Exercise Physiology Notes

Exercise Physiology

Outline

• Acute Vs Chronic
• Neuromuscular Physiology
• Metabolism
• Cardiovascular Physiology
• Respiratory Physiology
• Exercise in Special Conditions

Acute vs Chronic

Definitions

• Acute Responses: The physiological effects that occur during a single session of physical activity.
• Chronic Adaptations: Changes that occur in physiological systems as a result of repeated physical activity over time, reflecting the body's ability to adapt to varying levels of exercise.

Subcategories

• Rest: Assessment of physiological parameters at rest.
• Submaximal: Responses measured at levels of effort below the maximum capacity.
• Maximal: Responses observed during the highest level of performance.

Neuromuscular Physiology

Muscle Anatomy

• Myofilaments: Components of muscle fibers that include:
    - Actin (thin filament)
    - Myosin (thick filament)
• Myofibril: Bundles of myofilaments.

Muscle Structure

• Tendon: Connects muscle to bone.
• Muscle Belly: The main part of the muscle.
• Epimysium: A layer of connective tissue surrounding the muscle.
• Endomysium: Connective tissue between individual muscle fibers.
• Sarcoplasm: The cytoplasm of muscle cells where metabolic processes occur.
• Sarcolemma: The cell membrane surrounding a muscle fiber.
• Fasciculus: A bundle of muscle fibers protected by perimysium.

Components of Muscle Fiber Anatomy

• Mitochondrion: Powerhouse of the cell; responsible for aerobic ATP production.
• Sarcoplasmic Reticulum: Stores calcium, crucial for muscle contraction.
• T-tubule: Conducts action potentials into the muscle fiber.

Sarcomere Anatomy

Structure and Function

• Myofilaments cross-sections include:
    - Z-line: Boundary of the sarcomere.
    - A-band: Region containing myosin filaments.
    - I-band: Region containing actin filaments, which decrease in length during muscle contraction.
    - H-zone: Area within the A-band that contains only myosin.
• Cross-bridge Formation: The binding of myosin heads to actin during contraction, regulated by calcium.

Muscle Fiber Types

Types of Muscle Fibers

• Type I (Slow Twitch) Fiber:
    - Aerobic metabolism.
    - Resistant to fatigue.
    - Smaller motor neurons.

• Type IIa (Fast Oxidative):
    - Combines aerobic and anaerobic capabilities.
    - Moderate resistance to fatigue.

• Type IIx (Fast Glycolytic):
    - Primarily anaerobic metabolism.
    - High fatigue rates; generates more force but fatigues quickly.

Characteristics of Fiber Types

Neuromuscular Junction and Motor Units

Definitions

• Neuromuscular Junction: The point where a motor neuron communicates with a muscle fiber.
• Motor Unit: Composed of an alpha motor neuron and the muscle fibers it innervates; it is the fundamental operational unit of the neuromuscular system.

Types of Motor Units

• Fast Fatigable (FF):
    - Fast Glycolytic (FG)
    - High innervation ratio, large motor units.

• Fast Fatigue-Resistant (FR):
    - Fast Oxidative Glycolytic (FOG)
    - Moderate innervation ratio, intermediate size.

• Slow (S):
    - Slow Oxidative (SO)
    - Low innervation ratio, resistant to fatigue.

Important Neuromuscular Principles

Key Principles

• All-or-None Principle: All fibers within a motor unit contract fully when activated; partial contractions do not occur.
• Size Principle: Motor units are recruited in order of size; smaller units are recruited first, followed by larger units as force requirements increase.
• Rate Coding: Frequency of stimulation affects force production; closely spaced, rapid impulses will increase the total force output through summation.

Types of Muscle Contractions

• Concentric: Muscle shortens under tension.
• Isometric: Muscle generates force without changing length.
• Eccentric: Muscle lengthens while under tension, often causing damage to muscle fibers.