Biomechanical Analysis Of Children's Visual Deprivation Under Different Cognitive Tasks In Stair Descendent

Objects:By exploring the biomechanical changes of the legs in stair descendent of different visual inputs(eyes opening/closing)and cognitive tasks(single/double task),the research aims at revealing the characteristics and related mechanism of a person in stair descendent of different visual inputs and cognitive tasks,thus preventing and avoiding accidents of children falling off stairs.Methods:16 students from grade 3-6 of the Primary School Attached to Southwest University volunteered to participate in the research(4 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,JE-TB0810 eight-channel EMG tester of surface electromyography.Then the parameters were deal with a SPSS23.0 Statistical Analysis Software,with the significance level of all indexes set as ?=0.05.Results:1)For different visual inputs and cognitive tasks,the angle of leg joints at the moment of touching the steps and during the process of buffering shows the trend that the angle of the knee joint and the ankle joint with eyes closed and double tasks is obviously larger than that with eyes open and single task,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.2)For the parameters of gait length in stair descendent of different visual inputs and cognitive tasks,the gait cycle,length of stance phrase,swing phrase,twin stance phrase and single stance phrase with eyes closed and double tasks are all longer than those with eyes open and single task.3)For the stability of participants when touching the steps in stairdescendent of different visual inputs and cognitive tasks,the lengthways displacement RMS of COP,transverse displacement RMS of COP,length of swing trajectory of COP and the enveloping surface of COP with eyes open and double tasks are all smaller than those with eyes closed;the transverse displacement RMS of COP with eyes open and single task is smaller than that with eyes closed and double tasks while the transverse displacement RMS of COP with eyes open and double tasks is smaller than that with eyes closed and single task.4)For the activation area and length of major leg muscles during the first 200 ms prior to touching the steps and buffering period of different visual inputs and cognitive tasks in stair descendent,the average EMG 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 are all longer than those with eyes open and single task during the first200 ms prior to touching the steps;while the average EMG amplitude standardization parameter of the tibialis anterior and medial head of gastrocnemius during the buffer period with eyes closed and double tasks are smaller than those with eyes open and single task.Conclusions:1)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.What's more,the influence of visual deprivation to children's balance control is higher than the double tasks;2)The changes on parameters of space and time and 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.