脑卒中患者姿势控制的感觉系统特征

目的 研究脑卒中患者姿势控制的感觉系统特征,分析各感受器对脑卒中患者姿势控制能力的贡献率和利用率。 方法 老年脑卒中患者 30 例(患者组)和健康老年人 30 例(对照组)采用计算机动态姿势描记系统进行感觉统合测试(sensory organization test,SOT),记录 6 种条件下的平衡得分、平衡综合分,计算分析视觉、本体感觉、前庭觉在不同站立条件下的贡献率与整体利用率。 结果 患者组在闭眼/ 支撑面稳定(Z = -3. 248,P = 0. 001)、视觉干扰/ 支撑面稳定 ( Z = - 2. 829, P = 0. 005)、 闭眼/ 支撑面不稳 ( Z = - 4. 283, P = 0)、 视觉干扰/ 支撑面不稳(Z= -4. 074,P= 0)条件下的平衡分显著低于对照组,平衡综合分显著低于对照组(Z = -4. 133,P = 0)。 睁眼/ 支撑面稳定和闭眼/ 支撑面稳定测试中,患者组本体感觉占比分别为 16. 351% 、34. 942% ,对照组本体感觉占比分别为14. 307% 、18. 390% ,患者组本体感觉占比始终大于对照组,说明本体感觉对患者组作用大于对照组。 同理,视觉对患者组作用大于对照组。 不同站立条件下前庭觉的贡献率最低为 64. 648% ,说明维持人体平衡主要因素是前庭觉。 患者组本体感觉、视觉、前庭觉的利用率分别为 95. 092% 、72. 382% 、32. 879% ,其中本体感觉(Z = - 1. 984,P= 0. 047)、前庭觉(Z= -4. 283,P= 0)利用率显著低于对照组。 结论 脑卒中患者感觉系统的贡献率与利用率下降是脑卒中患者姿势控制障碍的重要因素之一,其中姿势控制贡献率前庭觉最大,其次为本体感觉、视觉。 而其姿势控制利用率最大的为本体感觉,其次为视觉、前庭觉。 影响脑卒中患者姿势控制能力下降的原因之一为脑卒中患者本体感觉、视觉的感觉信息输入效率下降,以及其本体感觉、前庭觉参与运动输出的部分降低。 建议脑卒中患者注重本体感觉、前庭觉的训练以提高其姿势控制能力。     

精神分裂症患者平衡功能特点

目的:探讨精神分裂症患者平衡功能特点及与临床症状的关系。方法:本研究采用横断面研究设计。选取35例符合《ICD-10精神与行为障碍分类临床描述与诊断要点》中精神分裂症诊断标准,目前药物治疗处于稳定期的门诊患者,及35例年龄、性别与病例组相匹配的健康对照。采用人体动静态姿势控制测试仪测试病例组和对照组的动静态平衡能力,包括感觉组织能力测试、单腿站立测试、走直线测试。用阳性与阴性症状量表(PANSS)、个人和社会表现量表(PSP)对病例组进行评定。结果:感觉组织能力测试中,病例组在6种状态下的平衡分及平均平衡分、视觉感觉分、前庭感觉分均低于对照组(均P0.05)。单腿站立测试中,病例组在左侧及右侧单腿站立闭眼情况晃动速度大于对照组,维持平衡持续时间短于对照组(均P0.05)。走直线测试中,病例组速度低于对照组(P0.05)。病例组平衡功能各项测试指标与PANSS各项评分及PSP评分未发现明显相关(r0.24,P0.05)。结论:本研究结果显示,精神分裂症患者动静态平衡功能明显差于正常对照。     

视觉因素对前交叉韧带重建患者足底压力中心的影响

目的 分析患者前交叉韧带重建(anterior cruciate ligament reconstruction, ACLR)术后早期与术后 1 年在视觉因素影响下足底压力中心面积(center of pressure area, COPA)和压力中心速度(center of pressure speed, COPS)等参数的变化。 方法 纳入 ACLR 患者 17 例,于术后早期和术后 1 年测试足底 COPA 和 COPS 等数据;匹配 17 例健康受试者作为对照组。 进行睁、闭眼不同视觉状态站立平衡测试,对各测量状态进行相关性分析。 结果 双足站立测试时,短期组 COPA 和 COPS 在睁眼和闭眼对比均有统计学差异(P<0. 05);长期组 COPS 睁眼和闭眼对比有统计学差异(P<0. 001)。 健侧站立时,各组间差异具有统计学意义(P<0. 05),伤侧站立时各组间差异无统计学意义(P>0. 05)。 健侧站立睁眼条件下,长期组 COPA 高于短期组和对照组,对照组 COPS 低于短期组和长期组(P<0. 01)。 健侧站立闭眼条件下,对照组 COPA 低于短期组和长期组,对照组 COPS 低于长期组(P<0. 01)。 双足睁眼与双足闭眼之间、双足睁眼与伤侧睁眼之间、健侧睁眼和伤侧睁眼之间、健侧闭眼和伤侧闭眼之间在 COPA 和COPS 上均呈正相关。 结论 通过对 ACLR 患者站立位压力中心相关数据的分析,发现视觉对姿势稳定控制有重要影响。 术后 1 年患者双足和单足站立时对比正常人稳定性波动较大,提示在临床上要加强术后长期训练以巩固康复效果,并对开展长期评估和制定精准训练计划具有一定的指导作用,以防止术后长时间功能退化和降低再次损伤的风险。     

健康成年人下肢本体感觉与姿势稳定性的关系

文题释义：本体感觉：是指运动器官(肌、腱、关节等)本身在运动或静止时产生的感觉,因位置较深,又称深部感觉,主要包括位置感和运动感、努力感、力量感和沉重感。足底压力中心：压力中心是人体静态站立或行走过程中足与地接触作用力的位置,压力中心的轨迹可反映人体静止或运动状态下的平衡和姿势稳定性。 背景：本体感觉是影响姿势稳定性的众多因素之一,但双下肢之间本体感觉和稳定性的关系和差异至今仍不明确。 目的：调查健康成年人优势腿和非优势腿之间的静态稳定性和本体感觉,探索本体感受与稳定性之间的相关性。 方法：30位健康成年人采用动静态平衡仪测量双下肢单腿静态站立时的姿势摆动,记录压力中心位移长度和位移面积;在同一台机器上测量本体感觉,记录下肢的平均轨迹误差和完成时间。研究经广东省第二中医院伦理委员会审议通过[粤二中医(2019)伦审第50号],所有参与者在研究开始前自愿签署知情同意书。结果与结论：①优势腿平均轨迹误差比非优势腿大(P < 0.05);②左右腿之间的本体感觉和稳定性关系密切(P < 0.05或0.01),左侧压力中心位移长度与右侧平均轨迹误差、右侧压力中心位移长度与左侧平均轨迹误差有显著相关性(P < 0.05);③优势腿单腿站立稳定性与双下肢站立稳定性关系密切(P < 0.05);④结果说明,优势腿比非优势腿本体感觉差,但二者稳定性无差异。下肢的稳定性不仅与同侧的本体感觉有关,还与对侧的本体感觉有关系。提示,在训练和临床康复治疗过程中,希望增强下肢本体感觉和稳定性时,不仅要加强同侧肢体训练,还要重视对侧肢体的训练。ORCID: 0000-0002-1204-679X(陈泽华) 中国组织工程研究杂志出版内容重点：组织构建;骨细胞;软骨细胞;细胞培养;成纤维细胞;血管内皮细胞;骨质疏松;组织工程     

慢性非特异性腰痛患者的静态平衡和稳定极限

背景：平衡能力是影响慢性非特异性腰痛患者姿势控制的重要因素和引发跌倒、骨折、残疾的主要原因。现有研究大多仅从双足站位下分析比较,却鲜见在辨别优势腿和非优势腿带来混杂因素等影响的前提下去探讨单、双足静态平衡和稳定极限的特征报道。目的：分析慢性非特异性腰痛患者的静态平衡和稳定极限特征。方法：2020年4月至2021年12月在广州市番禺区中心医院实习生中招募慢性非特异性腰痛患者20例(腰痛组),健康者20例(健康组)。选择Pro-kin平衡仪,进行单/双足站立静态平衡和稳定极限测试,并记录相应测试的指标数值,例如：双足站立时的足底压力中心和稳定极限,以及单双足站立下的前后和左右摆动幅度标准差、前后和左右平均运动速度、运动面积、运动长度等。结果与结论：(1)睁/闭眼状态下,健康组的足底压力中心呈轴心处集中分布,腰痛组相较呈更大离散分布,并以非优势腿上分布为主;(2)比较双足站立静态平衡：睁眼状态下两组间无显著差异(P> 0.05),闭眼状态下腰痛组各静态平衡指标数值大于健康组(P <0.05);(3)比较单足站立静态平衡：腰痛组优势腿各静态平衡指标数值大于非优势腿(P <0....     

膝骨关节炎患者本体感觉特征

目的 探讨行单髁膝关节置换术(unicondylar knee arthroplasty,UKA) 和全膝关节置换术(total knee arthroplasty,TKA)膝骨关节炎( knee osteoarthritis,KOA)患者术前膝关节本体感觉特征。方法 选取单间室KOA患者29名,15例接受 UKA 治疗（UKA组）,14例接受 TKA 治疗（TKA组）。术前1~3 d进行测试,对比UKA、TKA组KOA患者膝关节学会评分（knee society score, KSS）以及手术组与健康对照组的位置觉和运动觉特征。结果 UKA、TKA组之间KSS评分有显著差异,位置觉和运动觉无显著差异;UKA、TKA组患者术侧腿和未术侧腿之间位置觉和运动觉均无显著差异,对照组左、右腿位置觉和运动觉无显著差异;与对照组相比,UKA、TKA组在60°位置觉时术侧腿和未术侧腿均有显著差异,患者术侧腿和未术侧腿的运动觉也均有显著差异。结论 与健康对照组相比,KOA患者术前的膝关节本体感觉明显减退,但UKA、TKA组患者术前本体感觉特征相近。     

儿童下肢生物力学特征在视觉剥夺及双重任务时的变化

背景:人体平衡与控制有赖于内耳前庭系统、本体感受器及视觉系统的协调及中枢神经系统等共同配合才能完成,但人在视觉剥夺或双重认知任务时会引发神经控制与感觉统合的变化,进而改变下肢平衡控制能力及动作控制策略。目的:探讨儿童在不同视觉输入及执行不同认知任务时下阶梯时下肢生物力学特征的变化规律,从而揭示其作用机制,为预防及减少儿童下阶梯时的跌倒伤害提供一些有益参考。方法:共招募20名西南大学附属小学3-6年级的小学生志愿者,每个年级5名。运用运动学(JVC9800高速摄像机)、动力学(BIOFORCEN动态平衡训练评估系统)及肌电(JE-TB0810八通道肌电测试仪)等测试工具,同步采集受试者在不同视觉输入及执行不同认知任务时下阶梯动作的生物力学参数。结果与结论:(1)闭眼及双重任务下阶梯着阶瞬间的膝、踝关节角度显著大于睁眼及单一任务时的角度(P <0.05),但在身体重心处于最低瞬间时仅踝关节角度展现出闭眼及双重任务下显著大于睁眼及单一任务(P <0.05);(2)睁眼及双重任务下的压力中心前后方向位移均方根、左右方向位移均方根、摆动的轨迹总长及轨迹包络面积皆显著小于闭眼时(P &...     

支撑面稳定度在不同视觉输入条件下对轻度认知障碍老年人平衡能力的影响

背景：支撑面稳定度与视觉输入是影响静态平衡的重要因素，但目前对轻度认知障碍老年人平衡能力的研究大多集中在稳定的硬支撑面，对其在不同视觉输入条件下不稳定支撑面上的静态平衡控制尚未可知。目的：探讨轻度认知障碍老年人不同视觉输入条件下在软、硬支撑面上的静态平衡能力。方法：选择21名轻度认知障碍老年人和19名认知正常老年人为研究对象，使用Kistler三维测力台分别对其进行睁眼双脚硬支撑面站立、睁眼双脚软支撑面站立、闭眼双脚硬支撑面站立、闭眼双脚软支撑面站立4种测试，每次测试站立持续时间为30 s，采集2组人群不同视觉条件下在软、硬支撑面站立时的足底压力中心数据，并进行对比。结果与结论：(1)有视觉输入条件下，轻度认知障碍老年人在软、硬支撑面上足底压力中心的总摇摆路径(软支撑面：P=0.003)、内外总摇摆路径(软支撑面：P=0.001，硬支撑面：P <0.001)和95%椭圆置信面积(软支撑面：P=0.001，硬支撑面：P <0.001)显著高于认知正常老年人；(2)无视觉输入条件下，轻度认知障碍老年人在软支撑面上足底压力中心的均方根距离(P=0.014)、内外均方根距离(P=0...     

完善慢性功能性关节不稳定康复疗效评估体系

目的对慢性踝关节不稳患者常规康复训练前后进行综合功能评估;采用综合康复治疗方法,观察其治疗效果。方法门诊选取124例单侧踝关节不稳患者,年龄34~56岁,其中男性73例,女性51例。分别进行肌力及关节活动度训练,平衡训练,本体觉训练,疗程为2个月,康复前后分别做即时、行走后疼痛[500 m行走后,视觉模拟评分法(VAS)评定)]、患肢负重时间、星偏移距离平衡检查及动、静态足底压力评估。结果患足负重项康复前平均站立时间与康复后差异有显著统计学意义;即时VAS疼痛评分康复前与康复后差异显著(5.32±0.27,1.07±0.08);500 m步行VAS疼痛评分康复前后差异有显著性(8.79±1.78,4.51±1.78),且显著高于健侧(5.41±0.42,27.31±5.48)(P0.05);两组足底动、静态峰值压力分布无明显改变(P0.05),静态压力:健侧前足(1095.30±61.28)gr/cm~2,患侧前足(1670.30±151.22)gr/cm~2负重增加,动态压力:健侧(1654.98±294.27)gr/cm~2,患侧前足(2822.30±312.28)gr/cm~2(P0.05)。结论经过综合康复治疗后,患者即时疼痛得到明显缓解,平衡能力得到明显提高,但500 m步行后疼痛以及动静态足底压力无明显变化,生物力学未得到纠正,限制了治疗效果。     

帕金森病患者平衡功能障碍发生情况及其影响因素分析

目的:探究帕金森病患者平衡功能障碍发生情况及其影响因素.方法:回顾性分析2019年8月-2021年9月我院收治的帕金森病患者90例,分析患者一般资料,并分析患者平衡功能障碍发生情况、对比两组平衡功能障碍情况评分[Berg平衡量表(BBS)、静态平衡应用静态跌倒风险指数(SFI)、动态平衡应用动态跌倒风险指数(DFI)]、分析影响帕金森病患者平衡功能障碍发生的相关因素.结果:90例患者中BBS评分<40分共50例入障碍组,BBS评分≥40分共40例入正常组;障碍组Berg平衡量表(BBS)及动态跌倒风险指数(DFI)评分均低于正常组,静态跌倒风险指数(SFI)评分高于正常组(P<0.05).障碍组年龄≥50岁、病程≥7 y及闭眼视觉条件发生率均高于正常组(P<0.05).行Logistic回归分析可知,患者年龄、病程、视觉条件是影响帕金森病患者平衡功能障碍的独立危险因素(P<0.05).结论:帕金森病患者发生平衡功能障碍风险较高,且年龄、病程及视觉条件作为影响患者平衡功能障碍发生的独立危险因素,在临床上需予以积极措施进行防范,以降低或避免平衡功能障碍导致的跌倒等不良状况的发生.     

肥胖儿童短时间静态平衡特征

目的 通过比较肥胖和非肥胖儿童6种站立情况下的压力中心(center of pressure,COP)偏移,研究肥胖儿童短时间静态平衡特征.方法 应用Footscan人体平衡系统获取47名肥胖儿童和50名非肥胖儿童分别双足、单足睁眼和闭眼站立10 s时COP摆动参数.结果 在双足闭眼站立时,肥胖儿童前后方向上的最大动摇...     

Vestibular influence on the cardiorespiratory responses to whole-body oscillation after standing

We assessed the influence of vestibular stimulation by whole-body oscillation in the yaw plane on the cardiorespiratory responses after a change of posture from sitting to standing. Eighteen healthy subjects (21–70 years old) and six patients with bilateral vestibular loss (46–59 years old) were tested. For comparison, a subgroup, age matched to the patients, was created from the healthy group. After a 10-min rest, subjects who were sitting, back unsupported, stood on a platform affording en bloc head and body support. The platform was either static or oscillated at 0.1 Hz and 0.5 Hz (20° amplitude) for 2 min. Presentation of the three conditions was counterbalanced. Respiration, ECG, blood pressure and head position were recorded. During oscillation at 0.5 Hz, the respiratory responses were different between groups; healthy subjects showed a significant increase of the respiratory frequency (1.75±2.1 breaths/min), which was not observed in the patients (0.16±0.7 breaths/min) (p<0.05, ANOVA). Absolute changes of heart rate and blood pressure were similar for the three conditions in all the subjects. However, healthy subjects showed a decrease of power spectrum density of the high-frequency ('respiratory') component of heart rate variability on standing during all three conditions. This response was variable among the patients and the age-matched group. The study shows that semicircular canal activation influences the respiratory rhythm during movements in the yaw plane in standing subjects. In addition, we observed that changes of the respiratory influence on heart rate variability during orthostatic stress are not affected by yaw oscillation or chronic vestibular loss, but may be affected by factors related to age. Electronic Publication     

The relationship between postural stability and virtual environment adaptation

Currently little is known about how adaptive responses to virtual environments are different between individuals who experience sickness related symptoms and those who do not. It is believed that sensory interactions between visually perceived self-motion and static inertial cues from vestibular and/or proprioceptive sensory systems contribute to the development of adaptation symptoms. The aim of this study was to evaluate the relationship between adaptation symptoms and postural stability in a virtual environment (VE) driving simulator. In addition, the role of sensory interaction was assessed using direct electrical stimulation techniques of the vestibular and cutaneous sensory systems. Posture performance was measured using centre of pressure measures of single leg stance tests during eyes open and eyes closed conditions. Correlation analysis of postural measures and symptom scores were conducted, as well as analysis of variance of posture performance between SICK and WELL individuals. Results indicate that posture stability is negatively correlated to symptom reporting. WELL individuals displayed the greatest decrease in postural stability during eyes open single leg stance following VE simulation. Application of a secondary sensory stimulation (vestibular or cutaneous) resulted in increased visual dependency for postural control following simulation. Combined, these results suggest that sensory interactions drive postural changes that are observed following VE simulation and are related to how visual information is used to control posture.     

Postural control in children with strabismus: Effect of eye surgery

The purpose of this study was to examine the postural control in children with strabismus before and after eye surgery. Control of posture is a complex multi-sensorial process relying on visual, vestibular and proprioceptive systems. Reduced influence of one of such systems leads to postural adaptation due to a compensation of one of the other systems [3]. Nine children with strabismus (4-8 years old) participated in the study. Ophthalmologic, orthoptic, vestibular and postural tests were done before and twice (2 and 8 weeks) after eye surgery. Postural stability was measured by a platform (TechnoConcept): two components of the optic flux were used for stimulation (contraction and expansion) and two conditions were tested eyes open and eyes closed. The surface area of the center of pressure (CoP), the variance of speed of the CoP and the frequency spectrum of the platform oscillations by fast Fourier transformation were analysed. Before surgery, similar to typically developing children, postural stability was better in the eyes open condition. The frequency analysis revealed that for the low frequency band more energy was spent in the antero-posterior direction compared to the medio-lateral one while the opposite occurred for the middle and the high frequency bands. After surgery, the eye deviation was reduced in all children and their postural stability also improved. However, the energy of the high frequency band in the medio-lateral direction increased significantly. These findings suggest that eye surgery influences somatosensory properties of extra-ocular muscles leading to improvement of postural control and that binocular visual perception could influence the whole body.     

Sensorial organisation favouring higher visual contribution is a risk factor of falls in an occupational setting

The contribution of intrinsic balance control factors to fall mechanisms has received little investigation in studies on occupational accidents. The aim of this study was to assess whether postural regulation in falling workers might have specificities in terms of sensorimotor strategies and neuromuscular responses to balance perturbations. Nine multi-fall-victims (MF), 43 single-fall-victims (SF) and 52 controls (C) were compared on performance measurements of static and dynamic postural control. MF and SF had the worst postural performance both in the static and slow dynamic tests, particularly in eyes closed conditions, suggesting a high dependency on visual cues and a lower use of proprioception. Moreover, the sensorial analysis showed that MF and SF relied less on vestibular input in the development of balance strategy and had more difficulties in maintaining a correct upright stance when proprioceptive input was altered. Finally, MF showed longer latency responses to unexpected external disturbance. Overall, postural control quality increased in the order MF, SF and C. MF and SF adopted particular sensorimotor organisation, placing them at an increased risk of falling in specific sensory environments. Strategies incorporating visual information involve using the cognitive processes causing delayed and less accurate fall avoidance responses, in contrast to adaptative strategies based on proprioceptive and vestibular information.     

Body sway increases immediately after strabismus surgery

The purposes of this study were to examine whether body sway is altered immediately after strabismus surgery in children and to find preoperative clinical factors associated with body sway. In a prospective study, body sway was measured on 1-3 days before surgery and on the third day after surgery; for the measurements, computerized static stabilometry was carried out on 28 consecutive patients with strabismus (age range: 3 to 12 years old; mean: 7.4) who underwent strabismus surgery under general anesthesia. The linear length of the sway path (cm), the linear length of the sway path in a particular unit of time (cm/second), and the area of the sway path (cm2), indicative of the extent of body sway, all increased significantly among a total of 28 patients in both conditions of the patient's eyes open and closed, as well as among those in a subgroup of 16 patients with exotropia, after they had undergone strabismus surgery (p < 0.05, Wilcoxon signed ranks test). The center of pressure along the Y axis of orientation from the toe to the heel was found to deviate significantly toward the heel postoperatively, as compared with the preoperative center in the subgroup of 16 patients with exotropia (p < 0.05). Before surgery, 15 patients with no stereoacuity exhibited a greater amount of body sway when their eyes were open than did 13 patients with measurable stereoacuity (p < 0.05, Mann-Whitney U-test). In the subgroup of 16 patients with exotropia when their eyes open, 3 patients with abnormal head posture exhibited more extensive body sway than did 13 patients without abnormal head posture (p < 0.05). Body sway was found to significantly increase immediately after strabismus surgery in children with strabismus. Stereoacuity and abnormal head posture are 2 clinical factors associated with preoperative postural instability.     

Synchronization of motor units in human soleus muscle during standing postural tasks

During standing posture, the soleus muscles acts to control sway in the anteroposterior (AP) direction. The soleus muscles bilaterally share a common function during standing tasks. We sought to determine whether common descending inputs, as evidenced by the synchronization of bilateral motor unit pairs, were employed as a strategy to control this common function. Single motor units were recorded from the soleus muscles in subjects who stood on adjacent force platforms for 5 min with their eyes open or closed. While standing with the eyes open, only 4/39 bilateral motor unit pairs showed significant synchronization. Similarly, only 3/36 motor unit pairs were significantly synchronized during the eyes closed task. The low incidence of synchronization was observed despite a high correlation in the amount of sway in the AP direction between legs in both the eyes open and eyes closed tasks (rho = 0.80 and rho = 0.83, respectively). When the extent of synchronization was assessed between pairs of motor units within the same leg with the eyes open, 10/12 pairs were synchronized. Furthermore, when pairs of soleus motor units were recorded both bilaterally and unilaterally during voluntary isometric ankle plantarflexion, only 4/30 bilateral pairs showed significant synchronization, whereas 19/24 unilateral pairs had significant synchronization. In this study, there was little evidence of the existence of synchronization between bilateral soleus motor unit pairs in either postural tasks or voluntary isometric contractions. In cases in which bilateral synchronization was observed, it was considerably weaker than the synchronization of motor units within a single soleus muscle. The results of this study reveal that it is rather uncommon for bilateral soleus motoneurons to receive common descending synaptic inputs, whereas two motoneurons within a single soleus muscle do.     

Factors affecting the common modulation of bilateral motor unit discharge in human soleus muscles

The purpose of this study was to determine the factors that influence the co-modulation of motor unit discharge rate in soleus muscles of both legs during upright standing. Single motor units were recorded from the left and right soleus muscles under three experimental conditions: standing quietly with the eyes open and closed, standing with the eyes closed while vibration was applied to one Achilles tendon, and swaying voluntarily or producing variable low-force isometric contractions at a frequency of 0.05 Hz. Correlations in motor unit discharge rate between left and right soleus motor units were assessed using common drive analysis. The results showed that common drive to motoneurons of the two muscles did not differ between standing with the eyes open or closed, but there was an order effect with the second task having significantly lower common drive than the first. Common drive was also significantly lower when vibration was applied to one leg compared with when no vibration was applied. Common drive was higher as subjects swayed anteriorly as compared with when they swayed posteriorly. There were no significant differences in common drive across phases of the variable isometric force contraction. Common drive was higher during voluntary sway than during variable force production; both of these values were significantly lower than those derived from the quiet standing task. These results suggest that proprioceptive and sub-cortical inputs contribute to the co-modulation of the firing rate of soleus motor unit pairs of the left and right leg during standing posture.     

Loss of otolith function with age is associated with increased postural sway measures

Loss of balance and increased fall risk is a common problem associated with aging. Changes in vestibular function occur with aging but the contribution of reduced vestibular otolith function to fall risk remains unknown. We examined a population of 151 healthy individuals (aged 21–93) for both balance (sway measures) and ocular counter-rolling (OCR) function. We assessed balance function with eyes open and closed on a firm surface, eyes open and closed on a foam surface and OCR during ±20 degree roll tilt at 0.005 Hz. Subjects demonstrated a significant age-related reduction in OCR and increase in postural sway. The effect of age on OCR was greater in females than males. The reduction in OCR was strongly correlated with the mediolateral measures of sway with eyes closed. This correlation was also present in the elderly group alone, suggesting that aging alone does not account for this effect. OCR decreased linearly with age and at a greater rate in females than males. This loss of vestibular otolith-ocular function is associated with increased mediolateral measures of sway which have been shown to be related to increased risk of falls. These data suggest a role for loss of otolith function in contributing to fall risk in the elderly. Further prospective, longitudinal studies are necessary to confirm these findings.