Untitled Quiz

Advanced concepts in Exercise physiology

• Course name: DLSEM512
• Lecturer: Δρ. Έλενα Παπακώστα
• University: FREDERICK UNIVERSITY

Respiratory System: Function and Adaptations to Exercise

• This section delves into the functions of the respiratory system during exercise, emphasizing the structure, function, and adaptations to physical activity.
• Mechanisms governing pulmonary ventilation, gas exchange, and respiratory responses to exercise will be explored, including oxygen debt, oxygen deficit, arteriovenous oxygen difference, and the respiratory threshold.
• Topics covered:
  • Respiratory system overview of physiology
  • Pulmonary Ventilation and Respiratory Threshold
  • VO2 kinetics
  • Arteriovenous Oxygen Difference

Aerobic Performance

• The diagram depicts the interaction of the respiratory, cardiovascular, and muscular systems during aerobic exercise, emphasizing the delivery and utilization of oxygen.
• Three main systems are analyzed:

  • Respiratory System:

    • Pulmonary Ventilation: The process of inhalation and exhalation, ensuring the entry of oxygen into the lungs.
    • Oxygen Diffusion: The transfer of oxygen from the lungs to the blood, via the pressure difference. Efficiency depends on the surface area for gas exchange in the lungs.

  • Cardiovascular System:

    • Central Circulation: The heart pumps oxygenated blood to the tissues. Cardiac output and blood pressure are crucial factors. Hemoglobin, the protein that binds oxygen in red blood cells, plays a key role in oxygen transport.
    • Peripheral Circulation: Blood flow to the active muscles is vital. The network of capillaries facilitates oxygen diffusion from the blood to the muscles.

  • Muscular Metabolism:

    • Oxidative Enzymes: Enzymes catalyzing oxidation reactions, essential for energy production.
    • Energy Sources: Muscle activity depends on energy production through aerobic and anaerobic processes.

Muscular Function in Aerobic Exercise

• Myoglobin: A protein that transports oxygen to the muscles.
• Mitochondria: Organelles in cells that produce energy through aerobic respiration. Their density and function affect aerobic capacity.
• Muscle Fibers: Fast-twitch or slow-twitch muscle fiber types influence aerobic exercise capacity.

Respiratory System : Overview of Physiology

• Divided into upper and lower respiratory systems
• Core function: Gas exchange
• Mechanics of breathing: Inhalation and exhalation cycles
• Mechanisms of gas exchange
• Control of breathing rate: CO2 and pH levels

Respiratory Mechanics

• Inspiration: Diaphragm and intercostal muscles contract, expanding the thoracic cavity, reducing pressure (Palv < Patm).
• Expiration: Diaphragm and intercostal muscles relax, reducing the thoracic cavity volume, increasing pressure (Palv > Patm).

Mechanisms of Gas Exchange

• Occurs at the alveolar level.
• Oxygen diffuses from alveoli to blood—returning to the heart via pulmonary veins.
• Carbon dioxide diffuses from blood to alveoli—exhaled.

Regulation of Breathing

• Controlled by respiratory centers in the medulla oblongata.
• Responds to CO2 levels, pH, and oxygen demand.

Lung Volumes and Capacities

• Tidal Volume (TV): Amount of air inhaled/exhaled during normal breathing (~500 mL).
• Inspiratory Reserve Volume (IRV): Maximum air inhaled after normal inhalation (~3000 mL).
• Expiratory Reserve Volume (ERV): Maximum air exhaled after normal exhalation (~1200 mL).
• Residual Volume (RV): Air remaining in lungs after maximum exhalation (~1200 mL).
• Inspiratory Capacity (IC): Maximum air inhaled after normal exhalation (TV + IRV).
• Functional Residual Capacity (FRC): Air remaining in lungs at the end of a normal exhalation (ERV + RV).
• Vital Capacity (VC): Maximum air exhaled after a maximum inhalation (TV + IRV + ERV).
• Total Lung Capacity (TLC): Total volume of air in the lungs after a maximum inhalation (TV + IRV + ERV + RV).

Minute Ventilation (VE)

• Volume of air inhaled/exhaled per minute.
• Calculated as respiratory rate (RR) × tidal volume (TV).

VE during Exercise

• VE increases rapidly at exercise onset.
• The increase in breathing rate and volume helps to meet the increased metabolic demands of working muscles (e.g., 3-4 times resting levels, or more during high-intensity exercise).
• Respiratory threshold (VT) is a point where ventilation increases disproportionately relative to oxygen uptake, often associated with lactate accumulation.
• Different types of aerobic exercise may demonstrate different ventilatory responses.

Factors Affecting VO2 Kinetics

• Initial increase in VE is due to neural factors and immediate oxygen demands by working muscles.
• Exponential increase in VE reflects the body's transition from anaerobic to aerobic metabolism.
• Steady-state (phase III): VE stabilizes at a level sufficient to meet metabolic needs during the exercise.
• Recovery phase: Gradual decrease in VE as the body returns to the resting state.
• Rapid and slow components of the recovery phase reflect the body's restoration process.

VO2 and EPOC

• EPOC (Excess Post-exercise Oxygen Consumption): Elevated VO2 following exercise is needed to restore homeostasis, replenish energy stores, and remove metabolic byproducts.
• The magnitude and duration of EPOC fluctuate according to exercise type, intensity, and the individual's fitness level.
• High-intensity interval training (HIIT) is associated with greater EPOC compared to continuous moderate-intensity exercise, due to higher metabolic disruption.
• Duration of EPOC is longer after high-intensity exercise than low-intensity.

Arteriovenous Oxygen Difference (a-vO2 diff)

• Difference in oxygen content between arterial and venous blood.
• Reflects the extent to which tissues extract oxygen from the blood during metabolism.
• Several factors affect the a-vO2 diff during exercise, including exercise intensity, exercise type, and individual physiological factors
• Chronic training adaptations, particularly endurance training, improve mitochondrial density, oxidative capacity, and cardiovascular efficiency, resulting in increased a-v02 diff during exercise.
• Reduced a-v02 diff can occur during acute hypoxia, which reduces oxygen extraction capabilities. Factors affecting the a-vO2 diff include age, and conditions like heart failure with preserved ejection fraction (HFPEF).

Additional Points

• Factors like intensity and duration of exercise play a crucial role in determining the magnitude and dynamics of all aspects of the body's response to exercise.
• Different types of exercise (e.g. HIIT vs. LSD) can have varied physiological responses regarding respiratory parameters.
• Factors like age, fitness level, and environmental conditions impact individual responses to exercise.
• Understanding VO2 kinetics and EPOC is crucial for designing effective training programs focused on weight loss, increasing metabolism, or improving overall physical fitness.