Lecture 9 - Biomechanics of Muscle Intro

Question 1

What is meant by the term “extensibility” in the context of the musculotendinous unit?

Answer 1

the ability to be stretched or to increase in length

Question 2

How would you define “elasticity” concerning the musculotendinous unit?

Answer 2

ability to return to normal resting length following a stretch

Question 3

Can you differentiate between the parallel elastic component and the series elastic component within the musculotendinous unit?

Answer 3

Parallel elastic component (parallel to cross bridge formation)

Series elastic component (in line with cross bridge formation)

Question 4

What does “irritability” refer to regarding the musculotendinous unit?

Answer 4

ability to respond to a stimulus (muscle can be activated)

Question 5

How would you define the “ability to develop tension” concerning muscle function?

Answer 5

the contractile component of muscle function

Question 6

How many muscles does the human body approximately contain?

Answer 6

The human body contains approximately 434 muscles.

Question 7

What proportion of the total body weight in adults is made up of skeletal muscle?

Answer 7

Skeletal muscle makes up approximately 40-45% of the total body weight in adults.

Question 8

How many muscle pairs are responsible for bodily movements and posture?

Answer 8

75 muscle pairs are responsible for bodily movements and posture.

Question 9

Define “muscle fiber” in the context of skeletal muscle structure.

Answer 9

A muscle fiber refers to a single, elongated muscle cell that contracts to generate force.

Question 10

What does the term “motor unit” represent within the structural organization of skeletal muscle?

Answer 10

A motor unit consists of a single motor neuron and all the muscle fibers it innervates.

Considered the functional unit of the neuromuscular system (the smallest piece of the muscle that the brain can control)

Question 11

Can you explain the concept of “fiber types” in skeletal muscle?

Answer 11

Fiber types refer to the classification of muscle fibers based on their physiological and biochemical properties, such as their contraction speed and metabolic characteristics.

Question 12

What is meant by “fiber architecture” in the context of skeletal muscle structure?

Answer 12

Fiber architecture refers to the arrangement and orientation of muscle fibers within a muscle, which influences its function and mechanical properties.

Question 13

Where does force development occur within skeletal muscle fibers?

Answer 13

occurs in cross bridge between actin and myosin

Question 14

What distinguishes fast twitch (FT) muscle fibers from slow twitch (ST) fibers?

Answer 14

Fast twitch fibers can generate more force with a single twitch compared to slow twitch fibers.

Question 15

In terms of tension development, how do fast twitch fibers differ from slow twitch fibers?

Answer 15

Fast twitch fibers reach peak tension and relax more quickly compared to slow twitch fibers.

Question 16

What characteristic makes slow twitch fibers more advantageous in endurance activities?

Answer 16

Slow twitch fibers are more fatigue resistant, making them better suited for endurance activities that require sustained muscle contractions over an extended period.

Question 17

How does the attachment of muscle fibers to tendons influence the force production capability of a muscle?

Answer 17

The attachment of muscle fibers to tendons determines how much force the muscle can produce.

Question 18

What are the characteristics of a parallel (fusiform) fiber arrangement in muscles?

Answer 18

In a parallel (fusiform) fiber arrangement, fibers run roughly parallel to the longitudinal axis of the muscle. This arrangement allows for a larger range of length and velocity during muscle contraction.

Pro: larger range length and velocity (muscles are pulling in line)

The range of motion is more, but the force of contraction is less

Question 19

What is a potential disadvantage of the parallel fiber arrangement concerning force production?

Answer 19

potential disadvantage is the smaller potential for physiological cross-sectional area, which is proportional to force development. In this arrangement, there is less room for fibers to be parallel, limiting force production capability.

Question 20

Describe the organization of muscle fibers in a pennate fiber arrangement.

Answer 20

In a pennate fiber arrangement, short fibers attach at an angle to one or more tendons within the muscle.

Question 21

What advantages does the pennate fiber arrangement offer in terms of force production?

Answer 21

larger potential for physiological cross sectional area (you can stack a lot of fibres in parallel); you can also modify muscle fibre length during contraction

The range of motion is less but the force is greater

Question 22

Cons of Pennate fibre arrangement:

Answer 22

Cons: not all force developed is in line with the tendons

Question 23

How does the force developed in a pennate fiber arrangement relate to the angle of pennation?

Answer 23

Force in tendon = force in fibres x cos (angle of pennation)

Question 24

Terms used to describe muscle contractions based on change in muscle length:

Answer 24

Concentric
Eccentric
Isometric

Question 25

Concentric:

Answer 25

involving shortening

Question 26

Eccentric:

Answer 26

involving lengthening

Question 27

Isometric:

Answer 27

involving no length change

Question 28

What roles are assumed by muscles?

Answer 28

agonists, antagonists, or stabilizers

Question 29

role of an agonist muscle during movement.

Answer 29

Agonist: a muscle whose activation produces the acceleration required for a movement (needs to be on in order to do a certain activity)

Question 30

What characterizes an antagonist muscle in the context of movement?

Answer 30

Antagonist: a muscle whose activation produces an acceleration in a direction opposite that required for a movement (doesn’t need to be on)

It doesn’t necessarily need to be activated during the movement.

For instance, the triceps brachii acts as the antagonist to the biceps brachii during a bicep curl.

Question 31

When might a stabilizer muscle be engaged?

Answer 31

Stabilizer: acts to stabilize a body part against some other force