High school elite training programs are today more and more under development in several 'elite sport schools' in Belgium, in order to select and train future elite athletes already at young age. Little is known about the effects of sustained training on the potential development of asthma in adolescents during lung growth. It would be of great importance to be able to select the individuals at risk to develop exercise-induced asthma, already at the start of their enrollment in the 'elite sport school. This would allow physicians to follow their lung function parameters very closely and regularly; and, if necessary, start treatment early after the first signs of exercise-induced asthma.

Competitive swimmers, competitive indoor athletes and control individuals performing sports at a recreational level will be recruited for the study.

They will perform a sport-specific training (swimmers and controls: swimming for 90 minutes, indoor athletes: basketball or volleyball for 90 minutes)

Baseline measurements:

• Airway inflammation upper and lower airways will be assessed by collection of nasal fluid (nasal sponge will be inserted in nostril for 5 minutes), Fraction of exhaled Nitric Oxide measurement and sputum induction.
• Upper and lower airway symptoms will be assessed by questionnaires (SinoNasal Outcome Measure-22, Visual Analogue Score, Asthma Symptom Score and Juniper Score)
• Allergy will be assessed by skin prick test (on skin) and immunocap test (in blood, 1 tube of 10 ml).
• Lung function and nasal patency will be measured by spirometry and Peak Nasal Inspiratory Flow measurement.
• Exercise induced bronchoconstriction will be assessed by eucapnic voluntary hyperventilation test.

Measurements immediately after training:

• Collection of nasal fluid
• Assessment of upper airway symptoms (Visual Analogue Score)
• Spirometry and Fraction of Exhaled Nitric Oxide measurement
• Peak Nasal Inspiratory Flow measurement

Measurements 24 hours after training:

• Collection of nasal fluid
• Assessment of upper airway symptoms (Visual Analogue Score)
• Spirometry and Fraction of Exhaled Nitric Oxide measurement
• Peak Nasal Inspiratory Flow measurement
• Sputum induction
• Venous puncture (1 tube of 10 ml)

Inclusion Criteria:

• Performing sports at national or international level (swimmers and indoor athletes)

Exclusion Criteria:

• Performing sport at recreational level (not more than 4 hours/week for healthy individuals)

Competitive swimmers, competitive indoor athletes and healthy individuals

Overall results are presented in a closed session for participants and parents. Confidential individual data are afterwards discussed with the respective parents and participants.