Assessment of respiratory function at rest and after exercise in children, adolescents and adults living in areas with high air pollution

Observational part (baseline assessment): All participants undergo assessment of respiratory function at rest and after a progressive exercise test. Progressive exercise protocol: Incremental cycling test on an electronically braked cycle ergometer (Lode Excalibur Sport), starting at 25 W and increasing by 25 W every 2 minutes until volitional fatigue or symptom limitation (maximum approximately 20 minutes). Duration of session: Up to 2 hours including rest measurements, exercise test, spirometry, impulse oscillometry, respiratory muscle strength assessment and completion of symptom questionnaires. Measurements: Spirometry: forced expiratory manoeuvres to measure vital capacity (VC), forced expiratory volume in 1 second (FEV1), and forced vital capacity (FVC). Impulse oscillometry: participants breathe normally through a mouthpiece while small pressure oscillations (5–20 Hz) are applied to assess respiratory impedance (R5, R20, AX, R5–R20). Respiratory muscle strength: inspiratory and expiratory pressures (PImax, PEmax) measured using a handheld manometer. Assessments are conducted by a respiratory physiologist or respiratory physician at the Laboratory of Exercise Physiology and Metabolism, Academy of Physical Education in Katowice. Interventional part (training programme): A subgroup of participants performs Inspiratory Muscle Training (IMT) for 6 weeks using a pressure threshold device (POWERbreathe® or Threshold IMT). Each training day includes approximately 1 hour of respiratory training divided into two 30-minute sessions, with additional warm-up and stretching exercises. IMT is performed every other day according to the Hill protocol: seven 2-minute breathing cycles with 1-minute rest periods. The initial load is set at 30% of baseline PImax and progressively increased, according to tolerance, up to 60% of PImax over the course of the programme. Weekly supervised sessions (about 15 minutes each) are conducted by a physiotherapist trained in respiratory rehabilitation. Participants receive education on correct device use, breathing technique, and relaxation (autogenic training). Each participant keeps a training diary to record all unsupervised home sessions. PImax determination: The inspiratory pressure threshold is determined as the maximal inspiratory pressure (PImax) generated at the mouth during a maximal inspiratory effort against an occluded airway.