Marathon runners may be as unhealthy as couch potatoes when it comes to catching a cold.
On the other hand, a regular brisk walk can keep winter colds and flu at bay, a leading professor has revealed.
Moderate exercise strengthens the body’s defences against nose and throat infections such as the common cold, flu and sinusitis.
But too much exercise might be as bad as too little for the immune system, according to Professor Mike Gleeson.
Different levels of exercise significantly increase or decrease the chances of catching an upper-respiratory tract infection (URTI).
Physical activity helps determine individual susceptibility to infection along with other factors such as genetics, stress, nutrition and sleep.
Prof Gleeson, who was speaking out at a recent conference, says: ‘Research shows that those undertaking regular moderate exercise, can reduce their chance of catching a respiratory infection, such as a cold, by up to almost a third.
‘Conversely, in periods following prolonged strenuous exercise, the likelihood of an individual becoming ill actually increases. In the weeks following a marathon, studies have reported a two-six fold increase in the risk of developing an upper respiratory infection.
‘The heavy training loads of endurance athletes make them more susceptible to URTIs and this is an issue for them as infections can mean missing training sessions or underperforming in competitions.’
He adds: ‘Moderate exercise has a positive effect on the immune system. So to keep colds at bay, a brisk daily walk should help – it’s all about finding a happy medium.’