Krätschmer Rafael, Stingl Maleen, Holzer Denis, Paternoster Florian Kurt
Professorship of Biomechanics in Sports, Department Health and Sport Sciences, TUM School of Medicine and Health, Technical University of Munich, Munich, Germany.
Prevention Center, Department Health and Sport Sciences, TUM School of Medicine and Health, Technical University of Munich, Munich, Germany.
Sci Rep. 2025 Jul 14;15(1):25378. doi: 10.1038/s41598-025-10477-1.
Neuromechanical delay (NMD) quantifies the time lag between the neural drive to a muscle and muscle force production. While NMD varies with factors like contraction speed and muscle group, its response to different contraction intensities remains unclear. This study examined NMD in the quadriceps during isometric trapezoidal contractions at 10%, 30%, 50%, and 70% of maximum voluntary contraction (MVC) in 13 recreationally trained males (24.3 ± 2.8 years). High-density surface electromyography recorded motor unit firings in the vastus lateralis and medialis, with neural drive quantified via cumulative motor unit firings. NMD was determined by cross-correlating neural drive with force signals during steady-force phases. Results showed a significant NMD reduction (p < 0.001) with increasing contraction intensity, decreasing by 31% from 175.8 ms (± 44.1) at 10% MVC to 121.6 ms (± 34.6) at 70% MVC. This likely reflects changes in muscle mechanical properties due to higher-threshold motor unit recruitment. These findings enhance our understanding of neuromechanical coupling, revealing a force-dependent modulation of NMD that may have implications for neuromuscular function in health and disease.
神经机械延迟（NMD）量化了神经驱动肌肉与肌肉产生力量之间的时间滞后。虽然NMD会因收缩速度和肌肉群等因素而变化，但其对不同收缩强度的反应仍不清楚。本研究在13名接受过休闲训练的男性（24.3±2.8岁）中，以最大自主收缩（MVC）的10%、30%、50%和70%进行等长梯形收缩时，检测了股四头肌的NMD。高密度表面肌电图记录了股外侧肌和股内侧肌的运动单位放电情况，并通过累积运动单位放电来量化神经驱动。NMD是通过在稳定力阶段将神经驱动与力信号进行互相关来确定的。结果显示，随着收缩强度的增加，NMD显著降低（p<0.001），从10%MVC时的175.8毫秒（±44.1）降至70%MVC时的121.6毫秒（±34.6），降幅为31%。这可能反映了由于高阈值运动单位募集导致的肌肉机械性能变化。这些发现增进了我们对神经机械耦合的理解，揭示了NMD的力依赖性调节，这可能对健康和疾病中的神经肌肉功能具有重要意义。
