You are sneezing, spluttering and have trouble breathing through your nose. Surely, your workouts should be put on hold until you feel better? Not according to American researchers who have been studying the results of exercising with a cold. Professor Leonard Kaminsky, an exercise scientist at Ball State University in Indiana, found that colds have little effect on athletic performance and that exercise doesn't aggravate symptoms such as blocked nose and streaming eyes.A little sweating when you have a cold may even boost the activity of white blood cells that fight infection, Kaminsky says. “A lot of people in our trials said that they felt OK exercising,” he says. “In some cases, they even felt better.”

Kaminsky and his team studied a group of men and women who agreed to be infected with the rhinovirus responsible for most colds. Two days after being infected, when the colds were at their heaviest, the subjects were asked to run on a treadmill while physiological tests were carried out. Like the healthy control group, cold-sufferers experienced no drop in lung function or capacity.

“I was surprised that their performance was not affected, even though they said that they felt more tired than usual,” Kaminsky says. He urges people with light colds to keep active, although those with more severe, feverish symptoms should listen to their bodies and proceed with caution.

What do British experts think of his controversial advice? “It's a bit of a misnomer that you should take to your bed when you have a cold. For most people, working out is fine,” says Louise Sutton, head of the Carnegie Centre for Sports Performance and Wellbeing at Leeds Metropolitan University. “My suggestion would be to apply the “below the neck” rule. If you have fever, sore muscles or joints, vomiting or a very productive cough - symptoms that exhibit themselves from the neck down - then you probably need to avoid exercise for at least a couple of days. If you just have a runny or blocked nose, watery eyes and a light, tickly cough then go ahead.”

Indeed, keep moving and you might avoid the next cold altogether. Three years ago researchers found that women who exercised regularly - doing at least 45 minute of moderate activity on five days a week throughout a year-long study - were three times less likely to suffer a bout of the sniffles than their couch-potato counterparts. It seemed that activity strengthened the effect of immune cells that protect against viruses and bacteria that can cause infection.

However, while exercise does seem to boost immunity, it does so only to a point. Serious athletes or anyone in training for the London Marathon or another endurance event may find their defences are compromised as a result of longer or more intense workouts.

Dr David Nieman, director of the Human Performance Laboratory at Appalachian State University, North Carolina, has carried out research into the effects of strenuous workouts or prolonged periods of heavy training. “If you are running or exercising continuously for 90 minutes or longer, there is a temporary downturn in immunity,” he says. “At that point, carbohydrate stores drop causing a spike in the hormones cortisol and epinephrine that inhibit the protective effects of neutrophils and lymphocytes leaving you vulnerable to bugs.”

Other studies at the Rigshospitalet in Copenhagen, have shown that there is a “window” of impaired immunity for the highly active. Marathon runners, for example, are more at risk of catching colds during the 72 hours after they finish the race.

Boost your defences

1. A paper published in the US in 2007 showed that while vitamin C intake had little effect on most people, it halved the risk of getting colds for marathon runners, skiers and other endurance athletes. Vitamin C does not cure colds.

2. Taking a carbohydrate-rich isotonic drink can slow the rise in stress hormones and offset negative immune responses, Dr David Nieman found. He recommends drinking 400ml of a sports drink 30 min before a workout that exceeds 90 min, 400ml of the drink during every 30 min of activity and 400ml afterwards.

3. Athletes who took 1,000mg of quercetin, an antioxidant found in black tea and berries, for three weeks before a three-day period of intense exercise were found to have fewer upper-respiratory tract infections in the two weeks after the activity.

4. A study published in the New Scientist showed that people who drank 14 glasses of red wine a week (but not spirits or beer) halved their risk of getting a cold.

Dr Mark Porter, The Times doctor, says:

Professor Kaminsky's findings are reassuring for competitive athletes, anyone preparing for the London Marathon, or those with immovable fixtures on the court or sports field. Continuing your training, or playing that game of rugby or squash, will not do you any harm if you are battling with a minor cough or cold. But for the rest of us - people who exercise simply because we enjoy being active - it won't change much. If I am under the weather, then I don't go for a run. It's good to rest your body occasionally, so I'll continue to use colds as an excuse to curl up on the sofa and watch Midsomer Murders.

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