The investigators will test the hypothesis that a combination of normobaric hypoxia and exercise training elicits a synergistic effect on age-associated metabolic skeletal muscle dysfunction and the investigators will address the molecular mechanisms. In a randomized clinical study, the investigators will compare normoxic and hypoxic training conditions in elderly subjects. Outcome measures will focus on whole body insulin sensitivity and mitochondrial responses in skeletal muscle before and after the 8-week training intervention.