Hemodynamic and neuromuscular basis of reduced exercise capacity in patients with end-stage renal disease

Purpose The present study aimed to characterize the exercise-induced neuromuscular fatigue and its possible links with cerebral and muscular oxygen supply and utilization to provide mechanistic insights into the reduced exercise capacity characterizing patients with end-stage renal disease (ESRD). Methods Thirteen patients with ESRD and thirteen healthy males (CTR group) performed a constant-force sustained isometric contraction at 50% of their maximal voluntary isometric contraction (MVC) until exhaustion. Quadriceps muscle activation during exercise was estimated from vastus lateralis, vastus medialis, and rectus femoris EMG. Central and peripheral fatigue were quantified via changes in pre- to postexercise quadriceps voluntary activation (ΔVA) and quadriceps twitch force (ΔQ tw,pot ) evoked by supramaximal electrical stimulation, respectively. To assess cerebral and muscular oxygenation, throughout exercise, near-infrared spectroscopy allowed investigation of changes in oxyhemoglobin (∆O 2 Hb), deoxyhemoglobin (∆HHb), and total hemoglobin (∆THb) in the prefrontal cortex and in the vastus lateralis muscle. Results ESRD patients demonstrated lower exercise time to exhaustion than that of CTR (88.8 ± 15.3 s and 119.9 ± 14.6 s, respectively, P 0.05). There was no significant difference in muscle oxygenation (∆O 2 Hb) between the two groups ( P > 0.05). Cerebral and muscular blood volume (∆THb) and oxygen extraction (∆HHb) were significantly blunted in the ESRD group ( P