End-stage renal disease (ESRD) disrupts erythrocyte deformability due to osmotic imbalances, oxidative stress, and uremic toxins, leading to impaired microcirculation and oxygen transport. Dysregulation of ion channels, particularly the Gardos channel, exacerbates dehydration and eryptosis, further compromising vascular integrity. Given the critical role of erythrocyte flexibility in oxygen delivery, this study investigates its relationship with aerobic capacity in ESRD patients, highlighting potential mechanisms of microvascular dysfunction