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HLTH3018 - Advanced Biomechanics > Weeks 1-5 > Flashcards

Weeks 1-5 Flashcards

1
Q

Define Independent Variables

A

The variables that are not influenced by other variables and are the measure by which other variables are assessed.
Usually plotted on the x-axis.

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2
Q

Define Dependent Variables

A

The variable that is being assessed for changes.
Usually plotted on the y-axis.

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3
Q

Forces are used to do what?

A
  • Move objects
  • Stop objects
  • Change the direction of objects
  • Change the speed of a moving object
  • Balance another force to keep an object still.
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4
Q

What are the main examples of External Forces?

A
  • Gravity
  • Friction
  • Air resistance
  • Water resistance:
    – Wave drag and form drag
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5
Q

What is an example of Internal Forces?

A

Actions of muscles and tendons on skeletal muscles.

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6
Q

Define the Impulse-Momentum Relationship.

A

The impulse experienced by an object is equal to the change in momentum it undergoes. This emphasises how force applied over time alters an object’s velocity.

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7
Q

Define Kinematics

A

The description of motion without the consideration of the forces required.
It describes a movement, e.g., acceleration, position, velocity, etc.

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8
Q

Define Kinetics

A

The study of forces and their effects on the motion of objects, e.g., the force of friction, air resistance, propulsive forces, etc.

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9
Q

Describe the law of conservation of angular momentum.

A

The total angular momentum of a system remains constant if no external torques act on the system.

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10
Q

What is the formula to calculate torque?

A

Torque = rF

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11
Q

Define Anthropometry

A

The description of bodies, segments, and anatomical locations.

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12
Q

What are some main muscle properties that affect muscle mechanics?

A
  • Tension variance with length
  • Mass
  • Elasticity
  • Viscosity
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13
Q

What is EMG and what key relationships does its use show?

A
  • Electromyography
  • Muscle activation and tension
  • Muscle recruitment and fatigue status.
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14
Q

What is the relationship between the centre of mass (COM) and the base of support (BOS) when increasing/decreasing stability?

A

When the COM is outside of the BOS, this will create an eccentric force and reduce stability, however, when the COM is within the BOS, stability is increased due to a more linear GRF.

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15
Q

How can segment length be manipulated to increase/decrease angular momentum and how does this apply to the law of inertia?

A

Increasing the segment length increases angular momentum, whereas decreasing the segment length decreases angular momentum. The law of inertia states that the total angular inertia must remain the same unless acted on by an external force and, therefore, as segment length is reduced, angular velocity will increase and vice versa.

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16
Q

What is the formula to calculate an object’s inertia (point mass)?

A

I = mr^2

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17
Q

What are the key kinematic and kinetic considerations regarding rotational movement in biomechanics?

A

Kinematics:
- Joint centre (point of rotation)
- Radius of gyration
Kinetics:
- Segment mass
- COM
- Moment of inertia

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18
Q

What are the six types of joints in the human body?

A
  1. Hinge
  2. Pivot
  3. Ball and socket
  4. Condyloid
  5. Gliding
  6. Saddle
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19
Q

What aspect of a joint determines the degrees of freedom between two segments?

A

The joint structure.

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20
Q

What are the two ways in which segment mass is determined?

A
  1. Ms = Ps (%) x m total
  2. Determined through regression equations
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21
Q

What does ‘Regression’ mean?

A

Prediction

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22
Q

Define Centre of Mass (COM)

A

The point within an object where the mass of that object can be assumed to be concentrated.

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23
Q

Define the Net Gravitational Moment.

A

The overall tendency of an object to rotate due to the force of gravity acting upon it.

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24
Q

Describe the relationship between COM and Net Gravitational Moment.

A

The distribution of an object’s mass relative to its COM will influence the rotational equilibrium or Net Gravitational Moment.

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25
Q

In what order are the Load, Effort, and Fulcrum in a 1st Class Lever?

A

Effort, Fulcrum, Load

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26
Q

In what order are the Load, Effort, and Fulcrum in a 2nd Class Lever?

A

Effort, Load, Fulcrum

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27
Q

In what order are the Load, Effort, and Fulcrum in a 3rd Class Lever?

A

Fulcrum, Effort, Load

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28
Q

What class of lever is most found within the human body?

A

3rd Class

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29
Q

What are Segmental Interial Parameters often referred to as in biomechanics?

A

R Values

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30
Q

How are R Values calculated?

A

By determining the distance from each end of the segment to its centre of mass (COM) relative to the total length of the segment.

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31
Q

Define the Kinetic Link Method in the analysis of biomechanical movement.

A

A system to describe human movement using the idea that the body is a series of interconnected rigid segments, and the movement of one segment influences the movement of adjacent segments.

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32
Q

What is the main limitation of the Kinetic Link Method when assessing trunk movement?

A

The trunk is usually modelled as 1, 2, or 3 segments despite intervertebral joint DOF.

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33
Q

What is the formula for the Moment of Inertia?

A

I = m x r^2

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34
Q

What is the Parallel Axis Theorem?

A

The theorem that states that an object’s moment of inertia anywhere parallel along its axis is directly proportional to its distance from the COM.

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35
Q

When using digital analysis of segmental movements (i.e., Vicon), what is important to remember considering knee joint centre and axes of rotation?

A

That the knee has slight rotation along its axis (0-5 degrees) due to the screw-home-motion. This will not be anticipated in the simulation.

36
Q

Explain the Spring-Mass Model as it relates to running gait.

A

The Spring-Mass Model explains how elastic energy is used in running gait. It states that our tendons and muscles are compressed like springs storing elastic energy during the contact and stance phases. This stored energy is released during the push-off phase, facilitating forward propulsion. This process enhances running performance and reduces the overall metabolic cost.

37
Q

Define Parallel, Parallax and Perspective errors in 2D motion capture.

A

Parallel Error: a misalignment of a camera’s angle resulting in a distortion of the true position of markers or body segments.
Parallax Error: an error occurring due to the displacement of markers or objects when viewed from different camera perspectives.
Perspective Error: when the position or perspective of the observer affects the perception of the size, shape, or position of objects.

38
Q

What is the main limitation of Opto-electronic motion capture systems such as Vicon?

A

Limited to indoor use which restricts the ecological validity of the data.

39
Q

What are the four main methods for motion capturing?

A
  1. 2D digital cameras
  2. Opto-electronic (Vicon) 3D systems
  3. Marker-free systems
  4. Doppler radar systems
40
Q

Marker-free motion capture systems use what segment tracking?

A

Gross segment tracking

41
Q

What are marker-free motion capture systems generally used for?

A

Assessing motor control competencies, functional testing and rehabilitation, such as reaction time, in elderly populations.

42
Q

What is a common error when using Doppler radar systems?

A

The cosine effect angle.

43
Q

How do timing gates report speed and acceleration?

A

They interpolate what happened between data points and derive speed and acceleration from distance and time.

44
Q

What are the common sampling rates for 2D animation and high-speed (HS) cameras?

A

2D: 25Hz, HS Cameras: 1000Hz

45
Q

What is the theorem used to assess the suitability of sampling frequency for motion capture systems and what does it state?

A

The Nyquist-Shannon sampling theorem:
The sampling speed must be at least twice the highest frequency of the action, otherwise, you will get an inaccurate movement record.

46
Q

What are the five stretch-shortening cycle mechanisms?

A
  1. Use of movement
  2. Time for activation
  3. Storage and release of elastic energy
  4. Stretch/spinal reflexes
  5. Force potentiation
47
Q

What are the three forces reported on a force profile trace?

A

Fx: Mediolateral force
Fy: Anterior-posterior force
Fz: Vertical GRF

48
Q

What does the term “Segmental Inertial Parameters” refer to?

A

The mass of individual body segments as a percentage of whole-body mass.

49
Q

When reading DEXA T-scores, what does a + and a - measurement mean?

A

+ = > average
- = < average

50
Q

What anthropometric characteristics are optimal for endurance athletes regarding the lower limb and BMI? Why?

A

Smaller calf girth, shorter legs, and a lower BMI reduce the inertia of the body and moving segments.

51
Q

What are two examples of sports that favour shorter limbs and why?

A
  1. Gymnastics: lower MoI, lower resistance to angular impulse.
  2. Weightlifting: Less torque created by the load and less distance to lift the weight.
52
Q

What is the difference between stress and strain forces?

A

Stress: pushing force
Strain: pulling force

53
Q

What is the common sampling rate of force plates?

A

1000Hz

54
Q

If a small and large rubber band are pulled to the same length, which will shoot further when released? Why?

A

The shorter band. Because the smaller band has stored more elastic energy as it has experienced a greater change in length.

55
Q

What is the formula for Power?

A

P = F x v

56
Q

What is the formula for Velocity?

A

V = s / t

57
Q

When using multi-joint isokinetic dynamometry, what is required to assess Power and why?

A

Force plates (FP) and a linear position transducer (LPT).
The FP provide information on Force, while the LPT measures velocity (s / t).
Power = Force x velocity

58
Q

What is the formula for pressure (stress)?

A

Pressure = Force / Area

59
Q

What is a forward dynamics approach?

A

When the kinetics such as GRF are known we can calculate the kinematics, e.g., force applied to a ball, calculating a ball’s resultant motion.

60
Q

What is an inverse dynamics approach?

A

When kinematics are known and kinetics are calculated from them, e.g., if the torque and the mass of a golf club are known, then we can calculate the force exerted by the muscles during the swing.

61
Q

What are the three requirements for inverse dynamics? Provide examples.

A
  1. Body segment kinematics: position, acceleration.
  2. Body segment inertial parameters: CoM location, MoI.
  3. Any external forces: GFR
62
Q

What is the formula for Work?

A

W = Fs

63
Q

Define Contractility.

A

The ability to shorten and produce tension.

64
Q

Define Extensibility and Elasticity in the context of muscle physiology.

A

The ability of a muscle to be stretched and return to normal length.

65
Q

What does Adaptability provide to the MTU?

A

It allows the growth and regeneration capacity of the MTU.

66
Q

Define Excitability or Irritability in the context of muscle physiology.

A

The ability to respond to stimulation.

67
Q

Define Conductivity in the context of muscle physiology.

A

The ability of a muscle to propagate an excitation wave.

68
Q

What is the difference between muscle Macroscopic and Microscopic anatomy?

A

Macroscopic: what we can see; MT junction, epimysium, perimysium, endomysium, and muscle fibres.
Microscopic: what we can’t see; sarcolemma, myofibrils, and muscle sarcomeres.

69
Q

Myosin are the _____ filaments, and Actin are the _____ filaments.

A

Myosin: thick
Actin: thin

70
Q

What is the name of the tendon-like structure that runs through a pennated muscle?

A

Aponeurosis.

71
Q

What is generally the strongest pennation format, unipennate, bipennate, or multipennate?

A

Bipennate

72
Q

Does Physiological CSA (PCSA) or Anatomical CSA (ACSA) reflect the force generation capacity of a muscle?

A

PSCA.

73
Q

Long fibres allow ______ ROM over a _____ contraction time giving _____ shortening speed.

A

a) large
b) short
c) greater

74
Q

Short fibres _____ metabolic expenditure as they do _____ work to cover _____ ROM compared to longer fibres.

A

a) increase
b) more
c) equal

75
Q

What percentage of tendons are made of water?

A

70%

76
Q

Define hysteresis in the context of tendon physiology.

A

The tendency of a tendon to lose elastic storage capacity after being stretched and released over time.

77
Q

What is the formula for elastic potential energy?

A

E = 1/2 k.x^2
k = stiffness
x = elongation

78
Q

Stiffer tendons are _____ to stretch and will store ____ energy, therefore, they are good for _____ running.

A

a) harder
b) more
c) sprint

79
Q

What is the formula for strain?

A

Change of length / resting length.

80
Q

What is Hooke’s Law?

A

Hooke’s law states that the force needed to extend or compress a material is directly proportional to the amount of deformation produced, within the material’s elastic limit.
F = -kx

81
Q

What is Young’s Modulus?

A

The ratio of the stress (force per unit area) applied to the object and the resulting axial strain (displacement or deformation)

82
Q

Is a high or low hysteresis optimal for efficiency? What does this mean?

A

High.
A high amount of the elastic potential energy is returned.

83
Q

What is the hysteresis of tendons and muscles?

A

Tendons: 85-93%
Muscles: 40-60%

84
Q

What are the constituents of the Three Element Hill Muscle Model?

A
  1. Contractile element (CE): sarcomere
  2. Parallel element (PE): connective tissue
  3. Series element (SE): tendon
85
Q

Define the length-tension relationship.

A

The maximal isometric force of isolated sarcomere is length-dependent.

HLTH3018 - Advanced Biomechanics (2 decks)

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