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Biomechanics Flashcards

1
Q

what structure is responsible for the elastic behaviour of ligaments

A

elastin

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2
Q

ultimate stress occurs at what point on the stress-strain relationship curve

A

failure point

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3
Q

weight acceptance occurs during which component of the gait cycle

A

loading response

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4
Q

the ability of a material to absorb energy during plastic deformation before failure is called what

A

toughness

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5
Q

by how much (of resting length) can a muscle stretch before rupture

A

160%

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6
Q

the technique of surface emg is not generally used to provide information on which of the following…

  • when a muscle is actively contracting
  • the pattern of activation in skill aquisition
  • the onset of fatigue
  • potential adaptations within the nerves as a result of training
  • single motor action potentials
A

single motor action potentials

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7
Q

which of the following causative extrinsic factors affect the emg signal?

  • sampling rate
  • cross talk
  • orientation of electrodes with respect to the direction of fibres
  • analysis software
  • type of transducer
A

orientation of electrodes with respect to the direction of fibres

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8
Q

the hip and ankle positions during an isokinetic knee extension protocol are important considerations as they alter the length of which biarticular muscles

A

rectus femoris and gastrocnemius

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9
Q

during an isokinetic testing protocol, what happens to the duration of the isokinetic phase as the angular velocity increases

A

decreases

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10
Q

what sports performers would be more likely to display bilateral facilitation and why?

A

weightlifters as their movement uses both legs working at the same time

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11
Q

the measurement of the anatomical cross sectional area (ACSA) of a muscle should be made…

A

perpendicular to the long axis of the muscle

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12
Q

what is the advantage of an in-parallel muscle fibre arrangement

A

greater maximum force

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13
Q

what is the effect of the low pennation of the gastrocnemius in comparison to the high pennation of the soleus

A

gastrocnemius has increased range of motion

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14
Q

how does pennation effect the range of motion of a muslce

A

low pennation = higher range of motion

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15
Q

contralateral hamstring-quadriceps imbalances greater than what % are associated with greater injury risk

A

10%

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16
Q

the contraction velocity of type II motor units compared to that of the type I unit is…

A

three times greater

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17
Q

how do muscles with a small physiological cross-sectional area (PCSA) produce high joint torque

A

by having a large moment arm

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18
Q

which of the following testing conditions should not be violated when performing strength and power measurements

  • movement pattern
  • joint velocity
  • load characteristics
  • posture
  • all of the above
A

all of the above

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19
Q

the anteroposterior (x-direction) GRF at foot contact with the ground during a landing drop jump was 180 N. If the foot’s mass was 1.2 KG and its x-acceleration was 50m/s^2, what was the anteroposterior joint reaction force at the ankle?

A

-120 N

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20
Q

what electrical variable is measured when analysing muscular activity using EMG

A

voltage

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21
Q

the term pronation (at the subtalar joint) is often used interchangeably with what other term

A

Eversion

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22
Q

2 crucial factors in how & where injury occurs

A
  1. the load

2. characteristics of the loaded structures

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23
Q

types of injury

A

chronic (overuse) injury

acute (traumatic) injury

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24
Q

chronic (overuse) injury definition

A

results from repeated overloads with insufficient time for recovery

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25
Q

acute (traumatic) injury definition

A

results from a single or a few repeated episodes

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26
Q

what’re the differences between stress and strain

A
  • Stress: the measure of how much deformation arises from an applied load
  • Strain: the amount of resistance to this deformation
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27
Q

what is the Young’s modulus of Elasticity (E)

A

the ratio between stress and strain (strain/stress)

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28
Q

define Wolff’s Law

A

bone forms in reaction to the force placed on it (force not stress)

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29
Q

types of bone fractures (Bartlett, 1999) and the load causing them

A
  • Diaphyseal impaction (load = axial compression)
  • Transverse (load = bending)
  • Spiral (load = torsion)
  • oblique transverse/butterfly (load = axial compression and bending)
  • olblique (load = axial compression, bending and torsion)
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30
Q

examples of viscoelastic tissues

A
  • tendons (tough cords of closely packed collagen fibres)
  • aponeuroses (sheet-like tendons)
  • deep fascia (bind muscles together)
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31
Q

(Kibler & Chandler, 1993) trainable factors which have a genetic/intrinsic source

A
  • coordination
  • incorrect BW
  • poor posture
  • lack of joint mobility
  • lack or imbalance of muscle strength
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32
Q

anatomical differences in women that lead to increased injury risk…

A
  • a wider pelvis (resulting in altered hip and knee loading)
  • smaller bones and surfaces (typically 30% less than males)
  • greater rate of loss of bone with age
  • less muscle mass and higher fat content
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33
Q

reasons for abnormal gait (x7)

A
  • neurological disorders
  • skeletal disorders
  • muscular disorders
  • pain
  • age
  • personality (e.g. depression)
  • inability to hear and see?
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34
Q

what muscle acts as a stabiliser to the hip abductors

A

gluteus medius

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35
Q

describe the process of SSC fatigue (4 points)

A
  • deteriorated muscle function
  • reduced tolerance to impact
  • loss of elastic energy potential
  • increased work during push-off phase
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36
Q

3 potential sites of failure/fatigue

A
  • those within the CNS
  • those concerned with the neural transmission from CNS to muscle
  • those within the individual muscle fibres
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37
Q

sources of metabolic fatigue

A

1) simply muscles running out of fuel (muscle glycogen)

2) lactate build up in muscles, affecting the binding of calcium to troponin and also the functioning of enzymes

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38
Q

essential characteristics of a running shoes (x6)

A
  • attenuation of single/multiple impact forces
  • preservation of foot stability (rearfoot control)
  • adequate friction/traction
  • provision of different foot-strike patterns
  • heat dissipation
  • comfort
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39
Q

what are the neural factors which influence force generation (x3)

A
  • the number of motor neurons that are activated (recruitment)
  • the size of the activated motor neurons
  • the rate of which they discharge action potentials (rate coding)
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40
Q

process of picking up a signal (EMG)

A

detection of the potential fluctuations (electrodes) -> signal transmission (hard wire/telemetry/data logger) -> signal modification (amplifier) -> storage of the resulting waveform (computer)

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41
Q

examples of intrinsic (non-controllable) factors affecting EMG signal

A
  • physiological: number of active MU’s, MU firing rate, fibre type, blood flow…
  • anatomical: fibre diameter, depth & location of fibres
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42
Q

examples of extrinsic (causative) factors affecting EMG signal

A
  • impedance: skin prep, electrode impedance tester
  • orientation of electrodes
  • location of electrodes: not on outside edge/motor point/tendon
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43
Q

how can we manipulate neural factors during training

A

by manipulating…

  • training intensity
  • cadence
  • number of reps
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44
Q

methods of reducing cross talk

A
  • decrease electrode size and spacing
  • placing electrodes on muscle belly
  • double differential technique (3 electrodes)
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45
Q

advantages of MVC

A
  • allows comparisons with other muscles/subjects and between studies
  • eliminates any influence of the detection conditions
46
Q

disadvantages of MVC

A
  • ability to consistently elicit MVC varies between individuals
  • poor repeat ability of EMG from MVC
  • mechanics of movement (MVC at fixed angle)
47
Q

Baltzo and Gleeson (2001) produced a deterministic model highlighting several physiological and mechanical factors affecting strength and power. Within this model which of these factors is associated with joint position?

A

moment arm

48
Q

what is the % of force produced by a muscle that can be attributed to the CSA according to Semmler & Enoke (2001)?

A

50%

49
Q

the maximal conduction velocity of a large alpha motor neuron is…

A

up to 101 m/s

50
Q

mechanisms associated with PAP (x4)

A
  • an increased sensitisation to the phosphorylation process on the myosin light chains
  • increased alpha motor neuron recruitment
  • reduced reciprocal co-contraction
  • decreased angle of pennation
51
Q

methods of eliciting PAP (x3)

A
  • vibration activation methods
  • isometric activation methods (electrically/voluntary induced)
  • dynamic activation methods (isometric strength/plyometric exercises)
52
Q

Post-activation potentiation (PAP) definition

A

implementing a resistance exercise prior to an explosive movement has improved subsequent performance above the athletes perceived best

53
Q

physiological and mechanical factors affecting strength (x5)

A
  • types of muscular actions
  • length & velocity of isolated muscle
  • moment arm
  • joint velocity (muscle groups)
  • joint position (muscle groups)
54
Q

in a single muscle fibre, at what length is force the greatest (and why)

A
  • force is greatest at intermediate lengths & decreases at shorter & longer lengths
  • because… more binding sites available & consequently greater number of cross-bridge attachment at intermediate lengths
55
Q

at the whole muscle level, at what length is force the greatest (and why)

A

-strongest at most stretched due to elastic component of tendon

56
Q

in what type of muscle action is force production the greatest?

A

Eccentric

57
Q

variation in net muscle torque depends on… (x2)

A
  • the location of the attachments to the skeleton

- the contribution of multiple muscles to the net effect about a joint (one vs two joint muscles)

58
Q

what are the advantages when the tendon inserts further from the joint

A

the muscular moment arm will be longer and the mechanical advantage increased

59
Q

what are the disadvantages when the tendon inserts further from the joint

A
  • the muscle has to contract more to make the joint move through a given ROM
  • this translates to less speed
60
Q

how does the moment arm influence the demands of an exercise (dead lift)

A
  • dead lift = large moment arm which is a mechanical disadvantage
  • different stance = smaller moment arm, easier to produce force as hip is closer to the bar
61
Q

how does moment arm explain hamstring injuries (during sprint)

A
  • has smallest moment arm as it has to be stretched the most
  • inter muscle differences in hamstring moment arms about the hip & knee may be a factor contributing to the greater propensity for hamstring strain injuries to occur in the BF muscles
62
Q

how does moment arm explain the effect of stature (height)?

A

-tall athletes immediately at a disadvantage because levers are long and form huge resistance arms

63
Q

when and when is not PCSA equal to ACSA

A

PCSA = ACSA in parallel arrangements

PCSA does not = ACSA in pennate arrangements

64
Q

key properties of Type II Motor Unit

A
  • fast contraction velocity
  • fatiguable
  • increased Motor neuron size, fibre diameter & innervation ratio
65
Q

key properties of Type I Motor Unit

A
  • slow contraction velocity

- fatigue resistant

66
Q

how does high pennation influence muscles

A
  • increased strength

- pennation allows the PACKING OF MORE MUSCLE FIBRES PER CSA, thus generating greater force

67
Q

how does low pennation influence muscles

A

-increased range and velocity

68
Q

how does pennation influence muscle thickness

A

high pennation = decreased thickness

low pennation = increased thickness

69
Q

how does fibre length effect joint contractions

A
  • longer fibre length = greater ROM & velocity of contraction
  • shorter fibre length = increased force production BUT worse for fast contractions
70
Q

purpose of strength assessments

A
  • ability to distinguish between athletes at different levels
  • indicator of good athletic performance
  • correlation with athletic performance
  • sensitivity to training adaptations
  • availability of normative data for comparison
  • injury prevention
71
Q

benefits of strength testing

A
  • easily performed
  • execution of a similar movement to the one performed during the sporting activity
  • some quantification during submaximal lab based tests
  • suitable communication to coaches & athletes
72
Q

limitations of strength testing

A
  • typically little scientific analysis
  • some quantification techniques not as accurate as lab based tests
  • issues with accuracy and reliability
  • inability to test specific muscle groups
73
Q

strengths of isometric strength testing

A
  • muscle group isolation
  • accurate & reliable
  • quantification & detailed biomechanical analysis
  • allows collection of accurate & reliable EMG data
  • availability of normative data for comparisons
74
Q

limitations of isometric strength testing

A
  • specific joint position strength

- difficulty to elicit an MVC

75
Q

what 2 distinct bonds make up the ACL and what is their roles

A

anteromedial (protective when knee flexors) and posterolateral (protect when knee is extended)

76
Q

how could you reduce the chances of an ACL injury by altering the biomechanics of an athlete’s movement

A
  • decrease frontal plane knee joint angles
  • decrease frontal plane knee loading
  • increase sagittal plane knee joint angles
  • decrease sagittal plane knee loading
77
Q

key kinematic variables of a drop jump (x4)

A
  • impact loading rate 10-90%
  • peak impact force
  • average impact force
  • peak propulsive force
78
Q

how to calculate muscle tendon stiffness

A

maximal force / displacement CM

79
Q

what training methods have been observed to improve strength

A
  • iso-inertial training
  • isometric training
  • isokinetic training
  • neuromuscular electrical stimulation
80
Q

factors that can affect the type/magnitude of adaptations (x7)

A
  • age
  • training history
  • gender
  • genotype
  • concurrent activities
  • training programme design
  • nutritional status
81
Q

What adaptations did Cormie et al (2010) find in strength vs. power training (similarities and differences)

A

Similarities
-both methods increase jumping & sprinting performance (BUT via different pathways)
Differences
-power training = increased neural drive & force + RFD
-strength training = increased neural drive, muscle thickness, force and RFD

82
Q

what are the 3 primary stimuli of muscle hypertrophy

A
  1. tension
  2. muscle damage
  3. metabolic stress
83
Q

what is inclusion training + what does research say about it (include possible mechanisms)

A
  • method of restricting blood flow by placing an pneumatic cuff at the most proximal part of the arms/legs
  • been shown to increase muscle size and strength
  • possible mechanisms: increased MU recruitment, pooling of intramuscular metabolites
84
Q

strength improvements in the absence of increases in muscle size may result from… (x3)

A
  • non-hypertrophic muscular adaptations
  • neural adaptations
  • limitations with the techniques used to quantify changes in CSA
85
Q

potential sites of neural adaptations (x8)

A
  • enhanced output from supraspinal centres
  • reduced co-activation of antagonist muscles
  • greater activation of agonist & synergist muscles
  • enhanced coupling among spinal interneurons
  • changes in descending drive
  • shared input to motor neurons that increase MU synchronisation
  • greater muscle activation
  • heightened excitability & altered connections onto motor neurons
86
Q

to what extent does disuse halt the activation of involved muscles (Semmler et al, 2000 findings)

A
  • EMG of elbow flexor muscles with arm cast on
  • findings: decreased bicep brachii and brachioradialis by 38% & 29% respectively
  • also women displayed a greater reduction in EMG than men
87
Q

the underlying causes of immobilisation affecting muscle size

A
  • reduction in the rate of protein synthesis (Gibson et al, 1987)
  • loss of muscle fibres (Oishi et al, 1992)
88
Q

causes of hind limb suspension

A
  • no changes in EMG of suspended legs
  • muscle atrophy (greater in type I muscles)
  • increase in EMG of fore limb
89
Q

how does lower limb strength affect key gait characteristics in older adults

A

diminished peak GRF’s were associated with slower walking speeds…
-increased risk of mobility limitations, disability, poor health & loss of independence

90
Q

what is sarcopenia and what is it caused by

A 
What is..
-age associated reduction in muscle mass alongside reduction in muscle strength and/or function
Caused by...
-reduction in size of individual fibres
-loss of individual muscle fibres
-or BOTH
91
Q

which of these bones is commonly broken during strangulation;

  • atlas
  • axis
  • hyoid
  • mandible
A

Hyoid

92
Q

what is the name of the peg on the second cervical vertebra that projects upwards through the first cervical vertebra?

A

Dens

93
Q

what is the most commonly broken bone in the body

A

clavicle

94
Q

which of these is NOT a muscle forming part of the quadriceps femoris group;

  • vastus femoris
  • vastus lateralis
  • vastus medialis
  • vastus intermedius
A

vastus femoris

95
Q

what type of contraction will the trapezius muscle be undergoing during the raising phase of a barbell curl?

A

Isometric

96
Q

the cranial nervous system is made up of how many pairs of nerves?

A

12

97
Q

which of these is the only muscle which flexes both the hip and the knee;

  • rectus femoris
  • biceps femoris
  • gracilis
  • sartorius
A

Sartorius

98
Q

in which part of the body would you find the lunate bone

A

Wrist

99
Q

moving the thumb towards any other of the four fingers is known as…

A

Opposition

100
Q

what is the shoulder joint also known as?

A

Glenohumeral

101
Q

What bone has a surgical neck and an anatomical neck?

A

Humerus

102
Q

classic formula to calculate muscle size is…

A

total load lifted / BW (to the power of two thirds)

103
Q

what 2 lines make up the Q angle

A
  • ASIS to patella

- patella to tibial tubercule

104
Q

what can pes planus (flat feet) lead to…

A
  • internal tubial torsion

- increased internal femoral rotation

105
Q

how much more is muscle stiffness encountered in concentric than eccentric muscle contractions and down to what mechanism

A
  • x200 greater in concentric

- due to reflex control

106
Q

how does articular cartilage decrease stress on joints?

A

by increasing the load bearing area

107
Q

what’re the consequences from a ligament injury

A
  • loss of stability
  • joint misalignment
  • abnormal contact pressure
108
Q

3 stages of the SSC

A
  • preload
  • elastic energy stored
  • reflex potentiation
109
Q

what does the hysteresis loop show

A

-the energy absorbed during one loading-unloading cycle (area within loop on load-deformation graph)

110
Q

how do running shoes aid rear foot control

A

-materials of midsole should be different…
lateral = softer
medial = denser
-reduction of the flare can decrease joint pronation
-a neutral flare is ideal

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