Search

Mobile eye-trackers are currently used during real-world tasks (e.g. gait) to monitor visual and cognitive processes, particularly in ageing and Parkinson’s disease (PD). However, contextual analysis involving fixation locations during such tasks is rarely performed due to its complexity. This study adapted a validated algorithm and developed a classification method to semi-automate contextual analysis of mobile eye-tracking data. We further assessed inter-rater reliability of the proposed classification method. A mobile eye-tracker recorded eye-movements during walking in five healthy older adult controls (HC) and five people with PD. Fixations were identified using a previously validated algorithm, which was adapted to provide still images of fixation locations (n = 116). The fixation location was manually identified by two raters (DH, JN), who classified the locations. Cohen’s kappa correlation coefficients determined the inter-rater reliability. The algorithm successfully provided still images for each fixation, allowing manual contextual analysis to be performed. The inter-rater reliability for classifying the fixation location was high for both PD (kappa = 0.80, 95% agreement) and HC groups (kappa = 0.80, 91% agreement), which indicated a reliable classification method. This study developed a reliable semi-automated contextual analysis method for gait studies in HC and PD. Future studies could adapt this methodology for various gait-related eye-tracking studies.

Background: Cumulative dementia incidence in Parkinson's disease (PD) is significant, with major personal and socioeconomic impacts on individuals with PD and their carers. Early identification of dementia risk is vital to ensuring optimal intervention. Saccadic deficits often distinguish neurodegenerative disorders and cognitive impairment, but their ability to predict cognitive decline in PD has yet to be determined. The aims of this study were to (1) evaluate baseline (6.4 ± 6.1 months since PD diagnosis) differences in pro‐saccadic metrics between those with early PD and healthy age‐matched adults; and (2) assess the ability of baseline pro‐saccades to predict subsequent cognitive decline over 4.5 years. Methods: One hundred and forty‐one PD and 90 age‐matched participants recruited at diagnosis underwent saccadometric assessment of pro‐saccades at baseline and had cognition assessed at baseline, 18, 36, and 54 months. Pro‐saccadic characteristics included latency, duration, amplitude, peak, and average velocity. Cognitive assessment included executive function, attention, fluctuating attention, and memory. Linear mixed‐effects models examined pro‐saccadic metrics as predictors of cognitive decline over 54 months. Results: Pro‐saccades were significantly impaired at baseline in PD compared with controls. Pro‐saccadic characteristics of latency, duration, peak, and average velocity predicted decline in global cognition, executive function, attention, and memory over 54 months in PD. In addition, only reduction in global cognition and attention were predicted by pro‐saccadic metrics in age‐matched adults, indicating that PD findings were not purely age related. Conclusions: Saccadic characteristics are impaired in early PD and are predictive of cognitive decline in several domains. Assessment of saccades may provide a useful non‐invasive biomarker for long‐term PD cognitive decline in early disease. © 2019 International Parkinson and Movement Disorder Society

This paper presents a cross-disciplinary project based on an experiment in eye-tracking and motion capture (Sainsbury’s Centre for Visual Arts), which aimed to study viewers’ movements around an iconic sculpture: Edgar Degas’s Little Dancer Aged Fourteen. The experiment studies how viewers respond to this three-dimensional artwork not only by looking at it but also through their own bodily reactions to it, such as by unconsciously mimicking a represented attitude or gesture. We compared two groups of viewers: classically trained dancers and non-dancers. Our hypothesis was that the skills and embodied experiences of the dancers would alter the ways in which they engage bodily with the work compared to the non-dancers. Our underlying research question was: how are vision and the body interlinked in esthetic and kinesthetic experience? This paper does not give results, which are forthcoming. It focuses on methodology and provides a commentary on the design and development of the interdisciplinary collaboration behind the project. It explores an interdisciplinary collaboration that bridges the humanities and experimental sciences and asks how being confronted with unfamiliar methodologies forces researchers in a given field to critically self-examine the limits and presuppositions of their practices.

Detection of cysteine sulfenic acid in live cells is critical in advancing our understanding of cysteine redox chemistry and its biological function. Accordingly, there is a need to develop sulfenic acid-specific chemical probes with distinct reaction mechanisms to facilitate proteome-wide detection of this important posttranslational modification. Herein, we report the first whole-cell proteomics analysis using a norbornene probe to detect cysteine sulfenic acid in live HeLa cells. Comparison of the enriched proteins to those identified using dimedone and other C-nucleophilic probes revealed a complementary reactivity profile. Remarkably, 148 new members of the sulfenome were identified. These discoveries highlight how subtle differences in chemical reactivity of both the probes and cysteine residues influence detection. Overall, this study expands our understanding of protein oxidation at cysteine and reveals new proteins to consider for future studies of cysteine oxidation, redox regulation and signaling, and the biochemistry of oxidative stress.

Quantifying gait and postural control adds valuable information that aids in understanding neurological conditions where motor symptoms predominate and cause considerable functional impairment. Disease-specific clinical scales exist; however, they are often susceptible to subjectivity, and can lack sensitivity when identifying subtle gait and postural impairments in prodromal cohorts and longitudinally to document disease progression. Numerous devices are available to objectively quantify a range of measurement outcomes pertaining to gait and postural control; however, efforts are required to standardise and harmonise approaches that are specific to the neurological condition and clinical assessment. Tools are urgently needed that address a number of unmet needs in neurological practice. Namely, these include timely and accurate diagnosis; disease stratification; risk prediction; tracking disease progression; and decision making for intervention optimisation and maximising therapeutic response (such as medication selection, disease staging, and targeted support). Using some recent examples of research across a range of relevant neurological conditions—including Parkinson’s disease, ataxia, and dementia—we will illustrate evidence that supports progress against these unmet clinical needs. We summarise the novel ‘big data’ approaches that utilise data mining and machine learning techniques to improve disease classification and risk prediction, and conclude with recommendations for future direction.

Made available in DSpace on 2019-10-06T15:25:30Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-01-01 Biotechnology Research Center, Tabriz University of Medical Sciences Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) National Institute on Disability and Rehabilitation Research Performance of several tasks simultaneously (dual-tasks) is common in everyday walking. Studies indicate that dual-task walking performance declines with age together with cognitive function, but neural mechanisms underpinning deficits remain unclear. Recent developments in mobile imaging techniques, such as functional near infrared spectroscopy (fNIRS), allow real-time monitoring of cortical activity during walking. This study aimed to: 1) examine activity in motor and cognitive cortical regions when walking with a dual-task in young and older adults; and 2) determine the effect of cognition on dual-task cortical activity changes. Seventeen young (20.3 ± 1.2 years) and eighteen older adults (72.6 ± 8.0 years) performed dual-task conditions, lasting 5 min, with alternating 30-second experimental blocks. The primary outcome was cortical activity, assessed by measuring changes in oxygenated haemoglobin (HbO2) concentrations. Cortical regions of interest (ROI) included motor regions (premotor cortex (PMC), supplementary motor area (SMA), primary motor cortex (M1)), and cognitive regions (prefrontal cortex (PFC)). Cognitive domains were assessed using standard tests and accelerometers were used to extract gait features. Cortical activity increased with a dual-task in PMC, SMA and M1 but not in PFC regions across groups, with response most evident with initial task exposure. Older adults did not increase SMA activity with a dual-task to the same level as young adults. Dual-task cortical response was consistently associated with greater executive function across groups. In conclusion, both young and older adults responded in a similar manner to dual-task conditions. Dual-task walking activated multiple motor regions in both groups, but no significant change occurred for cognitive region activation. Cortical activation with a dual-task related to executive function. Department of Neurology Oregon Health and Science University Institute of Neuroscience Newcastle University Newcastle upon Tyne Hospitals NHS Foundation Trust Instituto de Biociências Universidade Estadual Paulista (UNESP), Campus Rio Claro Institute of Ageing Clinical Ageing Research Unit Campus for Ageing and Vitality Newcastle University Instituto de Biociências Universidade Estadual Paulista (UNESP), Campus Rio Claro

Biomarkers are required to track disease progression and measure the effectiveness of interventions for people with spinocerebellar ataxia type-6 (SCA6). Gait is a potential biomarker that is sensitive to SCA6 which can be measured using wearable technology, reducing the need for expensive specialist facilities. However, algorithms used to calculate gait using data from wearables have not been validated in SCA6. This study sought to examine the validity of a single wearable for deriving 14 spatio-temporal gait characteristics in SCA6 and control cohorts. Participants performed eight intermittent walks along a 7 m instrumented walkway at their preferred walking pace while also wearing a single accelerometer-based wearable on L5. Gait algorithms previously validated in neurological populations and controls were used to derive gait characteristics. We assessed the bias, agreement and sensitivity of gait characteristics derived using the instrumented walkway and the wearable. Mean gait characteristics showed good to excellent agreement for both groups, although gait variability and asymmetry showed poor agreement between the two systems. Agreement improved considerably in the SCA6 group when people who used walking sticks were excluded from the analysis, suggesting poorer agreement in people with more severe gait impairment. Despite poor agreement for some characteristics, gait measured using the wearable was generally more sensitive to group differences than the instrumented walkway. Our findings indicate mean gait characteristics can be accurately measured using an accelerometer-based wearable in people SCA6 with mild-to-moderately severe gait impairment yet further development of algorithms are required for people with more severe symptoms.

Contains fulltext : 167962.pdf (Publisher’s version ) (Closed access) BACKGROUND: Age-associated motor and cognitive deficits increase the risk of falls, a major cause of morbidity and mortality. Because of the significant ramifications of falls, many interventions have been proposed, but few have aimed to prevent falls via an integrated approach targeting both motor and cognitive function. We aimed to test the hypothesis that an intervention combining treadmill training with non-immersive virtual reality (VR) to target both cognitive aspects of safe ambulation and mobility would lead to fewer falls than would treadmill training alone. METHODS: We carried out this randomised controlled trial at five clinical centres across five countries (Belgium, Israel, Italy, the Netherlands, and the UK). Adults aged 60-90 years with a high risk of falls based on a history of two or more falls in the 6 months before the study and with varied motor and cognitive deficits were randomly assigned by use of computer-based allocation to receive 6 weeks of either treadmill training plus VR or treadmill training alone. Randomisation was stratified by subgroups of patients (those with a history of idiopathic falls, those with mild cognitive impairment, and those with Parkinson's disease) and sex, with stratification per clinical site. Group allocation was done by a third party not involved in onsite study procedures. Both groups aimed to train three times per week for 6 weeks, with each session lasting about 45 min and structured training progression individualised to the participant's level of performance. The VR system consisted of a motion-capture camera and a computer-generated simulation projected on to a large screen, which was specifically designed to reduce fall risk in older adults by including real-life challenges such as obstacles, multiple pathways, and distracters that required continual adjustment of steps. The primary outcome was the incident rate of falls during the 6 months after the end of training, which was assessed in a modified intention-to-treat population. Safety was assessed in all patients who were assigned a treatment. This study is registered with ClinicalTrials.gov, NCT01732653. FINDINGS: Between Jan 6, 2013, and April 3, 2015, 302 adults were randomly assigned to either the treadmill training plus VR group (n=154) or treadmill training alone group (n=148). Data from 282 (93%) participants were included in the prespecified, modified intention-to-treat analysis. Before training, the incident rate of falls was similar in both groups (10.7 [SD 35.6] falls per 6 months for treadmill training alone vs 11.9 [39.5] falls per 6 months for treadmill training plus VR). In the 6 months after training, the incident rate was significantly lower in the treadmill training plus VR group than it had been before training (6.00 [95% CI 4.36-8.25] falls per 6 months; p

Norbornene derivatives were validated as probes for cysteine sulfenic acid on proteins and in live cells. Trapping sulfenic acids with norbornene probes is highly selective and revealed a different reactivity profile than the traditional dimedone reagent. The norbornene probe also revealed a superior chemoselectivity when compared to a commonly used dimedone probe. Together, these results advance the study of cysteine oxidation in biological systems.

Made available in DSpace on 2019-10-06T15:24:07Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-11-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) National Institute for Health Research Background. Aging is associated with declining mobility, which negatively affects quality of life and incurs substantial economic costs. Techniques to maintain safe mobility in older adults are therefore essential. Rhythmic auditory cueing (RAC) can improve walking patterns in older adults. However, the neural correlates associated with RAC, how they are influenced by repeated exposure and their relationships with gait response, cognitive function, and depressive symptoms are unclear. Objectives. This study aimed to investigate the effects of RAC during walking on cortical activation and the relationship between RAC-related cortical changes and cognitive function, depressive symptoms, and gait response. Methods. Seventeen young adults and eighteen older adults walked on a motorized treadmill for 5 minutes (5 trials with alternating 30-second blocks of usual walking and RAC walking). Changes in oxygenated hemoglobin (HbO 2 ) in the frontal cortex were recorded using functional near-infrared spectroscopy. Cognitive domains were assessed through validated tests. A triaxial accelerometer measured gait parameters. Results. Gait variability decreased and prefrontal HbO 2 levels increased during cued walking relative to usual walking. Older adults showed greater HbO 2 levels in multiple motor regions during cued walking although the response reduced with repeated exposure. In older adults, lower depression scores, higher cognitive functioning, and reduced gait variability were linked with increased HbO 2 levels during RAC walking. Conclusion. These findings suggest that walking improves with RAC in older adults and is achieved through increased activity in multiple cortical areas. The cortical response decline with repeated exposure indicates older adults’ ability to adapt to a new task. Institute of Neuroscience Newcastle University Institute of Ageing Sao Paulo State University (UNESP) Institute of Biosciences, Campus Rio Claro The Newcastle upon Tyne NHS Foundation Trust Sao Paulo State University (UNESP) Institute of Biosciences, Campus Rio Claro FAPESP: 2016/22750-0

Eye movements are impaired by Parkinson's disease (PD) although limited research has explored if PD affects the relevance of visual fixations when walking. Visual fixations may provide crucial contextual information for safe navigation and important insights into fall risk. This study aimed to: investigate visual fixations made while walking under a range of conditions in PD; identify their task relevance; and explore their relationship with clinical features. Thirty-eight people with mild-moderate PD and forty age-matched control participants completed a straight walk with (i) no additional stimuli and (ii) with additional stimuli (visual cues or a high contrast obstacle), whilst wearing a mobile eye-tracker. Fixations were extracted and classified by location and relevance. PD participants made proportionally fewer task-relevant fixations (floor, walls and additional stimuli ahead), caused by significantly more task-irrelevant fixations (floor, walls and ceiling away from waking path) during normal walking (p = 0.014). These group differences were not apparent with visual cues (p = 0.359). During obstacle crossing trials, PD made significantly more task-relevant fixations than controls (p = 0.007). Reduced bilateral visual acuity was associated with fewer fixations in PD. Our findings suggest that people with PD visually explore complex environments less efficiently likely owing to underlying PD pathology. Visual exploration improved with the addition of salient stimuli (for example visual cues or an obstacle) and thus developing and optimising visual interventions could prove critical to improving locomotor safety and reducing falls risk in home environments.

Reduced foot clearance when walking may increase the risk of trips and falls in people with Parkinson’s disease (PD). Changes in foot clearance in people with PD are likely to be associated with temporal-spatial characteristics of gait such as walking slowly which evokes alterations in the temporal-spatial control of stepping patterns. Enhancing our understanding of the temporal-spatial determinants of foot clearance may inform the design of falls prevention therapies. Thirty-six people with PD and 38 age-matched controls completed four intermittent walks under two conditions: self-selected and fast gait velocity. Temporal-spatial characteristics of gait and foot (heel and toe) clearance outcomes were obtained using an instrumented walkway and 3D motion capture, respectively. A general linear model was used to quantify the effect of PD and gait velocity on gait and foot clearance. Regression evaluated the temporal and spatial gait predictors of minimum toe clearance (MTC). PD walked slower regardless of condition (p = .016) and tended to increase their step length to achieve a faster gait velocity. Step length and the walk ratio consistently explained the greatest proportion of variance in MTC (>28% and >33%, respectively) regardless of group or walking condition (p

Background: Virtual reality (VR) technology is a relatively new rehabilitation tool that can deliver a combination of cognitive and motor training for fall prevention. The attitudes of older people to such training are currently unclear. Objective: This study aimed to investigate: (1) the attitudes of fall-prone older people towards fall prevention exercise with and without VR; (2) attitudinal changes after intervention with and without VR; and (3) user satisfaction following fall prevention exercise with and without VR. Methods: A total of 281 fall-prone older people were randomly assigned to an experimental group receiving treadmill training augmented by VR (TT+VR, n = 144) or a control group receiving treadmill training alone (TT, n = 137). Two questionnaires were used to measure (1) attitudes towards fall prevention exercise with and without VR (AQ); and (2) user satisfaction (USQ). AQ was evaluated at baseline and after intervention. USQ was measured after intervention only. Results: The AQ revealed that most participants had positive attitudes towards fall prevention exercise at baseline (82.2%) and after intervention (80.6%; p = 0.144). In contrast, only 53.6% were enthusiastic about fall prevention exercise with VR at baseline. These attitudes positively changed after intervention (83.1%; p < 0.001), and 99.2% indicated that they enjoyed TT+VR. Correlation analyses showed that postintervention attitudes were strongly related to user satisfaction (USQ: r = 0.503; p < 0.001). Conclusions: Older people's attitudes towards fall prevention exercise with VR were positively influenced by their experience. From the perspective of the user, VR is an attractive training mode, and thus improving service provision for older people is important.

Tripping is a common cause of falls in older adults and people with Parkinson׳s disease (PD). Foot clearance during gait may be impaired when distracted by a dual task and thus inform trip risk. This study aimed to evaluate whether foot clearance is impaired in PD and is adversely affected by a dual task. 81 older adults and 76 PD walked at a comfortable pace for two minutes under single and dual task conditions (digit recall). Temporal spatial gait was measured using an instrumented walkway. Heel and toe trajectories were obtained bilaterally using 3-dimensional motion capture. Foot clearance was reduced in PD (p

Mobile eye-tracking is important for understanding the role of vision during real-world tasks in older adults (OA) and people with Parkinson's disease (PD). However, accuracy and reliability of such devices have not been established in these populations. We used a novel protocol to quantify accuracy and reliability of a mobile eye-tracker in OA and PD. A mobile eye-tracker (Dikablis) measured the saccade amplitudes of 20 OA and 14 PD on two occasions. Participants made saccades between targets placed 5°, 10° and 15° apart. Impact of visual correction (glasses) on saccadic amplitude measurement was also investigated in 10 OA. Saccade amplitude accuracy (median bias) was −1.21° but a wide range of bias (−7.73° to 5.81°) was seen in OA and PD, with large vertical saccades (15°) being least accurate. Reliability assessment showed a median difference between sessions of

Stair descent is an inherently complex form of locomotion posing a high falls risk for older adults, specifically when negotiating the transitional gait cycles linking level gait and descent. The aim of this study was to enhance our understanding of the biomechanical demands by comparing the demands of these transitions. Lower limb kinematics and kinetics of the 2-step transitions linking level and descent gait at the top (level-to-descent) and the bottom (descent-to-level) of the staircase were quantified in 36 older women with no falls history. Despite undergoing the same vertical displacement (2-steps), the following significant (p

Introduction Parkinson's disease (PD) is a common, clinically heterogeneous, neurodegenerative disease, which is characterised by motor symptoms such as gait deficit. Motor and non-motor (e.g. visual and cognitive) dysfunctions are common in PD and lead to increased falls risk. Fear of falling (FoF) has been associated with increased falls prevalence in PD, and likely relates to motor and non-motor dysfunction. Understanding the features that underpin FoF will improve therapeutic management. The objective of this study was to quantify and interpret important contributors to FoF in PD. Methods 70 participants with mild-to-moderate PD (Hoehn and Yahr Stage I:17, II:43, III:10) recruited from Movement Disorder Clinics in Newcastle upon Tyne were assessed for FoF using the Falls Efficacy Scale International (FES-I). Falls history was gained retrospectively over the 12-months prior to assessment. A range of demographic, clinical, visual, cognitive and gait outcomes were also obtained. The associations between FES-I and secondary outcomes were assessed using Spearman correlations, with variables demonstrating significance entered into multivariate regression models and Receiver Operating Characteristic (ROC) curves to determine significant predictors of FoF. Results Motor symptoms of reduced gait speed (beta = -0.239, p = 0.007), greater UPDRS II score (self-evaluation of motor experiences of Activities of Daily Living (ADL)) (beta = 0.611, p < 0.001), and a history of previous falls (beta = 0.278, p = 0.016) predicted FoF in PD. Notably, non-motor visual and cognitive deficits did not directly predict FoF in PD (F = 0.692, p = 0.678). Conclusions Impaired gait speed, impaired ADL function and a history of falls are associated with FoF in people with mild-to-moderate PD. The complex causal interaction between FoF, motor symptoms and falls remains unclear. Speculatively, interventions that target motor symptoms may help reduce FoF.

Objectives To quantify the variance attributable to age and estimate annual decline in physical function and self-reported health using a battery of outcome measures in healthy older females. To determine whether self-reported functional losses are similar to those measured objectively and which best represent overall physical capacity. Design Experimental study, cross-sectional analysis. Setting Human Performance Laboratory, University setting. Participants Thirty-nine community-dwelling women (mean [SD] age=71.5 [7.3] years, range 60 to 83 years) completed a battery of objective measures of function and a self-reported health status survey. Main outcome measures Objective measures : gait speed; TUG test; sit-to-stand; concentric knee flexor and extensor moments; self-reported : the SF-36. Results Using a cross-sectional approach, annual declines were estimated for: TUG time (2.1%); gait speed (1.2%); knee extensor (2.2%) and flexor moments (3.0%); and self-reported Physical Functioning (0.9 to 1.2%) ( p ≤0.001). Linear regression indicated that age explained moderate variance in the objective ( R 2 =21 to 34%) and self-reported ( R 2 =14 to 28%) outcomes. TUG time and gait speed was significantly correlated with all objective outcomes except sit-to-stand ( r =0.46 to 0.83) and most of the self-reported ( r =0.40 to 0.63) outcomes ( p Conclusions Age-related functional deterioration was estimated precisely across both objective and self-reported outcomes. Greater strength losses for the knee flexors compared to the extensors indicate an unequal strength loss of antagonistic muscle pairs which has implications for the safe completion of many functional tasks including obstacle negotiation, stair locomotion, postural transitions, and ultimately knee joint stability. Furthermore, walking speed and TUG time correlated most strongly with many of the outcomes highlighting their importance as global indicators of physical capacity.

Background Visual sampling techniques are used to investigate the complex role of vision during real-world activities in Parkinson's disease. Earlier research is limited to static simple tasks or measurement of eye movements alone, but more recent investigations involve more real-world activities. The approach to the objective measurement of eye movements varies with respect to instrumentation, testing protocols, and mediating factors that may influence visual sampling. Objectives The aim of this review was to examine previous work measuring visual sampling during real-world activities in Parkinson's disease to inform the development of robust protocols. Within this review a real-world activity was considered to be a goal-orientated motor task involving more than one body segment such as reaching or walking. Methods Medline, Embase, PsychInfo, Scopus, Web of Knowledge, PubMed and the Cochrane library databases were searched. Two independent reviewers and an adjudicator screened articles that described quantitative visual sampling in people with Parkinson's disease and healthy controls. Results Twenty full-text articles were screened and 15 met inclusion/exclusion criteria. A wide range of instruments and outcome measures were reported which were generally used in a task-dependent manner. Instrument reliability and validity was insufficiently reported in all studies. Few studies considered mediators of visual sampling such as visual or cognitive deficits. Conclusions Future research is required to accurately characterise visual impairments in Parkinson's disease and during real-world activities. Composite use of instruments may be required to achieve reliability and validity of visual sampling outcomes which need to be standardised. Recommendations also include assessment of cognition and basic visual function.

article i nfo Background: Stair ascent mechanics change with age, but little is known about the differing functional demands of transitioning and continuous ascent. Work investigating the risky transition from gait to ascent is sparse, and the strategies that older adults adopt to achieve these demanding tasks have not been investigated. Methods: This study compared the biomechanics of a 2-step transitional (floor-to-step2) and continuous ascent cycle (step1-to-step3) and investigated the role of limb preference in relation to dynamometer-derived knee strengthduring thistransition.Abiomechanical analysisof36 women(60-83years)ascendinga 3-stepstaircase was conducted. Findings: The 2-step transitioning cycle was completed quicker, with a larger range of motion, increased forces, larger knee flexor and dorsiflexor moments and ankle powers (P≤0.05), but reduced hip and knee flexion, smaller hip extensor moments and hip and knee powers compared to continuous ascent. During the transition, 44% of the participants demonstrated a consistent limb preference. In these cases large between-limb extensor strength differences existed (13.8%) and 71% of these participants utilised the stronger limb to execute the 2-step transitional cycle. Interpretation: The preferential stronger-limb 2-step transitioning strategy conflicts with previous recommendations of a stronger lead limb for frail/asymmetric populations. Our findings suggest that most healthy older women with large between-limb differences utilise the stronger limb to achieve the considerable propulsion required to redirect momentum during the 2-step transition. The biomechanical demands of ascent, relative to limb strength, can inform exercise programmes by targeting specific muscle groups to help older adults maintain/ improve general functioning.

• To identify the signal filter (transfer function) introduced by each step – (i) A 3 kg medicine ball was released from a 1-metre height and allowed to bounce once. Five trials were completed per condition. (ii) Spectral analysis of Fz was performed by Fast Fourier Transformation between 0-250 Hz in 2048 bins at a resolution of 0.122 Hz using Matlab (Mathworks, Natick, MA). (iii) Mean power spectra were produced. Transfer functions for conditions A-C with respect to the control condition were calculated using Fz and were analysed between 0-18 Hz.

L. Alcock1,2,∗, T.D. O’Brien3,4, N. Vanicek2,5 1 Institute for Ageing and Health, Newcastle University, UK 2 Department of Sport, Health and Exercise Science, University of Hull, UK 3 School of Sport and Exercise Sciences, Liverpool John Moores University, UK 4 School of Sport, Health and Exercise Sciences, Bangor University, UK 5 Discipline of Exercise and Sport Science, The University of Sydney, Australia

We investigated the biological systems involved in maintaining equilibrium during unstable and perturbed conditions in 39 healthy older women and estimated the annual difference in performance across the older age spectrum using regression. The largest annual difference in equilibrium occurred when the somatosensory system received inaccurate feedback and visual input was removed. With age, weight distribution became asymmetric at the onset of backwards perturbations, possibly in preparation for executing a stepping strategy. When one sensory system was challenged, postural responses were stable suggesting other systems compensated. When multiple sensory systems were challenged, significant differences in postural control emerged with age.

This study aimed to measure real world walking speed (RWS) in Parkinson's disease patients, then investigate its relationship to motor symptom severity as measured by the MDS-UPDRS III., {"references":["Kirk, Cameron et al. (2020). What does real-world walking speed tell us about Parkinson's disease?"]}