Patients with chronic kidney disease suffer from uremic toxin accumulation. Treatments with hemodiafiltration demonstrate the highest capacity for removing solutes, as well as improving mortality. While exercise has been proven as an adjunct therapy in patients on maintenance hemodialysis, little is known about the exercise influence in maintenance hemodiafiltration programs.

Methods: A retrospective observational study of chronic kidney disease patients at Fenix Nephrology group from 2021 until 2023. Patients were assessed at the start of the exercise program and after six months of rehabilitation. Physical tests included a step-test for endurance, handgrip and one-repetition maximum for muscle strength. The Kidney Disease Quality of Life Short Form evaluated patient-reported outcomes. Kt/V urea and urea reduction ratio were surrogates for hemodiafiltration adequacy. Patients carried out twice weekly aerobic exercises at 70% of the maximum heart rate during the step test, and resistance exercises at 60% of one-repetition maximum.

The objectives of this study were twofold: first, to understand if hemodiafiltration (HDF) combined with exercise is a safe and effective treatment for patients with end-stage renal disease (ESRD/CKD 5D); and second, to explore the efficacy of exercise performed during dialysis sessions (intradialytic) versus between sessions (interdialytic).

The study employed a retrospective observational design, analyzing data from CKD 5D patients undergoing maintenance HDF at the Fenix Nephrology group between 2021 and 2023. Inclusion criteria stipulated that participants were aged 18 years or older, on HDF with optimized medication, and agreed to participate in the exercise program with at least 80% adherence. Assessments were conducted at baseline and after six months of rehabilitation, including a step-test for endurance, handgrip strength measurement, one-repetition maximum (1RM) test for muscle strength, and the Kidney Disease Quality of Life Short Form (KDQOL-SF) questionnaire. Kt/V and urea reduction ratio (URR) were used as surrogates for HDF adequacy.

The exercise protocol involved twice-weekly sessions, with aerobic exercises performed at 70% of the maximum heart rate achieved during the step test, and resistance exercises at 60% of 1RM. Participants self-selected their exercise timing, either intradialytic (during HDF sessions) or interdialytic (on non-dialysis days). For the intradialytic group, exercise was seamlessly integrated into the HDF session, excluding the initial and final two hours of dialysis.

Inclusion Criteria:

• 18 years or older
• Undergoing maintenance hemodiafiltration (HDF)
• Optimized medication regimen
• Agreed to participate in the exercise program with at least 80% adherence

Exclusion Criteria:

• Patients who underwent kidney transplantation during the study period
• Patients with missing data
• Patients with exercise participation below 80% adherence
• Presence of comorbidities such as COPD, stroke, muscle weakness, or recent orthopedic surgery.

The study included patients with end-stage renal disease (ESRD/CKD stage 5D) undergoing maintenance hemodiafiltration (HDF) at the Fenix Nephrology Group between 2021 and 2023.

All data will be stored and only the manuscript results will be published.