Exercise and the heart, blood and lungs

Heart rate: 60-80 beats a minute at rest (72 typical), rising to 140-180 in exercise. Stroke volume: about 70 ml per beat for men and 50 ml for women at rest, rising with exercise.

Cardiac output = heart rate x stroke volume: about 5 litres a minute at rest, rising 4-5 times in exercise; endurance training raises it through a larger stroke volume. Long, hard training can enlarge the heart ('athlete's heart').

Endurance training raises resting blood volume (about 8 per cent) and plasma volume (about 12 per cent), adds and enlarges blood vessels and capillaries.

Breathing is controlled by the medulla oblongata. Tidal volume (about 500 ml at rest) and respiratory rate (12-20 a minute) both rise in exercise; minute ventilation = tidal volume x rate, about 8 litres a minute at rest.

Exercise raises the lungs' diffusing capacity for oxygen; faster, deeper breathing is hyperventilation; vital capacity is the most air breathed out after a full breath in.