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HUBS2503 > Lecture 12 - Recruitment of Muscle > Flashcards

Lecture 12 - Recruitment of Muscle Flashcards

1
Q

What is the primary tissue activated during exercise?

A

Skeletal muscle

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2
Q

What is the resting energy expendature of skeletal muscle

A

Skeletal Muscle: 54.4 kJ/kg (13.0 kcal/kg) per day

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3
Q

How much does skeletal muscle constitute a average adults body weight?

A

Constitutes around 42% of a healthy male’s body weight and 36% of a healthy female’s body weight.

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4
Q

What are the roles of skeletal muscle?

A

• Force
• Movement and posture
• Metabolism and thermoregulation
• Possible Endocrine Organ

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5
Q

What part of the NS is responsible for activation of skeletal muscle

A

Somatic - SNS (voluntary)

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6
Q

What are the 3 types of motor units and which muscle fibres do these motor units innervate?

A

• S - slow twitch; low tension; fatigue resistant (~Type I fibres)
• FFR - fast twitch; moderate force; fatigue resistant (~Type IIA fibres)
• FF - fast twitch; high force; highly fatiguable (~Type IIX/IIB fibres)

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7
Q

Why are muscle fibres and motor units varied?

A

Recruitment patterns adapt based on the task at hand, considering the required force, activity duration, energy availability, and fiber fatigue.

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8
Q

What is the size principle

A
  • The type and number of motor units recruited vary with increasing force requirements, affecting exercise intensity.
  • S motor units, with lower activation thresholds, are recruited first for activities of light to moderate intensity.
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9
Q

Describe the a) main activities, b) force required and c) contraction time for Type I muscle fibres

A

Aerobic (endurance)
Low to moderate
Slow

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10
Q

Describe the a) main activities, b) force required and c) contraction time for Type IIA muscle fibres

A

Anaerobic & Aerobic (power & moderate endurance)
Higher
Fast

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11
Q

Describe the a) main activities, b) force required and c) contraction time for Type IIX muscle fibres

A

Anaerobic (power)
High
Very fast

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12
Q

Describe the a) main activities, b) force required and c) contraction time for Type IIB muscle fibres

A

Anaerobic (power)
High
Extremely fast

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13
Q

Describe the a) main fuel stores, b) fatigue resistance and c) size of motor neurons for Type I muscle fibres

A

a) fats, b) high, c) small

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14
Q

Describe the a) main fuel stores, b) fatigue resistance and c) size of motor neurons for Type IIA muscle fibres

A

a) carbs and fats, b) moderate, c) medium

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15
Q

Describe the a) main fuel stores, b) fatigue resistance and c) size of motor neurons for Type IIX muscle fibres

A

a) ATP & carbs, b) low, c) large

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16
Q

Describe the a) main fuel stores, b) fatigue resistance and c) size of motor neurons Type IIB muscle fibres

A

a) ATP & carbs, b) very low, c) very large

17
Q

What does the colour of muscle fibres represent?

A

The color of muscle fibers (red vs. pale) is due to myoglobin content, which is tied to their oxidative capacity and role in oxygen storage.

18
Q

What type of muscle do most people have in legs and arms?

A

45-55% Type I in major arm and leg muscles

19
Q

When considering an endurance athlete and a power athlete, who would have type I and who would have type II fibres

A

E - Type I, P - Type II

20
Q

What is the relationship between motor unit to muscle fibre ratio and function?

A
  • Small motor units used for fine motor control (e.g., eye ~ 10 fibres/motor unit, finger ~ 300 fibres/motor unit)
  • Large motor units used for gross locomotor movements (e.g., gastrocnemius ~ 2000 fibres/motor unit)
21
Q

What is the relationship between power and velocity of movement

A

power increases and velocity increases

22
Q

What is the relationship between force and speed of movement

A

force decreases and speed increases

23
Q

Which fibre type produces more force and power and higher velocities?

A

Type II - much more

24
Q

what is synchronous and asynchronous recruitment?

A
  • Synchronous Recruitment: Utilized by highly trained individuals like weight-lifters to produce maximal forces.
  • Asynchronous Recruitment: Employed in activities requiring good fatigue resistance, such as continuous running, by cycling S/FFR motor units.
25
Q

What are the determinants of muscle force?

A

– Size of fibres
– Cross sectional area
– Muscle architecture
– Muscle length
– Sarcomere length
– Joint range of motion
– Velocity
– Fibre type

26
Q

What are the classifications of muscles based on the arrangement of fibres?

A

Parallel – fibres parallel to force-generating axis, Pennated- fibres at an angle relative to force-generating axis

27
Q

What is a complex muscle?

A

Muscle fibres do NOT run full length of the
muscle

28
Q

What are the effects of muscle pennation on force?

A

– Pennation decreases each fibre’s maximum force on the
tendon
– However, pennation increases fibre packing and sarcomere
number per physiological cross-sectional area (PCSA) of
muscles
– Net increase PCSA results in greater force

29
Q

What is the difference between teh length of fibres on producing force?

A

• Shorter fibres are usually stronger (force at a shorter length)
• Longer fibres can shorten faster (higher peak velocity)

30
Q

With regards to the quads and hamstrings, which is specialised for force and which for speed? Why?

A

• Quadriceps – specialised for force, pennated, shorter fibre length
• Hamstrings – specialised for speed, non-pennated, longer fibre length

31
Q

What is the relationship between muscle length and muscle force? Why is this the case?

A

Actin-myosin cross bridging developes force. Cross-bridge overlap influences the force generating ability of the muscle. Overlap is generally smallest at extremes of ROM and largest at the mid-point of ROM. This means that the muscles ability to generate force is typically larger mid-way through joints ROM.

32
Q

What does muscle architecture determine about a muscles ability to produce force at slower speeds?

A

Muscles with shorter fibres and largers PSCAs can produce more force at slower speeds

HUBS2503 (17 decks)

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