Brisk walk best way to prevent colds

MARATHON runners may be as unhealthy as couch potatoes when it comes to catching a cold it was claimed yesterday, as scientists revealed too much exercise might be as bad as too little for the immune system.

However, a regular brisk walk can keep winter colds and flu at bay. Moderate exercise strengthens the body’s defences against nose and throat infections such as colds, flu and sinusitis, according to Professor Mike Gleeson.

Different levels of exercise significantly increase or decrease the chances of catching an upper-respiratory tract infection (URTI), said Prof Gleeson, from the University of Loughborough.

Physical activity helps determine individual susceptibility to infection along with other factors such as genetics, stress, nutrition and sleep, he told the Association for Science Education conference at the University of Liverpool.

“If you have a tendency to be a couch potato then you probably have an average risk of catching an infection — typically two to three URTIs per year.

“Research shows that those undertaking regular moderate exercise [such as a brisk walk daily], can reduce their chance of catching a respiratory infection, such as a cold, by up to almost one 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 to 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.”

Immune system cells called natural killer (NK) are important weapons in the fight against viral infections, he said.

NK cells recognise cells invaded by viruses and force them to commit suicide. Moderate exercise boosts NK cells’ performance, while stressful endurance activity such as marathon running reduces it. The changes are regulated by stress hormones and other immune cells.