The role of exercise as an adjunctive therapy in patients on maintenance hemodiafiltration: clinical benefits and implications

The global burden of end-stage kidney disease (ESKD) is steadily increasing, with dialysis-dependent patients rising in number each year [1]. In Korea, the aging population has further accelerated this trend, contributing to a growing cohort of older adults requiring chronic dialysis. The average age of patients undergoing dialysis now exceeds 60 years, placing them at high risk for skeletal muscle loss, fatigue, and sarcopenia [2]. Patients with ESKD frequently have multiple comorbidities—such as cardiovascular disease, diabetes, and frailty—that significantly contribute to their overall morbidity and mortality. Functional decline in this population is not only associated with adverse outcomes but is also closely linked to decreased physical activity and impaired quality of life. Sarcopenia has emerged as a critical predictor of poor prognosis in dialysis patients [3]. Recent studies have shown that improving muscle mass and strength may positively influence survival and preserve independence [4,5]. Exercise therapy, long recognized for its benefits in various chronic diseases, has been increasingly studied in dialysis patients, with evidence supporting its role in enhancing muscle mass, physical function, and overall quality of life [6].

While hemodiafiltration (HDF) offers enhanced solute clearance and potential survival benefits over conventional hemodialysis [7], the role of exercise as an adjunctive therapy in patients receiving HDF has not been well studied. In this issue of Kidney Research and Clinical Practice, Andrade et al. [8] report a multicenter observational study examining the effects of structured exercise in patients undergoing maintenance HDF. Over a 6-month period, the authors compared outcomes between patients who participated in exercise programs—either intradialytically or interdialytically—and a usual-care control group. Participants were sedentary adults undergoing chronic HDF who voluntarily enrolled in the exercise program. Patients with exercise adherence below 80% or those who received kidney transplants during the study period were excluded. Clinical and functional assessments were performed at baseline and at six months. The intervention consisted of aerobic and resistance exercises delivered for 30 to 45 minutes per session. Aerobic exercise was prescribed at 70% of the peak heart rate achieved in the YMCA step test, while resistance training was performed at 60% of the one-repetition maximum. Physical therapists, who received standardized training, evaluated the clinical status of patients before each session to ensure safety and consistency. Importantly, no adverse events—including hypotension, arrhythmias, oxygen desaturation, or arteriovenous fistula (AVF) complications—were observed during the study period [7]. This finding highlights the safety and tolerability of exercise interventions in the HDF population. Both the exercise and control groups demonstrated statistically significant improvements in dialysis adequacy, as reflected by urea clearance and spKt/V. However, the exercise group showed additional benefits, including increased fat-free mass, greater handgrip strength, and improved performance in the step test. Interestingly, no significant differences in dialysis efficiency were observed between the intradialytic and interdialytic subgroups, suggesting that the timing of exercise may be less critical than its consistent implementation [8].

Although this study included only patients undergoing HDF and hypothesized that HDF may be more effective at removing exercise-induced middle- and large-molecular-weight uremic toxins, it did not provide sufficient evidence to support this assumption. Whether exercise protocols should be adjusted depending on the dialysis modality remains unclear and warrants further investigation. Nevertheless, if exercise is shown to enhance dialysis efficiency, it may be particularly valuable for patients with suboptimal dialysis adequacy and should be actively considered in that subgroup. Exercise is known to enhance regional blood flow to low-perfusion tissues such as skeletal muscle and skin, potentially improving both oxygen delivery and solute removal [9]. While prior studies have reported improved dialysis efficiency with exercise in hemodialysis patients [6,10], this study provides new evidence that both intra- and interdialytic exercise can similarly enhance performance outcomes in patients on HDF. These findings support the integration of structured exercise as a core component of care in ESKD patients, irrespective of the exercise timing. However, it is crucial to individualize exercise prescriptions based on each patient’s comorbidities and functional capacity. Conditions such as obesity, osteoarthritis, spinal stenosis, COPD, and heart failure may influence tolerance and response to physical activity. Therefore, personalized exercise regimens—adjusting the type and intensity of aerobic and resistance components—should be developed in collaboration with rehabilitation specialists, cardiologists, physical therapists, and dietitians. A multidisciplinary model of care that incorporates functional assessment, nutritional support, and exercise monitoring may help optimize outcomes and improve adherence. While this study provides encouraging evidence of exercise-related improvements in dialysis adequacy and physical function, it does not directly address long-term outcomes such as mortality or cardiovascular health. Future multicenter investigations are needed to evaluate the impact of exercise on echocardiographic parameters, including left ventricular ejection fraction and regional wall motion, as well as vascular access blood flow measured by AVF Doppler ultrasonography. Additional studies assessing cardiovascular outcomes and mortality will be essential to confirm whether exercise therapy can meaningfully improve clinical endpoints in patients with ESKD, beyond enhancing solute clearance alone.

To successfully translate exercise therapy into routine dialysis care, a multidisciplinary approach is essential (Fig. 1). Moreover, practical considerations—such as access to appropriate facilities, individualized exercise prescriptions, and patient-specific comorbidities—must be addressed. Social and economic disparities can act as barriers to implementation; thus, tailored community- and clinic-based solutions that account for real-world resource availability are necessary. Exploring innovations such as artificial intelligence-enabled exercise monitoring and virtual reality-guided rehabilitation may further enhance accessibility and engagement. Looking forward, emerging technologies such as artificial intelligence and virtual reality platforms may offer innovative approaches to enhance patient engagement and compliance with exercise regimens. These tools could help overcome logistical and motivational barriers, paving the way for more effective and scalable exercise programs in dialysis care. Ultimately, promoting physical activity in dialysis care will require not only clinical commitment but also structural support to ensure equitable, sustainable implementation.

Figure 1.

Advantages, limitations and key requirements of exercise in dialysis patients.

In conclusion, the study by Andrade et al. [8] demonstrated that structured exercise therapy in patients undergoing maintenance HDF is both safe and well-tolerated, regardless of whether it is performed during or between dialysis sessions. The intervention showed high adherence and was associated with improvements in dialysis adequacy and physical performance. These findings reinforce the essential role of exercise in the care of patients with ESKD and highlight the need for its systematic integration into routine dialysis practice.