Effects Of Aging On Postural Control During Stair Walking Under Dual-task Condition In Older Women

Objective : With the higher level of material living standard and better medical health care condition,older adults are living longer.However,the elderly's health is seriously threatened by what the aging caused,especially the falling leads to disability and incapacitation of daily life,which might bring a heavy burden to the family and the society.About two-thirds of the elderly who fall down during stair walking are females.The elderly women,due to their special physiological characteristics,will suffer serious injuries even death once they fall down.Compared to straight walking,stair walking is more challenging,and it is often affected by dual tasks,such as: calling up,carrying heavy objects in hand,chatting,and so on during stair walking.Some studies have demonstrated that the intervention of dual task will significantly ?consume? the gait performance of older adults,and as the difficulty of dual task increases,so does the ?consumption?.Therefore,it is important to investigate the effect of aging under different types of dual task condition on posture control during stair walking.The young and older females were studied under different types of dual tasks(single task,cognitive task,manual task,combined task)condition in our research to explore the effect of aging on physical stability by kinetics and kinematics data during stair walking.This study could provide the database of falls prevention for older adults during stair walking.Methods: 20 young female and 20 older female participants were recruited for this study through wechat and posters.All participants had no history of falls and regular exercise in the past 6 months.Two-way Manova was used for statistic analysis,and turky was applied for post-test when there was a interaction between groups and task types.The level of significance difference was set at p<0.05.Results: 1.Kinematics:compared to the young participants,the walking speed of the elderly was significantly decreased,and the clearence was significantly decreased,and the foot clearence decreased as the difficulty of task types increased.2.Kinetics:(1)Stair ascent:compared to young participants,older participants showed significantly lower peak value of hip extension moment,knee extension moment,knee flexion moment and toe flexion moment under all the task conditions.(2)Stair descent:under the same task condition,compared to young participants,older participants showed significantly larger peak value of hip extension moment,while the first and second peak value of knee extension moment and the first peak value of toe flexion moment are all significantly smaller.Compared with single task condition,young participants demonstrated a significantly smaller first peak value of knee extension moment and toe flexion moment,while the second peak value of toe flexion moment was significantly larger.3.Margin of Stability(MoS):(1)Stair ascent: Compared with single task condition,young participants showed a significantly lower velocity of the center of mass(COM)and lower extrapolated COM under cognitive,manual and combined dual task condition respectively.Compared with single task condition,older participants showed a significantly lower extrapolated COM and lower posterior margin of stability(MOS)under both manual and combined dual task conditions.Compared to young adults,older participants showed a significantly lower position of COM and smaller anterior boundary of the base of support(BOSAB),while the anterior MOS was significantly larger under cognitive dual task condition.(2)Stair descent: Compared with single task condition,young participants demonstrated a significantly higher position of COM and extrapolated COM,and both anterior MOS and posterior MOS were significantly larger,while the velocity of COM was significantly lower under cognitive,manual and combined dual task conditions respectively.Compared with single task condition,older participants exhibited a lower velocity of COM,while the extrapolated COM and anterior MOS were significantly larger under cognitive,manual and combined dual task conditions respectively.Under dual task condition,older adults presented significantly larger extrapolated COM,BOSAB and posterior boundary of the base of support(BOSPB).Conclusions:(1)The interference of dual task would decrease the the physical stability and increase the risk of falling during stair walking.Meanwhile,the risk of falling increases as the difficulty of dual task increases.(2)Compared to young adults,older adults presented lower foot clearence,peak value of joint moment in lower extremity and dynamic stability due to insufficient power output and poor support of lower limbs,leading to an increasement of risk of falls.