The Movement Characteristics Of The Head And Torso In The Stepping Movement

Background:Stepping plays an important role in the successful completion of walking.In the process of stepping,the dynamic stability of the body requires the coordination and adjustment of multiple systems.Therefore,many factors affecting the movements of the step also have different effects on maintaining the dynamic stability of the body.A well-behaved step-by-step action helps to create a higher dynamic stability of the body,which helps us better negotiation with postural disturbances and maintaining body balance.This study investigated the changes of the motions of head and neck?C₇?,center of mass?COM?,and center of pressure?COP?in different speed conditons.For exploring the movement characteristics of the head and trunk in the step initiation.Studying step initiation could help to understand the physiological mechanism of the body's dynamic stability and to prevent falls or to provide a powerful reference for analyzing the causes of human motor and neurological diseases.Objectives:By studying the characteristics of the COM acceleration,speed and COP displacement generated by the head and trunk during the step initiation under different speed conditions,to explore the motion characteristics of the head and trunk in different speeds.Methods:This study used two different step speeds as experimental conditions to perform COP-related parameters,the speed and the acceleration of the head,neck,and COM,of 8 healthy adults with right dominant legs.The experimental conditions were:?1?to maintain the normal step width,take a step forward at the normal step speed,recorded as NS?Normal speed?;?2?to take a step forward as fast as possible while maintaining the normal step width,recorded as:FS?Fast speed?.Under each experimental condition,10 test results were recorded.The experimental instruments used in this study were:a Kistler three-dimensional force platform system,a three-dimensional accelerometer?+/-2G?,a TeleMyo 2400T EMG system,and foot switch.Results:?1?Under the experimental conditions of NS and FS,there was no significant difference between the step duration,as well as the percentage of duration of each step in each phase.However,the unbalanced period,the reduced load period,the APAs period,and the length of the swing period were all expressed as the length of time used under the fast step condition was greater than that under the normal step condition.?2?Under the NS and FS conditions,there was no significant difference between the COP displacement.In anterior-posterior?AP?,the maximum and displacement ranges of the COP displacement during the load-reduction period,the swing period,the APAs period,and the entire swing period were:NS<FS.In the medio-lateral?ML?,the maximum displacement of the COP displacement during the swing period and the entire swing period was:NS>FS.?3?Under the NS and FS conditions,there was a significant difference in the maximum acceleration of the head and neck during the load reduction period and the APAs in the AP direction.In the ML direction,there all had no significant difference.?4?Under the NS condition,the accelerations of the head,neck and COM had significant differences in the maximum period of the load reduction period and the APAs period,and they were all between the neck and COM.And under the FS condition,there was no significant difference between the head,neck and COM.?5?Under the NS and FS conditions,the maximum speed of the head and neck in the AP direction during the AP direction was significantly different between the speed change period,the APAs period and the speed change range.In the ML direction,there were no significant differences in the parameters of the head and neck.In the AP direction,the maximum speed of the swing period COM was NS>FS,and the other phases were all NS<FS,and there were no significant difference among them.?6?Under the NS condition,the speeds of the head,neck and COM were significantly different in the period of de-loading,APAs and stride.Under the FS condition,the speeds of the head,neck and COM were significantly different in the imbalance period,the load reduction period and the maximum APAs period.Conclusions:?1?Healthy adults could increase the duration of anticipatory postural adjustments to maintain the body's dynamic balance when the step speed increases.?2?There was no significant difference in the dynamic stability of healthy adults between normal and fast steps,and there was a significant difference between the head and COM,indicating that the head plays an important role in regulating the dynamic stability of the body posture.?3?As the speed of the step increases,the effect of the head and COM on the adjustment of the body posture also increased,and it mainly occurs in the AP direction,not obvious in the ML direction.