A.3.3.1 Fatigue and recovery (HL)

Fatigue is:

• a reversible, exercise-induced decline in performance.

OR

• a disabling symptom in which interactions between performance fatigueability and perceived fatiguablity limit physical and cognitive function

There are two types of fatigue:

• Peripheral fatigue: term where fatigue is caused by factors that reside outside the CNS, distal to the neuromuscular joint

• During prolonged or intense exercise, chemical changes in the brain can impair its ability to effectively recruit and activate muscle fibres. This results in reduced muscle performance, characterized by decreased force and slower contraction speeds.

• Central fatigue: is there term for fatigue cause by factors that reside within the CNS

• Even when the brain sends signals, factors such as depleted energy stores, accumulation of metabolites, or mechanical stress can hinder muscle contractions. This leads to diminished muscle performance despite optimal neural input.

Causes of peripheral fatigue in high-intensity activity include:

• Depletion of energy systems (creatine/ATP)

• Accumulation of metabolic by-products (lactic acid/ H ions)

• Failure of muscle contractions

Causes of peripheral fatigue in low-intensity activity include:

• Depletion of muscle and liver glycogen stores

• Reduction in calcium ions release (for muscle contractions)

• Depletion of acetylcholine

• Dehydration

• Electrolyte loss

• Overheating