The patient numbers with metabolic syndrome and diabetes have doubled in the last decade. Data that physical exercise ameliorates the metabolic syndrome are convincing, although the mechanisms of the effect in man are not clear. Numerous endocrine or molecular mechanisms modified by physical exercise are known to be hypoxia-sensitive, i.e. by hypoxia-inducible factor-1 (HIF-1) regulation. Thus, relative hypoxia may link physical exercise and modification of endogenous metabolism. Medical communities seem ill equipped to address the primary issues involved. The investigators have experience with normobaric "hypoxia chambers" and will now test a (physical exercise) training program, using state-of-the-art assessments available nowhere else in Germany. The investigators will compare hypoxia chamber, to ambient training, to test the notion that specific exercise conditions could regulate specific molecular pathways involved in the pathogenesis of the metabolic syndrome. Indeed, hypoxia chamber training could be superior to conventional training in terms of reducing cardiovascular risk factors or improving fitness. The investigators will test overall metabolism-related effects with a metabolic chamber. The investigators will test local metabolism with microdialysis during exercise routines, and the investigators will perform fat and muscle biopsies to investigate tissue-related effects. The investigators include experience from a broad-ranging spectrum. The investigators findings might improve understanding mechanisms linking physical exercise and endogenous metabolism. Furthermore, they could influence decision-making regarding non-pharmacological interventions.