Fatigue - Factors affecting human performance Flashcards
What are the 5 factors affecting performance?
- Diet (carb, water intake)
- CNS function (arousal, motivation)
- Strength/skill (practise, natural endowment)
- Environment (altitude, heat, humidity)
- Energy production (anaerobic/aerobic sources)
What is fatigue?
Inability to maintain power output or force during repeated muscle contractions, which is reversible with rest.
Where does central fatigue occur?
Central nervous system
What contributes to peripheral fatigue?
- Neural factors.
- Mechanical factors.
- Energetics of contraction
What are the 4 different way of study muscle fatigue?
- Muscle in vivo
- Isolated muscle
- Isolated single fibre
- Skinned fibre
What is central fatigue characterised by?
Reductions in:
* Motor units activated.
* Motor unit firing frequency.
How can CNS arousal alter the state of fatigue?
- By facilitating motor unit recruitment.
- Increasing motivation.
- Physical or mental diversion.
What can excessive endurance training (overtraining) cause?
- Reduced performance, prolonged fatigue, etc.
- Related to brain serotonin activity
- and its ratio to Dopamine
What does the “Central Governor” model (Noakes) mention?
Conscious and subconscious brain, not spinal cord or motor unit.
What is the psycho-biological model?
Fatigue is a conscious process and exercise will persist if the motivation is greater than the perceived exertion.
Are NMJ the sites of fatigue?
No
How are sarcolemma and transverse tubules the site of fatigue?
- Altered muscle membrane to conduction and action potentials.
- Inability of Na+/K+ pump to maintain action potential amplitude and frequency.
- Can be improved by training.
- Inability of Na+/K+ pump to maintain action potential amplitude and frequency.
- An action potential block in the T-tubules.
- Reduced sarcoplasmic reticulum Ca2+ release.
Peripheral fatigue, mechanical factors - what does cross-bridge cycling and tension development depend on?
- Arrangement of actin and myosin.
- Ca2+ binding to troponin.
- ATP availability.
Peripheral fatigue, mechanical factors - how may high H+ conc contribute to fatigue?
- Reduce the force per cross-bridge.
- Reduce the force generated at a given Ca2+ concentration.
- Inhibit Ca2+ release from SR.
How does the imbalance between ATP requirements/generating capacity cause fatigue?
- Accumulation of Pi.
- Inhibits maximal force.
- Reduces cross-bridge binding to actin.
- Inhibits Ca2+ release from SR.