Carlos Tavares, Rui Soles Gonçalves, Rocío Llamas-Ramos
Neuromuscular electrical stimulation (NMES) has emerged as a potential alternative or adjunctive intervention for individuals with type 2 diabetes mellitus (T2DM) who experience barriers to conventional exercise participation. This systematic review aimed to synthesise NMES protocols and evaluate their effects on glycaemic outcomes in adults with T2DM. A systematic review was conducted according to PRISMA 2020 recommendations and registered in PROSPERO (CRD420251006814). PubMed/MEDLINE, EMBASE, CENTRAL, Scopus and Google Scholar were searched from inception to January 2026. Interventional studies evaluating NMES-induced skeletal muscle contractions and reporting glycaemic outcomes in adults with T2DM were included. Because of substantial clinical and methodological heterogeneity, findings were synthesised without meta-analysis using a structured Synthesis Without Meta-analysis (SWiM)-informed approach. Ten studies involving 163 participants met the eligibility criteria. Acute NMES interventions consistently attenuated postprandial or short-term CGM-derived glucose responses, whereas chronic effects on fasting glucose and HbA1c were more variable. Favourable outcomes were more frequently observed in studies using stimulation of large lower-limb muscle groups and greater cumulative exposure. NMES was generally safe, well tolerated and associated with high adherence. NMES may improve glycaemic regulation in adults with T2DM; however, adequately powered sham-controlled trials with standardised protocols remain necessary.