Exercise has a paradoxical relationship to asthma. It has been known for nearly 2000 years that exercise can provoke bronchoconstriction,1 termed exercise-induced bronchoconstriction or exercise-induced asthma. Yet exercise has also been prescribed to assist in the management of asthma as long ago as the middle of the 16th century.2 Over the last two decades, evidence has been accumulating that intense repeated exercise can injure airways and promote the development of airway hyperresponsiveness (AHR) and/or asthma in athletes with no past or family history of asthma.3 This issue of BJSM will focus on the third aspect of this triad.

Concerned that Olympic athletes may have been misusing inhaled β₂ agonists (IBA), in 2002 the International Olympic Committee (IOC) introduced the requirement that athletes had to demonstrate current asthma/AHR to use IBA before an event at the Olympic Games.4 It is stressed that this policy was introduced to protect the health of athletes and was not an antidoping measure. These requirements continued for four games and applications were managed by an IOC Independent Asthma Panel.5 After Beijing 2008, the World AntiDoping Agency (WADA) followed the IOC's lead by introducing similar requirements for athletes globally in 2009. However, this policy was short-lived being partially rescinded in 2010. For 2012, the three most frequently used IBA, formoterol, salbutamol and salmeterol may be prescribed in sport without restriction.6

The six members of the IOC's Panel with the assistance of two other experts combined to present a symposium on Respiratory Health at the IOC's Conference on the Prevention of Injury and Illness in Sport held in Monaco in April 2011. The following eight papers have been prepared to provide readers of BJSM with the messages presented in Monaco.

Donald McKenzie (Vancouver) takes readers through some basic exercise physiology (see page 381) noting that the respiratory system is built for exercise but lacks the ability to adapt to high-level endurance training. While for the average fit individual, the lungs have adequate reserve capacity, in elite endurance trained athletes, this lack of adaptation can be a limiting factor in maximal performance. This paper discusses some of the possible mechanisms by which this may occur.

Pascale Kippelen (London) and Sandra Anderson (Sydney) review the current state of knowledge of the pathophysiology of the effects that strenuous exercise have on the airways (see page 385). Discussing data from studies of airway secretions, blood and urine and endobronchial biopsies in animals and humans, they describe how severe exercise hyperpnoea may affect airway epithelial cells by respiratory water and heat loss. Such airway injury may be worsened if the inspired air contains pollutants such as chloramines. They discuss how the repair process, that follows injury, may explain the development of AHR. Mechanical shear stress and pressure gradients may further injure the airway epithelium and the short- and long-term consequences are discussed.

Anderson and Kippelen examine how to assess and prevent exercise-induced bronchoconstriction in athletes (see page 391). They evaluate the bronchial provocation tests that were recommended by the IOC and later by WADA to approve IBA use. This document emphasises the need to conduct appropriate lung function testing to provide the best medical care for athletes. It is hoped that this advice will be heeded by team doctors and sports physicians despite the cessation of the IOC's IBA programme and the marked reduction in the requirements of WADA for athletes to use IBA.

The focus then switches to environmental issues and the inspired air. Malcolm Sue-Chu lives in Trondheim Norway, located close to the Arctic Circle which is an ideal location to research snow-based athletes. He and his colleagues reveal the long-term effects of exercising vigorously while breathing high minute volumes of very cold air (see page 397). The pathophysiology of airway injury sustained by skiers is reviewed although it is mentioned that we do not know if the changes described are permanent or reversible after ceasing vigorous endurance exercise in the cold.

Although swimming has been recommended as a suitable exercise for asthma rehabilitation,7 there is now a lot of circumstantial evidence that by-products of chlorine, used to disinfect indoor swimming pools, are associated with airway injury that may account for the development of AHR/asthma in swimmers. Valérie Bougault (Lille, France) and Louis-Philippe Boulet (Quebec City, Canada) examine the considerable body of research that has been published in recent years including their own investigations (see page 402). They provide recommendations to limit exposure to chlorine by-products to minimise the potential to injure the airways that is occurring from swimming in indoor pools.

Ken Rundell (Exton, Pennsylvania) has undertaken considerable research into the consequences of athletes breathing air containing particulate matter derived from combustion engines. His paper discusses the short- and long-term effects of inhaling large minute volumes of air containing particulate matter and efforts that can be undertaken to reduce these consequences (see page 407). He raises the issue that there have been few studies on the effects of either long-term or acute exposure to air pollution on athletic performance.

Ken Fitch (Perth, Australia) reviews the data that the IOC's Independent Asthma Panel has accrued from around 1600 IBA applications (see page 413). This demonstrates that AHR/asthma is the most common chronic medical condition experienced by Olympic athletes and occurs predominately in athletes undertaking endurance training, more so if inspiring cold or polluted air. One aspect of interest is the relatively late onset of AHR/asthma in many older Olympic athletes. A surprising finding has been that Olympic athletes with proven asthma/AHR outperform their rivals.

Finally, Louis-Philippe Boulet provides readers with a detailed examination of cough and upper airway disorders that are very prevalent in elite athletes (see page 417). He discusses a range of conditions including rhinitis, allergic and non-allergic and the difficult topic of vocal cord dysfunction. The author advises readers on the clinical features of each, the appropriate investigations to be undertaken and their optimal management.