Lesson 8 - Neuromuscular System III

Question 1

Central Vs Peripheral Fatigue

Answer 1

Central Fatigue - Physiological
Anything proximal to neuromuscular junction

Periphral Fatigue - Psychological/Feeling
Nueromuscular junction and lower

Question 2

Mechanisms of peripheral fatigue

Answer 2

1. Anything to inhibit pre/post synaptic terminal
2. Not enough ACh is released
3. Not a good enough balance of sodium and potassium
4. Decrease in ATP, can’t restore ions
5. Muscle relaxation is not occurring, sarcoplasmic reticulum

Question 3

Mechanisms of central fatigue (sensory afferent feedback model)

Answer 3

-Harder to study
-Muscle Fatigue/Burn when tired

CNS sends signal for muscle contraction and we exercise

Build up of metabolites which actives muscle afferent feedback. The lowers central motor drive for next cycle

negative feedback loop

Strong drug like fentanyl when injected in back blocks CNS feedback and afferent loop) which leads to lots of peripheral fatigue and muscle contraction can’t keep up

Question 4

Mechanisms of central fatigue

Answer 4

Factors affecting cortical drive (motor drive)

Factors affecting spinal drive (courtocose spinal tract)

Afferent feedback (alpha neuron in ventral horn)

Question 5

Interpolated Twitch Technique (ITT)

Answer 5

How to measure fatigue (both)

Electrically stimulate nerve you want to focus on

For quad it is femoral nerve this whill stimulate every muscle fiber in quad

Question 6

Maximal Voluntary Contraction (MVC) and Voluntary Activation (VA)

Answer 6

Stimulus, if there is not a high superimposed twitch that means there is a deficit and not every fiber was stimulated (didn’t activate) which is central fatigue

Question 7

VA and peripheral fatigue

Answer 7

Voluntary Activation (VA) is ratio between super imposed and resting position

Peripheral fatigue on requires RT, artificially activate

Question 8

Central and Peripheral Fatigue summary

Answer 8

MVC force = capacity of central nervous system + muscles
- But cannot delineate (without measuring CNS and PNS)

Large SIT = ↓ CNS to drive muscles
* ↓ VA = ↑ central fatigue
* Need both SIT and RT to calculate VA

Small RT = ↓ muscles to produce force
* ↓ RT = ↑ peripheral fatigue

Question 9

What was done

Answer 9

Increased super imposed : central fatigue and can’t activate every fiber

example: Low intensity

Resting decrease: muscle could not produce enough force

Example: High intensity

Question 10

Effect of exercise intensity-duration

MVC, RT AND VA graph

Answer 10

MVC force isn’t really affected by level of intensity

In resting twitch, High intensity declined resting twice most, then middle and then low

In VA, RCP or low intensity declined VA most then middle, then high

Question 11

Effect of exercise intensity-duration
Rules

Answer 11

Neuromuscular fatigue is dependent on exercise intensity and duration

• Lower intensities/longer durations = ↑central fatigue

-Higher intensities/shorter durations = ↑peripheral fatigue

Question 12

Fatigue

Answer 12

Perceived vs Performance

Perceived = homeostasis and psychologial state

Performance = contractile function and muscle activation