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Biomechanics - Quantitative Analysis > Final > Flashcards

Final Flashcards

1
Q

What are the two common methods of recording EMG?

A

In-dwelling Electrodes and surface electrodes

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2
Q

Name three advantages to using in-dwelling Electrodes.

A
  1. Record activity from a single motor unit
  2. Access to deep musculature
  3. Little Cross-talk
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3
Q

Name three disadvantages to using in-dwelling Electrodes.

A
  1. Can be painful
  2. Single motor unit may not be representative of the entire muscle
  3. Limitations with recording dynamic muscle activity
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4
Q

How do Surface Electrodes work?

A

They record the difference in the electrical signal between two electrodes

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5
Q

Name three advantages to using surface electrodes.

A
  1. Easy to record
  2. Minimal discomfort
  3. Provides indication of global muscle activity
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6
Q

Name three disadvantages to using surface electrodes.

A
  1. Can be used only for superficial muscles
  2. Signal contaminated by cross-talk
  3. may affect movement patterns on subject
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7
Q

What are two examples of “noise” in an EMG signal?

A

Movement of the electrode or cable

Electronics

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8
Q

How does a differential amplifier work in a bipolar EMG? What is the new signal called?

A

It subtracts the m1-m2

It is called the Motor Unit Action Potential (MUAP)

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9
Q

What is the Henneman Size Principle? Why does the Nervous system recruit the MUs in this way?

A

The orderly recruitment from small MUs to large MUs

The reason for recruiting MUs in this way is to allow for smooth non-jerky production of force and allows the whole muscle to resist fatigue.

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10
Q

The electrodes must be placed on the muscle belly yet not on the innervation zone (motor end plates). T or F?

A

True

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11
Q

Where will the EMG not collect a signal on a muscle? Where will the signal be cancelled?

A

At the Tendon

At the innervation zone

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12
Q

What are three things that an EMG signal can tell us indirectly?

A

Timing of muscle activity

Force

Muscle Fatigue

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13
Q

What are the two steps of the most common way to process EMG?

A
  1. Take the absolute value of the signal (Full-Wave Rectification)
  2. Take an avg value over a certain time period
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14
Q

What is the electromechanical delay?

A

It is the delay between the neural activation of a muscle and the development of muscle tension
It lasts approximately 30-50ms, but depends on the muscle and joint.

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15
Q

The EMG-Force relationship is linear. T or F?

A

False it is non-linear

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16
Q

Does surface EMG of a submaximal contraction increase in amplitude with increaing muscle fatigue? If yes, why?

A

Yes, because more MUs are recruited to produce the same force

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17
Q

What is gait?

A

Gait is the pattern of movement of the limbs of animals, including humans, during locomotion over a solid substrate

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18
Q

What are some examples of human gait?

A

Walking
Running
Sprinting
Crawling

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19
Q

Gait progresses the body along a path while maintaining…

A

Weight-bearing stability
Conserving Energy
Absorbing shock

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20
Q

What are two reasons why we should we measure walking gait?

A
  1. To find out how we walk
  2. To use walking as a baseline measure to understand differences between healthy and unhealthy populations, Ages, Genders, and Races
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21
Q

Gait analysis involves the measurement of what three measures?

A

Kinematics, kinetics and EMG

22
Q

Describe Passive Marker Systems.

A

Using reflective markers and multiple cameras to analyse the kinematics of a gait
Multiple cameras are needed to digitize each marker and determine the 3D location

23
Q

Describe Active Marker Systems.

A

Similar to PMS, but the markers are triggered to illuminate.

24
Q

Describe Electromagnetic systems.

A

Track the position(X, Y, Z) and orientation of small sensors.
Used to measure Kinematics

25
Q

What is an Electrical Goniometer?

A

an electrical device for measuring joint angles.

simple and inexpensive compared to MoCap

26
Q

Other than EGs, EMS, PMS, and AMS; what else can be used to measure the kinematics of gait?

A

Accelerometers
Gyroscopes
Magnetometers

27
Q

What can be measured using a pressure mat? What is another device that can be used for the same measures?

A

A basic estimate of force and CoP movement.

A force plate (Better)

Kinetics

28
Q

What would combining kinematic and kinetics allow us to do?

A

It would allow us to use inverse dynamics to calculate joint forces, torques and muscle forces

29
Q

What are the percentages of the stance phase and swing phase that make up the gait cycle?

A

62% stance

38% Swing

30
Q

How much of the gait cycle does the double stance occupy?

A

25%

31
Q

What are main muscles that are active during the loading phase of the gait cycle?

A
  • Glutes
  • Quads
  • TA
32
Q

What are main muscles that are active during the Terminal stance phase?

A

-Calves

33
Q

What are main muscles that are active during the preswing phase?

A

TA

Iliopsoas

34
Q

What are main muscles that are active during the midswing?

A

TA

35
Q

What are main muscles that are active during the terminal swing?

A

TA

Hamstrings

36
Q

When does the hip change from extension to flexion during the gait cycle?

A

just before Toe-off

37
Q

When does the knee change from max flex to ext during the gait cycle?

A

during swing

38
Q

When does the ankle change from plantar to dorsi during the gait cycle?

A

just after Toe-off

39
Q

What determines the joint moment?

A

The muscle moment and the amplitude and line of action of the GRF

40
Q

What are the three functional tasks of walking?

A
  1. Weight acceptance
  2. Single-limb support
  3. Limb advancement
41
Q

What is a mechanical analogy of how we walk?

A

Inverted pendulum

42
Q

When is the only major energy expenditure during walking?

A

The redirection portion

43
Q

What are the 6 determinants of gait?

A
  1. Pelvic Rotation
  2. Pelvic Obliquity
  3. Knee flexion in stance phase
  4. Ankle mechanism
  5. Foot Mechanism
  6. Lateral Displacement of body
44
Q

What are two simple measures that can be used to compare between individuals?

A

Changes in swing stance ratio

Left/right Asymmetry

45
Q

What is the purpose of Lateral Trunk Bending? What are some common causes?

A

to reduce the forces in the abductor muscles and hip joint during single leg stance

Painful hip
Hip abductor weakness
Leg length discrepancy
Abnormal hip joint

46
Q

In a normal gait where does the LOA of the GRF vector pass with reference to the knee? Where does it pass in an individual who anterior trunk bends?

A

behind the knee and causes a knee flexor moment

In front of the knee and causes a knee extension moment

47
Q

What are the four gait abnormalities associated with functional leg length discrepancy?

A

Circumduction
Hip Hiking
Steppage
Vaulting

48
Q

What is the centre of mass?

A

The point on a body where all of the mass of the object can be concentrated

49
Q

What is the centre of gravity?

A

The point in a body or system around which its mass or weight is evenly distributed and through which the force of gravity acts

50
Q

Where is the CoG in a human?

A

55 to 57% of standing height along the middle

51
Q

What are the methods in which we can calculate the mass and CofG of a limb segment?

A
  1. Reaction Board Method
  2. Cadavers
  3. scanning techniques

Biomechanics - Quantitative Analysis (3 decks)

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