CONCLUSIONS
muscle gain, quadriceps femoris muscle, hypoxia, muscle dysfunction, nonhypoxemic COPD, COPD
COPD, HYPOXIA
To the best of our knowledge, this is the first randomized, controlled, double-blind trial to provide an evaluation of functional and morphological adaptations of thigh muscles after an exercise intervention with and without supplemental oxygen during training in patients with COPD. Supplemental oxygen significantly increased the training impact on peak work rate and fostered quadriceps femoris muscle growth. Our data may generate the hypothesis that exercise-induced peripheral hypoxia limits muscular training adaptations, which might, at least partially, explain the high interindividual variability, supporting the concept of a possible limb muscle dysfunction phenotype in COPD. However, this could be mitigated by providing supplemental oxygen during exercise training, which demonstrated great importance to ensure muscle gain and thus improve peak exercise capacity. Although the current evidence for providing supplemental oxygen during training for patients with nonhypoxemic COPD is limited, future studies should not anymore focus on the yes or no, but they may aim to understand when, how, and in which patients it could be best used.The authors thank the staff, collaborators, and technicians of the different involved institutions for their contribution and valuable support during study conduct.The The results of this study are presented clearly, honestly and without fabrication, falsification, or inappropriate data manipulation. The results of the present study do not constitute endorsement by the American College of Sports Medicine.Availability of data and material: Data are available on motivated request from the authors.Ethics approval: The ethics committee of the State of Salzburg approved the SCOPE study, which was performed in accordance with the ethical standards as laid down in the 1964 Declaration of Helsinki and its later amendments.Consent to participate: All participants provided written informed consent.Consent for publication: n.a.Code availability: n.a.Author contributions: D. Neunhäuserer was involved in study design, data acquisition, analysis, and interpretation, as well as in writing the article. M. H. was involved in data acquisition/interpretation, article writing, and revisions. D. Niederseer was involved in study design/conduct, and particularly as expert consultant, as well as in article revisions. M. V. was particularly involved in data interpretation, and literature and article revisions. W. W. was involved in data acquisition and article revisions. E. S.-K. was involved in study coordination/conduct and data acquisition. B. K. was involved in statistical study analyses, data interpretation, and article revisions. B. L. was involved in study design, data acquisition, and article revisions. A. E. was particularly involved as expert consultant and in data and article revisions. M. S. was involved in study design, data analysis, interpretation, and revision of the article. J. N. was involved in study design, data analysis and interpretation, and writing and revision of the article. All authors meet the criteria for authorship and read and approved the final version.