With the Olympics taking place in London this year, sport is headline news. However few of us – 40% of men and only 28% of women in England – meet the current guidelines of 30 minutes of activity on at least five days a week. According to Mike Gleeson, Professor of Exercise Biochemistry at Loughborough University, upping our exercise levels to a reasonable level affects our likelihood of catching a cold or other upper-respiratory tract infection (URTI). “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,” he explained.
“Research shows that those undertaking regular modular exercise (such as a daily brisk walk), can reduce their chance of catching a respiratory infection such as a cold, by up to almost a third.” Don’t expect it to happen overnight though. This benefit comes from the cumulative effect of regular exercise giving us long-term improvement in our immunity.
URTIs are usually caused by viruses but whether we succumb to the unpleasant symptoms depends mainly on whether our immune systems are in good shape. Having a fighting fit immune system depends on a range of factors – genetics, stress, poor nutrition, lack of sleep - and exercise.
“The major players in this immune regulation are immune cells called Natural Killer (NK) cells, which are important weapons in the fight against viral infections. NK cells recognise viral-infected cells as foreign invaders and force them to commit suicide,” says professor Gleeson.
NK cells are also highly influenced by physical exercise. “During moderate exercise the activity of NK cells is enhanced, whereas stressful endurance activities such as marathons can turn down NK cell activity, “ he explains. “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.
“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 and upper respiratory infection,” said Professor Gleeson. “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.
NHS Choices Live Well Health and Fitness pages