The occurrence of adverse events will be collected from all four randomization groups.The hemodialysis run-sheet, nursing notes, and exercise data collection form will be reviewed weekly for the occurence of adverse events. Hemodialysis unit staff and the exercise trainer have been instructed to report adverse events (defined a priori) as they occur. In addition, prior to each exercise session, participants will be asked if they have had any new health problems or symptoms since their last exercise session.