Exercise induced bronchoconstriction (EIBc) is a recognised response to exercise in asthmatics and athletes but is less well understood in an unselected broad population. Exercise induced bronchodilation (EIBd) has received even less attention. The objective of this study was to Investigate the effects of age, sex, forced expiratory volume in 1 s (FEV1), airflow limitation (FEV1/FVC<0.7) on the prevalence of EIBc and EIBd. Incremental CPET on cycle ergometry to symptom limitation was performed between 1988-2012 at McMaster University. The FEV1 was performed before and 10 mins after exercise. EIBc was defined as a % fall in FEV1 post exercise below the 5th percentile, whilst EIBd as % increase in FEV1 above the 95% percentile. 35 258 subjects between age 6-95 were included in the study (mean age 53, 60% male, 10.3% had airflow limitation (AL, FEV1/FVC7.6% fall in FEV1 post exercise (EIBc), whilst the top 5% a >11% increase (EIBd). The probability of both EIBc and EIBd increased with age and was highest in females across all ages (OR 1.76(1.60-1.94) p<0.0001). The probability of EIBc increased as the FEV1%predicted declined (<40% OR 4.38(3.04-6.31),p2× increased likelihood in females (OR 2.31(1.71-3.113)p<0.0001), with a trend with AL(p=0.06). The probability of EIBd increased as the FEV1%predicted declined, in the presence of AL (OR 1.55 (1.24-0.95) p=0.0001), but sex had no effect. EIBc and EIBd can be demonstrated at the population level and is influenced by age, sex, FEV1%predicted and airflow limitation.©The authors 2021. For reproduction rights and permissions contact firstname.lastname@example.org.