You are a helpful, respectful, and honest assistant. Always answer as helpfully as possible, while being safe. Your answers should not include any harmful, unethical, racist, sexist, toxic, dangerous, or illegal content. Please ensure that your responses are socially unbiased and positive in nature. If a question does not make any sense or is not factually coherent, explain why instead of answering something not correct. If you don't know the answer to a question, please don't share false information.
What is Exercise-induced bronchoconstriction and explain in detail?
Exercise-induced asthma, or E.I.A., occurs when the airways narrow as a result of exercise.  The preferred term for this condition is exercise-induced bronchoconstriction (EIB). While exercise does not cause asthma, it is frequently an asthma trigger.It might be expected that people with E.I.B. would present with shortness of breath, and/or an elevated respiratory rate and wheezing, consistent with an asthma attack.  However, many will present with decreased stamina, or difficulty in recovering from exertion compared to team members, or paroxysmal coughing from an irritable airway.  Similarly, examination may reveal wheezing and  prolonged expiratory phase, or may be quite normal.  Consequently, a potential for under-diagnosis exists.  Measurement of airflow, such as peak expiratory flow rates, which can be done inexpensively on the track or sideline, may prove helpful. In athletes, symptoms of bronchospasm such as chest discomfort, breathlessness, and fatigue are often falsely attributed to the individual being “out of shape”, having asthma, or possessing a hyperreactive airway rather than E.I.B.

Cause
While the potential triggering events for E.I.B. are well recognized, the underlying pathogenesis is poorly understood. It usually occurs after at least several minutes of vigorous, aerobic activity, which increases oxygen demand to the point where breathing through the nose (nasal breathing) must be supplemented by mouth breathing.  The resultant inhalation of air that has not been warmed and humidified by the nasal passages seems to generate increased blood flow to the linings of the bronchial tree, resulting in edema.  Constriction of these small airways then follows, worsening the degree of obstruction to airflow.  There is increasing evidence that the smooth muscle that lines the airways becomes progressively more sensitive to changes that occur as a result of injury to the airways from dehydration.  The chemical mediators that provoke the muscle spasm appear to arise from mast cells.

Diagnosis
Exercise-induced bronchoconstriction can be difficult to diagnose clinically given the lack of specific symptoms and frequent misinterpretation as manifestations of vigorous exercise.  There are many mimics that present with similar symptoms, such as vocal cord dysfunction, cardiac arrhythmias, cardiomyopathies, and gastroesophageal reflux disease.  It is also important to distinguish those who have asthma with exercise worsening, and who consequently will have abnormal testing at rest, from true exercise-induced bronchoconstriction, where there will be normal baseline results.  Because of the wide differential diagnosis of exertional respiratory complaints, the diagnosis of exercise-induced bronchoconstriction based on history and self-reported symptoms alone has been shown to be inaccurate  and will result in an incorrect diagnosis more than 50% of the time. An important and often over-looked differential diagnosis is exercise-induced laryngeal obstruction EILO. The latter can co-exist with EIB and is best differentiated using objective testing and continuous laryngoscopy during exercise (CLE) testing.

Spirometry
Objective testing should begin with spirometry at rest. In true exercise-induced bronchoconstriction, the results should be within normal limits. Should resting values be abnormal, then asthma, or some other chronic lung condition, is present. There is, of course, no reason why asthma and exercise-induced bronchoconstriction should not co-exist but the distinction is important because without successful treatment of underlying asthma, treatment of an exercise component will likely be unsuccessful.  If baseline testing is normal, some form of exercise or pharmacologic stress will be required, either on the sideline or practice venue, or in the laboratory.

Exercise testing
Treadmill or ergometer-based testing in lung function laboratories are effective methods for diagnosing exercise-induced bronchoconstriction, but may result in false negatives if the exercise stimulus is not intense enough.

Field-exercise challenge
Field-exercise challenge tests that involve the athlete performing the sport in which they are normally involved and assessing FEV1 after exercise are helpful if abnormal but have been shown to be less sensitive than eucapnic voluntary hyperventilation.

Eucapnic voluntary hyperventilation challenge
The International Olympic Committee recommends the eucapnic voluntary hyperventilation (EVH) challenge as the test to document exercise-induced asthma  in Olympic athletes.  In the EVH challenge, the patient voluntarily, without exercising, rapidly breathes dry air enriched with 5% CO2 for six minutes.  The presence of the enriched CO2 compensates for the CO2 losses in the expired air, not matched by metabolic production, that occurs during hyperventilation, and so maintains CO2 levels at normal.

Medication challenge
Medication challenge tests, such as the methacholine challenge test, have a lower sensitivity for detection of exercise-induced bronchoconstriction in athletes and are also not a recommended first-line approach in the evaluation of exercise-induced asthma.Mannitol inhalation has been recently approved for use in the United States.
A relatively recent review of the literature has concluded that there is currently insufficient available evidence to conclude that either mannitol inhalation or eucapnic voluntary hyperventilation are suitable alternatives to exercise challenge testing to detect exercise-induced bronchoconstriction and that additional research is required.

Treatment
Lifestyle
The best treatment is avoidance of conditions predisposing to attacks, when possible.  In athletes who wish to continue their sport or do so in adverse conditions, preventive measures include altered training techniques and medications.
Some take advantage of the refractory period by precipitating an attack by "warming up," and then timing competition such that it occurs during the refractory period.  Step-wise training works in a similar fashion