ASPIRE Centre for Disability Sciences, Institute of Orthopedics and Musculoskeletal Science, University College London, Brockley Hill, Stanmore, London HA7 4LP, UK.
J Electromyogr Kinesiol. 2011 Dec;21(6):1056-63. doi: 10.1016/j.jelekin.2011.08.011. Epub 2011 Oct 13.
The purpose of this study was to describe and examine the variations in recruitment patterns of motor units (MUs) in biceps brachii (BB) through a range of joint motion during dynamic eccentric and concentric contractions. Twelve healthy participants (6 females, 6 males, age=30±8.5 years) performed concentric and eccentric contractions with constant external loading at different levels. Surface electromyography (EMG) and mechanomyography (MMG) were recorded from BB. The EMGs and MMGs were decomposed into their intensities in time-frequency space using a wavelet technique. The EMG and MMG spectra were then compared using principal component analysis. Variations in total intensity, first principal component (PCI), and the angle θ formed by first component (PCI) and second component (PCII) loading scores were explained in terms of MU recruitment patterns and elbow angles. Elbow angle had a significant effect on dynamic concentric and eccentric contractions. The EMG total intensity was greater for concentric than for eccentric contractions in the present study. MMG total intensity, however, was lower during concentric than during eccentric contractions. In addition, there was no significant difference in θ between concentric and eccentric contractions for both EMG and MMG. Selective recruitment of fast MUs from BB muscle during eccentric muscle contractions was not found in the present study.
本研究旨在描述和探讨在肱二头肌（BB）进行动态向心和离心收缩过程中，不同关节运动范围内运动单位（MU）募集模式的变化。12 名健康参与者（女性 6 名，男性 6 名，年龄 30±8.5 岁）在不同水平下进行恒定外部负荷的向心和离心收缩。从 BB 记录表面肌电图（EMG）和肌声图（MMG）。使用小波技术将 EMG 和 MMG 分解为其在时频空间中的强度。然后使用主成分分析比较 EMG 和 MMG 频谱。根据 MU 募集模式和肘部角度，解释总强度、第一主成分（PCI）以及第一成分（PCI）和第二成分（PCII）加载分数形成的角度θ的变化。肘部角度对向心和离心收缩有显著影响。在本研究中，与离心收缩相比，向心收缩的 EMG 总强度更大。然而，与离心收缩相比，MMG 总强度在向心收缩时较低。此外，对于 EMG 和 MMG，θ在向心和离心收缩之间没有显著差异。在本研究中，未发现 BB 肌肉在离心收缩期间对快 MU 进行选择性募集。
