Fouad K, Bastiaanse C M, Dietz V
Brain Research Institute, University and ETH Zurich, Winterthurerstr, 190, 8057 Zurich, Switzerland.
Exp Brain Res. 2001 Mar;137(2):133-40. doi: 10.1007/s002210000628.
Load dependent reflex adaptations were studied in healthy subjects walking on a split-belt treadmill. Compensatory reflex responses were elicited in the right leg extensor muscles during mid-stance by a short acceleration of the right treadmill belt. Electromyographic activity (EMG) was recorded from the right medial gastrocnemius (GMR), soleus (SO) and tibialis anterior (TA) muscles of the right leg as well as from the gastrocnemius of the left unperturbed leg (GML). To study the adaptational reflex behavior, multiple measurements were taken during walking with normal (control) and increased body load and after removing the load. In most experiments the compensatory EMG response in the GMR consisted of a short inhibitory and a subsequent excitatory component. Both reflex components were larger when the body was loaded. During the course of continuous loading, divergent reflex adaptations of different degrees and directions were observed in the subjects. In one group of subjects the reflex response increased to a higher level of EMG activity. In a second group EMG activity first increased and afterwards decreased to baseline level. A subsequent removal of body loading resulted in a slow adaptation to the control reflex values in both groups. Neither the EMG activity in the GM nor the reflex responses in the GMR after increasing the load changed differently in the two groups. Our results suggest that load information is not simply used in a fixed input/output relationship of the actual biomechanical conditions of a subject. Load information is rather used to slowly modify the reflex response, to achieve the desired posture during walking.
在健康受试者在分离带跑步机上行走时，研究了负荷依赖性反射适应情况。在右跑步机带短暂加速时，在右下肢伸肌中引发了代偿性反射反应。记录了右下肢的右内侧腓肠肌（GMR）、比目鱼肌（SO）和胫骨前肌（TA）以及左未受干扰下肢的腓肠肌（GML）的肌电图活动（EMG）。为了研究适应性反射行为，在正常（对照）和增加身体负荷行走期间以及去除负荷后进行了多次测量。在大多数实验中，GMR中的代偿性EMG反应包括一个短暂的抑制性成分和随后的兴奋性成分。当身体负重时，两个反射成分都更大。在持续负荷过程中，在受试者中观察到不同程度和方向的发散性反射适应。在一组受试者中，反射反应增加到更高水平的EMG活动。在第二组中，EMG活动首先增加，然后降至基线水平。随后去除身体负荷导致两组都缓慢适应对照反射值。增加负荷后，GM中的EMG活动和GMR中的反射反应在两组中变化没有差异。我们的结果表明，负荷信息不是简单地以受试者实际生物力学条件的固定输入/输出关系来使用。负荷信息而是用于缓慢改变反射反应，以在行走期间实现所需的姿势。
