Effects of combined blood flow restriction and neuromuscular electrical stimulation versus neuromuscular electrical stimulation alone on skeletal muscle hypertrophy and strength in adults: a systematic review.

Objective: To systematically review and exploratorily analyze the effects of blood flow restriction combined with neuromuscular electrical stimulation (BFR-NMES) compared with neuromuscular electrical stimulation (NMES) alone on skeletal muscle strength and morphological adaptations in healthy adults. Methods: This systematic review was conducted in accordance with the PRISMA guidelines and registered in PROSPERO (CRD420251141357). Relevant studies published up to September 2025 were retrieved from PubMed, Web of Science, and Embase. Randomized and non-randomized controlled studies comparing BFR-NMES with NMES alone were included. Primary outcomes included muscle strength (isometric and isokinetic strength) and muscle morphology outcomes (muscle thickness, cross-sectional area, muscle mass, and thigh circumference). Risk of bias was assessed using the ROB 2.0 tool, methodological quality was evaluated using the modified Jadad scale, and evidence quality was assessed using the GRADE approach. Due to substantial clinical and methodological heterogeneity among studies, the present study primarily adopted a qualitative synthesis combined with exploratory quantitative visualization analyses. Results: Seven studies involving 124 healthy adults were included. Qualitative findings demonstrated that acute BFR-NMES interventions consistently induced greater immediate strength loss and neuromuscular fatigue, while simultaneously producing more pronounced acute muscle swelling and fluid shift responses. In contrast, long-term BFR-NMES interventions demonstrated more favorable trends in both muscle strength and muscle morphological adaptations compared with NMES alone. Exploratory forest plots further showed that acute studies generally favored NMES alone, whereas long-term studies consistently favored BFR-NMES. Collinearity analysis revealed substantial confounding between intervention duration and pressure prescription strategy: all long-term studies employed fixed-pressure protocols, whereas all acute studies adopted individualized arterial occlusion pressure (%AOP)-based strategies. No statistically significant differences were observed in the overall pooled analyses for muscle strength or rectus femoris thickness; however, substantial heterogeneity was present across studies. GRADE assessment indicated that the quality of evidence for most outcomes ranged from low to very low. Conclusions: Current evidence suggests that BFR-NMES may provide superior benefits over NMES alone in promoting acute muscle swelling and long-term muscle morphological adaptations, with potential advantages for long-term muscle strength development. However, the available evidence remains limited, and substantial confounding exists between intervention duration and pressure prescription strategies. Therefore, these findings should be interpreted cautiously. Future high-quality randomized controlled trials with larger sample sizes and independent manipulation of pressure strategies and intervention duration are warranted to clarify the true effects and optimal prescription strategies of BFR-NMES. Systematic review registration: PROSPERO, identifier: CRD420251141357.