| Purpose: To deal with sudden postural disturbances,central nervous system can use subconscious anticipatory postural adjustments(APAs)and compensatory postural adjustments(CPAs)to maintain and restore the stability of body posture.The current study investigated the relationship between APAs and CPAs and changes of center of mass(COM)and center of pressure(COP)displacement in the APAs and CPAs under the experimental conditions: Backward perturbation stepping condition(BS)and Forward perturbation stepping condition(FS).Thus,the influence of external interference direction on body posture adjustment during gait initiation of healthy young people was discussed,which provides an experimental basis for the prevention of falls and the evaluation of the balance under support surface interference conditions.Methods: This study was based on the support plane translation experiment paradigm.Seven healthy young subjects(24.7±1.2Yr,164.6±7.2cm,62.0±10.1Kg)participated in the study.The use of the "human mobile device" caused a translational support surface perturbations under the subjects' feet.The perturbations consisted of 5-cm forward or backward translations of the force plate,with peak ramp velocities of 5 cm/s,and peak accelerations of 0.05 g.Under the premise that the direction of interference was notified in advance,the subject took advantage of the dominant leg to take a step forward at his own normal speed while sensing the movement of the force platform.Analog signals from the Kistler force platform,Inline 3D accelerometer(attached to the fifth lumbar level at the back of the trunk)and DTS footswitch sensors will be converted to digital signals at the same sampling frequency(1500 Hz)after being synchronized by a Noraxon synchronization box.The parameters of the COM and COP in the anterior-posterior(AP)or medial-lateral(ML)directions and the length of each phase of the steps in the APAs and CPAs were recorded and analyzed.Results: 1)The direction in which the standing support surface moved horizontally affected the duration of the imbalance phase and unloading phase of gait initiation: the duration of the imbalance phase was shortened under the FS condition;the duration of the unloading phase was shortened under the BS condition.Under the BS and FS conditions,there was no significant difference in the duration corresponding to the APAs and swing phases.2)APAs had interference direction specificity: in the AP direction,the body produced strong APAs under FS conditions;in the ML direction,the body produced strong APAs under the condition of BS,and the body produced strong CPAs.3)Under the experimental conditions of BS and FS,there was no significant correlation between APAs and CPAs in the AP direction,and there was a strong negative correlation between APAs and CPAs in the ML direction.Conclusions: 1)Under the FS condition,the body suffered moderate backward interference in the imbalance phase,but it created favorable conditions for GI.Under the BS condition,the body adopted a fast-moving strategy in the unloading phase to maintain the balance of the body.Under the experimental conditions of FS and BS,healthy young people can perform the GI task at the end of the APAs to enable the body to return to a normal gait duration.2)Compare to the FS condition,healthy young subjects did not show earlier adjustments when performing walking start action under the BS condition.3)In the AP direction,although the body had strong APAs under the FS condition,it did not offset the perturbation of body posture prior to the single foot support,and it was necessary to strengthen the CPAs to maintain and enhance the stability of the body's dynamic posture.In the ML direction,comparing to the BS condition,the central nervous system needed to strengthen CPAs under the FS condition to maintain or enhance the dynamic stability of the body.4)In the AP direction,the body was subject to both internal(walking start motion)and external perturbation.The CNS needed to simultaneously enhance the APAs and CPAs to maintain the balance of the body.In the ML direction,the use of APAs in gait initiation of healthy young subjects under external disturbance condition reduced the body's demand for CPAs and leaded to greater postural stability.5)Under different interference directions,the differences in the various stages of gait initiation in the healthy young people indicate the flexibility and adaptability of the human body's postural adjustments. |
PDF Full Text Request