Intradialytic neuromuscular electrical stimulation improves muscle oxygenation and aerobic capacity in end-stage renal disease: a single-blind, randomized controlled trial.

Patients with end-stage renal disease (ESRD) undergoing hemodialysis (HD) often exhibit substantial impairments in aerobic capacity and skeletal muscle oxidative function, contributing to physical deconditioning and elevated cardiovascular risk. Adherence to traditional exercise programs during HD remains limited due to physical constraints and treatment fatigue. Intradialytic neuromuscular electrical stimulation (NMES) represents a low-effort alternative that may promote peripheral muscle adaptations without imposing significant cardiovascular strain. This study examined the effects of a 12-week intradialytic NMES intervention on aerobic capacity and muscle oxygenation in patients with ESRD. In this single-blind, randomized, controlled pilot trial, 24 male patients with ESRD were assigned to either a neuromuscular electrical stimulation training group (NSTG, n = 12) or a control group (CG, n = 12). The NSTG received quadriceps NMES during HD sessions (40 min/session, three times per week for 12 weeks). Before and after the intervention, participants completed an incremental exercise cycling test to assess peak oxygen uptake (VO2peak) and maximal aerobic power (MAP). Muscle oxygenation of the vastus lateralis was measured during exercise using near-infrared spectroscopy, quantifying changes in oxyhemoglobin (ΔO2Hb), deoxyhemoglobin (ΔHHb), and total hemoglobin (ΔTHb). A significant Group × Intervention interaction effect was observed for VO2peak (p < 0.05) and maximal aerobic power (MAP) (p < 0.01), indicating greater improvements in the NSTG compared with the CG. Descriptively, VO2peak increased by 27% in the NSTG, while remaining unchanged in the CG. MAP also increased by 26% in the NSTG (120.5 ± 25.3 to 151.8 ± 20.9 W, p < 0.01) while remaining unchanged in the CG. Within-group analyses indicated increased ΔHHb and ΔO₂Hb at high exercise intensities (≥ 90% VO2peak) following NMES training period (p < 0.05), while no changes were observed in the CG. However, these findings should not be interpreted as formal between-group differences. This pilot randomized controlled trial suggests that a 12-week intradialytic NMES program significantly improved aerobic capacity and skeletal muscle oxygen extraction in patients with ESRD, which may be related to peripheral muscular adaptations rather than central cardiopulmonary changes, although these mechanisms were not directly assessed. This improvement occurred without affecting heart rate, ventilation, or regional muscle blood volume. The findings support NMES as a practical and effective strategy to counteract physical deconditioning during routine hemodialysis. However, given the pilot nature of the study and the limited sample size, these findings should be considered preliminary and require confirmation in larger trials.Trial registration: Pan African Clinical Trial Registry Identifier: PACTR202206634181851 Registered on 21/06/2022. Registered trial name: Beneficial Effect of Intradialytic Electrical Muscle Stimulation in Hemodialysis Patients.