Lecture 5 - Central and Peripheral Fatique

Question 1

What causes fatigue in the CNS?

Answer 1

• Changes in brain neurotransmitters (serotonin - increase, dopamine - decrease,)
• Depletion of brain glycogen.
• Increase in core and brain temperature.

Question 2

How do we regulate performance?

Answer 2

• Using feed forward control and in response to afferent feedback from multiple central and peripheral sensors.

Question 3

What are the two types of fatigue?

Answer 3

• Central fatigue - Failure of the CNS to adequately drive the muscle
• Peripheral - impairment located in the muscle characterised by metabolic end point.

Question 4

What are the causes of fatigue ?

Answer 4

• Failure to supply enough o2
• Increasing lactate levels
• Increased H+ or Pi levels
• Glycogen depletion
• Heat retention

Question 5

What is pacing?

Answer 5

• The distribution of work rate throughout and exercise bout and largely influences the success or failure of the performance.

Question 6

What is efferent and afferent ?

Answer 6

• Afferent - sensory neuron that drive feedback from muscle to CNS (feedback)
• efferent - Messages from CNS to muscle (effector)

Question 7

What happens the CNS is blocked during exersie

Answer 7

• Because the CNS is blocked the muscles are not aware how to regulate the level of activity so the muscle will exercise at a much higher intensity
• Because the CNS is not feeling the feedback from the muscles it does not change the intensity at which they are working at.
• So if the athlete set off quickly the CNS would not send the signal to change this so peripheral fatigue will onset faster.

Question 8

What is fatigue?

Answer 8

A failure, limit or reduction in performance.

Question 9

What is the effect of locomotor muscle fatigue on subsequent performance ?

Answer 9

• Reduces power output and CMD

- However does not increase the level of fatigue as there is a mechanism to stop overexertion.

Question 10

What determine pacing strategy ?

Answer 10

• Initially controlled by anticipatory feedfowards algorithm, (am I going to set of quick or slow)
• Later determined by feedback form peripheral sensors, homeostatic changes and external stimuli (competitors/ environment.)

Question 11

When peripheral feedback is blocked during an exercise test?

Answer 11

• The CNS does not feel the feedback from the fatiguing muscles which results in it continuing to drive stimulus to these muscles. (Indicated by the increases in EMG, HR, VE + BP).
• This can result in overexertion as the brain continues to prescribe exercise to muscles unaware that they may be reaching their limits.

Question 12

What causes peripheral fatigue?

Answer 12

• Substrate depletion
• Accumulation of metabolites ( H+, Pi)
• Feedback from fatigue sensitive muscles (Afferent neuron send feedback = fatigue)

Question 13

What is CMG?

Answer 13

• Central motor drive