Serrien D J, Swinnen S P
Department of Kinesiology, K.U. Leuven, Heverlee, Belgium.
Exp Brain Res. 1998 Aug;121(3):223-9. doi: 10.1007/s002210050455.
Two-limb coordination of homologous and non-homologous effectors was examined during isofrequency (1:1) and multifrequency (2:1) conditions. The coordination patterns involved flexion and extension movements in the sagittal plane and were performed under unloaded and single-limb (right arm) loaded conditions. Previous studies suggested that the lower degree of 1:1 synchronization observed during nonhomologous as compared to homologous coordination results from natural differences in biophysical (inertial) properties. Elaborating on this idea, adding weight to the right arm was hypothesized to modulate its inertial characteristics, rendering homologous limbs more dissimilar and nonhomologous limbs more similar by enhancing and decreasing their inertial differences, respectively. Therefore, the observations made during unloaded conditions were predicted to be completely reversed during loaded conditions. Findings revealed that during 1:1 coordination (experiment 1) single-limb loading resulted in a decreased relative phase stability, whereas relative phase accuracy depended upon the limb combination. In particular, phase-locking was more accurately maintained for loaded homologous than for nonhomologous limbs, whereas loading the nonhomologous limbs resulted in a deterioration of the quality of synchronization. These findings suggest that there is an additional explanation of differential coordination capabilities among limb combinations. It is hypothesized that the neural networks subserving the control centers of the homologous limbs are more tightly connected than those of the nonhomologous effectors, allowing 1:1 synchronization to be more successfully preserved in the face of (load) perturbations. During 2:1 coordination (experiment 2), the loading procedure disturbed the coordination dynamics across all limb combinations. That no differential effect of loading on effector combination was observed is possibly a result of the fact that only an initial level of practice was studied in which optimal relative phase dynamics are still being explored for both homologous and nonhomologous limbs.
在同频（1:1）和多频（2:1）条件下，研究了同源和非同源效应器的双肢协调。协调模式涉及矢状面内的屈伸运动，且在无负荷和单肢（右臂）负荷条件下进行。先前的研究表明，与同源协调相比，非同源协调过程中观察到的1:1同步程度较低，这是由于生物物理（惯性）特性的自然差异所致。基于这一观点，推测给右臂增加重量会调节其惯性特征，分别通过增强和减小同源肢体与非同源肢体的惯性差异，使同源肢体更加不同，而非同源肢体更加相似。因此，预计在无负荷条件下的观察结果在负荷条件下会完全相反。研究结果显示，在1:1协调（实验1）过程中，单肢负荷导致相对相位稳定性降低，而相对相位准确性则取决于肢体组合。具体而言，负荷后的同源肢体比非同源肢体能更准确地维持锁相，而非同源肢体负荷则导致同步质量下降。这些发现表明，对于肢体组合之间不同的协调能力存在另一种解释。据推测，服务于同源肢体控制中心的神经网络比非同源效应器的神经网络连接更紧密，从而使1:1同步在面对（负荷）扰动时能更成功地得以保持。在2:1协调（实验2）过程中，负荷程序扰乱了所有肢体组合的协调动态。未观察到负荷对效应器组合的差异效应，这可能是因为仅研究了初始练习水平，此时同源和非同源肢体仍在探索最佳相对相位动态。
