5.2 Lung volumes and capacities

Lung volumes and capacities are key to understanding how our bodies handle air during breathing. They measure the amount of air we inhale, exhale, and keep in our lungs at different points in the breathing cycle.

These measurements are crucial for assessing lung function and can change with factors like age, gender, and exercise. Understanding lung volumes helps us grasp how our respiratory system adapts to exercise and impacts athletic performance.

Lung Volumes vs Capacities

Defining Lung Volumes

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• Lung volumes measure air quantity in lungs during respiratory cycle phases
• Tidal volume (TV) represents air inhaled or exhaled during normal resting breathing (~500 mL in adults)
• Inspiratory reserve volume (IRV) quantifies additional air inhaled after normal tidal inspiration (~3000 mL)
• Expiratory reserve volume (ERV) measures forcefully exhaled air after normal tidal expiration (~1200 mL)
• Residual volume (RV) indicates air remaining in lungs after maximal expiration (~1200 mL)

Understanding Lung Capacities

• Lung capacities combine two or more lung volumes
• Vital capacity (VC) calculates maximum air exhaled after maximal inhalation (TV + IRV + ERV)
• Total lung capacity (TLC) measures total air volume in lungs after maximal inhalation (VC + RV)
• Inspiratory capacity (IC) represents maximum air inhaled from resting expiratory level (TV + IRV)
• Functional residual capacity (FRC) indicates air remaining in lungs after normal expiration (ERV + RV)

Factors Influencing Lung Volumes

Physiological Factors

• Age affects lung volumes, peaking in early 20s and gradually declining thereafter
• Gender influences lung volumes, with males generally having larger volumes due to body size and composition differences
• Body size and composition correlate positively with lung volumes (height, lean body mass)
• Ethnicity causes slight variations in predicted lung volume values among different populations

Environmental and Lifestyle Factors

• Altitude acclimatization increases lung volumes as adaptation to lower oxygen partial pressures
• Smoking reduces lung volumes significantly (emphysema, chronic bronchitis)
• Chronic respiratory diseases decrease lung volumes (asthma, cystic fibrosis)
• Body position affects lung volumes (higher in upright position compared to supine or prone)
• Air pollution exposure may lead to reduced lung volumes over time (particulate matter, ozone)

Lung Volumes with Exercise Training

Aerobic Exercise Effects

• Endurance training modestly increases total lung capacity and vital capacity (5-10% improvement)
• Regular aerobic exercise enhances tidal volume during rest and submaximal exercise
• Chronic exercise adaptation improves chest wall flexibility and respiratory muscle strength
• Magnitude of lung volume changes with exercise training less pronounced than cardiovascular improvements

Specialized Training Impacts

• Inspiratory muscle training increases inspiratory capacity and overall lung function
• Specific respiratory exercises may decrease residual volume slightly
• High-intensity interval training potentially improves lung volumes more than moderate-intensity continuous training
• Swimming training often results in greater lung volume improvements compared to land-based exercises

Lung Volumes for Exercise Performance

Endurance Performance Implications

• Higher vital capacity and total lung capacity contribute to improved endurance by increasing oxygen uptake and carbon dioxide elimination
• Increased tidal volume during exercise enables more efficient gas exchange (delayed fatigue onset)
• Enhanced inspiratory capacity reduces breathing work during high-intensity exercise (improved exercise tolerance)
• Improved lung volumes may increase maximal oxygen uptake (VO2max), a key endurance performance determinant

Sport-Specific Considerations

• Athletes with larger lung volumes may have advantages in sustained high-intensity sports (swimming, rowing)
• Distance running performance relationship with lung volumes less direct due to other limiting factors (cardiovascular function, muscle metabolism)
• Individual lung volume measurements help tailor training programs and assess athletic potential
• Sports requiring breath-holding benefit from increased total lung capacity (diving, synchronized swimming)