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DPT 702: Biomechanics > Week 3 Pt.1: Test 1 > Flashcards

Week 3 Pt.1: Test 1 Flashcards

1
Q

Stable posture is a result of what

A

Balance of Competing forces

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2
Q

Movement results from

A

Unbalanced competing forces

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3
Q

Skeletal muscles adapt to what

A

Immediate and long term external forces that can destabilize the body

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4
Q

Describe the force range of skeletal muscles

A

Wide range

Fine motor to large lifting

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5
Q

Skeletal muscles respond to what

A

Both external environment to internal control mechanisms (I.e. nervous system)

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6
Q

Each muscle fiber is an individual …

A

Multinucleated cell

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7
Q

What is responsible for contraction of a whole muscle

A

Contraction at the muscle fiber level

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8
Q

Muscle shortening occurs because of shortening of what

A

Sarcomere

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9
Q

Describe the length of muscle fibers

A

Varying length

Can be tendon to tendon or much shorter

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10
Q

What contains many myofibrils that include tiny cylinders consisting of bundles of myofilaments

A

Cytoplasm or sarcoplasm

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11
Q

What is responsible for holding the components of the cell, storing the molecules for cellular processes, and responsible for giving the cells its shape

A

Sarcoplasm

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12
Q

Specialized membrane that surrounds striated muscle fiber cells; how calcium enters and leaves cells

A

Sarcolenna

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13
Q

What is the endomysium? External to? Partially attached to? Helps to…?

A

Thin layer of connective tissue that surrounds individual muscle fiber

Immediately external to sarcolemma

Partially attached to perimysium

Help transfer actin myosin contractile force

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14
Q

What is perimysium

A

Sheath of connective tissue surrounding bundle of muscle fibers

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15
Q

Contractile proteins of muscle

A

Actin

Myosin

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16
Q

Describe the noncontractile muscle structural proteins

A

Cytoskeleton with muscle fibers

Supportive structures between fibers

Contract but no role for force transmission

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17
Q

Titindoes provides what

A

Passive tension within muscle fiber

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18
Q

Desmin does what

A

Stabilizes alignment of adjacent sarcomeres

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19
Q

Describe fusiform fibers

A

Run parallel to one another and central tendon

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20
Q

Fusiform designed for what

A

Mobility and low force over long range

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21
Q

Pennate fibers run how

A

Approach central tendon obliquely

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22
Q

Describe pennate fibers

A

Large number of fibers
Generate larger forces
Most muscles fall in this group
Unipennate, Bipennate, and multipennate types

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23
Q

How does muscle architecture impact amount of force that can be created

A

Physiological cross sectional area and pen nation angle

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24
Q

Describe the purpose of understanding physiological cross sectional area

A

Determines amount of active proteins available to generate force

Max force potential proportional to CSA

I.e. thicker muscles have more force that thinner

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25
Q

Describe pennation angle

A

Fibers run at different angles

CSA needs to be perpendicular to fiber direction

Angle of orientation between fibers and tendons

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26
Q

What is the difference between alignment in series or in parallel

A

Parallel = all components connected across each other (bigger muscle)

Series = all components connected end to end forming a single path (longer)

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27
Q

what are series elastic components

A

tissues attached en dot end with active proteins

i.e. tendon, titan

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28
Q

what are parallel elastic components? Examples?

A

tissues that lie parallel with active proteins

i.e. epi, peri, endomysium

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29
Q

what is elongated when you stretch the whole muscle

A

elongates both parallel and series components

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30
Q

what is the critical length

A

all slack tissue much be brought to this initial level of tension

31
Q

what happens past the point of critical length

A

tension increases until muscle reaches high level of stiffness and fails

32
Q

role of passive tension within stretched muscles

A

can stabilize or assist movement

33
Q

what does it mean that muscle is viscoelastic

A

time changes its behavior

quick stretch elicits (increased velocity) increases its stiffness

34
Q

elasticity is a dampening mechanism that can help

A

protect a muscle

35
Q

how can passive tension affect force production

A

stretched muscle has elasticity and temporarily stores some of that energy (i.e. a spring)

releasing that stored energy can assist in force production

36
Q

what are two components of plyometric exercise

A

elasticity and viscoelasticity

muscles are loaded by eccentric action followed immediately by concentric action to reach optimum force

increasing stress load increases intensity

37
Q

the eccentric prestretch phase of a plyometric activity does what (stretches what)?

A

stretches muscle spindle of the muscle tendon unit and noncontractile tissue within muscle (SEC and PEC components)

38
Q

what does the term amortization describe

A

time from cessation of eccentric prestretch to the onset of concentric muscle action

“time to rebound”

39
Q

what happens if amortization phase is delayed? What isn’t activated?

A

stored energy lost as heat

stretch reflex not activated

resultant positive work of concentric contraction not as effective

40
Q

what is the ultimate force generator in the muscle

A

sarcomere

41
Q

what does the dark band of a muscle fiber represent

A

A band

thick myosin

42
Q

what does the light band of the muscle fiber represent

A

I bands

actin (thin)

43
Q

describe actin and myosin in resting muscle

A

slightly overlapping

44
Q

describe the sliding filament hypothesis

A

active force generated when actin filaments slide past myosin pulling Z discs within a sarcomere (narrows H band)

if sarcomere shortens, muscle shortens

H band = area of only myosin

Z discs = end of sarcomeres

45
Q

do active proteins themselves shorten? Describe

A

no

myosin heads attach to actin filament and form cross bridge

amount of force in given sarcomere depends on simultaneously formed cross bridges

force also depends on length at any moment (alters amount of potential overlap)

46
Q

describe the results of summation of active and passive tension

A

all force is generated actively

passive tension begins to contribute when muscle is stretched beyond resting length

passive tension then accounts for must of the force as the muscle is stretched further

(i.e. length tension curve)

47
Q

describe the relationship between load and velocity for eccentric and concentric contraction

A

eccentric = increase load, increase contraction speed

concentric = increase load, decrease contraction speed

48
Q

what are isokinetics

A

torque joint angle velocity relationship

49
Q

what are alpha motor neurons

A

lower motor neurons whose cell bodies are found in the anterior horn of the spinal cord ‘

axons travel down body to innervate skeletal muscle to cause contraction

50
Q

what is a motor unit

A

a single motor alpha neuron with its entire family of muscle fibers

51
Q

what are excitation sources

A

cortical descending neurons, spinal interneurons, and afferent (sensory neurons)

52
Q

what is rate coding

A

rate of sequential activation of motor units?

53
Q

what do alpha motor neurons innervate

A

extra fusal fibers

not intrafusal fibers

54
Q

what is an action potential and where/how does it travel

A

sum of all competing inhibitory and excitatory inputs

at critical voltage signal is propagated down the icon to the motor endplate at the neuromuscular junction

twitch occurs

55
Q

smaller motor units control what

A

less force and more fine motor control

low innervation ratio

56
Q

larger motor units control what

A

larger forces

high innervation ratio present

57
Q

describe slow oxidative motor units

A

slower contractile characteristics

little loss of force during sustained activation (remain more constant; endurance)

58
Q

describe fast glycol motor units

A

larger motor neuron units

recruited after the slow oxidative units when large forces are required

59
Q

describe fast oxidative glycolytic fibers

A

in between slow oxidative and fast glycolytic

60
Q

what is unfused tetanus

A

summated mechanical twitches

61
Q

what is fused tetanus

A

as time interval shortens between action potentials greater force is generated and the twitches fuse into a stable muscle force

62
Q

what two things operate in the rise of muscle force and are highly specific to demand

A

rate coding and recruitment

63
Q

do concentric or eccentric contractions require more motor units

A

at the same level of force, eccentric contractions require less units

B/c more cross bridges are occurring

64
Q

what is muscle fatigue

A

exercise induced decline in Max voluntary muscle force despite max effort

basis of neuromuscular overload and adaptation necessary for training

reversible with normal rest

65
Q

compare fatigue between men and women

A

women are less fatiguable than men for concentric/isometric when intensity is the same (more type I slow twitch)

66
Q

describe the fatigue difference between older and younger individuals

A

older = less fatiguable with isometrics, but more fatiguable with concentrics and fast velocities

67
Q

does eccentric or concentric contractions create more muscle fatigue

A

at same load/velocity eccentric produces less muscle fatigue

BUT repeated eccentric training can lead to delayed onset muscle soreness that peaks at 24-72 hours (caused by damage to sarcomeres and cytoskeleton)

68
Q

strength training can cause the greatest change in what type of fibers

A

fast twitch II

69
Q

why might an individual experience gains in strength within the first few days of starting a resistance training program

A

adaptation of nervous system

increased activity in brain cortex, supraspinal drive, motor neuron excitability, greater discharge of Motor units, and less neural inhibition

70
Q

describe the physiological changes that take place during muscle hypertrophy

A

increased protein synthesis within muscle fibers

increased physiological cross sectional area of whole muscle

sarcomeres added in parallel

serial addition of sarcomeres increase of speed in contraction and elongation

limited evidence of hyperplasia (added number of fibers/cells)

71
Q

describe the changes in muscle with reduced use

A

3-6% atrophy within the first week

10 days of immobilization = 40% less of 1RM

20% less cross sectional area = 40% reduction in strength

greater number of slow twitch fibers (because fast twitch are the first to be lost)

postural/single joint muscles show greater atrophy

72
Q

describe the changes in muscle with advanced age

A

changes are highly variable

greater loss of power than just the peak force

10% decline per decade after age 60

greater decline after 75

greatest in lower limb

73
Q

main mechanism for age related muscle changes

A

sarcopenia

loss of muscle tissue and infiltration of connective tissue, fat, and decrease in fibers and size

loss of alpha motor neurons reduce fivers

resistive exercise can help

DPT 702: Biomechanics (13 decks)

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