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 oxygenation during exercise performed post-dialysis and on non-dialysis days in maintenance hemodialysis patients, to characterize physiological differences that may inform rehabilitation timing.

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 (Peak WR), participants performed constant-load cycling exercise at 40% of Peak WR for 20 min on both a non-dialysis and a post-dialysis day. Heart rate, blood pressure, and perceived exertion (RPE) were measured, while NIRS assessed relative changes in skeletal muscle oxygenation saturation (SmO₂) and microvascular blood volume (intramuscular local hemoglobin concentration:tHb muscle).

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 muscle (ΔtHb muscle) 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.

STUDY REGISTRATION: This study is the clinical trial registered for clinical trials (UMIN number 000040680).