Physical activity is a potent way of relieving some of the adverse morbidities associated with COPD, such as muscle atrophy and reduced muscle quality. It is thus problematic that 20-30% of patients fail to elicit positive adaptations to training. This oddity has been ascribed inherent muscular properties, with potential links to comorbidities such as vitamin D and testosterone deficiency and the nature of the training program. In the present project, a double-blinded RCT will be performed to disclose the functional and biological efficacy of vitamin D supplementation (with concomitant ingestion of 1000 mg Ca2+) on the outcomes of 10 wks strength training in 100 aging individuals with or without COPD. The strength training intervention will be preceded by 3 weeks of progressive introduction to training protocols.