Abstract: This study compared the effects of varying aerobic training programs on pulmonary diffusingcapacity(TLCO),pulmonarydiffusingcapacityfornitricoxide(TLNO),lungcapillaryblood volume (Vc) and alveolar–capillary membrane diffusing capacity (DM) of gases at rest and just after maximal exercise in young athletes. Sixteen healthy young runners (16–18 years) were randomly assigned to an intense endurance training program (IET, n = 8) or to a moderate endurance training program (MET, n = 8). The training volume was similar in IET and MET but with different work intensities, and each lasted for 8 weeks. Participants performed a maximal graded cycle bicycle ergometer test to measure maximal oxygen consumption (VO2max) and maximal aerobic power (MAP)beforeandafterthetrainingprograms. Moreover,TLCO,TLNO andVcweremeasuredduring asinglebreathmaneuver. Aftereightweeksoftraining,allpulmonaryparameterswiththeexception of alveolar volume (VA) and inspiratory volume (VI) (0.104 < p < 0889; 0.001 < ES < 0.091), measured at rest and at the end of maximal exercise, showed significant group×time interactions (p < 0.05, 0.2 < ES < 4.0). Post hoc analyses revealed significant pre-to-post decreases for maximal heart rates (p < 0.0001,ES=3.1)andimprovementsforVO2max(p=0.006,ES=2.22)intheIETgroup. Moreover, post hoc analyses revealed significant pre-to-post improvements in the IET for DM, TLNO, TLCO and Vc(0.001
