Back to Sports MedicineLungs have a incomparable capacity of adapting to to greater works changes, as shown by the capacity of increase the pulmonary ventilation from 5 to 7 litres/min. at resting to 100 to 200 litres/min. during a intense exercise. Then, the celular metabolism at muscular level and the adaptive responses of cardiovascular system are the habitual limiting factors to the aerobic capacity. The normal athlete that uses in exercise his maximum hear hate , uses only about 60% of the maximum ventilatory capacity.
EIB is a condition in which vigorous exercise physical activity tiggers acute airway narrowing in people with higtended airway reactivity. Constriction of upper aiways are present , limiting the capacity of the lungs in adapting under increased demand conditions.
Asthma is an extremely common afection reported in 4% to 7% of north american population. The great majority of asthmatics has symptomatic EIB in recreational sports. However , some trials has shown a 10% to 15% incidence of EIB in competitive athletes, whom without any history of intrinsic asthma.
EIB has a negative impact on athletes performance and on the pleasure of exercising. Fortunatelly, medical intervention results in reducing of symptons during and after exercising and it allows people to enjoy exercising.
The tipical asthmatic response to exercise is characterized by an initial improvment of pulmonary function during a rapid, but intense exercise , followed by a great decrease of this function after the end of exercise. This kind of response was first described in the sixties and it was used to test new pharmacologic agents in treatment of asthma in resting. The EIB recieved the scientists attention a decade later after the introduction of bronchodilators.
The initial trials and clinical investigations were focused on improvement of the exercise tolerence in the patients with asthma which needed padronized therapy to have recreational activities without symptons. These trials resulted in improvment of symptons and in protocols for earlier indentification of EIB.
In Los Angeles 1984 Olympic Games, the US Olympic Training Center realized a program to identify athletes with EIB. This search shown that 11.2% of olympic athletes had EIB (67 of 597 studied). Only 26 of them related a history of previous asthma , what emphasize the EIB phenomenon among non-asthmatic athletes. Forty one medals, including 15 gold medals were won by these group , in 1984, showing the sucess of appropriated intervention.
EIB affects a broad segment of population. Up to 90% of people with asthma experience EIB during the course of their desease and most consider exercising to be a major precipitant of their symptons. In non-asthmatic population the incidence is much lower , about 3% to 10%. Considering both , an overall EIB incidence is about 12% to 15%. The incidence is somewhat higher in children. (figure 1)
It is generally accepted that the pathogenesis of EIB is closely associated with the fluxes in heat and water that develops within the tracheobrochial tree during the conditioning (warming and humidification) of large volumes of air. Grater moviment of heat and water from the mucosa is necessary to bring the inspired air to full saturation at body temperature. The larger the quatity of thermal energy that needs to be tranfered, the cooler the airways become, the more rapidly they rewarm and the more the bronchi are narrowed. Conversly, low ventilation or inhalation of air with high humidity minimizes these exchanges, thereby limiting the subsequent thermal changes that lead to the development of airway obstruction.
However it is not known how intra-aiway thermal fluxes produce bonchial narrowing. Evaporation of mucosal surface water and the airway wall hiperemia leading to edema are hypotesis to be confirmed. The role of inflamatory mediatores in the pathogenesis of EIB is controversial.
Athletes predisposed to EIB, often mention that exercise realised in cold and dry athmosfere is the most powerfull stimulus for bronchospasm. (figure 2)
The process of pre-season pysical examination gives an exellent opportunity of screenig for EIB. Athletes with previous diagnosis of asthma or allergy are high risk group for EIB. As exposed previously, the incidence of symptons has been reported from 40% in the allergic group and 90% in the asthma group.
It is also important to check the regular or occasional drugs use in each athlete , as theophyline, bronchodilators, and anti-inflamatories to detect the probality of EIB.
An other point it is to pay attention on classic signs and symptons of EIB, which are indistinguishable from those precipitated by other stimuli (singns and symptons will be discussed later at Diagnosing EIB).
Coach’s observation could be valious to identify high risk athletes. “The changing room coughing” is a good signal for risk. As well , athletes not in shape in the middle of competitive season and the ones with recurrent airway infections or with bronchitis have a high risk too.
At part II, it will be discussed Less tolerated sports, Diagnosing EIB, Treatment, and Why to continue exercising.
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