This is a controlled clinical trial with participants recruited from the dialysis unit of a university hospital (a tertiary-care centre). All patients from this unit who agreed and that had no medical contraindications had already been included in a resistance and aerobic intradialytic training program. In this unit, the size of the low flux polysulfone dialyzers is selected according to patient's body surface area and the dialyzers are reused up to twelve times. The target Kt/V is 1.2 or higher. The target hemoglobin level is from 10.5 to 12.5 g/dL. Dialysis is performed using On-Line Clearance Monitor (OCM)-equipped Fresenius 4008-S machines (Fresenius, Bad Homburg, Germany).