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Gait lecture Flashcards

1
Q

What is a concentric contraction?

A

It shortens the muscle and its fibers

Concentric contractions are often involved in lifting movements.

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2
Q

What is an eccentric contraction?

A

It lengthens the muscle and its fibers

Eccentric contractions are important for controlling movements and absorbing shock.

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3
Q

What is an isometric contraction?

A

Length of the muscle does not change, there is no velocity

Isometric contractions are often used for stability.

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4
Q

What is a gait cycle?

A

Movement starting with ground contact of foot and end with same foot ground contact

A gait cycle is a complete movement of walking or running.

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5
Q

How are gait phases divided?

A

Stance 60%, Swing 40%

This division helps in understanding the mechanics of walking.

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6
Q

What is a step?

A

Ground contact of one leg, then ground contact of the other

Steps are fundamental to walking and running mechanics.

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7
Q

What is a stride?

A

Movement during one gait cycle, two steps, one with each leg

Strides are used to measure walking or running efficiency.

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8
Q

How to walk faster?

A

Increase cadence and increase step length

A short person must increase cadence to walk as fast as a tall person.

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9
Q

Difference between walking and running?

A

Walking: one foot always in contact with the ground. Running: presence of a fly phase = two feet are off the ground

This difference is crucial for understanding biomechanics.

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10
Q

What are the stance phases?

A

60% of gait IC+LR+MS+TS+PS

These phases are critical for weight support during walking.

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11
Q

What is the 0% phase of the stance?

A

Initial contact: instant when the foot contacts the ground

This phase marks the beginning of the gait cycle.

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12
Q

What is the 1-15% phase of the stance?

A

Loading response: From immediately after IC –> to lift of contralateral extremity from ground

This phase involves weight shifting.

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13
Q

What is the 15-25% phase of the stance?

A

Mid-stance: From the lift of the contralateral extremity –> to the point where the ankles align in the frontal plane

Mid-stance is crucial for balance.

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14
Q

What is the 25-50% phase of the stance?

A

Terminal stance: From the moment when ankles cross –> to just before initial contact of the contralateral extremity

This phase prepares for the next step.

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15
Q

What is the 50-60% phase of the stance?

A

Pre-swing: From initial contact of contralateral extremity –> to just before lift of ipsilateral extremity

Pre-swing involves unloading weight.

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16
Q

What phases offer double support?

A

Loading response and Pre-swing

Double support occurs when both feet are on the ground.

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17
Q

What are the swing phases?

A

40% of gait, IS+MS+TS

Swing phases are essential for limb movement and clearance.

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18
Q

What is the 60-80% phase of the swing?

A

Initial swing: Lift of extremity from the ground -> to maximum knee flexion

This phase is crucial for limb advancement.

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19
Q

What is the 80-90% phase of the swing?

A

Mid swing: Immediately after knee flexion -> to vertical tibia position

This phase prepares the leg for landing.

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20
Q

What is the 90-100% phase of the swing?

A

Terminal Swing: Following vertical tibia position -> to just before IC

This phase transitions back to the stance phase.

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21
Q

What is the goal of gait?

A

Progress forward

Forward progression is the primary objective of walking or running.

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22
Q

What is the goal of stance?

A

Provide support, absorb shock, provide forward and backward force for progression

Stance phases are critical for stability.

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23
Q

What is the goal of swing?

A

Limb clearance, limb placement, transfer momentum

Proper swing mechanics are essential for efficient movement.

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24
Q

Are joint angles kinematic or kinetic variables?

A

Kinematic

Kinematic variables focus on motion without considering forces.

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25
What is a device that could measure joint angles during gait?
Electrogoniometer ## Footnote Electrogoniometers are used in biomechanics research.
26
what joint is this
Ankle ((dorsiflexion = +)
27
what joint is this
Knee (flexion = +)
28
what joint is this
Hip (flexion = +)
29
What is the center of mass?
The equal balance point ## Footnote The center of mass (COM) is a crucial concept in biomechanics and physics, representing the point at which the mass of an object is evenly distributed.
30
What happens to the center of mass (COM) during gait?
It moves laterally, vertically, and in combination of both ## Footnote This movement can be visualized as an infinity loop, reflecting the dynamic nature of walking.
31
How does the center of mass (COM) move laterally?
If weight is on R leg, COM goes to R ## Footnote This lateral shift helps maintain balance and stability during movement.
32
How does the center of mass (COM) move vertically?
COM is higher in single stance, COM is lower in double stance ## Footnote The vertical movement of the COM is influenced by the phase of gait.
33
Provide an example of combination of vertical and lateral displacement of COM.
If shift weight on R leg and only stand on R leg = COM moves to the right + COM moves up. When we bring L leg down = COM moves to middle and down. When weight shifts to L leg = COM moves to left upwards ## Footnote This illustrates the complexity of COM movement during dynamic activities.
34
What does the equation ΣFy = may represent?
It represents the relationship between ground reaction forces, body weight, and acceleration of the COM ## Footnote Here, ΣFy is the sum of vertical forces, may is the mass times acceleration of the COM, W is body weight, and GRF is ground reaction force.
35
What is the relationship between GRF and body weight during stance on double support?
GRF < 100% because shared between both feet ## Footnote This indicates that each foot bears part of the total weight.
36
What happens to the center of mass (COM) during stance on one leg?
COM accelerates upwards, so ay is + and GRF > W, GRF is above 100% ## Footnote This indicates that more force is exerted by the ground than the weight of the body to support the single leg stance.
37
What occurs when the body drops down during gait?
COM accelerates downwards, ay is – and GRF < W, GRF is below 100% ## Footnote This phase is critical for understanding how forces change during movement.
38
What happens when GRF is negative?
GRF is posterior
39
What happens when GRF is positive?
GRF is anterior
40
What does the 3rd law state about unbalanced forces?
An unbalanced force has an equal and opposite force in the opposite direction
41
What occurs when 0-20% of the foot pushes on the ground?
GRF pushes posterior
42
What occurs when 40-50% of the foot pushes on the ground?
GRF pushes anterior
43
What are net joint reaction forces and moments?
Summed effects of all structures (muscles, ligaments…) applying a force/moment to the joint
44
Why do we use the net joint reaction force?
Taking all structures individually would create too many variables for only 6 equations
45
What are inverse dynamics?
Calculate net joint forces and moments using kinematics information, inertial properties, and external forces
46
What is forward dynamics?
Use computer-simulated models and previously known force values to predict movement
47
How to use inverse dynamics?
Separate body into rigid segments, use Newton's laws
48
What is an example of inverse dynamics?
Use force plate to find force at foot, then calculate forces at joints up to the desired joint
49
What equation is used in inverse dynamics for slow movements?
ΣF = 0, ΣM = 0
50
What is used in inverse dynamics for fast movements?
Dynamic equations, ΣF = ma, ΣM = Iα
51
What are limitations of inverse dynamics?
Segments are not always rigid, sensitive to input data, cannot determine individual muscle contraction
52
What is a net external moment on a joint?
Moments applied to the joint due to external forces like GRF and Gravity
53
What is a net internal moment on a joint?
Moment applied to the joint by muscles and soft tissue
54
How does GRF act as an external moment?
GRF causes alternating extension and flexion moments at the knee
55
What is the relationship between external and internal moments?
They are opposite; when external causes net flexion, internal causes net extension
56
What type of contraction is most common in gait?
Eccentric
57
Muscle activation is measured with what?
Electromyography (EMG)
58
What can happen to muscle activation in people with disease?
Co-contraction can be increased to compensate
59
What is the role of the gluteus medius in gait?
Controls pelvic drop and works eccentrically
60
Why is looking only at the internal moment graph misleading?
It does not distinguish between co-contractions
61
What is power in biomechanics?
Rate of doing work (in watts) = joint moment x angular velocity
62
What does concentric contraction do to power?
Generates power (positive)
63
What does eccentric contraction do to power?
Absorbs power (negative)
64
What does isometric contraction do to power?
Power = 0
65
What caution should be considered when looking at muscle activation?
Muscles can impact joints they do not cross, and movement can continue even if muscle is turned off
66
What is the stretch-shortening cycle?
Muscle lengthens eccentrically then shortens concentrically to generate force
67
How to determine if a joint is absorbing or generating power?
Look at the power graph: + generates power, - absorbs power
68
How to identify which muscle is responsible for power generation?
Look at activation graphs for higher activation
69
How to determine if contraction is isometric, concentric, or eccentric?
Look at the power graph: negative is eccentric, positive is concentric also look at joint angles to determine if muscle shortens or lengthens

Biomechanics (13 decks)

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