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Factors Affecting Performance

Factors Affecting Performance. Factors Affecting Performance. Sites of Fatigue. Central fatigue Peripheral fatigue Neural factors Mechanical factors Energetics of contraction. Central Fatigue. Reduction in motor units activated Reduction in motor unit firing frequency

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Factors Affecting Performance

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  1. Factors Affecting Performance

  2. Factors Affecting Performance

  3. Sites of Fatigue • Central fatigue • Peripheral fatigue • Neural factors • Mechanical factors • Energetics of contraction

  4. Central Fatigue • Reduction in motor units activated • Reduction in motor unit firing frequency • Central nervous system arousal can alter the state of fatigue • By facilitating motor unit recruitment

  5. Peripheral Fatigue:Neural Factors • Neuromuscular junction • Not a site for fatigue • Sarcolemma and transverse tubules • Ability of muscle membrane to conduct and action potential • Repeated stimulation of sarcolemma can reduce size and frequency of action potentials • An action potential block in the T-tubules • Reduction in Ca++ release from sarcoplasmic reticulum

  6. Peripheral Fatigue:Mechanical Factors • Reduction in force per cross bridge • Reduction of force generated at a given Ca++ concentration • H+ interference with Ca++ binding to troponin • Inhibition of Ca++ release from SR • Lack of ATP to dissociate the cross-bridge from actin

  7. Peripheral Fatigue:Energetics of Contraction • Mismatch between rate of ATP production and utilization • Fatigue results in slowing of ATP utilization to preserve homeostasis • Muscle fiber recruitment in increasing intensities of exercise • Type I  Type IIa  Type IIb • Progression from most to least oxidative fiber type • Results in increased lactate production

  8. Pattern of Muscle Fiber Recruitment

  9. Ultra Short-Term Performance • < 10 seconds • Dependent of recruitment of Type II muscle fibers • Generate great forces that are needed • Motivation, skill, and arousal • Primary energy source • Anaerobic • Phosphocreatine

  10. Ultra Short-Term Performance

  11. Short-Term Performance • 10-180 seconds • Shift from anaerobic to aerobic metabolism • 70% energy supplied anaerobically at 10s • 60% supplied aerobically at 180s • Primary energy source • Anaerobic glycolysis

  12. Short-Term Performance

  13. Moderate-Length Performance • 3-20 minutes • Increasing reliance on aerobic energy production • 60% ATP generated aerobically at 3 min • 90% ATP supplied aerobically at 20 min • Requires energy expenditure near VO2max • Type II fibers recruited • High levels of lactate • Factors that interfere with O2 delivery are limiting • Altitude, anemia

  14. Moderate-Length Performance

  15. Intermediate-Length Performance • 21-60 minutes • Predominantly aerobic • Usually conducted at less than 90% VO2max • Environmental factors are important • Heat • Humidity • State of hydration

  16. Intermediate-Length Performance

  17. Long-Term Performance • 1-4 hours • Environmental factors important • Ability to deal with heat and humidity • Muscle and liver glycogen • Maintain rate of carbohydrate utilization • Diet and fluid ingestion influence performance

  18. Long-Term Performance

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