A Pounds 100,000 research project at Birmingham University could help to reduce the high incidence of infection among athletes specialising in sports such as long-distance running, cycling and swimming.
Mike Gleeson, senior lecturer in exercise biochemistry at Birmingham, says evidence showing that "endurance athletes" are more prone to infection than their colleagues in other sports is "considerable". The athletes' tough training regimes are believed to weaken the immune system, he says.
Dr Gleeson explains that heavy exercise typically results in the body generating high levels of stress hormones - chemicals such as cortisol - that help to control heart rate and the response of the cardiovascular system. Cortisol also mobilises fuel for use as energy by muscles.
But heavy training also leads to a depletion of certain plasma amino acids, such as glutamine, that help with tissue repair and production of cells to combat infection.
"The overall impact in both these changes is that the immune system is suppressed," he says.
Dr Gleeson, who leads a research team based at Birmingham's school of sport and exercise science, wants to find out what kinds of exercise cause the body to take action that suppresses the immune system.
He also wants to know how long it takes for the immune system to recover from a bout of heavy training, and whether changes in athletes' diet before and after exercise can minimise or prevent the weakening of the system.
"The overall aim is to give athletes and coaches guidelines on appropriate training requirements, recovery times and nutritional support that help to alleviate the side-effects without compromising performance," Dr Gleeson says.
Backed by the Sports Council, the researchers are working with middle- to long-distance runners. They are also collaborating with cyclists through the British Cycling Federation.