GLOSSARY

Vital capacity (VC) is the maximal volume of air a person can exhale after a full inspiration with a complete expiration, that is, all the air that can be moved voluntarily.
VC = IRV + VT + ERV, or TLC − RV; about 4.5–5 litres in a young man and 3–3.5 litres in a woman.

Influencing Factors

• Height: the most important factor; taller people have a larger VC.
• Sex, age (falling by about 20–30 millilitres per year after age 25–30), ethnicity, and body position (greater when standing).
• Respiratory muscle strength and chest wall flexibility.

History

John Hutchinson invented the spirometer in 1846 and chose the name “vital capacity” because he linked it with longevity.

Clinical Application

• Reduced VC: in restrictive diseases (pulmonary fibrosis, respiratory muscle weakness such as ALS or Guillain–Barré syndrome, severe scoliosis).
• Monitoring: a fall in VC below about 15–20 millilitres per kilogram in Guillain–Barré indicates a possible need for mechanical ventilation.

Relevance to Sport

• Scientific correction: a larger VC does not mean greater aerobic fitness; VC is only weakly related to VO₂max and endurance performance.
• Practical example: swimmers and wind instrument players often have a VC above predicted, which may reflect training from childhood and natural selection.