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2022, Vol. 26 ›› Issue (12): 1834-1842Changes in biomechanical characteristics of children’s lower limbs during visual deprivation and dual tasksOuyang Yiyi1, Peng Jie2, Wang Kun3, Zhang Tingran3, Luo Jiong3
Abstract: BACKGROUND: Human balance and control depend on the coordination of the inner ear vestibular system, proprioceptors and visual system, and the central nervous system. However, when a person is visually deprived or dual cognitive tasks, it will cause changes in neural control and sensory integration, and then change lower limb balance control ability and movement control strategy. OBJECTIVE: To explore the biomechanical changes of the legs in stair descendent of different visual inputs and cognitive tasks so as to reveal action mechanism, thus preventing and avoiding accidents of children falling off stairs in descending stairs. METHODS: Twenty students from grades 3-6 of the Primary School Attached to Southwest University were volunteered to participate in the research (n=5 for each grade). The biomechanical parameters of participants in stair descendent of different visual inputs and cognitive tasks were collected with such test tools as JVC9800 high-speed video camera of kinematics, BIOFORCEN dynamic balance training assessment system of dynamics, and JE-TB0810 eight-channel electromyogram tester of surface electromyography. RESULTS AND CONCLUSION: (1) The angle of the knee joint and the ankle joint with eyes closed and double tasks was obviously larger than that with eyes open and single task (P < 0.05), while the center of gravity was in the lowest level, the angle of the ankle joint with eyes closed and double tasks was obviously larger than that with eyes open and single task (P < 0.05). (2) The lengthways displacement root mean square of center of pressure, transverse displacement root mean square of center of pressure, length of swing trajectory of center of pressure and the enveloping surface of center of pressure with eyes open and double tasks were all smaller than those with eyes closed (P < 0.05). (3) The average electromyogram amplitude standardization parameter and activation length of the biceps femoris, rectus femoris, tibialis anterior and medial head of gastrocnemius with eyes closed and double tasks were significantly smaller than those with eyes open and single task during the first 200 ms prior to touching the steps (P < 0.05); while the average electromyogram amplitude standardization parameter of the tibialis anterior and medial head of gastrocnemius during the buffer period with eyes closed and double tasks were significantly smaller than those with eyes open and single task (P < 0.01). (4) It is concluded that the visual deprivation and double tasks in stair descendent will both block the information transmission of the central nervous system, influence the adjustment of body position and the activation of leg muscles, and further affect children’s balance control and gait steadily and increase their risk of falling off the stairs. However, the influence of visual deprivation to children’s balance control is significantly higher than that of the double tasks. The changes on balance control are caused by visual deprivation. The block of information transmission in the central nervous system will influence children’s cognitive choice, making them pay more attention on walking behaviors instead of cognitive operations. Key words:visual deprivation, cognitive tasks, kinematics, balance control, electromyography |