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biomech 2 Flashcards

(67 cards)

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1
Q

What is extensibility in the musculotendinous unit?

A

The ability to be stretched or increase length.

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2
Q

What is elasticity in the musculotendinous unit?

A

The ability to return to normal resting length.

Two components: Parallel elastic component and Series elastic component.

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3
Q

What does the parallel elastic component do?

A

Supplies resistance when muscle is passively stretched (prevents over stretching).

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4
Q

What does the series elastic component do?

A

Acts as a spring to store elastic energy when tense muscle is stretched.

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5
Q

What is irritability in the musculotendinous unit?

A

The ability to respond to a stimulus.

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6
Q

What is the ability to develop tension in muscle function?

A

The contractile component of muscle function.

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7
Q

How many muscles does the human body have?

A

About 434 muscles.

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8
Q

What percentage of total body weight in adults is from muscles?

A

40-45%.

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9
Q

What are the two types of muscle fiber arrangements?

A

Fusiform and pennate.

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10
Q

What is the parallel (fusiform) fiber arrangement?

A

Fibers are roughly parallel to the longitudinal axis of the muscle.

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11
Q

What is a pro of fusiform fiber arrangement?

A

Larger range of length and velocity.

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12
Q

What is a con of fusiform fiber arrangement?

A

Smaller potential for physiological cross-sectional area (proportional to force development).

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13
Q

What is the pennate fiber arrangement?

A

Short fibers attach at an angle to one or more tendons within the muscle.

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14
Q

What happens when a pennate muscle shortens?

A

It causes a rotation about their attachment and increases the angle of pennation.

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15
Q

What is a pro of pennate fiber arrangement?

A

Larger potential physiological cross-sectional area (able to produce more force).

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16
Q

What is a con of pennate fiber arrangement?

A

Not all force developed is in line with tendons, which means some force will be lost.

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17
Q

What is a motor unit?

A

A single motor neuron and all the fibers it innervates.

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18
Q

What are the two types of muscle fiber types?

A

Fast twitch fibers and slow twitch fibers.

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19
Q

What is the difference between fast twitch and slow twitch fibers?

A

Fast twitch fibers reach peak tension faster and relax quicker, while slow twitch fibers reach a smaller peak later on but last longer.

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20
Q

What are the types of muscle fibers?

A

Type 1 (slow twitch oxidative), Type 2a (fast twitch oxidative glycolytic), Type 2b (fast twitch glycolytic).

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21
Q

What is concentric muscle action?

A

Shortening of the muscle; faster shortening results in lower force.

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22
Q

What is eccentric muscle action?

A

Lengthening of the muscle; faster lengthening results in greater force.

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23
Q

What is isometric muscle action?

A

No change in muscle length.

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24
Q

What is an agonist muscle?

A

The muscle whose activation produces an acceleration required for movement.

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25
What is an antagonist muscle?
The muscle whose activation has an acceleration on the opposite side, relaxing/slowing down.
26
What is a stabilizer muscle?
Acts to stabilize a body part against some force (e.g., deltoids stabilizing during bicep curls).
27
What is muscle tension?
The pulling force by muscles when activated; it is constant throughout the muscle, tendon, and bone in general.
28
What is torque?
The turning force created when a muscle pulls on a bone; it depends on the amount of force generated and the moment arm.
29
What is net torque?
Every force acting on a joint.
30
31
What is muscular strength?
Torque developed at a joint, derived from the tension the muscles can generate and the moment arms of contributing muscles with respect to the joint center.
32
What factors affect muscular strength?
1. Force: tension generating capability of muscle tissue affected by muscle cross-sectional area and training state. 2. Moment arm: affected by distance between muscle attachment to bone and joint center, and angle of muscle attachment to bone.
33
What is the muscle force-length relationship?
The force a muscle can produce is dependent on its length at that time, combining active force (contractile component) and passive force (elastic structures).
34
What is active insufficiency?
Failure to produce force when slack due to muscles being too shortened and crossing two joints.
35
What is passive insufficiency?
Restriction of joint range of motion when fully stretched due to muscles being too stretched at crossing two joints.
36
What is the stretch-shortening cycle?
Eccentric contraction followed immediately by concentric contraction, where elastic tissues store potential energy released during concentric contraction.
37
What is muscular power?
The product of muscular force and velocity of muscle shortening, calculated as force (tension) x velocity.
38
What is Newton's first law of motion?
A body will maintain its state of rest or constant velocity unless acted on by an external force.
39
What is Newton's second law of motion?
A force applied to a body causes an acceleration that is directly proportional to the force and inversely proportional to the body's mass. F = m x a.
40
What is Newton's third law of motion?
For every action, there is an equal and opposite reaction.
41
What is friction?
A force acting over the area of contact between two surfaces, preventing slipping and allowing acceleration.
42
What factors determine the magnitude of friction?
1. Applied force resisting friction. 2. Whether motion is occurring. 3. Coefficient of friction. 4. Magnitude of normal force.
43
What are rolling friction factors?
Coefficient of friction, normal force, radius of curvature, and contact area.
44
What protects our joints from friction?
A layer of fluid that reduces friction, influenced by the nature of the fluid, temperature, and velocity between surfaces.
45
Does greater surface area increase friction?
No, friction force is affected only by the coefficient of friction and normal force.
46
What is ground reaction force?
The force exerted by the ground, with a vertical component supporting body weight and a horizontal component aiding forward progression.
47
What is torque?
The rotational effect created by an applied force, calculated as T = applied force x moment arm length.
48
What are the four parts of a lever?
Fulcrum (A), bar, applied force (F), and resistance force (R).
49
What are the three classes of levers?
1st class: R–A–F (good for balance, ROM, and force). 2nd class: F–R–A (good for force). 3rd class: R–F–A (good for speed and ROM).
50
How is mechanical advantage calculated?
Mechanical advantage = force arm / resistance arm.
51
How do muscles create torque?
Muscles pull along their line of action, which runs from the muscle's origin to its insertion point on the bone.
52
What acts as axes of rotation during movement?
Joints act as axes of rotation.
53
What is the offset line of action in muscles?
Muscles typically pull offset from the axis of rotation, creating a lever arm or moment arm.
54
What is a moment arm?
The moment arm is the perpendicular distance between the line of action and the axis of rotation.
55
How does the moment arm affect torque?
A larger moment arm provides a greater mechanical advantage, allowing a muscle to apply more torque for the same amount of force.
56
What determines the effectiveness of a muscle in generating torque?
The angle of pull of the muscle.
57
When is torque maximized?
When the muscle's line of action is perpendicular to the bone.
58
How can the moment arm be calculated?
Moment arm can be calculated by L sin theta.
59
How can torque be calculated?
Torque can be calculated by T = applied force x moment arm.
60
What is the center of gravity (CG)?
CG is the point where mass and weight of a body are balanced.
61
What does the center of gravity represent?
It is a balance point about which all the particles of the object are evenly distributed.
62
Can the center of gravity be outside the physical limits of the system?
Yes, CG can be outside the physical limits of the system.
63
What is the difference between center of gravity and mass?
Center of gravity is the balance of weight with gravity, while mass is just with mass without gravity.
64
What is one method to locate the center of gravity?
Suspension: Suspend the object from a point and let it hang freely.
65
What is the balancing method for locating CG?
Balance the body on a board with a fulcrum; CG would be from the fulcrum up.
66
What is the reaction board method?
A board acts as a lever; one end on a fulcrum and the other on a scale to measure torque.
67
What does the segmental method use?
It uses film or electronic images of the body to estimate the location of the body CG.

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