Tidal Volume, Vital Capacity and Breathing Rate

This lesson covers the key lung volumes and breathing measurements required by the Edexcel GCSE PE specification (1PE0 — Topic 1). You need to know the definitions of tidal volume, vital capacity, and breathing rate, understand how they change during exercise, and recognise how training affects them.

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Key Definitions

Term	Definition	Typical Value
Tidal volume (TV)	The volume of air breathed in or out in one normal breath at rest	~500 ml
Vital capacity (VC)	The maximum volume of air that can be forcefully exhaled after the deepest possible inhalation	~4,800 ml (males); ~3,200 ml (females)
Breathing rate (BR)	The number of breaths taken per minute	12-20 breaths/min at rest
Minute ventilation (VE)	The total volume of air breathed in or out per minute	VE = TV × BR
Residual volume	The volume of air that always remains in the lungs after maximum exhalation (the lungs never fully empty)	~1,200 ml
Inspiratory reserve volume	The extra volume of air that can be forcefully inhaled beyond a normal tidal breath	~3,100 ml
Expiratory reserve volume	The extra volume of air that can be forcefully exhaled beyond a normal tidal breath	~1,200 ml

Exam Tip: The most commonly tested measurements on Edexcel papers are tidal volume, vital capacity, and breathing rate. You must also know the formula for minute ventilation (VE = TV × BR) and be able to use it in calculations.

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Tidal Volume

Tidal volume is the volume of air breathed in (or out) during one normal, relaxed breath. At rest, this is approximately 500 ml.

How Tidal Volume Changes During Exercise

During exercise, tidal volume increases significantly because the body needs more oxygen:

State	Approximate Tidal Volume
At rest	~500 ml
Light exercise	~1,000-1,500 ml
Moderate exercise	~2,000-2,500 ml
Heavy exercise	~3,000+ ml

The increase in tidal volume is achieved by the stronger contraction of the diaphragm and intercostal muscles, and the recruitment of additional breathing muscles. This draws more air into the lungs with each breath.

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Vital Capacity

Vital capacity is the maximum volume of air that can be forcefully exhaled after the deepest possible inhalation. It represents the total usable lung capacity.

Vital capacity = Tidal volume + Inspiratory reserve volume + Expiratory reserve volume

Factors Affecting Vital Capacity

Factor	Effect
Age	Vital capacity generally decreases with age as lung tissue loses elasticity
Sex	Males typically have a larger vital capacity than females (larger lungs)
Height/body size	Taller individuals tend to have larger vital capacity
Fitness level	Regular aerobic training can increase vital capacity slightly
Smoking	Reduces vital capacity by damaging lung tissue and reducing elasticity

Long-Term Training Effects

Regular aerobic training can lead to a modest increase in vital capacity due to:

• Strengthened respiratory muscles (diaphragm and intercostals).
• Improved elasticity of the lungs and chest wall.
• Increased efficiency of the respiratory muscles.

However, the increase is relatively small compared to other adaptations (such as the improvement in cardiac output).

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Breathing Rate

Breathing rate is the number of breaths taken per minute. At rest, this is typically 12-20 breaths per minute.

How Breathing Rate Changes During Exercise

State	Approximate Breathing Rate
At rest	12-20 breaths/min
Light exercise	20-30 breaths/min
Moderate exercise	30-40 breaths/min
Heavy/maximal exercise	40-60+ breaths/min

What Controls Breathing Rate?