Transient Effects of Gaze Stability Exercises on Postural Stability in Patients With Posterior Circulation Stroke

The authors sought to investigate if short-term gaze stability exercises have an effect on postural stability of dynamic standing during neck movement in patients with posterior circulation stroke (PCS). Patients in both PCS and non-PCS groups were assigned to either an intervention or control group. The intervention group performed the gaze stability exercises for 10 min while the control group was merely resting. The center of pressure velocity was calculated to evaluate the postural stability. After intervention, PCS and non-PCS showed a significant reduction in center of pressure velocity during dynamic standing with eyes closed condition, and the PCS group showed a significant improvement in eye-opened condition. This study indicated that gaze stability exercises improve PCS patients' postural control, especially during dynamic standing.     

Local Dynamic Stability of the Locomotion of Lower Extremity Joints and Trunk During Backward Upslope Walking

Backward slope walking was considered as a practical rehabilitation and training skill. However, its gait stability has been hardly studied, resulting in its limited application as a rehabilitation tool. In this study, the effect of walking direction and slope grade were investigated on the local dynamic stability of the motion of lower extremity joints and trunk segment during backward and forward upslope walking (BUW/FUW). The local divergence exponents (λ_S) of 16 adults were calculated during their BUW and FUW at grades of 0%, 5%, 10%, and 15%. Mean standard deviation over strides (MeanSD) was analyzed as their gait variability. Backward walking showed larger λ_S for the abduction-adduction and rotational angles of knee and ankle on inclined surface than forward walking, while λ_S for hip flexion-extension angle at steeper grades was opposite. No grade effect for any joint existed during BUW, while λ_S increased with the increasing grade during FUW. As to the trunk, walking direction did little impact on λ_S. Still, significant larger λ_S for its medial-lateral and vertical motion were found at the steeper grades during both FUW and BUW. Results indicate that during BUW, the backward direction may influence the stability of joint motions, while the trunk stability was challenged by the increasing grades. Therefore, BUW may be a training tool for the stability of both upper and lower body motion during gait.     

Postural Stability in Children with High Sacral Level Spina Bifida: Deviations from a Control Group

Abstract

Objective: To assess static and dynamic postural stability changes in children with high sacral level spina bifida.

Methods: Thirty-five children with high sacral level spina bifida and 35 age-matched healthy controls were enrolled. Their lower extremity muscle strengths and static and dynamic postural stability parameters were measured with the use of a dynamometer and the NeuroCom Balance Master^® device, respectively. Functional gait and balance were evaluated using the five times sit-to-stand test (5STS) and the 6-minute walk test (6MWT). Spinal, hip, and ankle deformities of the patient group were measured by radiologic evaluation.

Results: In comparison with controls, patients were found to have lower ankle dorsiflexion and plantar-flexion strength, increased 5STS duration, and decreased 6MWT distance while both static and dynamic postural stability parameters were significantly different. Bilateral ankle muscle strengths were found to be negatively correlated with postural stability parameters. The presence of hydrocephalus or meningomyelocele in the patient group was found to have negative effects on static postural stability.

Conclusion: Static and dynamic postural stability is affected even in children with high sacral level spina bifida who are expected to have best condition in this patient population. The ankle muscle strength is the main factor influencing these changes.     

Slip and Trip Perturbations During an Object Transport Task Requiring a Lateral Change in Support

The ability to counteract destabilizing external forces while simultaneously executing a complex task presents a novel way to ascertain one's ability to generate adaptive postural control responses to avoid a potential fall. In this study, participants performed an upper limb object transport task requiring a lateral change in support on a robotic platform that could remain fixed in space or translated (mimicking a slip or trip perturbation). No significant stability differences were observed at initial recovery step between slip and trip perturbations. Variability measures were greatest during the trip perturbations; though stability was at its greatest level preceding these perturbations. These results will aid in the design of future studies that will investigate adaptive postural control responses generated by older adults when executing similar, ongoing complex upper body tasks interrupted by a destabilizing support surface perturbation.     

Textured Foot Orthotics on Dynamic Stability and Turning Performance in Parkinson’s Disease

Abstract

The purpose of this study was to facilitate sensory feedback, with textured foot orthotics, to evaluate dynamic stability and turning behavior in Parkinson’s disease individuals. Seven participants with a diagnosis of idiopathic Parkinson’s disease, aged 55–80?years old, participated in this study. Participants completed three testing sessions; baseline, 4?weeks post-baseline, and 5?weeks post-baseline. Three experimental conditions were tested: footwear only (F), footwear?+?non-textured orthotic (FO), and footwear?+?textured orthotic (FOT). Kinematic, kinetic, and video data were collected during the steps preceding a turn task. Variables of interest included dynamic stability (maximum mediolateral (ML), minimum ML, and ML range of the center of mass (COM)-base of support (BOS) relationship) and turning performance (gait velocity and step count). There was a statistically significant increase in maximum ML COM-BOS distance (week 4 [0.1298 m?±?0.054] compared to week 0 [0.1069 m?±?0.050] p = .0076), and a significant decrease in step count (week 0-F [5.52 steps ± 1.08] to week 0-FO [5.23 steps ± 0.87] p = .0296) and (week 4-FO [5.24 steps ± 1.31] to week 4–FOT [4.67 steps ± 0.76] p = .0004). Textured foot orthotics modified dynamic stability and turning performance in Parkinson’s disease individuals completing a 180° degree turn. These preliminary results support this potential treatment option for rehabilitation professionals treating Parkinson’s disease.     

Prospective dynamic balance control during the swing phase of walking: Stability boundaries and time-to-contact analysis

This study examined the prospective control of the swing phase in young healthy adults while walking at preferred speed over unobstructed ground and during obstacle clearance. Three aspects of swing were examined: (1) the relation of the body Center of Mass (CoM) to the stability boundaries at the base of support; (2) a dynamic time-to-contact analysis of the CoM and swing foot to these boundaries; and (3) the role of head movements in the prospective control of gait and field of view assessment. The time-to-contact analysis of CoM and swing foot showed less stable swing dynamics in the trail foot compared to the lead foot in the approach to the unstable equilibrium, with the CoM leading the swing foot and crossing the anterior stability boundary before the swing foot. Compensations in temporal coupling occurred in the trail limb during the late swing phase. Time-to-contact analysis of head movement showed stronger prospective control of the lead foot, while fixation of the field of view occurred earlier in swing and was closer to the body in the obstacle condition compared to unobstructed walking. The dynamic time-to-contact analysis offers a new approach to assessing the unstable swing phase of walking in different populations.     

Stability in force-production tasks

Exerting a force on a mechanical system can induce mechanical instability. To overcome that instability, humans may take advantage of their upper limb mechanical impedance (e.g., hand stiffness). The authors investigated what stiffness is required to maintain static stability and how humans can achieve that stiffness in the context of the task of pushing on a pivoting stick. Results showed that the stiffness required is in the range of measured human upper limb stiffness. To avoid an ill-posed problem, one can better express the requirements for stability as a simple geometrical criterion related to the curvature of the potential energy field at the hand. A planar model of the upper limb revealed that individuals can use both hand rotational and translational stiffness to stabilize a stick. Although hand rotational stiffness does not participate in producing the axial force on the stick, it can significantly contribute to achieving a limb stiffness appropriate for maintaining static stability. Hand rotational stiffness can be important for the design of hand tools, because humans can increase it only by augmenting grip force, a biomechanical factor associated with cumulative trauma injuries of the upper extremities.     

论动态稳定

目前,人类认识在两方面取得了共识：一方面,认识到了可持续发展的意义．另一方面,认识到了可持续发展与稳定的关系,并提出稳定是压倒一切的主题。现在的问题是,对稳定主要是从平衡方面去理解：经济稳定就是经济平衡,自然稳定就是生态平衡等。实际上这仍然是一种静态的稳定,这种平衡的稳定是没有活力的,因而是同进化和发展的目标正相矛盾的。本文则指出,具有活力的稳定是一种非平衡的稳定,其在本质上是一种动态稳定,其同进化和发展的目标正相一致。     

Adaptation in motor strategies for postural control associated with sensory reweighting

The purpose of this study was to identify and differentiate the motor strategies associated with sensory reweighting adapted during specific sensory integration tasks by healthy young adults. Thirty-six subjects (age range: 21–33 years) performed standing computerized dynamic posturography balance tasks across progressively increasing amplitudes of visual (VIS), somatosensory (SOM) and both (VIS+SOM) systems perturbation conditions. Adaptation in the motor strategy was measured as changes in electromyographic (EMG) activities and joint angles. The contribution of the perturbed sensory input in maintaining postural stability was calculated to determine the sensory reweighting. A multivariate design was used to model a linear combination of motor adaptation variables that discriminates specific sensory integration tasks. Results showed a significant progressive decrease in postural sway per unit amplitude of sensory perturbation in each condition, indicating dynamic sensory reweighting. Linear discriminant function analysis indicated that the adaptation in motor strategy during the VIS condition was associated with increased activity of EMG and joint angles in the upper body compared to the lower body. Conversely, during the SOM and VIS+SOM conditions, the adaptation in motor strategy was associated with decreased activity of EMG and joint angles in the lower body compared to the upper body. Therefore, the adaptation in motor strategies associated with sensory reweighting were different for different sensory integration tasks.     

Effect of Heel Heights on Female Postural Control During Standing on a Dynamic Support Surface With Sinusoidal Oscillations

The authors aimed to investigate female balance or stability control with comparative analysis of the center of pressure trajectory and plantar pressure distribution with different high-heeled shoes while standing on a dynamic surface with multidirectional perturbations. College females with at least 2 years' history of wearing high-heel shoes voluntarily participated in the test with a Novel Pedar insole (Novel, GmBH, Munich, Germany. With heels height increasing, the pressure time integral obviously transfer to the medial forefoot region, with center of pressure trajectory medially deviated significantly, either under anteroposterior or mediolateral perturbations. The passive plantarflexion position of ankle incurred by high heel increased the range of motion in the frontal plane but decreased ankle stability, thus increasing the challenge of body balance maintenance.     

Practical Reason and the Stability Standard

Practical reasoning, reasoning about what to do, is a very familiar activity. When we think about whether to cook or to go out for dinner, to buy a house or rent, or to study law or business, we are engaged in practical reasoning. If the kind of reasoning we engage in is truly a rational process, there must be some norms or standards that govern it; the process cannot be arbitrary or random. In this paper I argue that one of the standards that governs practical reasoning is the stability standard. The stability standard, I argue, is a norm that is constitutive of practical reasoning: insofar as we do not take violations of this norm to be relevant considerations, we do not count as engaged in reasoning at all. Furthermore, I argue that it is a standard we can explicitly employ in order to deliberate about our ends or desires themselves. Importantly, this standard will not require that some ends are prescribed or determined by reason alone. The stability standard, therefore, allows us to retain some of the attractive features of instrumentalism without accepting the implication that there is no rational way to evaluate ends.     

Stability and prediction of parenting stress

The study focused on stability and prediction of parenting stress experiences over a 6‐year period. Mothers (N=93) who had received a clinical intervention for feeding or sleeping problems during infancy (Time 1; T 1) were followed‐up when the children were 5–10 years old (Time 2; T 2). An age‐ and sex‐of‐child matched normal group was used for comparison of stress levels at T 2. Parenting stress was measured by the Swedish Parenthood Stress Questionnaire, which consists of a general parenting stress scale and sub‐scales tapping different aspects of parenting stress experiences. T 1 predictors were clinical assessments of child problem load, maternal unresponsiveness, and family psychosocial problems. T 2 predictors were mother‐reported concurrent child problem load and psychosocial problems. The individual stability in stress experiences was moderate. Effect sizes indicated that mothers with early clinical contacts had reduced their stress to levels close to those in the normal sample. Parenting stress at T 2 could be predicted from early and from concurrent child and family problems. The results point to the relevance of early clinical assessments and to the importance of a sub‐area approach in parenting stress research, as there were differences between stress sub‐areas regarding both prediction and stability. Copyright © 2007 John Wiley & Sons, Ltd.     

父亲养育压力的稳定性及对儿童学步期问题行为的预测

本研究采用追踪研究及多重报告法,考察了儿童从6个月至14个月间父亲养育压力的稳定性特点,以及6个月与14个月时的父亲养育压力对儿童24个月时的问题行为的影响。结果发现:(1)儿童6个月与14个月时的父亲养育压力具有中等程度的相关;从6个月到14个月,父亲的总体养育压力和育儿愁苦维度的平均压力水平没有显著变化,亲子互动失调维度显著降低,儿童困难特质维度的平均压力水平显著上升;(2)儿童6个月时,父亲的育儿愁苦显著预测儿童24个月时的内隐问题行为;14个月时,父亲的育儿愁苦显著预测儿童24个月时的外显问题行为;6个月和14个月时,儿童困难特质维度的压力都可显著预测儿童24个月时的外显问题行为。     

Stability of Family Interaction from Ages 6 to 18

Research has demonstrated the stability of juvenile offending during childhood and adolescence but generally has not focused on the continuity of family interactions associated with juvenile offending. The present report focused on the stability of several family interaction events and attributes (i.e., physical punishment, communication, supervision, positive parenting, and parent–child relationship) for a large sample of male adolescents and their primary caretakers, drawn from a multiyear longitudinal study that represented middle childhood through late adolescence (ages 6–18). We also assessed the impact of ethnicity, family composition, teenage motherhood, and youth delinquency on these interactions. Test–retest correlations and growth-curve analyses were used to assess relative and absolute stability of the interactions, respectively. As predicted, relative stability of family interaction was high. There was an absolute change in scores of physical punishment (decreased) compared to poor supervision and low positive parenting (both increased), whereas poor communication and bad relationship with the caretaker did not measurably change with age. Single-parent families and families with teenage mothers experienced significantly worse interactions over time than did families consisting of two biological parents present in the household. These findings are discussed in relation to the development of juvenile offending.     

The Stability of Child Problem Behaviors: A Longitudinal Analysis of Inner-City African American Children

We focused on the stability of child problem behaviors in a sample of 124 low-income inner-city African American families. Internalizing and externalizing problems were assessed longitudinally across four years. Test-retest correlation coefficients indicated that the relative stability of both internalizing and externalizing problems over the four-year assessment was high for both child and mother reported variables. Partial support was obtained for absolute stability of child problem behavior as analyses of variance revealed that two of four variables of interest did not change significantly over time. Mother report of child problem behavior was more stable than child report, but gender of child or type of problem behavior (internalizing vs. externalizing) was not related to stability. Hierarchical multiple regression analyses revealed that the historical context of child problem behaviors is important to consider, as earlier problem behaviors accounted for unique variance in later problem behaviors, beyond that accounted for the most recent assessment.     

A Typology of LDS Sociopolitical Worldviews

Members of the Church of Jesus Christ of Latter-Day Saints (Mormons, Latter-Day Saints, or LDS) are sometimes thought of as a monolithic block of economic and social conservatives. This article addresses whether this is caused by strong religious effects, or whether it is an artifact of unrepresentative sampling. Q methodology is used to identify six "types" of political worldviews among a multinational and multiracial sample of active Latter-Day Saints. The six types reveal some interesting ideological variations among Mormons, particularly on economic issues, and even some unique LDS issues. A second-order factor analysis indicates a high level of commonality across types on social issues, but important differences on orientation toward government. I conclude that the failure to include racial and cultural variation in Mormon samples has led us to overestimate the otherwise significant influence of LDS doctrine on members' political views.     

Cognitive control processes underlying time-based prospective memory impairment in individuals with high depressive symptomatology

The current study compared time-based prospective memory (PM) for individuals with high depressive symptomatology (HDS) and low depressive symptomatology (LDS). We examined PM accuracy rate, clock-checking frequency, and decrements in ongoing task performance (i.e., costs to ongoing tasks) associated with an embedded time-based PM task. HDS participants demonstrated numerically lower but statistically comparable clock-checking frequency to LDS participants. However, their PM performance was significantly poorer than that of LDS participants. The pattern of observed costs to ongoing tasks and correlational analyses between ongoing task performance and PM accuracy showed that, relative to LDS participants, HDS participants were restricted in their allocation of attentional resources to support PM. We concluded that although HDS and LDS participants externally controlled their time-based PM task performance (i.e., clock-checking) similarly, the HDS participants lacked the cognitive initiative to allocate attentional resources to internally control PM task performance. Such internal control might reflect time-estimation processes, the resources required to maintain the PM task response intention, and/or the ability to coordinate the PM task response with ongoing task demands. To our knowledge, this is the first paper to have examined time-based PM strategies used by HDS individuals beyond clock-checking. The data suggest that interventions that encourage intermittent strategic reviews of PM goals may be beneficial for individuals with high depressive symptomatology.     

Stability of the Millon Clinical Multiaxial Inventory among psychiatric inpatients

This study investigated the stability of the Millon Clinical Multiaxial Inventory (MCMI) in a sample of psychiatric inpatients over a longer time period and from different perspectives than previous reliability studies. Test-retest reliability was assessed from three perspectives: correlation/regression, equivalence of dimensional structures across testings upon different admissions, and stability of personality style across testings. Some stability from a correlational perspective was found, with higher stability estimates indicated for the basic personality scales in comparison with the clinical symptom scales which is consistent with Millon's theory. The internal structure of the MCMI was essentially identical across testings. Although source of reinforcement and instrumental or coping style were stable across testings beyond chance, the MCMI profiles of a considerable number of subjects were inconsistent across testings. Correspondingly, clinicians should be cautious in using the MCMI to make categorical decisions regarding personality style with inpatients who are tested at admission and who have had repeated hospitalizations.