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HLTH3018 - Advanced Biomechanics > Exam Prep > Flashcards

Exam Prep Flashcards

HLTH3018

1
Q

What are the four electrical concepts?

A
  1. Potential difference (Volts)
  2. Current
  3. Conductance
  4. Resistance
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2
Q

What is the potential difference in human nerve cells?

A

70mV

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3
Q

Within nerve cells, is there a lower level of conductivity or resistance? What is this level in SI units?

A

A) Conductivity
B) 50-500 μS/cm2

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4
Q

Which has a higher level of conductivity, lean muscle or fat?

A

Lean muscle

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5
Q

What is the resting potential for:
A) Lean muscle
B) Fat

A

A) -85mV
B) -40mV

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6
Q

In the neuromuscular junction, the axon branches with what structure?

A

The perimysium.

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7
Q

____________ release ACh in the ___________..

A

A) Synaptic terminals
B) Synaptic cleft

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8
Q

What is the action potential threshold of an axon?

A

-60mV to -55mV

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9
Q

A gain in resting potential of an axon leads to what?

A

Depolarisation

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10
Q

Define a Motor Unit.

A

A single peripheral nerve (neuron) and the group of muscle fibres that it activates.

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11
Q

What system in the body controls the number of muscles that are activated?

A

The CNS

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12
Q

What two broad categories of information are required for the CNS to activate motor units?

A

How much force is required and are there any inhibiting factors (e.g., temperature, pain, etc.)

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13
Q

Different parts of a muscle contain _____________ that are task-specific. These are called ___________.

A

A) Population groups
B) Neuromuscular Compartments.

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14
Q

What are the terms given to:
A) Muscle contractile speed, and
B) Motor unit force?

A

A) Twitch
B) Tetanus

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15
Q

What are the SI units used for muscle tetanus?

A

Pulses per second (pps)

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16
Q

What is the measurement for maximal force in human tetanic muscle contractions?

A

80-100 pps

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17
Q

What is the conduction velocity of Type I muscle fibres?

A

60-70m/s

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18
Q

What is the twitch velocity of Type I muscle fibres?

A

110 milliseconds

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19
Q

What is the conduction velocity of Type IIb muscle fibres?

A

80-90m/s

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20
Q

What is the twitch velocity of Type IIb muscle fibres?

A

50 milliseconds

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21
Q

The Size Principle is the main factor in what biomechanical model?

A

The Orderly Motor Unit Recruitment model.

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22
Q

What is the main mechanism by which Orderly Motor Unit Recruitment occurs and what are the three main influences on this?

A

A) Spinal mechanisms
B) The size principle
C) Training history (although this will still occur)
D) Level of skill (control the firing)

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23
Q

The last motor units to be recruited will be the first to be what?

A

De-recruited.

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24
Q

Does efferent stimuli increase/decrease activation, and are these stimuli positive/negative, and facilitating/inhibiting?

A

A) Increases activation
B) Positive
C) Facilitating

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25
Q

Does afferent stimuli increase/decrease activation, and are these stimuli positive/negative, and facilitating/inhibiting?

A

A) Decreases activation
B) Negative
C) Inhibitory

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26
Q

What SSC mechanism can improve central drive due to the overstretching of agonist muscles?

A

Stretch/spinal reflexive afferent feedback.

27
Q

Inhibitory afferent feedback loops can reduce muscle activation most due to which three sensors?

A
  1. Type Ib afferents (GTOs)
  2. Type III afferents (mechanical stimuli, e.g., pressure)
  3. Type IV afferents (pain and temperature)
28
Q

What do the following afferent sensors detect within the muscles:
A) Muscle spindles
B) Pacinian corpuscles
C) GTOs?

A

A) Change in length
B) Balance
C) Change in tension

29
Q

How do mechanoreceptors support correct body position during movement, and when does this occur? Why?

A

A) They cause the muscles to stiffen/contract.
B) Peak stiffness occurs early.
C) This occurs to facilitate increased force for both performance and injury prevention.

30
Q

How does GTO activation change when you are aware/not aware of a landing occurrence or landing’s surface?

A

They facilitate the co-contraction of extensor muscles to prepare for impact when the occurrence or surface is known. Therefore, greater laxity in the muscles occurs when there are unknown variables.

31
Q

How can the following variables of resistance training be factored into programming to modify afferent responses within the muscles:
A) Specificity
B) Overload
C) Progression
D) Recovery?

A

A) Development of movement patterns and velocity
B) Must provide overload
C) Must continue to apply varying stimuli
D) We only adapt when we recover.

32
Q

How much can 1RM vary?

A

18% with a 36% range.

33
Q

Out of a strength-trained or power-trained athlete, which would have greater:
A) Force output, and
B) Rate of Force Development?

A

A) Strength-trained
B) Power-trained.

34
Q

Define Post-activation Potentiation.

A

A phenomenon by which muscle force is increased due to a previous contraction

35
Q

At what distance does a 100m sprinter generally decrease velocity?

A

40-60m

36
Q

What are the four main proposed mechanisms of PAP?

A
  1. Phosphorylation of regulatory light chains
  2. Increased recruitment of higher-order MUs.
  3. Acute changes in pennation angles, and
  4. Training history.
37
Q

Define an Innervation Number.

A

The number of fibres in an area of a muscle.

38
Q

What kinetic measure is the innervation number correlated to?

A

Peak Force.

39
Q

Orderly Motor Unit Recruitment is associated with what physiological principle?

A

The size principle.

40
Q

Are smaller or larger MUs recruited first?

A

Smaller

41
Q

According to Orderly Motor Unit Recruitment, which muscles are the first to be de-recruited? Why?

A

The last ones to be recruited. These will be the larger MUs that generate greater force and therefore use more energy.

42
Q

What is it that EMG sensors are picking up?

A

Small changes in voltage.

43
Q

Type II muscle fibres will show up as having _______ and ______ amplitude.

A

a) Faster
b) Higher

44
Q

What are the three types of EMG electrodes?

A

a) Surface
b) Needle
c) Fine wire

45
Q

What are intrinsic variables that affect EMG readings? Can these be controlled by an experimenter?

A

a) Physiologically and anatomically induced cross-talk such as co-activation of muscles and other structures with electrical output.
b) No, although steps can be taken to minimise their effects.

46
Q

What are extrinsic variables that affect EMG readings? Can these be controlled by an experimenter?

A

a) Cross-talk due to the location or orientation of the electrodes or due to wire movement or other electrical equipment.
b) Yes, an experimenter should be able to control these accurately with the correct protocols.

47
Q

What is the conductivity of:
a) Fat
b) Muscle?

A

a) -40mV
b) -85mV

48
Q

What are the main advantages and disadvantages of surface EMG usage?

A

a) Advantages:
- More repeatable
- Not dependent on exact positioning
b) Disadvantages:
- Only large and superficial muscles can be analysed
- Prone to cross-talk and pressure fluctuations.

49
Q

Where should surface EMG sensors be placed on a muscle?

A

Over the muscle’s largest population of MUs.

50
Q

When reading EMG measures, __________ is the number of signals over time and _________ is the height of the signal.

A

a) Frequency
b) Amplitude.

51
Q

What is the name of the function created in bipolar surface EMG sensors to eliminate cross-talk? How does it work?

A

a) Common-Mode Rejection (CMR)
b) CMR works as the two sensors are placed apart and ‘listen’ simultaneously. If they hear the same noise, this is eliminated as cross-talk.

52
Q

What are the three stages of EMG data collection required to record usable data?

A
  1. Full-Wave Rectification (FWR)
  2. Application of a linear envelope
  3. Normalisation to MVIC.
53
Q

What is Full-Wave Rectification (FWR) and why is it important?

A

The process of turning EMG values into absolute values as opposed to negative and positive. This is important as otherwise, the average would be zero.

54
Q

Why do you need to apply a linear envelope to EMG data readings?

A

To smooth averaged data to be able to read the measurements without interference from outlier data points.

55
Q

When normalising EMG data, how should this be written?

A

As a percentage of MVIC.

56
Q

What is the name of the sampling rate theorem for motion capture and what does it state?

A

a) Nyquist-Shannon
b) The sampling rate used to capture motion needs to be at least twice that which is required for the movement.

57
Q

___________ segments move faster than ___________ segments.

A

a) Distal
b) Proximal

58
Q

When using EMG, the recorded signal is equal to the true ______ + ______.

A

a) Signal
b) Noise

59
Q

What is polynomial smoothing and what type is best for smoothing data?

A

It is a smoothing technique for raw EMG data that fits a number of inflection points over the raw data.
Higher-order polynomials will smooth the data better.

60
Q

What are splines and when are they best used?

A

Splines are used as a smoothing technique for raw EMG data.
They are used to interpolate to fill gaps in the data or to time-match intra-individual trial data or different durations.

61
Q

a) Explain the use of moving average smoothing in EMG data collection.
b) What is the main limitation of this technique?

A

a) It is a smoothing technique in which you choose a specific interval of data points (e.g., n = every 3rd or 5th etc.) to achieve a best-fit line.
b) It does not distinguish between signal and noise.

62
Q

How does Fourier smoothing work?

A

It transforms EMG data from the time domain to the frequency domain. This creates sine waves of varying amplitudes to show occurrences of specific data.

63
Q

a) Describe how digital filtering is used as a smoothing technique for raw EMG data.
b) What is the difference between a low-, high-, and band-pass filter?

A

a) It uses weighted coefficients to attenuate specified frequencies of suspected noise.
b) Low-band pass allows low-frequency data points through and attenuates the high frequency while a high-band filter does the opposite. A pass-band filter sets a mid-range bandwidth and attenuates all noise outside this range.

64
Q

What is a Butterworth digital filter and how does it work?

A

It is a tool used to smooth raw EMG data. It works by creating roll-offs instead of cut-offs for data over a specific frequency.

HLTH3018 - Advanced Biomechanics (2 decks)

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