The Effect Of Aging On The Stability Of The Body's Dynamic Posture At The Start Of The Step

Purpose:The purpose of this study was to observe the displacements of center of pressure(COP)and acceleration of center of mass(COM)in a forward stepping to external perturbations.The experimental results of this study could be of help to understand the stability of elderly people in maintaining upright posture,and provide valuable experimental basis for evaluating the risks of falls.Methods:The subjects of this study were six healthy elderly people and six healthy adults.The experimental group contained elderly people aging from 55 to 65 years old,while the age range of the control group was 20-29 years old.There were two experimental conditions: 1)standing support surface was still,with no moving disturbance,and 2)the supporting surface moved forward.In the experiment,a Kistler force-plate,a-foot pressure switch,and a 3D accelerometer were used.Results: 1.Under the perturbation condition,the duration of imbalance phase in the elderly group was significantly shorter than that of the control group,the step duration in gait initiation was significantly longer than the control group.There were no differences between the duration of unloading phase and swing phase.Under the perturbation condition,the duration of imbalance phase and stepping were significantly longer than the of the quiet stepping condition.There were no differences between the duration of unloading phase and swing phase.2.In the medio-lateral direction,there was no significant difference in the COP displacement of each phase under the different experimental conditions.In the anterior-posterior directions,the peak COP displacements of the elderly group in the imbalance phase were significant decreased than that of the control group.There were no differences in the peak COP displacement in the unloading phase and swing phase between groups.Under the perturbation condition,the peak COP displacement of the elderly group in the imbalance phase was significant less than that in the quiet stepping condition,the peak COP displacement of the control in the unloading phase was significant more than that in the quiet stepping condition,There were no differences in the imbalance phase and swing phases.3.In the medio-lateral direction,the peak speed of COP displacement in the imbalance phase was significant less than that of the controlgroup.In the stepping condition,the average speed of COP displacement of the elderly group was significant less than that of the control group.Under the perturbation condition,the duration of unloading phase and step duration in the elderly the peak speed of COP displacements was significant more than that in the quiet stepping condition,in the anterior-posterior,the peak displacement speed of COP displacements of the elderly group in unloading phase was significant less than that of the adults.Under the perturbation condition,the duration of unloading phase in the peak speed of COP displacement was significant less than that in the quiet stepping condition.4.In the medio-lateral direction,the peak COM acceleration of the elderly group in the phase and swing phases were significant less than that of the control group.Under the perturbation condition,the duration of phase were the peak COM accelerations in the imbalance and unloading phases were significant less than that in the quiet stepping condition.In the anterior-posterior directions,the peak COM acceleration of the elderly group in the swing phase were significant less than that the control group.Under the perturbation condition,there was no significant difference in the peak COM acceleration of each phase under the different experimental of step conditions.5.The peak COM acceleration in the imbalance phase had high level of relevance to the COP displacement under the influence of aging.Conclusion: Aging leads to a decline in the ability to maintain body's balance in step initiation,by increasing the movement amplitudes in dynamic balance.