Special feature for the Olympics: effects of exercise on the immune system. Overview: exercise immunology.

The review articles in this special feature reflect the current status of knowledge in the field of exercise immunology, with a focus on how exercise affects the human immune system and the health implications for resistance to infections and neoplastic diseases. In an Olympic year, the emphasis of exercise immunology research tends to be on elite athletes and the prevention of infections in the quest for optimum performance. However, research presented in this issue also covers recreational athletes, as well as highlighting the benefits of exercise for our ageing population.