Intensive exercise 'damages lungs'

Cross country skiiers may be at risk

Too much intensive physical exercise can damage the lungs, researchers have warned.

Experts at the World Congress on Lung Diseases in Florence, Italy, said athletes who take part in high endurance sports such as marathon running, swimming and cross-country skiing may run the risk of developing breathing difficulties.

The conference heard about a Finnish survey of 58 marathon runners which found one in four suffered a tightening of their airways, either in spring due to pollen, or in winter due to the cold.

The researchers concluded that the runners were three times more likely to suffer from asthma than ordinary people.

Other evidence includes:

• A survey of 1,600 top athletes by the Norwegian University of Sport and Physical Education found one in ten suffered from asthma or wheezing
• 16% of athletes who responded to a US Olympic Committee survey after the 1996 summer games in Atlanta reported suffering from asthma. Among cyclists the figure was 50%
• A study by the Olympic Committee of Colorado (USA) following the 1998 winter games in Nagano found more than a quarter of athletes on the American team suffered from spasms of the airways. Worst affected were cross-country skiers

Swimmers also appear to be at greater risk of developing asthma - although this may be due to inhaling chlorine molecules added to pool water.

Marathon runners can suffer a tightening of their airways

Professor Leif Bjermer, of University Hospital, Trondheim, Norway, told BBC News Online that there were two probable reasons why intensive training may lead to lung damage.

First, exercise increases the rate and depth of breathing, so more potentially allergic particles would be taken down into the airways, increasing the possibility of asthma and other allergic reactions.

In addition, more heat and water vapour is drawn out from the airways, placing more stress on the system.

Secondly, intense exercise appears to suppress the function of the immune system, making the body more vulnerable to infection.

Professor Kai-Hakon Carlsen, of the Voksentoppen Children's Asthma and Allergy Center in Oslo, Norway, said rest was important if athletes developed respiratory problems.

He said: "If an athlete gets an infection they should not train, but try to take it easy, that way they will recover much quicker."

Researchers have also shown that the risk of lung damage may be linked to the climate where training takes place.

Three times as many Swedish skiers reacted negatively to a test of lung function than their Norwegian counterparts.

Experts believe this is due to the fact that the Norwegian skiers train in more humid conditions, while the Swedes are exposed to a cold, dry atmosphere.

Breathing in dry, cold air places even more stress on the airways by drawing higher quantities of moisture out of the tissues. It also reduces the effectiveness of the mucus-based system that removes pollutants from the airways.

They suggest one solution may be to warm inhaled air by wearing a mask.

Other solutions put forward in Florence included anti-inflammatory prophylactic treatments, like the steroid-based remedies often given to asthmatics, and drugs that can be taken 15 minutes before training, which effectively block the constriction of the airways.