THE PHYSIOLOGY OF MUSCLE FATIGUE

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THE PHYSIOLOGY OF MUSCLE FATIGUE
Dawn MacIsaac Ph.D. Candidate Institute of
Biomedical Engineering University of New Brunswick
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OVERVIEW
Muscle Physiology
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Muscle Physiology
Motor Unit
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Muscle Physiology
Myofibrils
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Mechanics of Muscle Contraction
Cross Bridging
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Mechanics of Muscle Contraction
Cross Bridging
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Mechanics of Muscle Contraction
Cross Bridging
Tm
Tm
Tm
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Mechanics of Muscle Contraction
Cross Bridging
Energy Requirements
Each of these process requires
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Mechanics of Muscle Contraction
Production of ATP
Aerobic Metabolism
H
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Origins of Localized Muscle Fatigue
SITES OF THE SOURCES OF FATIGUE
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Origins of Localized Muscle Fatigue
Depletion Theory of Fatigue
Fatigue results from the depletion of metabolites
necessary for energy production
Glucose
Oxygen
ADP or CP
Reaction Enzymes
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Origins of Localized Muscle Fatigue
Accumulation Theory of Fatigue
Fatigue results from an accumulation of certain
by-products produced as a result of metabolic
processes associated with the mechanisms of
muscular contraction
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Origins of Localized Muscle Fatigue
Accumulation Theory of Fatigue
Lactic Acid and free H
K
NH3
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Myoelectric Manifestations of Fatigue

• Difficult to measure but may be easier to
  estimate instantaneously

• Easy to measure but difficult to estimate
  instantaneously

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Myoelectric Manifestations of Fatigue
MF Estimation
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Myoelectric Manifestations of Fatigue
MF Estimation
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Myoelectric Manifestations of Fatigue
MF Estimation

• Good index of fatigue in static contractions

- Averaging is possible - No Joint Angle or Force
Effect

• Poor index of fatigue in dynamic contractions

- Averaging is not possible under all
conditions - Joint Angle or Force Effect
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Myoelectric Manifestations of Fatigue
CV Estimation
CV d/?
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Myoelectric Manifestations of Fatigue
Conduction Velocity vs Joint Angle for different
Force Levels
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Myoelectric Manifestations of Fatigue
Conduction Velocity vs Joint Angle for different
Force Levels
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Myoelectric Manifestations of Fatigue
CV Estimation

• Possible index of fatigue in dynamic contractions

- Small Joint Angle or Force Effect which may not
obscure a trend with fatigue - Outliers could be
problematic - Instantaneous estimation technique
must be developed
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Myoelectric Manifestations of Fatigue
Muscle fatigue assessment has many practical
applications
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SUMMARY

• Mean Frequency
• Conduction Velocity

• Depletion Theory
• Accumulation Theory

• Fibres
• Myofibrils
• Microfilaments

• Cross Bridging
• Energy Reqirements

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QUESTIONS ??