A successful backward step correlates with hip flexion moment of supporting limb in elderly people.

Yahiko Takeuchi,Consuelo Borras

doi:10.1371/journal.pone.0190797

Abstract

PurposeThe objective of this study was to determine the positional relationship between the center of mass (COM) and the center of pressure (COP) at the time of step landing, and to examine their relationship with the joint moments exerted by the supporting limb, with regard to factors of the successful backward step response.MethodsThe study population comprised 8 community-dwelling elderly people that were observed to take successive multi steps after the landing of a backward stepping. Using a motion capture system and force plate, we measured the COM, COP and COM-COP deviation distance on landing during backward stepping. In addition, we measured the moment of the supporting limb joint during backward stepping. The multi-step data were compared with data from instances when only one step was taken (single-step). Variables that differed significantly between the single- and multi-step data were used as objective variables and the joint moments of the supporting limb were used as explanatory variables in single regression analyses.ResultsThe COM-COP deviation in the anteroposterior was significantly larger in the single-step. A regression analysis with COM-COP deviation as the objective variable obtained a significant regression equation in the hip flexion moment (R2 = 0.74).ConclusionsThe hip flexion moment of supporting limb was shown to be a significant explanatory variable in both the PS and SS phases for the relationship with COM-COP distance. This study found that to create an appropriate backward step response after an external disturbance (i.e. the ability to stop after 1 step), posterior braking of the COM by a hip flexion moment are important during the single-limbed standing phase.

Highlights

Falls can cause elderly people to require nursing care, and prevention of falls is an important issue in this population
The center of mass (COM)-center of pressure (COP) deviation in the anteroposterior was significantly larger in the single-step
This study found that to create an appropriate backward step response after an external disturbance, posterior braking of the COM by a hip flexion moment are important during the single-limbed standing phase

Summary

Introduction

Falls can cause elderly people to require nursing care, and prevention of falls is an important issue in this population. Methods of reducing, as much as possible, the impact of falls are necessary in order to decrease the severity of fractures and other injuries [1,2]. The step response involves taking a step to support the body when balance is lost in the standing position. The step response is considered an important postural response for preventing falls and reducing the impact of falls in elderly people. The step response dramatically increases the base of support, providing more dynamic stability than postural responses that correct the body’s alignment along the axis of the ankle or the hip [3]. The degenerative kyphosis that occurs with age increases the likelihood of elderly people losing their balance backwards [4,5]; it is necessary to focus on the backward step response

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Discussion

Conclusion