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Limits of stability—defined by the maximum distances a person is willing to reach without falling or changing the base of support—are measures of dynamic balance. Research question: What are infants' sitting stability limits in the forward and right directions? Twenty-one 6- to 10-month old infants participated in this cross-sectional study. To incentivize infants to reach beyond arm's length, caregivers began by holding a toy close to their infants at shoulder height. Caregivers then moved the toy farther away as infants tried to reach for it until infants lost balance, placed their hands on the floor, or transitioned out of sitting. All sessions were conducted via Zoom™ and video-recorded for further analyses using DeepLabCut for 2D pose estimation and Datavyu to determine timings of the reach and to code infants' postural behaviors. Infants' trunk excursions in the anterior-posterior plane (for forward reaches) and medio-lateral plane (for rightward reaches) represented their stability limits. Most infants ended the reach by returning to their original sitting position; however, infants with higher Alberta Infant Motor Scale (AIMS) scores transitioned out of sitting and infants with lower AIMS scores sometimes fell (mostly during rightward reaching). Trunk excursions were correlated with months of sitting experience. Rightward trunk excursions were also correlated with AIMS scores and age. Overall, infants' trunk excursions were larger in the forward than in the right direction, and such discrepancy was consistent across infants. Lastly, the more often infants adopted movement strategies with their legs (e.g., bending the knees), the greater the trunk excursion they attained. Sitting control entails learning to perceive the boundaries of stability limits and acquiring anticipatory postures to suit the needs of the task. Tests and interventions that target sitting stability limits could be beneficial for infants with or at risk of motor delays. • We used video and DeepLabCut to examine infants' sitting stability limits. • Stability limits were larger with more months of sitting experience. • Stability limits were larger in the forward than in the right direction. • Larger stability limits to the right required more advanced gross motor skills. • Movement strategies with the legs were associated with larger stability limits. [ABSTRACT FROM AUTHOR]

Background: Essential tremor (ET) is a neurological disorder characterized primarily by action tremor. Balance impairments in ET patients were formerly considered to be uncommon and simply age-related. However quantitative assessment with posturography has revealed impairments in control of both static and dynamic balance.Research Question: The aim of the present study is to assess postural stability with different posturographic techniques in ET patients.Methods: A prospective cross-sectional study conducted in two University Hospitals. Eleven patients diagnosed with essential tremor and twelve healthy controls were included. Balance assessment were performed with: sensory organization test (SOT) and limits of stability (LOS) of the computer dynamic posturography (CDP), results of free-field body sway analysis with mobile posturography (Vertiguard®), modified timed up and go test (TUG), Dizziness handicap inventory (DHI) and activities-specific balance confidence scale (ABC).Results: Patients with ET showed poorer scores in the SOT than controls for composite balance and somatosensory input. They also performed worse in LOS tests and Vertiguard® device indicated a higher risk of falling. There were no differences in the modified TUG. The mean score of DHI was 15.64 and 85.16 for ABC.Significance: Posturography assessment (CDP and Vertiguard®) is more accurate in showing balance impairment in ET patients than clinical evaluation (modified TUG). Balance impairment involves deteriorated processing of somatosensory input which could be explained by cerebellar dysfunction. Balance deficits could be included into future diagnostic criteria. [ABSTRACT FROM AUTHOR]

Objective: The aim of this study was to determine whether there is a difference in postural control between nulligravida women and women who have given birth by vaginal or cesarean section.Methods: Women who had only vaginal delivery in the previous 1-3 years were included in the vaginal delivery group (n = 27), those who had only cesarean delivery in the previous 1-3 years were included in the cesarean section group (n = 28), and those who had never given birth were included in the control group (n = 32). Evaluations were administered 6-8 days after the ovulation phase. Postural control of the participants was evaluated with the computerized dynamic posturography device.Results: A total of 87 women with a mean age of 29.4 ± 4 years and a mean body mass index of 24.1 ± 3.1 kg/m2 were included in the study. Antero-posterior somatosensory organization test values of the vaginal delivery group were lower than the control group (p = 0.0016). The cesarean delivery group had statistically lower antero-posterior somatosensory (p < 0.001 and p = 0.0013) and medio-lateral somatosensory (p = 0.002 and p = 0.017, respectively) test scores compared to the control group and the vaginal delivery group.Conclusions: It was observed that women who birthed with vaginal or cesarean delivery had impaired somatosensory postural control. There is definitely a need for further studies with a long-term follow-up examining the effects of postural control during pregnancy and the postpartum period. [ABSTRACT FROM AUTHOR]

Gait initiation (GI) includes automatic and voluntary movements. However, research on their impact on the first step in patients with Parkinson's disease (PD) and their relationship to freezing of gait (FOG) is lacking. We examined the effects of automatic movements (anticipatory postural adjustments [APAs]) and voluntary movements (limits of stability [LOS]) on the first step (first-step duration and first-step range of motion), along with their early recognition and prediction of slight FOG. Twenty-three patients with PD and slight freezing (PD + FOG) and 25 non-freezing patients with PD (PD-FOG) were tested while off medications and compared with 24 healthy controls (HC). All participants completed a 7-m Stand and Walk Test (7 m SAW) and wore inertial sensors to quantify the APAs and first step. LOS was quantified by dynamic posturography in different directions using a pressure platform. We compared differences among all three groups, analysed correlations, and evaluated their predictive value for slight FOG. In PD + FOG, APAs and LOS were worse than those in the PD-FOG and HC groups (p < 0.001), and the first step was worse than that in HC (p < 0.001). APAs were correlated mainly with the first-step duration. APAs and LOS were correlated with the first-step range of motion. APAs have been recognized as independent predictors of FOG, and their combination with LOS enhances predictive sensitivity. APAs and LOS in patients with PD directly affect the first step during GI. In addition, the combination of APAs and LOS helped predict slight FOG. • Anticipatory postural adjustments and limits of stability in patients with PD directly affected first-step duration and first-step range during the gait initiation. • Automatic movements such as anticipatory postural adjustments are more sensitive for predicting the occurrence of FOG than voluntary movements such as limits of stability. • The combination of anticipatory postural adjustments and limits of stability was helpful for predicting slight FOG. [ABSTRACT FROM AUTHOR]

Background: People with from Parkinson's disease (PD) and freezing of gait (FoG) have more frequent falls compared to those who do not freeze but there is no consensus on which, specific objective measures of postural instability are worse in freezers (PD + FoG) than non-freezers (PD-FoG).Research Question: Are functional limits of stability (fLoS) or postural sway during stance measured with wearable inertial sensors different between PD + FoG versus PD-FoG, as well as between PD versus healthy control subjects (HC)?Methods: Sixty-four PD subjects with FoG (MDS-UPDRS Part III: 45.9 ± 12.5) and 80 PD subjects without FoG (MDS-UPDRS Part III: 36.2 ± 10.9) were tested Off medication and compared with 79 HC. Balance was quantified with inertial sensors worn on the lumbar spine while performing the following balance tasks: 1) fLoS as defined by the maximum displacement in the forward and backward directions and 2) postural sway area while standing with eyes open on a firm and foam surface. An ANOVA, controlling for disease duration, compared postural control between groups.Results: PD + FoG had significantly smaller fLoS compared to PD-FoG (p =  0.004) and to healthy controls (p <  0.001). However, PD-FoG showed similar fLoS compared to healthy controls (p =  0.48). Both PD+FoG and PD-FoG showed larger postural sway on a foam surface compared to healthy controls (p =  0.001) but there was no significant difference in postural sway between PD+FoG and PD-FoG.Significance: People with PD and FoG showed task-specific, postural impairments with smaller fLoS compared to non-freezers, even when controlling for disease duration. However, individuals with PD with or without FoG had similar difficulties standing quietly on an unreliable surface compared to healthy controls. Wearable inertial sensors can reveal worse fLoS in freezers than non-freezers that may contribute to FoG and help explain their more frequent falls. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Functional Reach normative value is 26.6 cm for community older adults. • Functional Reach normative value is 15.4 cm for non-community older adults. • Functional Reach Test values should be adjusted according to the patient age. • Functional Reach Test should not be used to predict risk of falls on older adults. Abstract Objective To identify the evidence about the usefulness of the Functional Reach Test to evaluate balance and falls risk; to verify the Functional Reach Test assessment method and other variables that could interfere in its results; and to establish normative data for older adults. Data sources Manual and electronic searches (MEDLINE, Embase, Web of Science, LILACS, CINAHL, AgeLine and PsycINFO) were conducted with no language restrictions and published since 1990. Study selection Observational studies about the Functional Reach Test in older adults with no specific health condition were selected. Data extraction Two independent reviewers extracted data from studies and a third reviewer provided consensus. The studies methodological quality was appraised using the Newcastle-Ottawa Scale. Studies were submitted to critical analysis and meta-analysis. Results 40 studies were selected (8 prospective and 32 cross-sectional). 33 studies used the Functional Reach to assess balance and 21 studies the falls risk. The meta-analysis of Functional Reach normative data was 26.6 cm [95%CI: 25.14; 28.06] for community-dwelling older adults (n = 21 studies) and was 15.4 cm [95%CI: 13.47; 17.42] for non-community older adults (n = 5 studies), with statistics differences between settings. Functional Reach Test performance was found to decrease with age. Sex and prospective history of falls did not influence the test results. Methodological quality analysis determined high to low risk of bias of the studies. Conclusion This review revealed that the method of assessment and data of the Functional Reach Test varied greatly. Different values should be used for community- and non-community-dwelling older adults. [ABSTRACT FROM AUTHOR]

Abstract Objective To assess whether variables from a postural control test relate to and predict falls efficacy in prosthesis users. Design Twelve-month within- and between-participants repeated measures design. Participants performed the limits of stability (LOS) test protocol at study baseline and at 6-month follow-up. Participants also completed the Falls Efficacy Scale-International (FES-I) questionnaire, reflecting the fear of falling, and reported the number of falls monthly between study baseline and 6-month follow-up, and additionally at 9- and 12-month follow-ups. Setting University biomechanics laboratories. Participants Participants (N=24) included a group of active unilateral transtibial prosthesis users of primarily traumatic etiology (n=12) with at least 1 year of prosthetic experience and age- and sex-matched control participants (n=12). Interventions Not applicable. Main Outcome Measures Postural control variables derived from center of pressure data obtained during the LOS test, which was performed on and reported by the Neurocom Pro Balance Master, namely reaction time, movement velocity (MVL), endpoint excursion (EPE), maximum excursion (MXE), and directional control (DCL). Number of falls and total FES-I scores. Results During the study period, the prosthesis users group had higher FES-I scores (U =33.5, P =.02), but experienced a similar number of falls, compared to the control group. Increased FES-I scores were associated with decreased EPE (r = −0.73, P=.02), MXE (r = −0.83, P<.01) and MVL (r = −0.7, P=.03) in the prosthesis users group, and DCL (r = −0.82, P<.01) in the control group, all in the backward direction. Conclusions Study baseline measures of postural control, in the backward direction only, are related to and potentially predictive of subsequent 6-month FES-I scores in relatively mobile and experienced prosthesis users. [ABSTRACT FROM AUTHOR]

Research question The purpose of this study was to examine the postural sway characteristics of the ballet dance experts in quiet standing and at their limits of stability with an approach not used before in dancers. Methods The study was conducted on thirteen female ballet dancers and thirteen non-training females. The data were collected with a use of a force plate. To gain a better insight into the postural control processes, we used the rambling-trembling and sample entropy analyses in the COP data processing. Results The main findings of the study showed professional dancers to have higher values of postural sway characteristics in comparison to the non-trainees while performing simple motor tasks. Also, higher values of the trembling component in the group of dancers during quiet standing and the inclined positions were observed. This might be a sign of higher capacity of the postural system to deal with postural instability in dancers. Importance Our results confirmed that the visual information is important in the process of postural control of dancers’, which is proven by increased dislocations of the COP without visual feedback. The sample entropy results indicated more irregular characteristics of postural sway in ballet dancers representing more automated postural control. The data analysis methods showed high sensitivity to the subtle changes in postural control due to the dance training. [ABSTRACT FROM AUTHOR]

The aims of this study were to empirically quantify reliability and learning effects of a Limits of Stability protocol for transtibial prosthesis users. Outcome variables from center of pressure and center of mass were tested on: 1) multiple test repetitions within a single test occasion; and 2) between multiple test occasions. Trantibial prosthesis users (n=7) and matched controls (n=7) executed five trials of the Limits of Stability protocol on two occasions per day, on two consecutive days. Inter-trial learning effects and reliability of outcomes extracted via center of mass and center of pressure were evaluated utilizing standard biomechanics laboratory equipment. Reliability was good to excellent except the reaction time variable which was poor (Pooled 95%CI of ICC=0.248-0.484). An inter-trial learning effect was present in directional control for prosthesis users when the first trial was included in analysis (center of mass: 95%CI of r=0.065-0.239; center of pressure: 95%CI of r=0.076-0.249). The use of standard biomechanics lab equipment can produce reliable results for the Limits of Stability protocol. Researchers should be aware of low reliability of reaction time variable in the protocol assessed and should execute at least one practice trial prior to that which is used in subsequent analysis. [ABSTRACT FROM AUTHOR]

Balance impairment, frequent in Multiple Sclerosis patients (MS), is difficult to detect promptly with routine clinical examination. Computerized platforms can measure subtle deficit but, given the complexity of postural system, multiple tests should be adopted. To evaluate whether platform was more sensitive than Romberg Test (RT) in detecting balance abnormalities, we 1) chose a battery of posturographic tests, 2) collected normative data from 58 healthy subjects 3) applied the tests to Clinically Isolated Syndrome (n=42) and minimally impaired MS (n=76). Subjects underwent 3 trials of quiet standing with eyes open and closed (modified Clinical Test of Sensory Interaction on Balance, mCTSIB) and 4 trials of voluntary anterior and lateral maximal leaning on right and left sides (Limits of Stability, LOS), giving 10 postural indexes. For every subject, the best trials were selected for subsequent analysis. Normative values were established in a range from 1st to 99th percentile, defining balance impairment by the presence of at least 2 indexes out of range. Even adopting the above mentioned strict definition of balance impairment, the forceplate resulted more sensitive than RT, detecting abnormalities in 25% of patients, while RT was abnormal in 7% only. In RT-negative patients with 1-year follow-up (n =67) the detection of a single abnormal index was able to predict a subsequent onset of symptomatic balance impairment. The proposed procedure is quick, easy to perform and can improve the assessment of the clinical course of MS, from a pre-clinical stage up to medium degree of disability. [ABSTRACT FROM AUTHOR]

Introduction: Limits of stability (LOS) have extensive clinical and rehabilitational value yet no standard consensus on measuring LOS exists. LOS measured using a leaning or a circling protocol is commonly used in research and clinical settings, however differences in protocols and reliability problems exist.Objective: This study measured LOS using a four-way-leaning test and a circular-leaning test to test which showed larger LOS measurements. Furthermore, number of adaptation trials needed for consistent results was assessed.Method: Limits of stability were measured using a force plate (Metitur Good Balance System®) sampling at 50Hz. Thirty healthy subjects completed 30 trials assessing LOS alternating between four-way-leaning test and circular-leaning test.Results: A main effect of methods (ANOVA:F(1,28)=45.86, P<0.01) with the four-way-leaning test showing larger values than the circular-leaning test (NK, P<0.01). An interaction between method×directions was found (ANOVA:F(3, 84)=24.87, P<0.01). The four-way-leaning test showed larger LOS in anterior (NK, P<0.05), right (NK, P<0.01) and left direction (NK, P<0.01). Analysis of LOS for the four-way-leaning test showed a difference between trials (ANOVA:F(14,392)=7.81, P<0.01). Differences were found between trial 1 and 7 (NK, P<0.03), trial 6 and 8 (NK, P<0.02) and trial 7 and 15 (NK, P<0.02). Four-way-leaning test showed high correlation (ICC>0.87) between first and second trial for all directions.Conclusion: Four-way-leaning test yields larger LOS in anterior, right and left direction making it more reliable when measuring LOS. A learning effect was found up to the 8th trial, which suggests using 8 adaptation trials before reliable LOS is measured. [ABSTRACT FROM AUTHOR]

Previous research has indicated that muscle fatigue due to repeated bouts of physical activity can have negative residual effects on balance; however investigations using multi-joint forms of exercise involved in everyday settings and determination of how control of posture is altered during the physical activity itself are limited. The purpose of this investigation was to evaluate alterations in postural stability before, during, and after prolonged multi-joint STS exercise in healthy young adults. Center of pressure (COP) acquisitions were collected during repetitive STS exercise, while voluntary limits of stability (LOS) testing was performed before, immediately after, and 10min after STS exercise. By 50% total STS exercise time, fatigue resulted in increased anterio-posterior (y) and medio-lateral (x) COP path lengths (p=0.003 and p=0.018 respectively) and an anterior shift of COP at seat-off towards the mid-foot (p=0.010). No significant change in LOS mean amplitude was found after STS exercise; however a significant fatigue effect resulted in increased COPy sway velocity at maximal lean positions (p=0.006), but returned to PRE values after 10min of rest. Declines in postural stability during repetitive STS exercise was associated with reduced control of COP, as well as a reduced ability to stably control COP at extreme postural limits; however, 10min was adequate in young adults for recovery. These results may have important implications for monitoring fall risk due to acute bouts of exercise induced muscle fatigue from repetitive multi-joint activities such as the STS. [ABSTRACT FROM AUTHOR]

Multicomponent exercise programs have been demonstrated to prevent falls in older adults. However, the underlying responsible mechanisms are not clear. We aimed to analyze the association between changes in the limits of stability (LOS) as a relevant balance component, and falls occurrence during a multicomponent physical exercise program. Retrospective study, including ninety-one participants who had experienced a fall in the previous year, and were attended in a falls unit. All of them were included in a twice-a-week multicomponent exercise program during 16 weeks. Pre- and post-program measurements were collected for leg press, gait speed, the short physical performance battery (SPPB), and LOS (point of excursion [POE] and maximal excursion [MEX]) with posturography. Falls occurrence was assessed between the beginning and the completion of the exercise program (16 week). The mean age was 77.2 years, and 72 were female. Thirty-two participants fell at least once during the exercise period. The global baseline POE was 47.6 %, and the MEX was 64.7 %, and there were no differences between fallers and nonfallers. Nonfallers presented greater improvements in POE (6.3 % versus 1.3 %; p <.05) and MEX (9.2 % versus 3.0 %; p <.01) than fallers. The POE and MEX were independently associated with a reduced probability of having had a fall, OR: 0.95 (95 % CI: 0.91 to 0.99) and 0.94 (95 % CI: 0.90 to 0.99), respectively. Changes in SPPB results or leg press strength were not associated with decreased falls. Adjusted probability of fall occurrence decreased by 5 % and 6 % per 1 % improvement in absolute values in POE and MEX, respectively. Improvements in LOS after a multicomponent physical exercise program in older adults with previous falls may be associated with a decreased occurrence of falls. • Limits of stability improvement after a multicomponent exercise program in older adults is associated with decreased falls • Multicomponent exercise programs are the most complete method for improving physical function in frail older adults • The intervention reduced fall risk and improved physical function, muscle strength and power, body composition, and mood [ABSTRACT FROM AUTHOR]

Limit of stability (LOS) is an important yet under-examined postural control ability in children with developmental coordination disorder (DCD). This study aimed to (1) compare the LOS and fall frequencies of children with and without DCD, and (2) explore the relationships between LOS parameters and falls in the DCD population. Thirty primary school-aged children with DCD and twenty age- and sex-matched typically-developing children participated in the study. Postural control ability, specifically LOS in standing, was evaluated using the LOS test. Reaction time, movement velocity, maximum excursion, end point excursion, and directional control were then calculated. Self-reported fall incidents in the previous week were also documented. Multivariate analysis of variance results revealed that children with DCD had shorter LOS maximum excursion in the backward direction compared to the control group (p=0.003). This was associated with a higher number of falls in daily life (rho=-0.556, p=0.001). No significant between-groups differences were found in other LOS-derived outcomes (p>0.05). Children with DCD had direction-specific postural control impairment, specifically, diminished LOS in the backward direction. This is related to their falls in daily life. Therefore, improving LOS should be factored into rehabilitation treatment for children with DCD. [ABSTRACT FROM AUTHOR]

Objectives Impaired postural control in individuals with multiple sclerosis (MS) is associated with falls. The objective was to evaluate the direction-specific limits of stability in people with MS. Methods Balance control of 18 individuals with relapsing-remitting MS and 18 healthy controls was assessed using instrumented (Limits of Stability (LOS) test) and clinical (Berg Balance Scale (BBS) and Activities-specific Balance Confidence (ABC) scale) tests. Results There were significant differences in reaction time, movement velocity, endpoint excursion, maximum excursion, and directional control measures of the LOS test between individuals with MS and healthy controls. The BBS and ABC clinical balance measures were significantly lower in individuals with MS compared to control subjects. The directional control impairment was seen in the right side and backward diagonals (backward-right and backward-left) directions. A significant difference between the fallers and non-fallers was found on all the components of the LOS test. There was a significant correlation between the BBS and ABC scores and different components of the LOS test. Conclusions Direction-specific impairment of limits of stability components was observed in individuals with MS. This information could be used in balance rehabilitation of people with MS. [ABSTRACT FROM AUTHOR]

The Nintendo Wii Fit is a balance training tool that is growing in popularity due to its ease of access and cost-effectiveness. While considerable evidence now exists demonstrating the efficacy of the Wii Fit, no study to date has determined the specific mechanism underlying Wii Fit balance improvement. This paucity of knowledge was addressed in the present study using the NeuroCom Balance Manager's Sensory Organization Test (SOT) and Limits of Stability (LOS) test. These well-recognized posturography assessments, respectively, measure sensory weighting and dynamic stability mechanisms of balance. Forty healthy, young participants were recruited into two groups: Wii Fit Balance Intervention (WFBI) ( n = 20) and Control (CON) ( n = 20). Balance training consisted of seven Wii Fit exer-games played over the course of six consecutive weeks (2–4×/week, 30–45 min/day). The WFBI group performed Neurocom testing before and after the intervention, while the CON group was tested along a similar timeline with no intervention. Mixed-design ANOVAs found significant interactions for testing time point and condition 5 of the SOT ( p < 0.02), endpoint excursion ( p < 0.01), movement velocity ( p < 0.02), and response time ( p < 0.01). These effects were such that greater improvements were seen for the WFBI group following Wii Fit training. These findings suggest that individuals with known issues regarding the processing of multiple sources of sensory information and/or who have limited functional bases of support may benefit most from Wii Fit balance training [ABSTRACT FROM AUTHOR]

This study aimed to investigate the effect of horse riding simulation (HRS) on balance and trunk muscle activation as well as to provide evidence of the therapeutic benefits of the exercise. Thirty elderly subjects were recruited from a medical care hospital and randomly divided into an experimental and a control group. The experimental group performed the HRS exercise for 20 min, 5 times a week, for 8 weeks, and conventional therapy was also provided as usual. The muscle activation and limits of stability (LOS) were measured. The LOS significantly increased in the HRS group ( p < 0.05) but not in the control group ( p > 0.05). The activation of all muscles significantly increased in the HRS group. However, in the control group, the muscle activations of the lateral low-back (external oblique and quadratus lumborum) and gluteus medius (GM) significantly decreased, and there was no significant difference in other muscles. After the intervention, the LOS and all muscle activations significantly increased in the HRS group compared with the control group. The results suggest that the HRS exercise is effective for reducing the overall risk of falling in the elderly. Thus, it is believed that horse riding exercise would help to increase dynamic stability and to prevent elderly people from falling. [ABSTRACT FROM AUTHOR]

Highlights: [•] Both children with hemiplegia (USCP) and with typical development participated. [•] Maximum sway during voluntary leaning and arm movements while standing was analyzed. [•] Limits of stability were asymmetric in children with USCP contrary to other children. [•] During movement maximum sway on more-affected side exceeded the limits of stability. [•] In USCP supra-postural task jeopardized the self-perceived safe limits of stability. [Copyright &y& Elsevier]

Abstract: Objectives: To quantitatively detect the nature of balance impairment in patients with progressive supranuclear palsy (PSP) using dynamic posturography. Methods: Twenty clinically diagnosed PSP patients (8 women, 12 men; age: 62.1±7.7 years; duration: 2.6±1.3 years) and 20 healthy controls were studied. All subjects were right side dominant. They were evaluated by dynamic posturography (Biodex, USA). The measurements included (i) balance indices: ability to control balance in all directions (overall balance index, OBI), front to back (anterior–posterior index, API) and side-to-side (medio-lateral index, MLI), and (ii) the limits of stability (LOS) in 8 directions: forward (FW), backward (BW), right (RT), left (LT), forward-right (FW-RT), forward-left (FW-LT), backward-right (BW-RT) and backward-left (BW-LT). Results: Compared to controls, patients showed significantly higher OBI (p <0.001), API (p =0.003) and MLI (p <0.001), implying impaired balance. The total LOS score was significantly lower (implying poor stability) in PSP than in controls (18.3±7.3 vs. 28.4±8.5, p <0.001). Patients took significantly longer time to complete LOS test (262.7±33.0s vs. 135.4±20.6s, p <0.001). Direction-wise analysis showed that PSP patients had significantly lower LOS scores in FW, BW, RT, FW-RT, BW-RT and BW-LT directions compared to controls. However the scores in LT and FW-LT did not differ significantly. Conclusions: PSP patients showed impaired balance indices and decreased overall LOS compared to controls. Though LOS is affected in PSP, the scores in the left (non-dominant side) and forward-left (non-dominant forward diagonal) directions were preserved. [Copyright &y& Elsevier]

Abstract: A framework is proposed for the solution of fluid phase equilibrium (P–T flash) for binary mixtures described by equations of state of general form. The framework is based on decomposing the phase equilibrium problem into sub-problems with more convenient and tractable mathematical and numerical properties. Systematic procedures are used to identify the mapping of the problem in the density and composition space, referred to as the density–composition pattern, at specified temperature and pressure. A series of stability tests is then carried out to explore the existence or non-existence of phases. Once the existence of a phase has been determined, the limits of stability and physical bounds on the problem are used to define the search area for that phase in the density–composition pattern. Finally, all available information from this detailed analysis is used for the solution of phase equilibrium between the phases identified in order to find the stable state at the specified conditions. The features of the proposed approach are exposed in detail through an algorithm for the fluid phase equilibria of the augmented van der Waals equation of state applied to non-azeotropic mixtures. [Copyright &y& Elsevier]

Abstract: Background: The voluntary, maximum inclined posture reflects the self-perceived limits of stability. Parkinson’s disease is associated with small, bradykinetic postural weight shifts while standing but it is unclear whether this is due to reduced limits of stability and/or to the selection of abnormal strategies for leaning. The aim of this study was to investigate the effects of Parkinson’s disease and levodopa medication on voluntary limits of stability and strategies used to reach these limits. Methods: Fourteen subjects with Parkinson’s disease (OFF and ON levodopa) and 10 age-matched controls participated in the study. Functional limits of stability were quantified as the maximum center of pressure excursion during voluntary forward and backward leaning. Postural strategies to achieve functional limits of stability were assessed by (i) body segments alignment, (ii) the difference between center of pressure and center of mass in preparation for a lean, (iii) the timing and the velocity of the preparation phase. Findings: Functional limits of stability were significantly smaller in subjects with Parkinson’s disease compared to control subjects. Subjects with Parkinson’s disease maintained their stooped posture while leaning, initiated leaning with a smaller difference between center of pressure and center of mass and had a slower leaning velocity compared to control subjects. Levodopa enlarged the limits of stability in subjects with Parkinson’s disease because of an increase in maximum forward, but not backward leans, but did not significantly improve postural alignment, preparation for a leaning movement, or velocity of leaning. Interpretation: Parkinson’s disease reduces functional limits of stability as well as the magnitude and velocity of postural preparation during voluntary, forward and backward leaning while standing. Levodopa improves the limits of stability but not the postural strategies used to achieve the leaning. [Copyright &y& Elsevier]

Abstract: The present paper describes an investigation on parametric resonance in head seas in which a new third-order coupled mathematical model is considered. The restored modes of heave, roll and pitch are contemplated. The discussion is illustrated for the case of a transom stern fishing vessel at different speeds. It is pointed out that numerical simulations employing the new model are successfully compared to experimental results previously obtained for the vessel. Considering that analyticity is an important tool when handling complex stability issues, some theoretical dynamic characteristics of the equations are discussed. By means of the analysis of the coupled linear variational equation derived from an extended third-order model, the appearance of super-harmonics and increased rigidity proportional to wave amplitude squared due to third-order terms is demonstrated. In the present paper, an important tool is explored, that is the analysis of the limits of stability obtained from the new model. Limits of stability are a well-known and practical way of looking into the problem of parametric resonance. New limits of stability are derived and compared to the more conventional Strut diagram. Dynamic characteristics associated with the new limits of stability are discussed. The influence of different parameters is investigated, including vessel speed, damping and tuning. Consistent and revealing results are obtained through the analysis of the new limits of stability for different speeds and damping. [Copyright &y& Elsevier]