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Kinesiology and Biomechanics > Mechanical Behavior of tissues (bone/articular cartilage/tendon/ligament) > Flashcards

Mechanical Behavior of tissues (bone/articular cartilage/tendon/ligament) Flashcards

1
Q

Connective Tissue: structure and mechanical properties

A

s

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2
Q

structure of connective tissue

A
  • characterized by a wide dispersion of cells in the presence of a large extracellular matrix (ECM)
  • microscopic level
  • -interfribrillar (ground substance/collagen) and fibrillar (fibrous) components
  • CT are unique among body structures. function determined by ECM unlike muscle/nerve where cell behavior dictates function
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3
Q

fibroblast

A

basic cell of most connective tissue

  • may become:
  • chondroblast: cartilage
  • osteoblast: bone
  • tenoblast: tendon
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4
Q

extracellular matrix

A
  • interfibrillar (ground substance)
  • -hydrated proteins:
  • -PGs
  • -glycoproteins
  • fibrillar (fibrous compenent)
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5
Q

PGS

A

proteoglycans
-attached are one or more polysaccaride chains called glycosaminoglycans (GAGs) (chondroitin and chondroitin sulfate, hyaluronon)

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6
Q

glycoproteins

A

-compound containing a carbohydrate (sugar type molecule) covalently linked to protein

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7
Q

Pgs and gags

A
  • proportion of PG’s in extracellular matrix effects hydration
  • GAGs are negatively charged such that a concentration of negatively charged PG’s creates a swelling pressure=water flows into the extracellular matrix
  • collagen fibers resist and contain the swelling (via tensile stress w/osmotic swelling pressure)=creates regidity of matrix, therefore, can resist compressive forces
  • tissues subjected to high compression forces have a high PG content and those that resist tensile loads have a low content
  • GAGs have affinity for H2O, tension load increased on collagen fibers, creates rigidity
  • PGs found in all connective tissues
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8
Q

types of connective tissue

A

blood
bone
cartilage
connective tissue proper (tendons and ligaments)

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9
Q

fibrillar component

A

2 major components: collagen and elastin

  • collagen: main substance of most connective tissues
  • -most abundant protein in body
  • -tensile strength similar to steel, resistance to tensile forces
  • elastin: uncoils into a more extended formation when the fiber is stretched and recoils psontaneously when the stretching force is removed
  • tissues that require more give contain more elastin
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10
Q

collagen type I

A

-predominantly in ll, tendons, menisci, and joint capsules

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11
Q

collagen type II

A

-predominantly in hyaline articular cartilage and nucleus pulposus of disk

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12
Q

elastin

A
  • properties allow the fibers to deform under force and return to original state (rubber band)
  • generally elastin smaller in in proportion to collagen in connective tissues (varies greatly)
  • ligamentum flavum has higher elastin
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13
Q

composition and structure of connective tissue

A
  • sparsely vascularized, “parallel” fibered (primarily type 1 collagen), dense connective tissue in tendon and ligament
  • delayed healing
  • structure and chemical composition of ligaments and tendons identical in humans and many other mammalian models
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14
Q

composition and structure

A
  • fibroblasts synthesize and secrete procollagen (pre-collagen) which is cleaved extracellularly to produce type I collagen
  • each polypeptide chain is coiled in a left-handed helix. these three alpha chains are then coiled together in a right handed-helix. such structure increases molecular strength
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15
Q

cross links

A
  • formed by GAG’s between collagen molecules provide strength to fibrils
  • cross links are few and fairly easily broken in new collagen, become strong with maturation
  • aid resistance of tension loads
  • orientations of collagen makes them good tension load resistors
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16
Q

elastin content

A
  • more in ligaments than tendons
  • proportion of elastin important in determining mechanical properties
  • tension loaded ligament=preloaded
  • assists in ability to come back up
  • may be why ligamentum flavum has more elasitin in it
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17
Q

general mechanical principles

A

overload

  • specificity
  • reversibility
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18
Q

overload

A
  • tissues increase their structural or functional capability in response to overloading (stimulus and response)
  • develop tissue=impart stimulus
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19
Q

specificity

A

-specific stimulus for adaptation elicits specific structural and functional changes in specific elements of tissues

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20
Q

reversibility

A
  • discontinuing training stimulus will result in de-training and the adaptive changes regress (disuse atrophy)
  • lose muscle benefit that you gained in 72 hours if not stimulated again
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21
Q

SAID

A

Specific Adaptations to Induce Demands

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22
Q

elasticity

A

-property of a material or structure to return to its original form following removal of deforming load (compression, tension, sheer)

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23
Q

plasticity

A
  • property of a material to deform permanently when its loaded beyond its plastic (compression resistance) range
  • permanent change in density
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24
Q

viscosity

A
  • property of a material to resist loads that produce shear, controls fluid rate of flow
  • higher viscosity=slower deformation/rate of flow
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25
Q

elastic materials

A
  • return to normal form/shape following removal of deforming load (solid property)
  • energy is stored during loading and released completely during unloading-no energy loss (if in elastic region)
  • loading-unloading curves are the same
  • every tissue contains visco-elastic tissue
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26
Q

visco-elastic materials

A
  • a combination of viscosity and elasticity
  • sensitive to rate of loading or deformation
  • higher rate: greater energy stored cannot dissipate rapidly througha single crack, comminution of bone and extensive S.T. (soft tissue) damage occurs
  • low rate: energy can dissipate through a crack, bone, and S.T. remain relatively intact. little displacement occurs
  • faster-rate=more damage
  • all connective tissues
  • makes behavior time, rate, and history dependent
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27
Q

CREEP

A
  • load (stress) is applied and then held constant over time (not cyclic)
  • continued deformation over time though load is held constant
  • deformation=strain
  • use to enhance ROM in tissues like ligaments and tendons that respond to longer period of time stretching
  • force remains constant while length changes
  • initial elastic deformation, continues to elongate over time (CREEP)
  • constant force, increasing length
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28
Q

stress-relaxation

A
  • tissue stretched to a fixed length while the force required to maintain this length decreases over time
  • length remains constant while force decreases
  • less force is required to maintain same tissue length/stretch
  • constant length, decreasing load (force) (naturally)
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29
Q

cyclical loading

A
  • causes a shift of curve to the right
  • shift decreases in magnitude with each repetition
  • repeated on and off force
  • load=stress
  • strain=elongation (deformation)
  • demonstrating elasticity of tissues
  • stretch=permanent plastic change
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30
Q

hysteresis

A
  • a load-deformation curve that reveals that the forces applied and removed do not follow the same path
  • not all the energy gained as a result of the lengthening work is recovered during the exchange from energy to shortening work
  • some energy is lost, usually as heat
  • energy lost/deformation can be a good thing, CREEP and stress-relaxation are trying to create a hysteresis curve to permanently change tissues (stretch them)
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31
Q

load (tension/stress)/Elongation(length/strain) graph

A

see stress strain curve

1: more elongation w/load
- “toe” region, straightening out of fibers
2. elastic zone-tissue releases to same place
3. yield point/stress(load)=point of no return. no longer elastic change, created hysteresis loop
4. rupture

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32
Q

viscoelastic behavior

A
  • increased stiffness with increased strain RATE (faster=stiffer tissue)
  • stress relaxation and creep deformation as per other tissues
  • increase rate, going to tear
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33
Q

creep vs stress relaxation

A

-constant load vs constant strain

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34
Q

tendon loading

A
  • tendon loading differs from other connective tissues due to its direct attachment to skeletal muscles
  • thus muscle contraction force and relative cross-sectional area of muscle to tendon must be considered
  • though muscle forces may be very high, tendon tensile strength tends to be twice that of its muscle
  • thus muscle ruptures more common than tendon rupture
  • tendon loading is typically 5-10% of ultimate stress (typical day only imparts 5-10% of stress tendon can hold)
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35
Q

investing DCT

A
  • paratenon: outside sheath of tendon
  • epitenon: synovial tissue only in high friction locatoins
  • endotenon: continuous with perimysium(outside muscle) and periosteum(sharpeys fibers)
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36
Q

sharpeys fibers

A

come down into bone-cement tendon into bone

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37
Q

functional implications

A

Consequences of increased tissue stiffness in DCT surrounding muscle, peri-articular…:

  • rapid, eccentric loading can be problematic especially achilles tendon of males 35-55
  • posture: aging and sitting behaviours self-perpetuating
  • ability to retain water decreases with age and increase stiffness with less water
  • # 1 way pts strain their muscle is eccentrically
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38
Q

injury and repair in tendons

A
  • cellular reaction: inflammatory phase (days)
  • collagen synthesis: proliferation (7days-7weeks)
  • remodeling: maturation(7weeks-months)
  • cross links form over time
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39
Q

immobilization effects on tendon repair

A
  • no movement for 9 weeks dimished load tolerance
  • controlled immobilization is key, need to use some motion
  • type of motion is important: stress/strain curve
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40
Q

post injury immobilization vs early mobilization

A
  • immobilization in tendon reduces water content, PG content and strength
  • immobilization weakens bone-ligament-bone complex just after 8 weeks in ACL
  • tendon softening in first 1-2 weeks pronounced with immobilization
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41
Q

early intermittent passive mobilization in canine tendon

A
  • ultimate load (strength/stress) increased with immediate mobilization
  • reduction in adhesions (scar tissue)
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42
Q

functions of myotendinous junction

A
  • adhesion
  • force transmission (muscle, tendon, bone)
  • force must not exceed strength of interface(myotendinous junction) and adhesion
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43
Q

muscle tendon and bone-ligament-bone failure under tension

A
  • muscle-tendon injuries due to stretching or combined stretching and contraction tend to occur at myotendinous junction
  • age dependent behavior:
  • pre-epiphyseal closure-failure at epiphysis (growing years)
  • post-epiphyseal closure-failure at MTJ
  • clinically midsubstance tears of bone-ligament-bone are more common in adults than avulsion
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44
Q

4 variables to consider when prescribing exercise

A
  1. mode (type of exercise)
  2. intensity(load and pt feeling)
  3. frequency(how long)
  4. duration (number times per week)
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45
Q

therapeutic effect of loading on per-articular DCT length

A
  • low load of minutes in duration
  • mechanoreceptors inhibit nociceptors
  • tendon, ligament, capsule all benefit from elongation
  • 5-40 min
  • non-thrust will not change length of a tissue
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46
Q

therapeutic effect of loading on muscle length

A
  • 30 second duration minimum to elongate muscle
  • continuous duration
  • once daily, 5 days a week
  • heat up tissue will help stretch
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47
Q

tissue training: strength

A

3-5 sets of 8-10 reps

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48
Q

tissue training: endurance

A

3-5 set of 20-30 reps

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49
Q

tissue training: endurance

A

3-5 sets of 30-40 reps

50
Q

tissue training: ligament

A

1000s of reps (timed)

51
Q

tissue training: cartilage

A
  • hours of reps

- 30-40 minutes of multiple modes, 5-7 minutes per exercise

52
Q

some of articular cartilage’s clinically relevant gross structural/physiological features

A
  • an avascular, aneural tissue with a low metabolic rate

- it is designed to withstand rigorous loading without failure to distribute loads and to provide a low friction surface

53
Q

what is articular cartilage made of?

A
  • superficial=sheer resistant

- deep=shock absorber/compression resistance

54
Q

tide mark

A

demarcation between calcified layer with uncalcified layer

  • loses superficial layer with age
  • ossification of cartilage->wolfes law
  • cancellous bone increases
  • loses shock absorption
  • bone is not aneural, pain with arthritis comes from bone on bone contact (subchondral bone)
55
Q

chondrocytes

A
  • make and secrete matrix, inhibiting cell-cell contact
  • matrix transmits mechanical signals to cell membranes
  • these cells may act as transducers in that the mechanical stress elicits a cell response to change synthetic activity
56
Q

what is the most unique AC material property as it relates to its mechanical behavior

A
  • fluid component
  • key feature both structurally and mechanically in this hydraulic tissue
  • water content decrease and PG content increases with increased depth of tissue
  • deeper we go, smaller pores in cartilage, H2O has difficult time going through it
  • solid component:
  • porous, permeable matric primarily of type II collagen and PG
  • extremely low permeability coefficient
  • anisotropic tissue-will not resist forces in all directions (sheer hurts)
  • heterogenous CT (solid and semi-solid materials)
  • allows permeability for H2O in cartilage. compression forces force fluid out of cartilage like a sponge, but decreasing pore size slows down compression (viso-elastic)
57
Q

how would you describe AC’s visco-elastic mechanical behavior

A
  • stress developed in collagen-PG solid matrix
  • frictional drag generated by interstitial fluid flow through matrix
  • greater PG aggregation=increased elastic response and rupture strength
  • aging reduces degree of PG agregation
58
Q

mechanical behavior: permeability

A
  • rate of creep is an indicator of tissue permeability (increased creep, decreased permeability)
  • small pores result in low permeability and high friction to flow (increased creep)
  • compression further reduces pore size
  • mode=cyclic loading for cartilage (want that bottleneck, dont want to continously stress b/c pushes out fluid)
59
Q

structural macromolecules

A

-aging: decreased aggregation, decreased GAG content and shorter chains. structural modifications may be linked to changes in chondrocyte synthetic function

60
Q

biphasic creep response in compression

A
  • rapid initial exudation of fluid from articular surface
  • external compressive load creates creep which is resisted by stress developed in collagen-PG solid matrix and frictional drag
  • continued slower exudation until deformation equilibrium reached
  • external compressive load ultimately equals stress developed in collagen_PG solid matrix alone
  • -4-16 hours of constant load to cessation of fluid flow (starts to hurt)
  • older people have pain because of the increasing tide mark, less surface between bones and it takes less time to reach that equilibrium and pass it
61
Q

biphasic stress-relaxation response in AC

A
  • stress is increased until a given deformation is reached and then deformation/strain maintained, stress decreases under constant strain until equilibrium is reached
  • fluid redistribution is responsible for tissue stress relaxation
  • rapid redistribution of load throughout tissue reduces peak stresses and thus contributes to articular cartilage’s resilience
  • constant strain/deformation and the load required to create that decrease over time
  • fibers more compliant internally
  • CREEP is when you keep pushing (increasing stress) to further stretch
  • 2 things cause equlibrium: fluid distribution and collagen fiber alignment
62
Q

joint lubrication

A
  • often under speculation

- engineering based models attempt to apply it to body, not perfect system

63
Q

AC lubrication systems

A

2 types: boundary and fluid

  • boundary: each load bearing surface is coated with lubricin (like poles of a magnet) (diarthrodial joints), two surfaces do not touch each other
  • –most effective at low loads
  • fluid: a film of fluid interposed between 2 joint surfaces
64
Q

boundary lubrication

A
  • lubricin prevents surface to surface contact

- most important under low loads, at low speeds and long duraction (standing)

65
Q

fluid

A

4 types

  1. hydrostatic
  2. hydrodynamic
  3. squeeze film
  4. elastohydrodynamic
66
Q

hydrostatic

A

weeping

  • film of lubrication that is maintained under pressure (weep out) of cartilage with pressure and returns with unloading
  • -most effective under high loads but effective under most conditions (supplied by contraction of mm or compression in CKC-jumpiing, contract muscles)
  • on/off loads
  • non-parallel force
67
Q

hydrodynamic

A

wedge of fluid is created when non parallel opposing surfaces slide on one another-lifting pressure occurs in wedge of fluid and increases viscosity, keeps surfaces apart

  • riding a bike at high speed decrease resistance will separate knee joint and lifting pressure
  • pushing a wave of fluid
  • lifting pressure, speed speaks to lift/separation retropatellar
68
Q

squeeze-film

A
  • pressure created in fluid film by surfaces moving that are perpendicular to one another
  • fluid is squeezed out as surfaces approximate=increased fluid viscosity with pressure
  • -most beneficial for high loads maintained for a short duration
  • orientation of force makes it different from hydrostatic lubrication
69
Q

elastohydrodynamic

A
  • fluid film is maintained at a uniform thickness by elastic deformation of articular surfaces
  • the cartilage deforms slightly to maintain adequate layer of fluid between surfaces
70
Q

aberrant lubrication systems

A
  • adhesive wear: osteochondritis dessicans (drying out, no fluid in joint)
  • -complete or incomplete separation of a portion of cartilage and bone
  • abrasive wear: joint mouse irritation-loose body (rocks in a dryer)
  • fatigue wear: PG washout, aging, DJD
71
Q

theoretical mixed mode model during gait

A
  • heel contact: squeeze film predominates
  • stance phase: combo of boundary and fluid film
  • swing: hydrodynamic predominates
72
Q

loss of PG matrix

A
  • caused by prolonged immobilization, some anti-inflammatory drugs, trauma/sx, infection and/or as a normal component of aging
  • may be reversible dependent upon degree and duration
  • NSAIDS can cause proteoglycan washout in tissues long term
73
Q

development of osteoarthritis

A
  • early stages: fraying of collagen bundles in superficial layer
  • often see rapid progression once fraying has begun due to fiber orientation within tissue
  • superificial layer of cartilage is sheer force oriented, but as it wears and tears the lower levels cannot withstand sheer because of their orientation and they degrade faster
74
Q

tissue degeneration in chondromalacia

A

-softening of cartilage appears to begin in layers 3 and 4. thus early visualization of pathology is difficult
-negative effect of chondromalaysias (disuse) at layers 3-4
-DJD too much
Chondromalaysia: too little

75
Q

continuous passive motion

A
  • increase blood flow
  • promotes lubrication
  • cycles fluid in and out to nutrient it
  • prevents contactures
  • stimulate mechanoreceptors to inhibit nociceptors
76
Q

controlled weight bearing

A
  • rabbit knee joint cartilage grew faster and thicker in areas of WB vs NWB regions
  • constant load is detrimental while intermittent loading may help healing via explants. vascular tissue necessary in transplantation process
77
Q

aggressive exervise

A
  • treadmill exercise rats show greater degree of artic. cartuilage damage with aging than sedentary rats
  • long distance running is detrimental to WB articualr cartilage in healthy beagles
78
Q

what intervention/tactics should we use to facilitate ac growth

A
  1. intensity: (load, quality, what they feel)
    - pain as guide??-no pain should be present, just pressure
    - edema or effusion as guide?-doing too much if present
    - full body weight loading may be excessive
    - less is more
  2. duration and/or frequency
    - high repetition (100s-1000s) cyclical loading
    - 5-7 minutes per exercise, functional exercise
    - closed chain
  3. mode: attempt to mimic function loading characteristics
    - may consider minimizing combinations of shear and compressive
79
Q

what makes bone a good material to serve as a mechanical lever?

A

intercellular calcified bone matrix:

  • inorganic matter (mineral)
  • 60-70% bone dry weight
  • water(5-8%)
  • organic matter(22-35%)
80
Q

extracellular organic matter

A
  1. type I collagen:
    - organization varies with bone type
    - -resist stretching and have little extensibility
    - -accounts for 90% of ECM and 25-30% of dry weight
  2. amorphous ground substance
    - GAGs serve as cementing substance between osteons (bridges)
    - associated with proteins primarily in form of PGs
    - specific glycoproteins contain glutamic acid causing them to bind avidly to calcium
    - each haversian system is a ring connected by GAGs
    - allows bone to absorb stress and share it equally through bridges
81
Q

intercellular bone matrix

A
  • inorganic matter: calsium and phosphorus abundant in form of hydroxyapatite crystals
  • decalcified bone retains shape but is as flexible as tendon
  • removal of organic matter in matrix leaves bone again with its original shape, but is fragile and brittle (osteoporosis)
  • need both organic and inorganic together for strong bone
82
Q

what makes bone such a dynamic tissue

A
  1. bone cells
    - osteocyte: mature cells
    - osteoblasts: young cells, growth of bone
    - osteoclasts: break down bone
  2. existing bone structure: balance of ongoing bone deposition and bone tissue resorption
    - growth: deposition
    - aging: resorption
    - disuse:resorption
    - healing: balance
    - exercise: blastic
83
Q

wolffs law

A

effective applied load decreased:

  • bone deposition decreases: disuse atrophy
  • immobilization
  • -casting and NWB status: following 8 weeks of immobilization may see a 3 fold decrease in load to failure, stiffness and energy storing capacity
  • -plates/screws implanted to reduce stress at fracture site may reduce/slow healing to normal strength. however, fixation site strength may increase
  • bone needs to take up load after surgery, not plates
  • just enough offloading to help healing, but not enough to prevent strength/load intolerance once removed
  • micro-motion of screws may stimulate bone to lay down more bone
84
Q

biomechanical properties of bone

A
  • cortical bone/compact bone is stiffer than cancellous bone: steeper slope of stress/strain curve (take a lot of load but will not deform well)
  • cancellous bone porous structure=greater capacity for energy storage (spongy-gags)
  • bone becomes more brittle with age
  • bone is more brittle with increasing velocity of loading–time for bone to absorb force is needed
  • -bone demonstrates anisotropic mechanical behavior (have to respond to forces put on them on a daily basis, bone behavior changes depending on load put on it)
85
Q

bone demonstrates anisotropic mechanical behavior

A
  • strength is greatest in direction in which loading is most common
  • strength decreases as direction of loading changes from:
  • -compression-longitudinal tension-oblique tension-transverse loading
  • -best served compression/tension
86
Q

stress

A

force per unit area applied to a structure

87
Q

strain

A

deformation (change in shape) of a structure produced by an applied force/stress

88
Q

stress strain bone

A
  • cortical bone is stiffer than cancellous
  • cortical bone can withstand greater stress but less strain than cancellous bone
  • cancellous bone can sustain strains of 75% before failing
  • cortical bone can sustain straing sof only 2% before failing
89
Q

compression

A
  • structure shortens and widens-bone somewhat widens
  • produces common fractures in vertebrae
  • constant compression may hinder growth
  • unequal loading may produce valgus/varus deformity
  • cyclical loading of appropriate parameters may facilitate growth and repair
90
Q

piezo-electric effects of bending forces

A
  • (-) charge on side of compression and (+) charge on side of tension
  • osteoblasts tend to migrate toward (-) electrode; while osteoclasts tend to migrate toward (+) electrode
  • bone deposition increases on side of compression
  • standing on one leg loads femur, bends in outwardly (concave side is + charge)
91
Q

effect of muscle contractions on bone

A
  • usually oppose antagonist or gravity to counterbalance bending (abductors resisting tension on superior femoral neck with WB-standing on one foot, abductors resist convexity of force)
  • acting independently creates bending of bones
  • create tension at tendon-bone junction
  • create tuberosities/trochanters developmentally-develop as you apply force to that area of bone
  • pathologically may create avulsion fractures
92
Q

constant vs intermittent loading

A
  • constant compressive loading produces increase in endosteal diameter and increase in intracortical porosity
  • not good for long bones
  • intermittant loading produces increased bone mass
93
Q

torsion loading

A
  • spiral fractures are common withthese forces
  • epiphyseal plate is most sensitive to torsion forces
  • under torsional load, newly forming bone will grow away from epiphysis in a spiral fashion
  • -ie structural scoliosis, femoral or tibial torsion
94
Q

bone geometry: mechanical property

A
  • cross sectional area: greater area=stiffer and stronger bone
  • healing fracture begins with large callus
  • screw holes to stabilize fracture sites initially weaken the bone to which they are attached. 8 weeks to return to normal strength due to remodeling
  • same issue with removal of hardware (bridge of tension/compression needs to reheal)
95
Q

what intervention tactics/parameters should we use to facilitate growth

A
  1. intensity:
    - loading within tissue structural tolerance
    - move carefully into the plastic zone
    - pain free loading
  2. duration and/or frequency
    - many repetitions-cyclical loading: 100-1000s of reps, time based
  3. mode: attempt to mimic functional loading characteristics
96
Q

muscle mechanics

A

s

97
Q

strength depends on..

A
  • depends on both: muscle force x moment arm (torque)
  • mechanical factors: rotary component of muscle force and length of moment arm
  • physiological factors: length of the muscle, velocity of contraction, fiber orientation, cross sectional area, and fiber type
  • strength=ability to generate torque
98
Q

fiber type

A

-each skeletal muscle in the human body contains type I, IIa, and IIb fibers

99
Q

type I

A
  • slow twitch oxidative
  • characteristics: small diameter, red in color, dense in capilaries, speed of contraction is slow, rate of fatigue is slow (soleus)
100
Q

type IIA

A
  • fast twitch oxidative glycolytic
  • characteristics: as in type I except-intermediate diameter, fast speed of contraction, and intermediate rate of fatigue
101
Q

type IIb

A
  • fast twitch glycolytic
  • characteristics: large diameter, white in color, sparse capillarity, fast speed of contraction, and fast rate of fatigue
  • muscles predominantly type II/fast twitch often called mobility, non-postural, phasic muscles
102
Q

muscle in cross section

A
  • epimysium surrounds the whole muscle
  • perimysium surrounds the fascicules
  • endomysium surrounds the individual muscle cells
103
Q

contractile element

A
  • CE

- contractile proteins

104
Q

parallel elastic elements

A
  • PEC

- peri, epi, and endomysium (fascia)

105
Q

series elastic elements

A
  • SEC

- tendons

106
Q

can mysiums generate force

A

-yes, just not sympathetically. indirectly generate force through muscle contraction

107
Q

isometric contraction

A
  • contractile element shortens and the series elastic element lengthens
  • PEC go on slack
  • ex=contract bicep with arm flexed to 90
108
Q

muscle twich

A
  • passively pulling on the muscle beyond rest length will stretch the PEC and they will also contribute to the tension
  • muscle contraction creaetes tension
  • optimal length tension=mid position of a joint
  • add sarcomeres to lengthened muscle
  • mysiums generate force to resist muscles lengthening further
109
Q

torque

A

muscle force x moment arm

  • muscle force will vary with muscle length in accordance with the length tension curve
  • too short or too long will not produce optimal force
110
Q

active insufficiency

A
  • agonist muscle is too short to produce effective tension and thus no further ROM can be actively achieved
  • typically bi or multi-articulate muscles
  • long head biceps vs long head triceps
  • rectus femoris vs hamstring
  • triceps is elbow extender and GH extentendor
  • LH biceps is elbow flexor and GH flexor
111
Q

passive insufficiency

A
  • antagonist muscle is on stretch and is too short (too far elongated) to allow further passive range of motion
  • typically bi or milti-articulate muscles
  • can be either actively insufficient of biceps or passively insufficient in triceps for elbow flexion (tests to determine)
112
Q

torque

A
  • muscle force x moment arm
  • muscle force varies with cross sectional area of the muscle
  • fiber arrangement is a key issue in determining total cross sectional area
  • greater cross sectional area=greater force output
  • larger cross sectional area means there is more to contract (biceps vs. pecs major)
113
Q

changes with aging

A
  • cross sectional area increases years 0-20s then decreases to a lesser degree 30s+
  • thus maximal strength 20s-30
  • at age 65, have about 85% of muscle strength they had at age 20
  • loss is reversible +/or can be minimized
  • loss of strength more in legs than arms
  • males stronger than females
114
Q

muscle force generation (isolated muscle studies)

A
  • velocity of muscle contraction is a function of the load being lifted
  • speed of shortening of the myofilaments is the rate at which the myofilaments are able to slide past one another and form/re-form cross bridges
  • speed is related to fiber type and length
115
Q

muscle force varies with velocity of the contraction (clinical perspective)

A
  • force generated is a function of the velocity of muscle contraction
  • max shortening speed occurs when there is no resistance to shortening, however, no tension is developed in the muscle b/c there is no resistance
  • concentrics: as shortening speed decreases, tension increases
  • isometrics: speed is zero, therefore, greater tension generated compared to concentrics
  • eccentrics: as speed of lengthening increases, tension increases (trying to slow down muscle harder to prevent tear against fast speed)
  • isometrically generate a force greater than concentrically, so when doing isometric exercises you really want to be doing sub-isometrics because there is a greater load, and the muscle will probably be healing still
116
Q

muscle force varies with the velocity of the contraction

A
117
Q

muscle force varies with type of contraction

A
  • isometric: great strengthening but only at that joint angle +/-10 degrees
  • concentric: dynamic, but velocity-tension relationship often limits strengthening at higher (more functional) velocities
  • eccentric: great strengthening, possible tissue damage (micro tears) due to potential for large muscle force production
  • isotonic: dynamic contractions, but intensity limited by capability in weakest part of ROM (typically end ranges)(umbrella term for isometric, concentric, and eccentric contractions)
  • isokinetic: good strengthening throughout the range of motion. functional?
  • any and all types can be prescribed, depends on pt
118
Q

torque

A

strength

-force x moment arm

119
Q

force dependent on

A
  • cross sectional area
  • fiber type
  • length-tension
  • velocity of contraction
  • elastic components
120
Q

moment arm dependent on

A
  • deflection of tendon by bone or bony prominence
  • changes with joint angle
  • changes with person’s size

Kinesiology and Biomechanics (6 decks)

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