Effects Of Directions Congruency And Time Certainty On Anticipatory And Compensatory Postural Adjustments

Background:Anticipatory postural adjustments(APAs)and compensatory postural adjustments(CPAs)are the early postural control mechanisms of the postural control system to deal with sudden external postural interference,which play an important role in controlling body stability,maintaining limb spatial positioning,and completing the random movement.Previous studies have found that psychological expectation can be used by the central nervous system(CNS)to control posture.Also,the consistency of interference direction and the certainty of interference time is closely related to maintaining upright posture and avoiding falling.However,it is not clear about the effect of time certainty and direction consistency of interference on the early posture control mechanism.Objective:Based on the theoretical perspective of early postural control and posture control psychological expectation effect,this study takes the stance stabilizer muscles as the observation object,adopts the interference paradigm of movable platform forward and backward translation,and change the direction consistency and time determination of the expected interference direction and the actual direction,the interference time certainty under single-task and dual-task The effect of the control mechanism of the early posture muscles of the pose stabilizing muscles provides a scientific basis for the explanation of the neurophysiological mechanism of the early postural control by conscious activities.Methods:To investigate the direction congruency effect of the early posture control of the standing stable muscle,the interference pattern of movable platform forward and backward translation was studied.Combined with the surface electromyography(sEMG)signal of the stance stabilizer muscles and the analysis technology of the center of posture(COP),the activation modes of APAs and CPAs of the shank muscles and the COP displacements were compared under the three conditions of the same movement direction,different and random condition.To investigate the time certainty effect of the early postural control of standing stable muscle,the two task models of single task and upright standing posture+upper limb task were used in the second and third experiments respectively.The changes of APAs and CPAs activation modes of the shank muscles and COP and the center of mass(COM)displacements were compared under the conditions of platform movement time determination and random conditions.Results:(1)Compared with the random condition,under the congruent condition the activation intensity of CPAs decreased,and the time for COP displacement to reach the peak was shortened.Otherwise,the activation intensity of CPAs increased and the time of peak displacement of the COP was prolonged when the incongruent trials were not.(2)Under the condition of standing upright,the uncertainty of interference time had no significant influence on the activation time point,APAs and CPAs activation intensity,COP,and COM displacements of shank muscles.(3)Under the condition of standing upright+upper limb weight-bearing,the interference time can be determined in advance of APAs activation time point of stance stabilizer muscles,increase the activation intensity of APAs,increase the COP and COM displacements before interference,reduce COP and COM displacements after interference,shorten the duration of COP and COM shaking,but it has no significant influence on the CPAs activation intensity of stance stabilizer muscles.Conclusion:The consistency of the interference direction and the expected direction and the certainty of the interference time can regulate the early postural control mechanism of the shank stance stabilization muscle:(1)the consistency of the interference direction and the expected direction can induce the CPAs control mechanism of the tibialis anterior muscle and optimize the CPAs posture control efficiency;(2)Under the single-task condition of standing upright,the certainty of the interference time will not trigger the early posture control of the shank stance stabilizer muscles;(3)The results showed that under the dual task of standing upright and upper limb weight-bearing,the cognitive resource redistribution and the stability maintenance mechanism initiated by CNS can trigger the time deterministic effect of early control of shank stance stabilizer muscles.