Aim: We wished to determine if an 8-week program of exercise during dialysis in end-stage renal disease (ESRD) patients would increase urea removal (enhance dialysis efficacy) with subsequent improvements in work performance and perception of quality of life, and/or alterations in cardiovascular status.
Methods: Self-care hemodialysis patients (EX, n = 6) performed cycle ergometry exercise 3 times per week during their dialysis session at 40-50% maximal work capacity for 15 min during each of the first 3 hours of dialysis and were matched for age, protein catabolism rate, and WLmax with a CON group (n = 7). Dialysis efficacy was measured using serum urea clearance (Kt/V) and dialysate urea clearance (DUC) during the first 2 hours of dialysis. Resting blood pressure was monitored on a sessional basis, pre- and postdialysis and during exercise in the EX group. QOL, measured using the SF-36 questionnaire, and WLmax were determined prior to and at 4 and 8 weeks of the exercise program.
Results: DUC was significantly elevated in the EX group at the end of the exercise program, but was of insufficient magnitude to result in an overall increase in Kt/V. DUC decreased in the CON group but Kt/V remained unchanged. No changes in resting blood pressure occurred in either group over the course of the study, however, pulse pressure tended to increase in the CON group but decrease in the EX group, indicating a potential beneficial adaptation of the cardiovascular system in patients undergoing an exercise program. The exercise program had no effect on QOL scores and this was most likely due to the short duration of the exercise program and high-functioning level of the population studied as compared to normative data for this patient population. We also found that 33% of the exercise sessions in the 3rd hour of dialysis were not performed due to hypotensive events.
Conclusion: Exercise during dialysis enhanced dialysate urea removal but not serum urea clearance. Alterations in the modality and the timing of exercise during dialysis may be required to elicit increases in serum urea clearance. It is also recommended that exercise during dialysis be performed during the first 2 hours of dialysis.