Lecture 1 - Fatigue

Question 1

What is the difference between fatigue and exhaustion ?

Answer 1

Fatigue is a process that develops progressively throughout exercise and is categorised by a gradual reduction in MVC.

Exhaustion is a complete failure to continue working at a given intensity.

Question 2

What are the two components of central fatigue ?

Answer 2

• Supraspinal fatigue
• Spinal fatigue

Question 3

During a 3 minute all out test what happens to the power output ?

Answer 3

Power output initial spikes then crashes down. It then levels off to a point that is maintainable by the athlete. Known as the critical power (CP).

Question 4

What did Black et al., (2017) show about the mechanisms of fatigue at different intensities?

Answer 4

• During higher intensity exercise fatigue is caused by cell acidosis, lactate build up and PCr depletion.
• In long duration exercise glycogen depletion is the main cause of fatigue.

Question 5

What did the Goodall et al., (2017) study show about MVC and fatigue over the course of a football match ?

Answer 5

They showed that by looking at MVC and potentiated twitch that fatigue does develop fairly early and could explain the reduction in MVC seen at half time.

However, Peripheral fatigue stabilised here but MVC continued to drop, indicating a central limitation. This is how superimposed twitch changed before and after the game.

Question 6

What are some causes AND symptoms of peripheral fatigue ?

Answer 6

Causes

• Metabolite accumulation ( H+ , Pi, CO2)
• Substrate depletion
• Reduced membrane excitability

Symptoms

• Reduced excitation-contraction coupling
• Impaired calcium release and uptake
• Reduced PFK activty = Reduced glycolisis rate

Question 7

Why is assessing surpraspinal fatigue via Fatigue Transcranial Magnetic Stimulation usefull.

Answer 7

It showed that by stimulating the motor cortex you can increase force production during exercise, and that a reason for central fatigue can be reduced excitability of the motor cortex.

Question 8

What is Excitation-contraction coupling and Membrane excitability?

Answer 8

• Excitation-contraction coupling determines how how you can generate force in response to electrical impulse that arrive at muscle.
• Membrane excitability is how well the electrical signal that arrives at the muscle is translated into muscle contraction. More excitable the better.

Question 9

What are the results of central fatigue ?

Answer 9

• Reduced neural drive
• Reduced motor unit recruitment and firing frequency
• Incresed afferent muscle feedback sensation

Question 10

Define Fatigue

Answer 10

A condition in which there is a loss in the capacity for developing force and/or velocity of a muscle, resulting from muscle activity under load and which is reversible by rest.

Question 11

What did Thomas et al., (2015) show about what type of exercise is limited by what type of fatigue ?

Answer 11

• Peripheral fatigue limits short duration exercise performance more
• Central fatigue limits long duration exercise performance more
• However, there is always a contribution of both in each distance.