Asthma can occur at any age and, if left untreated, can cause attacks of coughing, wheezing, tightness in the chest and breathlessness. Symptoms are often worse at night and with exercise but their severity and duration are highly unpredictable.
However, many asthmatics go on to successful careers in sport. Olympian Rebecca Adlington is asthmatic, as are runners Paula Radcliffe and Sebastian Coe and cyclist Bradley Wiggins.
Here we show how you can relieve any attacks by varying your breathing and by altering your diet.
We tend to take breathing for granted because it happens with little effort. However, the way you breathe can affect your asthma. In particular, overbreathing - where more air is taken in than needed - can lead to breathlessness and muscle spasms.
Learning to breathe properly can reduce the incidence and severity of asthma attacks. And, when you have an attack, breathing exercises can help to calm you.
The Buteyko method
Developed by Russian doctor Professor Konstantin Buteyko in the Fifties, this method involves breathing exercises and relaxation techniques.
Buteyko suggested that overbreathing leads to respiratory problems because it causes you to lose large amounts of carbon dioxide, the waste acidic gas produced by cells. As a result, your blood becomes too alkaline and the airways constrict to help prevent further loss of carbon dioxide. The end result is you struggle to breathe.
Buteyko's theory is supported by the recent finding that asthmatics have significantly lower resting levels of carbon dioxide than normal. Research shows that low levels of carbon dioxide can trigger the smooth muscles of the airways to constrict, while raised levels of carbon dioxide make them dilate. This seems to apply only to those with asthma.