Exercise-induced bronchodilation is not different in healthy males and females

Exercise-induced bronchodilation (EIBD) is the dilation of the airways that occurs during whole body dynamic exercise. Females have greater β2-adrenergic receptor activity in the peripheral vasculature, which accentuates vasodilation, but it is unknown if this translates to the airways. EIBD can be quantified by performing maximal expiratory maneuvers before and immediately after exercise; however, the assessment is impacted by thoracic gas compression. Accordingly, we sought to determine if there are sex differences in the extent of EIBD. Twenty-two healthy adults (n = 11 female) performed multiple forced expiratory maneuvers in a custom-designed volume-displacement body plethysmograph, before and after incremental cycle exercise to volitional exhaustion. The customized body plethysmograph allows for simultaneous assessment of compressed and compression-free flow-volume loops. During exercise, inspired air was warmed (24 ± 0.7°C) and humidified (94 ± 6%) and postexercise pulmonary function was completed <10 min after exercise cessation. Males had a greater maximal oxygen uptake than females (51 ± 7 mL kg^-1min^-1 vs. 42 ± 6 mL kg^-1min^-1, P < 0.01). Using compressed flow-volume loops, forced expiratory volume in 1 s was increased following exercise in males (5.03 ± 0.58 L vs. 4.80 ± 0.63 L, P < 0.01) and females (3.96 ± 0.32 L vs. 3.81 ± 0.31 L, P < 0.01), but the relative change from baseline was not different between the sexes (P = 0.39). Likewise, the relative change in mid-expiratory flows was not different between sexes (P = 0.77). Using compression-free flow-volume loops, bronchodilation was evident using mid flows in both sexes. In conclusion, the extent of EIBD is not different between the sexes, but the use of compression-free flow-volume curves only shows EIBD for mid flows in both sexes similarly.NEW & NOTEWORTHY The magnitude of exercise-induced bronchodilation (EIBD) was not different in healthy young males and females. Both sexes exhibited a ∼5% improvement in forced expired volume in 1 s and an 8%-20% improvement in mid-expiratory flows. When accounting for thoracic gas compression using a volume displacement plethysmograph, the lack of sex differences in EIBD persisted but the absolute magnitude of EIBD was diminished.