A.3.3.1 Fatigue and recovery (HL)

what is fatigue

a reversible, exercise-induced decline in performance

what are the two types of fatigue

• peripheral fatigue

• central fatigue

what is peripheral fatigue

where fatgue is caused by factors that resdie outside the CNS

what happens during prolonged or intense exercise and the result of this

chemical changes in the brain impair its ability to recruit muscle fibres = reduced muscle performance

what is central fatigue

fatigue caused by factors that reside in the CNS

what can hinder muscle contraction even when the brain sends optimal signals

depleted energy stores, accumulation of metabolites, mechanical stress

what is the result of hindered muscle contractiosn despite optimal nerual input

diminished muscle performance

what are some causes of peripheral fatigue in high-intensity activites

• depletion of energy systems (creatine/ATP)

• accumulation of metabolic by-products (H ions/lactate)

• accumulation of inorganic compounds

depletion of energy systems

CP is used for anaerobic conditions, maintaining ATP, depletion will cause muscle fatigue

accumulation of metabolic by-products (H⁺ ions/lactate) - 1

these activities rely heavily on anaerobic glycolysis and produce large amounts of the byproducts

accumulation of metabolic by-products (H⁺ ions/lactate) - 2

increase in ions = decreased pH = decreased energy production = decreased contraction force in muscle

what does this interfere with - 3

roles of calcium in forming the cross-bridge formation

what inorganic compound builds up during intense muscle activity

inorganic phosphate (Pi)

how does Pi interfere with cross-bridge cycling

Pi binds to myosin heads, weakening their interaction with actin and reducing force production

how does Pi affect calcium availability during muscle contraction?

Pi forms calcium-phosphate (CaPi), reducing free Ca²⁺ and impairing contraction strength

how does Pi slow ATP regeneration

disrupts creatine kinase and oxidative phosphorylation, lowering energy availability for contractions

what are some causes of peripheral fatigue in low-intensity/endurance activities

• depletion of muscle glycogen stroes

• reduction in calcium release

• electrolyte loss

• depletion og acetycholine

• dehydration

• overheating

why is glycogen important for aerobic glycolysis

provides stored energy used to produce ATP

what happens to the glycogen concentration during prolonged exercise

decreases and can deplete after 2 hours of activity

what role do calcium ions play in muscle contractions

help initiate contraction via sliding filament theory

how does reduced calcium ions affect muscle contractions

inhibits contraction, especially when the sarcoplasmic reticulum is repeatedly stimulated

what can result from a disruption in sodium and potassium levels

hyponatremia, especially in endurance athletes who over-hydrate

why are sodium (Na⁺) and potassium (K⁺) important for muscle function?

essential for nerve signal transmission and muscle contraction

what happens during the action potential involving Na⁺ and K⁺

sodium enters the neruon (polarisation) and potassium exits (depolarisation) enabling singla to travel

what is the effect of acetylcholine depletion on muscles

inhibits the muscle’s ability to contract

what does dehydration do to the blood volume

decreases it

how does the body respond to reduced plasma volume during dehydration

HR increases to maintain cardiac output (CV drift) = fatigue

how does overheating contribute to fatigue during exercise

blood is redirected to the skin to cool the body, reducing blood flow to working muscles imparing contractions