Acute Effects of Low-Load Blood Flow Restriction Exercise on Vastus Lateralis Electromyographic Activity in Healthy Young Adults: A Pilot Randomized Study

Background: Low‐load resistance exercise with blood flow restriction (BFR) may increase neuromuscular stimulation while reducing external load. This pilot study examined the acute effects of unilateral knee extension at 20% one‐repetition maximum (1RM) with BFR at 80% estimated arterial occlusion pressure (AOP), compared with the same protocol without BFR, on vastus lateralis surface electromyographic (sEMG) activity in healthy young adults. Methods: Twenty participants were randomized to receive BFR on either the dominant (n = 10) or non‐dominant limb (n = 10); the contralateral limb completed the non‐BFR condition. Both conditions were performed in randomized order during one session, separated by 10 min. Each limb completed 75 repetitions (30‐15‐15‐15) at 20% of its limb‐specific 1RM. The prespecified primary outcome was normalized RMS amplitude across 12 protocol windows, analyzed using a linear mixed model. Results: Normalized RMS amplitude was higher under BFR (between‐condition difference, 21.12%MVIC; 95% CI, 14.54 to 27.71; p < 0.001). Exploratory analyses showed higher global mean and peak RMS under BFR, whereas within‐protocol RMS change and temporal slope did not differ. The post‐exercise percentage reduction in MVIC‐derived RMS amplitude was smaller under BFR (‐0.6 ± 14.1% vs. ‐15.4 ± 12.3%; p = 0.002). Significant secondary findings remained significant after Holm adjustment. No adverse events were spontaneously reported or observed immediately. Conclusions: Under this acute laboratory protocol, individualized BFR was associated with higher vastus lateralis sEMG amplitude than unrestricted exercise. MVIC‐derived findings were exploratory and should not be interpreted as evidence of preserved strength or reduced neuromuscular fatigue. Larger studies, including clinical populations, are required.