Blood flow restriction modulates common drive to motor units and force precision: implications for neuromuscular coordination

Purpose: Blood flow restriction (BFR) is a resistance training technique that enhances muscle adaptation and strength gains under hypoxic conditions. However, its impact on motor unit (MU) coordination remains unclear. This study investigated how BFR influences intra- and inter-muscular common drives to MUs in two functional agonists during a static precision pinch task. Methods: Eighteen adults (23.9 ± 1.3 years; nine men, nine women) performed a thumb–index finger precision pinch under BFR and non-BFR conditions, while force fluctuation dynamics and MU activities in the flexor pollicis brevis (FPB) and first dorsal interosseous (FDI) were analyzed. Results: The results revealed a significant reduction in maximal voluntary contraction following BFR application (p = 0.003). In addition, BFR significantly increased force fluctuations (p = 0.007), potentiated discharge variability (p = 0.018), and strengthened force–discharge coupling specifically in the FPB (p = 0.010). BFR increased the mean recruitment threshold of motor units in the FDI (p < 0.001), but not in the FPB (p > 0.05) during finger precision pinch. Intra-muscular common drive increased within the FDI (p < 0.001) and FPB (p < 0.001), whereas inter-muscular common drive between agonist MUs decreased (p < 0.001). Conclusion: BFR application disrupts force precision stability and neuromuscular coordination between functional agonists during precision pinch. It increases global discharge variability and intra-muscular MU synchrony. However, the resulting force fluctuations are only partially compensated by reduced inter-muscular MU synchrony, offering limited coordination flexibility among agonists.