Lecture 5 - Central & Peripheral Fatigue and Pacing Flashcards
What are the two types of fatigue?
Central and Peripheral
What is central fatigue?
What are the causes of this?
Failure of the CNS to drive the muscle
Disturbances in brain neurotransmitters
Depletion of brain glycogen
Increased core and brain temperature
What is peripheral fatigue?
What are the causes of this?
Impairment in the muscle characterised by metabolic end point
Substrate depletion Metabolite accumulation (H+ and Pi)
What are the 2 different types of feedback?
Afferent = muscle to CNS
Efferent = CNS to the muscle
What are some of the generic causes of fatigue?
Blood lactate build up
Oxygen supply failure
Failure to lose heat
What the general outcome of Amann’s 1st investigation?
What was found?
Muscle fatigue has substantial dose dependent inverse effect on central motor drive and power output
Increasing levels of pre-existing fatigue
Reduction in average CMD and PO
No further fatigue found other than pre-existing
What the general outcome of Amann’s 2nd investigation?
What was found?
Without peripheral afferent feedback you still have CMD
Increase EMG - stronger drive to perform when not getting any feedback
Increased CV and respiratory response despite the lower power output = CMD present
What was the general outcome of Amann’s 3rd investigation?
What was found?
Peripheral fatigue rises when you have less CMD activity
CNS tolerated exercise induced fatigue beyond levels observed with intact neural system
Crucial role of feedback to CMD in pacing events
What was the take home message from the Amann study?
When reduced feedback from CMD and when the CNS prevented receiving the feedback - muscles were still able to become fatigued
What is pacing?
Distribution of work rate throughout exercise which largely influences the success/failures of the performance
How is pacing controlled?
1) Initial strategy controlled by anticipatory feedforward algorithm
2) Pace alterations due to peripheral feedback sensors, homeostatic responses and environment changes
3) Event duration, fitness, nutrition etc.
What factors were controlled during the sub-2 hour marathon attempt in 2017?
Terrain (Monza)
Optimal Temperature
Pacemakers
Nike created shoes
What characteristics did the runners show to be picked to attempt the record?
VO2 max high
High running economy
Early 20’s
Why use pacing in endurance/intermittent exercises?
Endurance -> pace and regulate fatigue to complete it
Intermittent -> don’t go all out at the start - most goals scored in the end of games due to fatigue
