• COPD
• vitamin D
• exercise capacity
• VO₂
• COPD mechanisms
• COPD pathology
• exercise

Janssens and colleagues1 have recently reported that vitamin D deficiency is very common in patients affected by chronic obstructive pulmonary disease (COPD) and that vitamin D status correlates with lung function. In the same issue of Thorax, Quint and Wedzicha2 discuss potential effects of vitamin D deficiency and supplementation in COPD with special focus on immunomodulatory function. However, they do not consider a potential impact of the hormone on muscle mass and function, and consequently on exercise capacity in these patients.3

Since exercise …