Differences in Circulatory Dynamics and Skeletal Muscle Blood Flow During Exercise Between Post-Dialysis and Non-Dialysis Days in Hemodialysis Patients

Purpose: Patients undergoing hemodialysis often experience impaired exercise tolerance and circulatory instability due to fluid removal and metabolic alterations during dialysis. Although rehabilitation is recommended for this population, the physiological effects of exercise performed after dialysis remain unclear. This study aimed to compare circulatory dynamics and skeletal muscle blood flow during exercise performed on dialysis and non-dialysis days to develop safe and effective post-dialysis rehabilitation strategies. Methods: Twelve stable hemodialysis patients from Seirei Sakura Citizen Hospital participated in this cross-sectional study. After a graded exercise test to determine peak work rate (PeakWR), participants performed constant-load cycling exercise at 40% of PeakWR for 20 minutes on both a non-dialysis and a post-dialysis day. Heart rate, blood pressure, and perceived exertion (RPE) were measured, while skeletal muscle oxygen saturation (SmO₂) and total hemoglobin (THb) were evaluated using near-infrared spectroscopy (NIRS). Results: Heart rate at rest and during exercise was significantly higher after dialysis than on non-dialysis days (p < 0.05). The change in THb (ΔTHb) during exercise was significantly smaller post-dialysis (p < 0.05), indicating reduced skeletal muscle blood flow. Post-exercise RPE values for both lower limbs and respiration were significantly higher after dialysis (p < 0.05). No significant differences were observed in SmO₂ between conditions. Conclusions: Exercise performed after dialysis results in greater cardiovascular load and perceived exertion, accompanied by reduced skeletal muscle blood flow compared to non-dialysis days. These findings emphasize the need to tailor post-dialysis exercise prescriptions by adjusting intensity or extending warm-up periods to accommodate altered circulatory dynamics. This study provides important physiological evidence for optimizing post-dialysis rehabilitation in hemodialysis patients.