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Zara Horner

SORE THROAT, runny nose, painful joints ... but you still feel like hitting the gym. If you're trying to shake the aches as quickly as you can, is exercise or rest the best?

Colds are probably the most frequently occurring illness  and can be caused by more than 200 viruses, which inflame the upper respiratory tract. Coughing is the body's way of trying to clear the air passages.

As for whether you should exercise when you're feeling low, Wan Chai general practitioner Sarah Borwein recommends what's called the neck check. If the symptoms are above the neck (such as a stuffy nose, sneezing and headache), then exercise shouldn't be a problem.

If they're below the neck (such as a fever that affects the whole body, muscle aches, diarrhoea or chest congestion), Borwein recommends skipping the gym.

'Above the neck, it's OK to work out - but it's important to take it easy,' she says. 'Go at half speed. If symptoms are below the neck and a person insists on exercising, they run the risk of all sorts of complications, from dehydration to heatstroke and even heart failure.

'Being well hydrated is even more important if you're not well, so drink plenty of fluids and listen to your  body.'

Naturopath Des Gurung agrees. 'Adequate fluid intake is vital when you're sick - particularly if you're exercising with above-the-neck symptoms,' he says. 'Keeping well-hydrated will help reduce a fever and keep secretions loose. At least eight glasses of water or juice are recommended - more if you have a fever. And take fluids warm to ease a sore throat.'

Exercise won't ease symptoms or shorten the duration of a cold, but some research suggests that regular, mild-to-moderate exercise can be helpful  because it can boost the immune system,  reducing the risk of infection.

Borwein  says that people who exercise 'report fewer colds than their inactive peers'. Although the immune system quickly returns to pre-exercise levels  after a session,   working out appears to reduce the risk of infection over the long term.

There are several theories about why exercise helps   ward off bacteria and viral infections. 'It's believed that exercise flushes out bacteria from the lungs, decreasing the chance of illness,' says Borwein. 'The increased bodily waste output in urine and sweat is thought to do the same. Antibodies and white blood cells, the body's defence team, move through the body at a quicker rate with exercise, detecting illness faster and triggering the release of hormones that warn the immune cells about intruding bacteria or viruses.'

The temporary elevation of body temperature may also play a role by inhibiting viral growth and allowing the body to fight infection more effectively.

'Exercise also slows down the release of stress-related hormones,' she says. 'As stress is known to increase the likelihood of illness, it's thought that physical activity could have the reverse effect.'

Although Gurung doesn't dispute this, he says it's best to rest if you're unwell. 'Mild to moderate exercise is OK for above-the-neck symptoms, but  the human immune system functions better when adequately rested,' he says.

'During sleep, chemicals are released into the nervous system  that control the immune functions. These chemicals improve  the body's immunity, so it's always important to get enough rest,  particularly when you're already under the weather.'

It's different at the elite sports level. A survey of about 3,000 top athletic trainers by David Nieman from the Gatorade Sports Science Institute in the US found that 90 per cent thought too much exercise could make a person sick.

Clinicians at winter and summer Olympic Games have reported that upper respiratory infections are prevalent in Games villages, and that infections are one of the biggest problems for athletes,  according to a 1998 report from the American College of Sports Medicine.

A study of competitors in the 1987 Los Angeles Marathon  found that one in seven became sick during the week after the race - about five times the rate of runners who trained for, but didn't take part in, the marathon.

'Exercise immunologists believe the steep drop in immune function which occurs after a high-intensity race and lasts at least six to nine hours allows viruses already in the body to spread and gain a foothold,' Borwein says.

And once a person has a cough or cold there's little to be done except to let it run its course. 'Doctors often joke that a cold lasts seven days without treatment and a week with it,' says Borwein. 'Antibiotics fight bacteria - they have no effect in the treatment of cold viruses. So, prevention rather than cure is the order of the day. Adequate sleep, training at appropriate intensity, drinking plenty of fluids and allowing enough recovery time are vital to a well-functioning immune system.'

A well-balanced diet is also important, she says. A good  guide is 10-15 calories per pound of desired body weight. For example, if you're 170 pounds (77kg), consume about 1,700 calories a day if sedentary and up to  2,500 calories if extremely active.

Mild to moderate exercise when you're sick doesn't seem to be harmful and may even help build the immune system in the long term, which means reducing the risk of getting a cold next year. However, the likes of fever, extreme fatigue or swollen lymph glands require medical attention and rest. 'A person with severe flu-like symptoms shouldn't exercise until the below-the-neck symptoms have improved,' says Borwein.

In Hong Kong, there are other exercise inhibitors to consider.  Anyone who exercises outdoors in urban areas is exposed to  air pollution. Car exhaust fumes are a mixture of suspended particles and gases, the most common being sulphur dioxide, nitrogen dioxide, carbon monoxide and ozone. These ultra-fine particles are easily inhaled because exercisers usually breathe through their mouths, bypassing the nasal cleaning system, and increasing penetration to the lower gas-exchange regions of the lungs.

'Harmful effects from these pollutants are numerous and include cardiovascular disease, and local and systemic inflammation,' says Borwein. 'And some compounds are  suspected carcinogens. Healthy adults might not notice any problems in the short term, but in the long term, it's been well documented that lung function is severely inhibited and chronic respiratory and cardio diseases can result.'

Exercisers who aren't well are particularly susceptible to poor air quality, which can irritate eyes and lungs and even trigger an asthma attack, Borwein says.

She recommends checking the air pollution indices and listening to your  body. If you don't feel like it, don't do it.



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