This prospective, multicenter, cross-sectional, repeated-measures comparative study compared functional and biochemical response profiles to exercise between 2 groups of chronically ill patients (chronic renal failure dialysis patients and patients with metabolic syndrome) and a group of healthy subjects. The hypothesis is that the addition of plasma metabolic intermediates associated with energy disorders linked to insulin resistance, will improve the sensitivity of the assessment of muscle oxidative metabolism abnormalities, as reported in exercise intolerant subjects. In this way, the metabolomics approach during exercise would provide a biological and functional signature of insulin resistance of muscular origin, discriminating between insulin-resistant patients, healthy control subjects and dialysis patients, with an exercise metabolic profile approaching that observed in insulin-resistant patients. A better understanding of metabolic abnormalities could guide muscle rehabilitation. Participants will be asked to perform an exercise test, with several blood samples taken at different exercise intensities. Researchers will compare the metabolic profile of three groups: patients with chronic kidney disease, patients with metabolic syndrome and healthy subjects: * V'O2-adjusted lactate at rest and during exercise * The combination of exercise energy metabolism intermediates reflecting insulin resistance among Krebs cycle cofactors/substrates, ß-oxidation cofactors/substrates, amino acids