Impact of varying physical activity levels on airway sensitivity and bronchodilation in healthy humans

The purpose of this study was to determine if the amount of physical activity influences airway sensitivity and bronchodilation in healthy subjects across a range of physical activity levels. Thirty healthy subjects (age, 21.9 ± 2.6 years; 13 men/17 women) with normal pulmonary function reported to the laboratory on 2 separate occasions where they were randomized to breathe either hypertonic saline (HS) (nebulized hypertonic saline (25%) for 20 min) or HS followed by 5 deep inspirations (DIs), which has been reported to bronchodilate the airways. Pulmonary function tests (PFTs) were performed prior to both conditions and following the HS breathing or 5 DIs. Moderate to vigorous physical activity (MVPA) level was measured via accelerometer worn for 7 days. Following the HS breathing, forced expiratory volume in 1 s (FEV₁) and forced vital capacity (FVC) significantly decreased from baseline by –11.8% ± 8.4% and –9.3% ± 6.7%, respectively. A 2-segment linear model determined significant relationships between MVPA and percent change in FEV₁ (r = 0.50) and FVC (r = 0.55). MVPA above ∼497 and ∼500 min/week for FEV₁ and FVC, respectively, resulted in minor additional improvements (p > 0.05) in PFTs following the HS breathing. Following the DIs, FEV₁and FVC decreased (p < 0.05) by –7.3% ± 8.6% and –5.7% ± 5.7%, respectively, from baseline, but were not related (p > 0.05) to MVPA. In conclusion, these data demonstrate that higher MVPA levels attenuated airway sensitivity but not bronchodilation in healthy subjects.