week 6

Question 1

what can we improve when it comes to metabolic pathways?

Answer 1

• faster phosphagen system
• faster anaerobic glycolysis
• faster aerobic system
• more efficient aerobic system

Question 2

what are the neural factors that can influence muscle tension?

Answer 2

1. motor unit recruitment (number coding)
2. neuron firing frequency (rate coding)
3. inter-muscular coordination

Question 3

write down and annotate the table on page 3 of muscle tension III

Question 4

what is a motor unit

Answer 4

1 motor neuron and all the muscle fibers it innervates

Question 5

what is a motor nerve

Answer 5

a bundle of axons from multiple motor neurons

Question 6

how can whole muscle contractions be graded?

Answer 6

whole muscle tension is proportional to motor unit activity

more muscle units means more fibers which means more sarcomeres
- more xbs means more tension

we can change motor unit activity by increasing or decreasing
- number of active motor units
= motor unit recruitment or number coding
- rate at which motor units discharge
= rate coding

both strats contribute in different contexts

we can use one or both at any time

Question 7

what does motor unit recruitment influence

Answer 7

tension you fuck

Question 8

how does motor unit influence tension

Answer 8

• we modulate tension by altering the nervous signal (from CNS) to recruit more/fewer motor units
• this is called number coding because we change the number of active motor units
• but muscle tension also depends on the type of fibers that are recruited

Question 9

What does the all or none principle mean?

Answer 9

1. Means that all the muscle fibers in a motor unit will twitch (or not) together
2. Means that all the sarcomeres in a muscle fiber will twitch (or not) together

Question 10

If a muscle fiber is slow-twitch, then all the ___ will also be slow twitch

Answer 10

Other fibers in the same motor unit

Question 11

What do smaller neurons have?

Answer 11

• lower excitation threshold (recruitment/activation threshold)
  
  • require smaller stimulus to trigger contraction = more excitable, easier to recruit
• slower conduction velocities
  
  • longer lag time

Question 12

What are motor units recruited according to?

Answer 12

The size principle of a neuron

Question 13

What does the size principle ensure?

Answer 13

That task-appropriate recruitment happens by enlisting the precise muscular work force that is needed to achieve desired contraction
- recruits the most efficient and least fatigable fibers first
- recruits the expensive and messy ones only when needed
- can adjust very quickly if more tension is needed

Question 14

What does increased motor unit recruitment lead to and why?

Answer 14

More tension because more crossbridges = more tension

Question 15

The signal from the CNS will be proportional to tension needed, what does each signal make happen?

Answer 15

Subthreshold signal means no contraction

Low signal (above type I threshold) means SO contract

Higher signal (above type II threshold) means FG/FOG also contract

Even higher signal means more and more FG/FOG motor units are recruited

Question 16

Draw and annotate the graph on page 7 of muscle tension III

Question 17

What does increased neuron firing frequency (rate coding) result in and why

Answer 17

More tension because summation stacks contractions on top of each other
- more XBs form before others have released
- more XBs = more tension
- the faster the frequency, the greater the tension (to an extent)

Question 18

What is the agonist, synergist, and antagonist

Answer 18

Agonist: prime mover
synergist: helper
Antagonist: opposer

Question 19

What does coordination lead to?

Answer 19

More tension because different muscles cooperate as much as possible to turn contraction into functional force

Question 20

What do the strongest contractions do?

Answer 20

1. Recruit LOTS of motor units (number coding) - gets as many fibers involved as possible
2. Are at max firing frequency (rate coding) - summation leads to increased force produced by each fiber
3. Are well-coordinated - make the most of the force that is produced

Question 21

Can we increase recruitment of motor units?

Answer 21

Yes!

Motor neurons become more excitable (easier to recruit)

Motor drive increases (more stimulus from CNS)

Question 22

Can we increase neuron firing frequency?

Answer 22

Yes!

Increasing max firing rate increases summation which leads to more tension

Increasing motor unit synchronization leads to more efficient timing of motor unit contractions which leads to more tension

Question 23

Can we improve intermuscular coordination?

Answer 23

Yes!

Increasing coordination of recruitment/inhibition or agonists/synergists/antagonists leads to:
- increased efficiency of mvmt
- increased production of useful force

Question 24

What does the golgi tendon organ do and what can we do to it?

Answer 24

The golgi tendon organ senses muscle tension and INHIBITS contraction beyond a set threshold - protective mechanism to limit excessive force generation/self-injury

We can blunt the golgi tendon reflex

Question 25

Copy down page 12 of muscle tension III

Question 26

Copy down tables on page 13 of muscle tension III

Question 27

What causes early gains in strength?

Answer 27

• neural adaptations
  Motor neuron excitability
  Central motor drive
  Firing frequency
  MU synchronization
  Inter-muscle coordination
  Blunted Golgi tendon reflex
  Psychological factors

Question 28

Can you get strength gains without actually training?

Answer 28

Yes! (Sort of)

• training one limb can induce adaptations in the contralateral limb
• cross-education