Lecture 9 - Biomechanics of Muscle Intro Flashcards
What is meant by the term “extensibility” in the context of the musculotendinous unit?
the ability to be stretched or to increase in length
How would you define “elasticity” concerning the musculotendinous unit?
ability to return to normal resting length following a stretch
Can you differentiate between the parallel elastic component and the series elastic component within the musculotendinous unit?
Parallel elastic component (parallel to cross bridge formation)
Series elastic component (in line with cross bridge formation)
What does “irritability” refer to regarding the musculotendinous unit?
ability to respond to a stimulus (muscle can be activated)
How would you define the “ability to develop tension” concerning muscle function?
the contractile component of muscle function
How many muscles does the human body approximately contain?
The human body contains approximately 434 muscles.
What proportion of the total body weight in adults is made up of skeletal muscle?
Skeletal muscle makes up approximately 40-45% of the total body weight in adults.
How many muscle pairs are responsible for bodily movements and posture?
75 muscle pairs are responsible for bodily movements and posture.
Define “muscle fiber” in the context of skeletal muscle structure.
A muscle fiber refers to a single, elongated muscle cell that contracts to generate force.
What does the term “motor unit” represent within the structural organization of skeletal muscle?
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)
Can you explain the concept of “fiber types” in skeletal muscle?
Fiber types refer to the classification of muscle fibers based on their physiological and biochemical properties, such as their contraction speed and metabolic characteristics.
What is meant by “fiber architecture” in the context of skeletal muscle structure?
Fiber architecture refers to the arrangement and orientation of muscle fibers within a muscle, which influences its function and mechanical properties.
Where does force development occur within skeletal muscle fibers?
occurs in cross bridge between actin and myosin
What distinguishes fast twitch (FT) muscle fibers from slow twitch (ST) fibers?
Fast twitch fibers can generate more force with a single twitch compared to slow twitch fibers.
In terms of tension development, how do fast twitch fibers differ from slow twitch fibers?
Fast twitch fibers reach peak tension and relax more quickly compared to slow twitch fibers.
What characteristic makes slow twitch fibers more advantageous in endurance activities?
Slow twitch fibers are more fatigue resistant, making them better suited for endurance activities that require sustained muscle contractions over an extended period.
How does the attachment of muscle fibers to tendons influence the force production capability of a muscle?
The attachment of muscle fibers to tendons determines how much force the muscle can produce.
What are the characteristics of a parallel (fusiform) fiber arrangement in muscles?
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
What is a potential disadvantage of the parallel fiber arrangement concerning force production?
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.
Describe the organization of muscle fibers in a pennate fiber arrangement.
In a pennate fiber arrangement, short fibers attach at an angle to one or more tendons within the muscle.
What advantages does the pennate fiber arrangement offer in terms of force production?
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
Cons of Pennate fibre arrangement:
Cons: not all force developed is in line with the tendons
How does the force developed in a pennate fiber arrangement relate to the angle of pennation?
Force in tendon = force in fibres x cos (angle of pennation)
Terms used to describe muscle contractions based on change in muscle length:
Concentric
Eccentric
Isometric
Concentric:
involving shortening
Eccentric:
involving lengthening
Isometric:
involving no length change
What roles are assumed by muscles?
agonists, antagonists, or stabilizers
role of an agonist muscle during movement.
Agonist: a muscle whose activation produces the acceleration required for a movement (needs to be on in order to do a certain activity)
What characterizes an antagonist muscle in the context of movement?
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.
When might a stabilizer muscle be engaged?
Stabilizer: acts to stabilize a body part against some other force
