视觉剥夺状态阶梯动作下肢肌肉组织刚度调节及肌电变化

Muscle stiffness regulation and electromyographic changes of the lower limbs during descending stairs after visual deprivation

背景:人体平衡与控制有赖于内耳前庭系统、本体感受器及视觉系统的协调及中枢神经系统等共同配合才能完成,但蒙眼(视觉剥夺)所引发的神经控制与感觉统合变化对下肢肌肉刚度调节能力及动作控制策略并不清楚。目的:比较蒙眼与不蒙眼两种情况下下阶梯动作过程中下肢肌肉组织的刚度及肌电变化,从而揭示视觉对青少年神经肌肉控制及刚度的调节作用。方法:将20名视力正常的青少年随机分成蒙眼及不蒙眼组各10人,要求两组受试者分别在3种不同高度(20,30,40cm)下阶梯并在着地后尽最大用力实施蹲踞跳。所有受试者被要求每个动作做3次,取动作最为自然的一次进行分析。运用视迅运动图像解析系统、JP6060多维测力平台及JE-TB0810八通道无线表面肌电测试系统对受试者下阶梯动作进行运动学(着地膝角与着地踝角)、动力学(关节刚度与下肢刚度)及肌电(股直肌、股二头肌、胫骨前肌、腓肠肌)测试,并运用SPSS 17.0统计分析软件对相关指标进行处理。结果与结论:①3种不同高度下阶梯着地瞬间:蒙眼组膝、踝角显著大于不蒙眼组,着地时反作用力出现峰值瞬间蒙眼组膝角小于不蒙眼组,而蒙眼组踝角表现与阶梯高度有关;②不同高度着地垂直力第1峰值大小及相对值:均表现为不蒙眼组显著大于蒙眼组,且两值随着阶梯高度增加而显著增加;③不同高度着地下肢膝关节刚度及下肢刚度:均表现为不蒙眼组显著大于蒙眼组,且随着阶梯高度的上升两种刚度均呈显著增加趋势;④不同高度着地前期,股二头肌、胫骨前肌及腓肠肌肌电活动:均表现为不蒙眼组显著高于蒙眼组,而在缓冲期,蒙眼组股直肌、股二头肌、胫骨前肌、腓肠肌的肌电活动均显著小于不蒙眼组;⑤结果说明,蒙眼组在不同高度下阶梯过程中,因无视觉回馈,会降低辨别与环境观测能力,这种由于视力不足,会导致实施动作时无法提供信息给中枢神经系统,而造成相关动作表现力显著下降。

BACKGROUND:The balance and control of the human body depend on the coordination between the vestibular system of the inner ear,the proprioceptors and the visual system,as well as the central nervous system.However,it is unclear about the muscle stiffness regulation and motion control strategy for the lower limbs by the changes in neural control and sensory integration caused by visual deprivation(the eyes are blindfolded).OBJECTIVE:To compare the difference of muscle stiffness regulation and electromyography changes of the lower limbs during descending stairs in children and adolescents with the eyes blindfolded or not,and then to reveal the regulatory effects of visual sense on neuromuscular control and muscle stiffness regulation in adolescents.METHODS:Twenty adolescents with normal vision were randomly divided into blindfolded group and unblindfolded group(n=10 per group).The two groups of subjects were required to descend stairs from three different heights(20,30,40 cm)and do their best to perform a squat jump after landing.All subjects were asked to repeat the above-mentioned action thrice,and the data for the most natural actions were analyzed.Vision-based motion imaging analysis system,JP6 060 3D force-plate,and 8-channel wireless surface electromyography testing system were utilized to test the kinematic(landed knee and ankle joint angles),kinetic(joint stiffness and stiffness of the lower limbs),and electromyography parameters(rectus femoris,biceps femoris,tibialis anterior,gastrocnemius)of the subjects during descending stairs.All the data were processed using SPSS17.0 software.RESULTS AND CONCLUSION:(1)During landing from three different heights,the knee and ankle joint angles of the blindfolded group were significantly larger than those of the unblindfolded group.At the moment of the appearance of the peak reacting force during landing,the knee joint angle of the blindfolded group was smaller than that of the unblindfolded group.Furthermore,the intergroup difference in the ankle joint angle was related to the height of the stair.(2)The first peak vertical force and its relative mean value during landing from different heights were significantly higher in the unblindfolded group compared to the blindfolded group,and both parameters significantly increased with the height increase.(3)During landing from different heights,the stiffness values of the knee joints and lower limbs in the unblindfolded group were significantly higher than those in the blindfolded group,and the stiffness values in the two groups were significantly increased with the height increase.(4)At the moment of pre-landing from different heights,the electromyography activities of the biceps femoris,tibialis anterior,gastrocnemius in the unblindfolded group were significantly higher than those in the blindfolded group,whereas during the buffer period,the electromyography activities of the rectus femoris,biceps femoris,tibialis anterior,gastrocnemius were significantly lower in the blindfolded group than in the unblindfolded group.(5)In conclusion,during descending stairs from different heights,visual deprivation(no visual feedback)reduces the capabilities of identification and environmental observation.The lack of vision may result in a significant decline in the performance of related movements,and thus the central nervous system cannot receive information,thereby impacting the implementation of the action.