Liu Jing Z, Dai Te H, Sahgal Vinod, Brown Robert W, Yue Guang H
Department of Biomedical Engineering, The Lerner Research Institute, The Cleveland Clinic Foundation, Cleveland, OH 44195, USA.
Brain Res. 2002 Dec 13;957(2):320-9. doi: 10.1016/s0006-8993(02)03665-x.
Muscle fatigue has been studied for over a century, but almost no data are available to indicate how the brain perceives fatigue and modulates its signals to the fatiguing muscle. In this study, brain activation was measured by functional magnetic resonance imaging (fMRI) during a sustained (2-min) maximal-effort handgrip contraction while handgrip force and finger muscle electromyographic (EMG) data were recorded simultaneously by a magnetic resonance environment-adapted force-EMG measurement system. The results showed decoupled progresses in brain and muscle activities when muscle was fatigued and correlated behaviors among the cortical areas being analyzed. While handgrip force and EMG signals declined in parallel during the course of muscle fatigue, fMRI-measured brain activities first substantially increased and then decreased. This similar signal modulation occurred not only in the primary sensorimotor areas but also in the secondary and association cortices (supplementary motor, prefrontal, and cingulate areas). The nonlinear changes of brain signal may reflect an early adjustment to strengthen the descending command for force-loss compensation and subsequent inhibition by sensory feedback as fatigue became more severe. The close association in the activation pattern in many cortical regions may reflect integrated processing of information in the brain.
肌肉疲劳的研究已经进行了一个多世纪，但几乎没有数据能够表明大脑如何感知疲劳并调节其向疲劳肌肉发送的信号。在本研究中，通过功能磁共振成像（fMRI）测量了在持续（2分钟）最大努力握力收缩过程中的大脑激活情况，同时通过磁共振环境适应性力-肌电图（EMG）测量系统同步记录握力和手指肌肉肌电图（EMG）数据。结果表明，当肌肉疲劳时，大脑和肌肉活动出现了解耦进展，并且所分析的皮质区域之间存在相关行为。在肌肉疲劳过程中，握力和EMG信号平行下降，而fMRI测量的大脑活动首先大幅增加，然后下降。这种类似的信号调制不仅发生在初级感觉运动区域，也发生在次级和联合皮质（辅助运动区、前额叶和扣带区）。大脑信号的非线性变化可能反映了一种早期调整，即加强下行指令以补偿力量损失，随后随着疲劳加剧，通过感觉反馈进行抑制。许多皮质区域激活模式的紧密关联可能反映了大脑中信息的整合处理。
