Background Soccer is one of the most attractive sports around the globe for children and adolescents, and the benefits of soccer training are often shown. Due to the intermittent character of soccer with random changes between high-intensity activity and low-intensity play, athletes’ aerobic (respiratory) capacity is specifically stimulated. However, little is known about the effects of regular soccer practice on pulmonary diffusion capacity (TL) in young players, even though it is the most popular sport in the world. Objectives To analyze the effects of 28 weeks of regular soccer training versus a non-activity control period on the TL, the alveolar-capillary membrane diffusion capacity (DM) as well as the capillary blood volume (Vc) in healthy prepubertal boys aged 6 to 10 years. Methods For this purpose, boys were randomly assigned to a soccer training group (SG, n = 40) or a control group (CG, n = 40). Pre and post-intervention, all participants performed an all-out graded bicycle ergometer test to measure maximal oxygen uptake (VO2max) and maximal aerobic power (MAP). A respiratory maneuver was performed at rest and just at the end of the test to measure the TL for carbon monoxide (TLCO) and nitric oxide (TLNO), DM, as well as Vc. Conclusion Regular soccer training significantly improves pulmonary vascular function and increases DM and Vc after exercise in prepubertal boys. The observed adaptations are most likely due to better recruitment of additional pulmonary capillary function. However, the stepwise linear regression analyses indicated that increases in pulmonary vascular function were not related to improvements in VO2max and MAP.
