Data will be analyzed according to an intention-to-treat principle (i.e., according to assigned instead of received treatment). With an enrollment target of 110 participants in each arm (considering a drop out of 20%) we estimate the 86 patients will complete the follow up in each arm, what will provide the trial a 90% power to detect a 20% effect with respect to the primary outcome (predefined as a 20% increase in average total steps at the dialysis day in the HDF group compared to the HD group). Because of the nature of the intervention, it will not possible to blind the patients, the local study nurses, or the investigators for the treatment assignment.