Predicting incident falls: Relationship between postural sway and limits of stability in older adults

BackgroundWe have previously shown that objective measurements of postural sway predicts fall risk, although it is currently unknown how limits of stability (LOS) might influence these results.Research question: How integrated postural sway and LOS measurements predict the risk of incident falls in a population-based sample of older adults.Methods:The sample for this prospective observational study was drawn from the Healthy Ageing Initiative cohort and included data collected between June 2012 and December 2016 for 2396 men and women, all 70 years of age. LOS was compared to postural sway with measurements during eyes-open (EO) and eyes-closed (EC) trials, using the previously validated Wii Force Plate. Fall history was assessed during baseline examination and incident falls were collected during follow-up at 6 and 12 months. Independent predictors of incident falls and additional covariates were investigated using multiple logistic regression models.Results:During follow-up, 337 out of 2396 participants (14%) had experienced a fall. Unadjusted regression models from the EO trial revealed increased fall risk by 6% (OR 1.06, 95% CI 1.02–1.11) per each centimeter squared increase in sway area and by 16% (OR 1.16, 95% CI 1.07–1.25) per 1-unit increase in Sway-Area-to-LOS ratio. Odds ratios were generally lower when analyzing EC trials and only slightly attenuated in fully adjusted models.Significance:Integrating postural sway and LOS parameters provides valid fall risk prediction and a holistic analysis of postural stability. Future work should establish normative values and evaluate clinical utility of these measures.     

Human Energy Expenditure and Postural Coordination on the Mechanical Horse

The authors investigated and compared the energy expenditure and postural coordination of two groups of healthy subjects on a mechanical horse at 4 increasing oscillation frequencies. Energy expenditure was assessed from the oxygen consumption, respiratory quotient, and heart rate values, and postural coordination was characterized by relative phase computations between subjects (elbow, head, trunk) and horse. The results showed that the postural coordination of the riders was better adapted (i.e., maintenance of in-phase and antiphase) than that of the nonriders, but the energy expenditure remains the same. Likewise, we observed an energy system shifting only for nonriders (from aerobic to lactic anaerobic mode). Finally, cross-correlations showed a link between energy expenditure and postural coordination in the riders (i.e., effectiveness).     

认知任务对直立姿势的视觉控制的影响

为揭示认知任务对直立姿势的视觉控制的影响, 本研究采用双重任务的方法, 要求18名健康的成年被试在4种条件(2认知条件×2视觉条件)下尽力保持直立姿势的稳定。姿势动摇的测量采用头顶拍摄的方法并计算误差均方根、平均速度以及Romberg商数。研究结果显示认知任务和视觉条件之间的交互作用显著, 而且当有认知任务时姿势动摇的Romberg商数显著降低。这些结果说明认知任务抑制了直立姿势控制过程中的视觉加工。     

Effects of A Dual-Task Intervention in Postural Control and Cognitive Performance in Adolescents

Abstract

The aim was to assess dual- versus single-task training for motor performance and cognitive performance in adolescents. Two experiments were performed. In the first, 30 adolescents were randomized to three groups to determine the effect of dual-task difficulty on postural control: α-scaling and root mean square (RMS). In the second, 20 adolescents were randomized to two groups to determine the effect of dual-task practice to improve working memory. RMS in the post-test was lower than the pre-test in both dual-task groups, while α-scaling was lower in post-test than pre-test only in the high-difficulty dual-task group. A practice effect was observed on the percentage of correct answers only in the dual-task group (p?=?0.035). Thus, dual-task training could enhance motor and cognitive performance more than single-task training.     

Effects of Visual Manipulation in Sit-to-Stand Movement in Children With Cerebral Palsy

The authors sought to verify the effects of vision on sit-to-stand (STS) movement performance by means of postural sway in children with cerebral palsy (CP) and typical children (TC). Participants were 42 TC and 21 children with CP. STS movement was assessed with eyes open and with eyes closed. Area and velocity of center of pressure sway were analyzed in each of the 3 STS phases. We observed greater postural sway during STS movement with eyes closed. Children with CP presented greater postural sway than TC did. Both groups exhibited greater postural instability with absence of vision expressing the role of vision to keep postural stability. Moreover, the greater postural instability was observed in children with CP.     

The Influence of an Acute Bout of Whole Body Vibration on Human Postural Control Responses

The use of vibrating platforms has become increasingly available, and popular at sports and rehabilitation institutes. Given the discrepancies in the literature regarding whole body vibration (WBV) and human reflexive responses, the purpose of this study was to examine the acute effects of WBV on postural response latencies, as well as associated electromyography measures of the lower extremities during balance perturbations. Reflexive responses during backward and forward balance perturbations were examined before, after, and 10 min after a bout of WBV. The findings suggest that following an acute bout of whole body vibration, muscle activity of the lower extremities is decreased during a reflexive response to an unexpected perturbation, and may be associated with faster reaction time.     

Computing the COM from the COP in postural sway movements

A method is described for computing the centre of mass (COM) from empirical estimates of the centre of pressure (COP) obtained by means of a force platform. The method is based on a biomechanical model of sway movements in quiet standing, according to which the horizontal acceleration of the COM is approximately proportional to the COM–COP difference. The equations are solved by approximating the solution with best fitting spline functions. The implications for movement control are discussed.     

姿势干扰强度的心理预期效应

本研究基于经典快速举臂试验与落球试验范式, 采用表面肌电信号分析技术, 研究内、外姿势干扰强度的心理预期对腰部姿势肌肉和上肢动作肌肉预期姿势调节(APAs)和补偿姿势调节(CPAs)的影响, 探讨中枢神经系统(CNS)对内、外姿势干扰的控制策略。20名健康受试者先后完成不同负荷强度的快速举臂试验和落球试验, 同步采集腰部竖脊肌、腰部多裂肌和上肢肱二头肌的表面肌电信号, 计算肌肉预激活时间和APAs与CPAs积分肌电值, 观察内、外姿势干扰强度的心理预期对中枢APAs和CPAs控制机制的影响。结果显示内部姿势干扰条件下, 干扰强度的心理预期对腰部多裂肌、腰部竖脊肌和上肢肱二头肌的APAs强度有显著影响, 而对预激活时间和CPAs强度无显著影响; 外部姿势干扰条件下, 干扰强度的心理预期对腰部多裂肌、腰部竖脊肌和肱二头肌的APAs强度有显著影响, 对肱二头肌和腰部多裂肌预激活时间有显著影响, 而对CPAs强度无显著影响。突发可预期姿势干扰条件下姿势的快速反应是一个由CNS主导的神经肌肉运动控制过程。受姿势干扰强度心理预期的影响, CNS对内、外突发姿势干扰条件下腰部姿势肌肉的活动采取了不同的控制策略。在内部姿势干扰条件下, 干扰刺激发生时间明确, CNS主要通过对APAs强度的调节来实现姿势肌肉的优化控制; 而在外部姿势干扰条件下, 干扰刺激时间不明确, CNS则通过对局部稳定肌APAs预激活时间以及局部稳定肌和整体稳定肌APAs强度的双重调节实现姿势肌肉的优化控制。干扰强度的心理预期对姿势肌肉APAs和CPAs的作用表明, 心理预期效应主要源自于CNS对局部和整体稳定肌APAs控制机制的调制。     

Vis‐à‐vis the Couch: Where is Psychoanalysis?

The author discusses ways in which the couch or chair (lying down versus sitting up) may be used to maintain safety and defend against perceived dangers in the analytic process. Several dialectics are relevant as they intersect with that of danger and safety, including engagement/privacy, interiority/exteriority and subject/object. The author discusses these dialectics in terms of the ways in which the analyst is used at different points in time, i.e. as an objectifi ed other, a subjective object or part-object, or as a subject with an internal world. The therapeutic action associated with sitting up (versus lying down on the couch) has been undertheorized, despite the fact that many, if not most, analysands sit up for some portion of their analysis. Through the use of a heuristic visual-spatial metaphor as represented by the use of the couch or chair, the author discusses the signifi cance of lying down and sitting up for therapeutic action.     

Short-Term Repeatability of Stabilometric Assessments

The authors evaluated the short-term (within-day, between-days) repeatability of center of pressure (COP) displacements. COP sway area and speed were obtained in the morning and afternoon of two separate days, both with open (EO) and closed (EC) eyes, in 10 healthy adults. Agreement and variability among conditions were tested by ANOVA and Bland-Altman plots. Mode (EO/EC, area: p = .032; speed: p < .004), and day (day1/day2, area: p = .006; speed: p = .02) showed significant differences. The EC condition and the second test day showed the largest values, with medium-large effect sizes. Time-of-day did not influence COP displacements. Speed had better agreement than area (Bland-Altman plots). COP displacements were well reproducible within-day, but had significant between-days variations. COP assessments should be performed in the same session.