Asthmatic children should be encouraged to join in for their general good health, although they may need to use a bronchodilator before exercise. No one is certain why exercise sets off asthma, although experts believe asthmatics wheeze when they exercise because faster, deeper breathing dries out the airways and triggers a spasm.
The cold air can also be a factor. Breathing through the nose instead of the mouth causes less wheezing. Exercising in cold, dry weather is more likely to cause wheezing, while swimming is especially good for asthmatics because the air in swimming pools is warm and damp. If you jog in early in the morning or evening and the air is cold, tie a bandana loosely around your face to cover your mouth and nose - this will warm the air and is of great help, according to some asthmatic joggers.