Understanding of lung volumes and the impact of and on physical activity…

The idea

Lung volumes describe how much air the lungs move and retain, and they change with the demands of physical activity and sport. Tidal volume is the air moved in or out in one normal breath at rest, roughly 0.5 dm³ for a healthy adult. Inspiratory reserve volume is the extra air inhaled after a normal inspiration, and expiratory reserve volume is the extra air exhaled after a normal expiration. Vital capacity is the largest volume exhaled after a maximal inspiration, combining tidal volume with both reserve volumes. During exercise, tidal volume rises and breathing rate rises, so minute ventilation, the volume breathed per minute, increases steeply. Trained performers often show larger vital capacity and greater tidal volume at a given intensity, which supports oxygen delivery to working muscles.

What earns the marks

• Tidal volume is the volume of air inspired or expired in one normal breath at rest, approximately 0.5 dm³ in a healthy adult.
• Inspiratory reserve volume is the additional volume of air that can be forcibly inspired after a normal inspiration.
• Expiratory reserve volume is the additional volume of air that can be forcibly expired after a normal expiration.
• Vital capacity is the greatest volume of air that can be expelled from the lungs after a maximal inspiration, and it combines tidal volume with inspiratory and expiratory reserve volumes.
• Minute ventilation equals tidal volume multiplied by breathing frequency, so it rises during exercise because both factors increase.
• Regular training can increase vital capacity and tidal volume during exercise, improving the delivery of oxygen to working muscles.

Common mistakes and how to put them right

• Confusing tidal volume with vital capacity.

  Put it right: Tidal volume is one normal breath at rest, whereas vital capacity is the maximum volume exhaled after a maximal inspiration.

• Assuming breathing rate alone explains the rise in minute ventilation during exercise.

  Put it right: Tidal volume also increases, so both factors raise minute ventilation.

• Treating lung volumes as fixed for every performer.

  Put it right: Age, sex, body size and training status all influence the values recorded.

Exam tips

• Learn each volume with its definition and a typical resting value so you can distinguish similar options quickly.
• Use the relationship minute ventilation equals tidal volume multiplied by breathing frequency to reason about exercise responses rather than memorising isolated numbers.
• When a question describes a trained performer, link larger vital capacity and tidal volume to greater oxygen delivery during activity.