

It is harder to maintain control of the weight and therefore the speed of the contraction on the eccentric, and larger loads are usually used on the eccentric than on the concentric.

Question 204

Are eccentrics less fatiguing?

Answer 204

Body is more efficient with eccentric contractions because we’re working with gravity

Question 205

What muscle prevents collapsing on a typical walking stride?

Answer 205

Quadriceps absorbs force and prevents collapsing

Question 206

How do moments effect muscle contraction?

Answer 206

Concentric
(internal moment of muscle greater than external moment of gravity)

Eccentric
(external moment of gravity greater than internal moment of muscle)

Question 207

Do concentrics or eccentrics have higher 02 consumption and EMG activation?

Answer 207

Concentrics have higher 02 consumption and EMG activation

Question 208

What is the most important aspect of plyometrics?

Answer 208

Speed, try to perform the task in less than a second

Question 209

What are the 4 periods of muscle contraction?

Answer 209

Muscle twitch
Latent period
Contraction period
Relaxation period

There is a latency period between all muscle contractions in sequence

If you let the twitch go completely down, you will need a latency period before the next twitch is sent

If you don’t let it go down, it will build and build until it reaches the peak

Question 210

What is tetanus in muscle contractions?

Answer 210

Smaller latent period without fully relaxing over numerous contraction cycles until it eventually levels out at maximum tension

Question 211

What is the tradeoff in muscle contraction?

Answer 211

Force generation to rotate around the axis of the joint at acute angles and stabilization to stabilize the joint

Question 212

What do the elbows want to do when holding heavy bags in your hands?

Answer 212

Body system engages the bicep isometrically to make sure the joint is protected from injury and is stable and there will be slight flexion in the elbow

Question 213

Where should you work the bicep isometrically to build strength?

Answer 213

90 degrees to become the most efficient and have the least stress on the joint

Question 214

What is the best way to train to increase strength in the bicep?

Answer 214

Start with a full range of motion from the bottom , go slow on the eccentric and fast on the concentric

Question 215

How does rotational torque change during the bicep curl?

Answer 215

Rotational torque is highest near the top end of the concentric when the hand is close to the shoulder

Question 216

How to train somebody if they want to return from an injury

Answer 216

Start with isometrics at 90 degrees to give the body some proprioception, slowly build range of motion with light weight until you’re doing the full ROM and slowly add weight from there

Question 217

What type of training would have the goal to be move as fast as possible rather than using slow and controlled movements?

Answer 217

Power training

Question 218

What is the optimal zone for force generation from actin-myosin crossbridges?

Answer 218

2.0-2.25 nm

Question 219

Do eccentrics or concentrics generate more force?

Answer 219

Eccentrics

Question 220

What is the effect of temperature on muscles?

What range of degrees in there a linear relationship between tension & stiffness?

Answer 220

Warm muscles can generate the same torque in less time and the muscle is able to act faster

6-34 degrees celsius

Question 221

What is sacropenia?

What should we do to prevent loss of muscle mass?

Answer 221

Degradation of muscle mass to a point where the patient cannot function/
perform their daily tasks

Eat a high protein intake and increase protein intake as we age

Question 222

What is the myotendinous junction?

Where is it located?

Answer 222

Region where muscle fibers
(contractile proteins) join the
tendon (collagen).

Perimyseum

Question 223

What is the osteotendinous junction?

Where is it located?

Answer 223

Region of connection between
bone and tendon (gradual
transition from tendinous to
bone tissue)

Periosteum

Question 224

What type of cells are present in the tendons?

What are 2 of their functions?

Answer 224

Cells: Specialized fibroblasts called Tenocytes

– Controls metabolism within tissue
– Respond to mechanical stimuli (especially tension)

Question 225

What is the main role of the tendon matrix?

What is it’s composition?

Answer 225

Matrix
Main Role: maintain the structure of the
tendon and facilitate the response to mechanical load.

Water (55-70%)
* Proteoglycans (<0.2%)
* Elastin (~2%)
* Other proteins (~4.5%)
* Collagen (Type 1) (60-85%)

Question 226

What is the difference in parallel vs transverse arrangement in tendons?

Answer 226

Parallel arrangement: resists tension

Transverse arrangement: resists rotation

Question 227

What is the hypothesis for the mechanotransduction pathway in tendons?

Answer 227

Refer to slide 6 of lecture 4

Question 228

What are the 4 functions of ligaments?

Answer 228

Functions:
*Attachment between bones
*Maintains joint configuration
*Helps guide movement
*Sensory feedback: joint positioning

Question 229

What are 3 functions of epiligaments?

Answer 229

Epiligament:
*Loose shell: protects against friction
*Supports neurovascular structure
*Controls the flow of water and metabolites

Question 230

What is the main protein in ligaments?

Answer 230

Collagen
* Fibers are wavy
* Oriented along the long axis

Question 231

What are the 4 functions of neural endings/mechanoreceptors in tendons & ligaments?

Answer 231

• Proprioception and nociception
• Allows sensation of joint positioning
• Monitors ligament tension
• Initiate protective reflexes

Question 232

What is the function of blood vessels in tendons & ligaments?

Answer 232

Nourishes cells to help make them
metabolically active

Question 233

What kind of cells are ligaments made of?

How are they organized and what do they manage?

Answer 233

Cells - Fibroblasts:

• sparse and scattered
• manage the prevention and
  repair of microscopic damage.

Question 234

What is the composition of the ligament matrix?

Answer 234

Matrix
* Water (~66%)
* Collagen (70%)
* Proteoglycans (1%)
* Elastin (1.5%)…but can be more
in some ligaments (depending on
function)

Question 235

What are 4 similarities between tendons & ligaments?

Answer 235

1. Cells aligned with collagen
2. Collagen: Type 1
3. Insertion on bone
4. Minimal vascularization

Question 236

What are 2 differences between tendons & ligaments?

Answer 236

1.Arrangement of collagen
(collagen fibers are parallel in tendons,
collagen fibers are nearly parallel in ligaments)
2.Proportion of elastin

Question 237

What is a similarity and difference between the external structures of tendons & ligaments?
(paratenon & epiligament)

Answer 237

Similarities: Outer layers made of connective tissues.
Difference: Organization

Question 238

What are the 4 layers at the insertion area of tendons/ligaments into bones?

Answer 238

Zone 1: Collagen Fibers
Zone 2: Fibrocartilage - non-mineralized
Zone 3: Fibrocartilage - mineralized
Zone 4: Compact Bone

Question 239

What is the definition of proprioception?

Answer 239

your body’s ability to sense movement, actions, and location

Question 240

What are 3 things that the mechanical properties of tendons & ligaments depend on?

Answer 240

*Architecture (arrangement) and properties of collagen fibers
*Proportion of elastin
*Substrate Foundations
– Cement-like substance between collagen microfibrils
– Stabilization of tendons/ligaments
– Contributes to the overall strength of tissues

Question 241

What is the stress-strain relationship of tendons & ligaments?

Answer 241

Non-Linear

Question 242

What are the 4 zones on the stress-strain relationship of tendons & ligaments?

Answer 242

Zone 1:
Rapid deformation without great force
Zone 2:
Flattening of fibers, ↑ stiffness
Zone 3:
Heterogeneous distribution - deferred
recruitment
Zone 4:
↑ tension on intact fibers = ↑ fiber breakage

Question 243

What is the visco-elastic property of tendons and ligaments?

Answer 243

Tissue is stronger with load applied quickly (less time to disperse in viscous
component)

Question 244

What are the 2 types of load-deformation curves in tendons & ligaments?

Answer 244

Loosening:
constant deformation
load relaxation
length held constant

Creep:
constant force
creep phenomenon
load held constant

Question 245

What are 2 ways that inflammation affects the load/deformation curves in tendons & ligaments?

Answer 245

A:
-After several successive cycles, curve moves to the right and hysteresis
decreases.
-For the same level of force, the deformation is greater and the response
is less and less viscoelastic.

B:
-After several successive cycles, the curve moves upwards.
-For the same level of strength, the release is less and less important

Question 246

What are 4 ways that exercise influences the integrity of tendons & ligaments?

Answer 246

1. Biochemically, ligaments are modestly affected by exercise
2. Increases number of collagen fibers.
3. Trained ligaments fail at higher levels of loadings
4. Are a bit stiffer than the untrained ones

Question 247

What are 3 ways that immobilization influences the integrity of tendons & ligaments?

Answer 247

1. Increases bone resorption and
   indirectly weakens ligament
   insertions
2. Reduction in water and
   collagen
3. Longer immobility = increased
   risk of damage/injury and longer recovery

Question 248

What are the effects of age similar to in tendons & ligaments?

What 2 things do younger tissues have more of?

Answer 248

The effects of age are similar to those produced by immobilization!

Younger tissues have greater viscosity and a greater amount of water and collagen

Question 249

What are 3 things that decrease as we age past 20, in the tendons & ligaments?

Answer 249

As Age Increases (after 20 years old)
↓ force before rupture
↓ storage capacity
↓ rigidity

Question 250

What are 2 ways that metabolic influencers like anabolic steroids affect the integrity of tendons & ligaments?

Answer 250

Anabolic steroids
↓ stiffness of the tendons as
well as the ultimate strength of
the tendon.
↑ Collagen degeneration and
proliferation of small collagen
fibrils rather than large fibrils

Anabolic steroids hinder the healing of tendon injuries… predispose to injury!

Question 251

The higher rate of (blank) leads to higher rates of soft tissue failure

Are collagen fibers different after injury?

What percent do tissues return to after injury?

Answer 251

• The higher the rate of loading = more likely to have soft tissue failure (vs bone level)
• Morphologically: 40 weeks after injury,
  collagen fibrils are different from those of healthy ligaments.
  Over time, the tissues return to 10-20%
  compared to normal…why??

Question 252

What is the most common cause of tendinitis?

What are 4 different mechanisms behind it?

What is most often related with it and what is that accompanied by?

How long does healing take?

Answer 252

Sports activity is the main culprit of tendonitis

variable mechanisms and locations in
body
* Excessive and repeated motions/loading(i.e. tennis elbow)
* Shock absorbance (i.e. Achilles)
* Friction on a structure (i.e. ‘lace bite’ in
hockey)
* Anatomical

Most often related to the rupture of some tendon fibers (partial rupture)
which are accompanied by local swelling (edema)

Healing takes several months!

Question 253

What layer of tissue is different between tendons and ligaments?

Answer 253

Endotenon because it’s what allows the tissues to adhese to the correct structures (muscle to muscle or bone to bone)

Question 254

Is the patellar tendon a ligament or a tendon?

Answer 254

It is technically a ligament because it attaches bone to bone.

Question 255

Why do we call the patellar tendon a tendon then if it is technically a ligament?

Answer 255

It’s a continuity from the tendon that attaches to the quad muscles and it structurally resembles a tendon more than a ligament.

Question 256

What is necessary in order to increase the collagen and strength of tendons?

Answer 256

Mechanical loading (tensile loads) through activity

Question 257

What is important about the orientation of the fibers of the ligaments?

Answer 257

The fibers are oriented with the movement of the joint to help guide movement.

Question 258

If you had to tear the fibers in the muscle, tendons, and ligaments, rank them from best to worst scenario? (Yes they’re all bad)

Answer 258

You’d first want to tear muscle fibers because of how much more blood flow goes to the muscle and so they are able to resynthesize those fibers.

You would then usually prefer to tear the tendon fibers as they get more blood flow than the ligaments and ligaments don’t always fully heal back to 100%. In some locations of the body you would rather tear ligaments but in general you would say tendons.

Question 259

Which ligament has a lot more elastin than the others?

Answer 259

Ligamentum flavum which is a ligament than goes down the spine. It has more elastin to provide the spine a little bit of give without damaging the ligament too much.

Question 260

How will the elastin fibers be oriented at rest (not stretched)?

Answer 260

The elastin fibers will be in a bundle (bowl of noodles) and they will straighten out as the tendon/ligament is stretched.

Question 261

Which part of the spine is at the greatest risk when submitted to compression forces? Why?

Answer 261

The cervical spine because its form is based on its function (which is a lot of rotational movement). It isn’t built in a way to optimally resist compression forces.

The lumbar spine is also at some risk because it is the part of the spine that absorbs most of the forces in the body, but it was designed to do this so is less at risk than the cervical spine.

Question 262

Why is it important to contract the glutes while running?

Answer 262

Contracting the glutes is so important because the shortening of the muscles counteracts the bending forces on the neck of the femur.

Question 263

What is the most common injury in older adults?

What can you do to train these people to to avoid the fracture?

Answer 263

Hip fracture (which is really a fracture of the femoral neck)

Strengthen the glutes so that they can resist the bending stress on the femoral from walking/falling.

Question 264

When talking about spine health, why do you need to have a strong core?

Answer 264

Strong core muscles are needed to resist shear forces in the spine (mainly thoracic spine)

Question 265

What is Osgood Schlatter’s?

Answer 265

Pain/swelling on the tibial tuberosity caused by the patellar tendon pulling on this section of the bone.

Question 266

What is a greenstick fracture?

Answer 266

A greenstick fracture is a partial thickness fracture where only the cortex and periosteum are interrupted on one side of the bone but remain uninterrupted on the other.

Question 267

What tissue is normally damaged by tension forces?

Answer 267

Tension will normally result in damage to the muscles, ligaments, and tendons whereas bone is more likely to be damaged during compression.

Question 268

What is spondylolisthesis?

What kind of forces would cause spondylolisthesis?

Answer 268

Spondylolisthesis is a condition that occurs when one vertebral body slips with respect to the adjacent vertebral body causing radicular or mechanical symptoms or pain. It is graded based on the degree of slippage of one vertebral body on the adjacent vertebral body.

Shear forces.

Question 269

Potential exam question format: If a blank force is put on a blank bone, what types of force (compression, tension, shear, bending) will be felt at different parts of the bone?

• memorize this, no answer

Question 270

What is collagen?

Answer 270

Collagen is the most abundant protein in your body. It accounts for about 30% of its total protein. Collagen is the primary building block of your body’s skin, muscles, bones, tendons and ligaments and other connective tissues.
They are resistant to stretch, not to compression

Question 271

What part of your bone makes it hard?

Answer 271

Minerals (phosphate, calcium, etc.). These are the inorganic parts of the bone. The organic material (collagen) is what makes your bone flexible and resilient.

Question 272

Why does our collagen in the bone go in all directions?

Answer 272

It allows bone to absorb tensile forces from all directions.

Question 273

What is osteoporosis?

Answer 273

Osteoporosis is a bone disease that develops when bone mineral density and bone mass decreases, or when the structure and strength of bone changes. This can lead to a decrease in bone strength that can increase the risk of fractures (broken bones).

Question 274

What can you do to prevent developing osteoporosis?

Answer 274

Do physical activity to put stress on the bones to encourage more bone growth.

Question 275

What type of physical activity would be more beneficial, running or swimming? Why?

Answer 275

Running because you’ll get compressive forces from gravity as well bending forces (simultaneous tension and compression).

Question 276

Is swimming still beneficial? Why?

Answer 276

Yes because the muscles will create tensile forces on the bones when it contracts.

Question 277

What does anisotropic mean?

Answer 277

The behaviour/resistance of a material depends on the direction of the force being applied.

Question 278

What is the problem with youth football helmets?

Answer 278

They’re too big so they put stress on the kid’s neck muscles

Question 279

What is the problem with kid’s backpacks?

Answer 279

Kids with backpacks that are too big are constantly bent over to counteract their back pack so they develop a hunched over posture

Question 280

What causes bone growth with running?

Answer 280

Contact with the ground reaction forces from the ground, which increases forces within the muscle

Question 281

What is unique about astronauts?

Answer 281

They need wheelchairs after getting back from space because their body isn’t used to the mechanical loading from gravity

Question 282

What is the rate of bone loss for immobilized patients?

Answer 282

1% bone loss per week

Question 283

Why does osteoporosis have it’s name?

Answer 283

Bone becomes more porous

Question 284

How does ability to withstand compressive forces change with age?

Answer 284

Drops with age

Question 285

What is the best way to prevent osteoporosis?

Answer 285

Try to start with a very high bone density in 20s/30s through strength training so you can start the decline from as high of a point as possible

Question 286

Why are wrist and hip fractures most common in older adults?

Answer 286

Outstretched hands during fall and hip will fracture if you fall on your side and aren’t able to outreach their hands

Question 287

What is unique about osteoporosis in women?

Answer 287

In women who are not physically active, they lose both the inner and outer layer of bone because of hormonal changes with menopause but men only lose outer layer

Question 288

What is the only real thing that can prevent bone loss with aging?

Answer 288

Physical activity, strength training specifically, is the only real thing you can do

Question 289

What type of PA are both genders more likely to engage in?

Answer 289

Men are more likely to strength train (increase muscle) and women are more likely to do cardio (decrease fat), but crossfit has changed culture

Question 290

Which piece of fitness equipment is better for asymmetries?

Answer 290

DBs are better than BBs and free weights are better than machines

Question 291

How do reps/weight change with different goals?

Answer 291

High reps/low weights are better for rehab, Low reps/high weights are better for strength & power

Question 292

What is it called when cartilage is calcified?

Answer 292

Called synostonosis, when there are lots of fibers very densely packed

Synostonosis is the change from cartilage to bone

Question 293

What are the 6 types of synovial articulations?

Answer 293

hinge (elbow)
saddle (carpometacarpal joint)
planar (acromioclavicular joint)
pivot (atlantoaxial joint)
condyloid (metacarpophalangeal joint) ball and socket (hip joint).

Question 294

What is the ROM of and type of movement of each of the 6 synovial articulations?

Answer 294

1. Ball and Socket Joints: These joints allow for the greatest range of motion. The joint involves a ball fitting into a concave surface. Because these joints allow for more motion, they are at greater risk for instability. Ball and socket joints allow for movement in many planes, and circumduction.

The shoulder and hip are both ball and socket joints.

2. Condyloid Joints: Allow for flexion, extension, and some lateral movement at the joint. There is also some circumduction that takes place. The circumduction is limited however, because the shape of the joint is oval compared to the more mobile ball and socket joints. Fingers should be able to move in a circular motion, although it is small. Condyloid joints are also referred to as ellipsoidal joints.

The base of each finger is a condyloid joint.

3. Saddle Joints: These joints are made of two concave and convex surfaces that intersect. Saddle joints allow for flexion, extension, and lateral movement. Saddle joints may present as a condyloid joint, but if you try to move your thumb in a perfect circle, you will notice its movement will not be smooth like the circular movement possible with a finger.

The base of the thumb is an example of a saddle joint.

4. Hinge Joints: Hinge joints allow for movement in one plane only. Think of a door hinge. It allows the door to open and close, but not move up or down.

Knees and elbows are some common examples of hinge joints.

5. Pivot Joints: This type of joint allows for rotation. Unlike many other synovial joints, it does not allow for any flexion or extension.

The first two cervical bones (the atlas & axis) form a pivot joint. The atlas sits on top of the axis and enables a “no” movement of the head (left & right rotation)

6. Planar joints have bones with articulating surfaces that are flat or slightly curved faces. These joints allow for gliding movements, and so the joints are sometimes referred to as gliding joints. The range of motion is limited in these joints and does not involve rotation.

Question 295

What type of movement is a volleyball spike related to axis’ and planes of motion?

Answer 295

Moving in the sagittal plane
Shoulder is rotating around the frontal axis
Torso is rotating around the transverse axis
Legs counteract the torso in the opposite direction during the spike

Question 296

What type of movement is a jumping jack related to axis’ and planes of motion?

Answer 296

Moving in the frontal planer, hips are rotating around the sagittal axis

Question 297

Why does thinning of cartilage cause pain?

Answer 297

Thinning of cartilage causes pain because it leads to contact with the bones

Question 298

What is a good way to maintain hip mobility?

Answer 298

Practicing full squats

Question 299

What is usually the main problem with full squats?

Answer 299

Not usually an anatomical abnormality, it’s usually ankle mobility

Question 300

What is the definition of functional mobility?

Answer 300

Functional mobility is mobility that allows you to optimally perform your daily activities

Question 301

Why does cartilage need movement?

Answer 301

There’s no blood supply to the cartilage so it has a slow metabolism, cartilage absolutely needs movement to stay healthy and receive nutrients

Question 302

What is the best way to time rehab sessions?

Answer 302

Try to time rehab sessions very closely to when the pain medication is given for people that are rehabbing from surgery

Question 303

What does it mean that cartilage is anisotropic?

Answer 303

Cartilage being anisotropic means that it is aligned in all different positions so it can react to stress from different directions

Question 304

When does cartilage get into a vertical position?

Answer 304

Cartilage gets into a vertical position within the deeper layers to prevent the surface layer from collapsing, the surface layer has more water to absorb impact, the vertical position allows the cartilage to anchor to the bone

Question 305

What is the top layer of cartilage able to do?

Answer 305

The top layer of cartilage is filled with water and positioned in all different directions, which makes it able to collapse and absorb impact

Deep layer of cartilage is positioned vertically and is anchored to the bone and resists collapsing

Question 306

What are 2 examples of orthopedic conditions that would alter your visual platform?

Answer 306

-Scoliosis, contorted spine will alter ability for vision

-Osteoporosis, inability to stand up or being in a wheelchair will affect vision

Question 307

Why is bone spongy?

Answer 307

Sponginess allows the bone space to deform and return to form

Sponginess moving in all different directions allows the bone to handle forces from all different directions

Question 308

Why is children’s bone marrow red and adult’s bone marrow yellow?

Answer 308

Adults don’t need as many red blood cells and 5% protein is enough

Question 309

What kind of movements does the skull perform?

Answer 309

Skull has micromovements to allow for the brain to shift around in the skull

Question 310

What does compact bone do while jumping?

Answer 310

Muscles use eccentric contraction to absorb force, one side of the bone is resisting stretch and the other side is resisting compression

Question 311

What are shin splints?

How do you treat shin splints?

Answer 311

Inflammation of the periosteum on the tibia due to repetitive stress

Treat shin splints by reducing the intensity and load of training, as well as the RICE method

Question 312

What does the periosteum pull on in the case of shin splints and what does it lead to?

Answer 312

Periosteum pulls on the bone and creates microfractures that lead to stress fractures in long distance runners

Question 313

How can you prevent shin splints?

Answer 313

Prevent shin splints by making sure you have a progression in your training and you slowly increase training volume

Question 314

What are dorsiflexors used for?

Answer 314

dorsiflexors are used for heel strike and runners that are taught with that technique have higher prevalence in shin splints

Question 315

What does osteoporosis break down?

Answer 315

Osteoporosis breaks down osteons in compact and leads to increased air pockets leading to more breaks

Question 316

Why do we have so many layers of osteons?

Answer 316

Circles of osteons help to distribute force, we have a lot of structures that do the same thing in case one breaks then another can take over

Question 317

Why do we need a good ratio of osteoblasts and osteoclasts?

Answer 317

we need a good ratio of osteoblasts & osteoclasts in order to create new bone, not enough obsteoblasts leads to osteoporosis

Question 318

What are osteocytes?

Answer 318

osteocytes are mature osteoblasts that are formed into the bone

Question 319

What does pulling on the bone create?

Answer 319

pulling on bone creates bone matter, teenagers that run too much have tibias that are overgrown

Question 320

What is a side effect of reduced physical activity?

Answer 320

Reduce bone density with reduce physical activity, PA will cause new bone to be created

Question 321

Why does diaphysis have more remodeling than epiphysis?

Answer 321

Outside forces create internal forces in the bones because the bones absorb forces on the extremities(epiphysis) and causes the middle to bend(diaphysis)

Question 322

What are 5 ways that the structure of bones follow their function? (chatgpt)

Answer 322

Here are some ways in which the structure of bones reflects their functions:

Shape and Composition: Bones have specific shapes that are suited to their functions. Long bones, like those in the arms and legs, are designed to support weight and facilitate movement. Flat bones, such as those in the skull, offer protection to underlying organs. The composition of bones, which includes a combination of collagen (for flexibility) and calcium salts (for strength), allows them to withstand mechanical stress while maintaining a degree of flexibility.

Bone Marrow and Blood Cell Production: Certain bones contain bone marrow, a soft, spongy tissue responsible for producing blood cells. The structure of bones is adapted to accommodate this function, with spaces within the bone for the proliferation and maturation of blood cells.

Joints and Mobility: The structure of bones at joints, including the shape of the bone ends, cartilage, and ligaments, reflects their role in enabling movement. Joints allow for various types of movements, such as rotation, flexion, extension, and abduction. The smooth articular surfaces and synovial fluid within joints reduce friction and allow for smooth movement.

Strength and Support: The compact and cancellous (spongy) bone tissues in different parts of the bone provide the necessary strength and support required for withstanding the forces exerted on the skeleton during various activities. The arrangement of compact and cancellous bone in specific areas caters to the need for strength while minimizing weight.

Mineral Storage and Release: Bones serve as a storage site for minerals like calcium and phosphorus. The structure of bones allows for the deposition and release of these minerals based on the body’s metabolic demands. This mechanism helps regulate the levels of essential minerals in the bloodstream, contributing to overall physiological balance.

Question 323

What is the difference between creep and relaxation?

Answer 323

In biomechanics, creep and relaxation are both terms used to describe the behavior of materials, including biological tissues, under mechanical loading over time. While they both pertain to the response of materials to applied stress or strain, they represent different phenomena:

Creep: Creep refers to the tendency of a material to deform gradually under a constant load or stress over an extended period. In the context of biomechanics, this can apply to biological tissues such as tendons, ligaments, or other connective tissues. When a constant load is applied, these tissues may exhibit a slow increase in deformation over time. The gradual elongation or deformation occurs without an increase in the applied stress. Creep is essentially a time-dependent strain that happens in response to a constant stress.

Relaxation: Relaxation, on the other hand, refers to the gradual decrease in stress within a material when it is subjected to a constant strain over time. In the realm of biomechanics, relaxation often describes the behavior of viscoelastic materials like tendons or muscles. When a constant strain is applied, the stress within the material decreases over time, implying that the material gradually accommodates the imposed strain without any further increase in the applied strain.

In summary, while creep involves a gradual increase in strain under a constant load, relaxation pertains to a decrease in stress under a constant strain. Both phenomena are relevant in understanding the mechanical properties of biological tissues and play a significant role in the study of their behavior under various physiological conditions and mechanical loading.

Question 324

What are the different types of collagen in bones/cartilage vs tendons/ligaments?

Answer 324

Bones/cartilage have type 2
Tendons/ligaments have type 1

Question 325

Can tendons/ligaments sense proprioception? T or F

Answer 325

True, as well as joints and muscles

Question 326

Do tendons or ligaments have more elastin?

Answer 326

Tendons have a very small amount of elastin and ligaments have more elastin

Question 327

Are tendons & ligaments stronger with load applied fast or slow? what principle does this involve?

Answer 327

Visco-elastic property of tendons and ligaments

Tissue is stronger with load applied quickly (less time to disperse in viscous
component)

Question 328

-Why is passive muscle force
important?
-Would it be the same in each
muscle? Why, why not?

Answer 328

Passive muscle force refers to the tension or force generated within a muscle when it is stretched or lengthened passively, without any active contraction or neural stimulation. This force is primarily a result of the passive properties of muscle tissue, including the elasticity and viscoelasticity of the muscle fibers and connective tissues. Passive muscle force is important for several reasons:

Joint stability: Passive muscle force helps stabilize joints, especially during movements that involve stretching or lengthening of the muscles. This passive tension assists in maintaining joint integrity and preventing excessive joint displacement.

Energy storage: Passive muscle force allows for the storage of elastic energy within the muscle-tendon unit during stretching. This stored energy can be subsequently utilized during active muscle contraction, enhancing the efficiency and effectiveness of muscular movements.

Postural support: Passive muscle force contributes to maintaining proper posture and alignment of the body, assisting in the distribution of loads and minimizing the risk of injury or strain on the musculoskeletal system.

Movement efficiency: By providing a level of resistance and support during stretching, passive muscle force aids in the control and coordination of movements, allowing for smoother and more controlled muscle actions.

While the concept of passive muscle force applies to all muscles, the magnitude of this force can vary depending on the specific characteristics of each muscle. Factors such as the muscle’s architectural design, composition of muscle fibers, arrangement of connective tissues, and the presence of muscle-tendon units influence the extent of passive muscle force generated.

Different muscles have varying proportions of muscle fibers and connective tissues, leading to differences in their passive stiffness and elasticity. Additionally, the length-tension relationship and the specific roles of muscles in different movements contribute to variations in the manifestation of passive muscle force. Thus, while the concept of passive muscle force applies universally, its expression can differ among different muscles based on their unique structural and functional properties.

Question 329

-Why is there a decline before a steep incline in muscle force after the resting muscle length is passed in active muscle contraction?

Answer 329

The decline and subsequent steep incline observed after passing the resting muscle length during active muscle contraction can be attributed to the mechanical properties of muscle fibers, particularly the sarcomeres, which are the basic contractile units of muscle. This phenomenon is related to the force-length relationship of muscle fibers and the overlap of actin and myosin filaments within the sarcomeres.

When a muscle is stretched beyond its resting length, there is initially a decline in force production. This decline occurs because the actin and myosin filaments start to move farther apart, reducing the number of cross-bridges formed between them. As a result, the force generated by the cross-bridges decreases, leading to a decline in overall muscle force.

However, as the muscle continues to lengthen beyond the resting length, the actin and myosin filaments start to overlap more extensively. This increased overlap allows for a greater number of cross-bridges to form between the actin and myosin, leading to a steep incline in force production. The steep incline represents the increasing number of cross-bridge interactions and the enhanced force-generating capacity of the muscle fibers at longer lengths.

This pattern of decline followed by a steep incline beyond the resting muscle length is known as the descending limb and ascending limb of the force-length relationship, respectively. It highlights the complex interplay between the sliding filaments within the sarcomeres and the generation of muscle force during active contraction. Understanding this relationship is essential in the study of muscle physiology and the mechanics of muscle function, providing insights into the optimal muscle lengths for force production and the implications for muscle performance in various activities and movements.

Question 330

How does velocity and force change in concentric muscle contraction?

Answer 330

Concentric contraction

Velocity increases = Force decreases
* Actin-Myosin bridges do not have
sufficient time to form!

Question 331

How do lower velocities impact concentric contraction?

How is maximum power achieved?

Answer 331

For concentric force…
Lower velocities leads to the Contraction being more efficient
Power 1/3 force + 1/3 velocity = Maximum power

Question 332

What is the force-velocity relationship in muscles?

Answer 332

External load imposed is small, the velocity of contraction is max.

Load increases, the speed of contraction
decreases

When the load is equal to the maximum force that the muscle can exert, then the contraction is isometric.

When the load is greater than the max force then the muscle stretches.

The more the load increases, the faster the speed increases.

Eccentric: the force stops abruptly at rapid speed when you can no longer control the movement.

Question 333

How does temperature affect muscle force?

Answer 333

Muscle creates the same force but the muscle is able to produce that force in less time

Question 334

What are the 3 mechanical effects of fatigue on muscle performance?

What is the chemical effect of fatigue on muscle performance?

Answer 334

Mechanical Effects
* Modification of the movement
* Change in the load
* Decreased ability to absorb impacts

Chemical Effects
-Decrease in ATP

Question 335

How does vibration effect muscle force?

Answer 335

Increased force, velocity, lower
Maintains muscle structure and force at rest
Decreases sarcopenia