Age-related differences during a gaze reorientation task while standing or walking on a treadmill

Gait smoothness during high-demand motor walking tasks in older adults with mild cognitive impairment

Early signs of Mild Cognitive Impairment (MCI)-related gait deficits may be detected through the performance of complex walking tasks that require high gait control. Gait smoothness is a robust metric of overall body stability during walking. This study aimed to explore gait smoothness during complex walking tasks in older adults with and without MCI. Participants were 18 older adults with MCI (mean age = 67.89 ± 4.64 years) and 18 cognitively intact controls (mean age = 67.72 ± 4.63 years). Gait assessment was conducted under four complex walking tasks: walking a narrow path, walking around an obstacle, horizontal head turns while walking, and vertical head turns while walking. The index of harmonicity (IH), representing gait smoothness associated with overall body stability, was measured in anteroposterior, mediolateral, and vertical directions. A multivariate analysis was employed to compare the differences in IH between groups for each complex walking task. The MCI group demonstrated a reduction of IH in the mediolateral direction during the horizontal head turns than the control group (MCI group = 0.64 ± 0.16, Control group = 0.74 ± 0.12, p = 0.04). No significant differences between groups were found for the IH in other directions or walking conditions. These preliminary findings indicate that older adults with MCI have a decline in step regularity in the mediolateral direction during walking with horizontal head turns. Assessment of the smoothness of walking during head turns may be a useful approach to identifying subtle gait alterations in older adults with MCI, which may facilitate timely gait intervention.

Keeping balance during head-free smooth pursuit: The role of aging

Standing balance is often more unstable when visually pursuing a moving target than when fixating on a stationary one. These effects are common in both young and older adults when the head is restrained during visual task performance. The present study focused on the role of head motion on standing balance during smooth pursuit as a function of age. Three predictions were tested: a) standing balance is compromised to a greater extent in older than young adults by gaze target pursuit compared to fixation, b) older adults pursue a moving target with greater and more variable head rotation than young adults, and c) greater and more variable head rotation during the smooth pursuit task is associated with greater Center of Pressure (CoP) sway. Twenty-two (22) older (age: 71.7 ± 8.1, 12 M / 10 F) and twenty-three (23) young adults (age: 23.6 ± 2.5, 12 M / 11 F) stood on a force plate while either fixating a stationary or smoothly pursuing a horizontally moving target (31.9° peak-to-peak visual angle). CoP (Bertec Balance Plate), head kinematics (Vicon Motion Analysis) and head-unconstrained gaze (Pupil Labs Invisible) were synchronously recorded. The root means square (RMS) of CoP velocity increased during smooth pursuit compared to fixation regardless of age (p < .05), while the interquartile CoP range increased only in older and not in young participants (p < .05). We also calculated the head rotation range (peak to peak cycle amplitude) of motion and variability (SD of range of motion) across the cycles of the smooth pursuit task. Older adults pursued the moving target employing more variable (p = .022) head yaw rotation than young participants although the mean range of head rotation was similar between groups (p =. 077). The amplitude and variability of head yaw rotation did not correlate with CoP sway measures. Results suggest that head-free pursuing of a moving target decreased balance to a greater extent in old than young individuals when compared to fixation. Nevertheless, postural sway during head-free smooth pursuit was not associated with the extent or variability of head rotation.

Impact of dual tasking on gaze behaviour and locomotor strategies adopted while circumventing virtual pedestrians during a collision avoidance task

We investigated gaze behaviour and collision avoidance strategies in 16 healthy young individuals walking towards a goal while exposed to virtual pedestrians (VRPs) approaching from different directions (left, middle, right). This locomotor task and an auditory-based cognitive task were performed under single and dual-task conditions. Longer gaze fixation durations were observed on the approaching vs. other VRPs, with longer fixations devoted to the upper trunk and head compared to other body segments. Compared to other pedestrian approaches, the middle pedestrian received longer fixations and elicited faster walking speeds, larger onset distances of trajectory devitation and smaller obstacle clearances. Gaze and locomotor behaviours were similar between single and dual-task conditions but dual-task costs were observed for the cognitive task. The longer gaze fixations on approaching vs. other pedestrians suggest that enhanced visual attention is devoted to pedestrians posing a greater risk of collision. Likewise, longer gaze fixations for the middle pedestrians may be due to the greater collision risk entailed by this condition, and/or to the fact that this pedestrian was positioned in front of the end goal. Longer fixations on approaching VRPs' trunk and head may serve the purpose of anticipating their walking trajectory. Finally, the dual-task effects that were limited to the cognitive task suggest that healthy young adults prioritize the locomotor task and associated acquisition of visual information. The healthy patterns of visuomotor behaviour characterized in this study will serve as a basis for comparison to further understand defective collision avoidance strategies in patient populations.

A comparison of gait stability between younger and older adults while head turning

Head turning while walking may challenge stability by altering visual and vestibular information. Whether there are age-related changes that affect gait stability while head turning during walking remains unknown. The aim of the current study was to compare gait stability between younger and older adults immediately following a head turn while walking. Ten younger [mean (SD)] [23.4 (3.3) years] and ten older [68.8 (6.0) years] healthy adults walked on a treadmill at their preferred gait velocity and performed head turns by responding to a visual cue. The margin of stability (MoS) in the mediolateral (MoS_ML), anterior (MoS_A) and posterior (MoS_P) directions, foot placement (mean step length and width) and rotation of the head, trunk and pelvis were calculated for the four steps immediately following a cue to head turn and compared to walking only. Older adults increased their MoS_ML and younger adults increased their MoS_P immediately following a head turn. However, older adults had a significantly greater MoS_P than younger adults during this time. Older adults also had greater pelvic rotation velocity and a trend towards smaller head-on-trunk rotation compared to younger adults. Age does not compromise the stability of healthy older compared to younger adults immediately following or when completing a head turn. However, older adults may use a different motor strategy to perform a head turn to limit isolated movement of the head and the effects of a changing sensory frame of reference.

Aging affects postural tracking of complex visual motion cues

Postural tracking of visual motion cues improves perception-action coupling in aging, yet the nature of the visual cues to be tracked is critical for the efficacy of such a paradigm. We investigated how well healthy older (72.45 ± 4.72 years) and young (22.98 ± 2.9 years) adults can follow with their gaze and posture horizontally moving visual target cues of different degree of complexity. Participants tracked continuously for 120 s the motion of a visual target (dot) that oscillated in three different patterns: a simple periodic (simulated by a sine), a more complex (simulated by the Lorenz attractor that is deterministic displaying mathematical chaos) and an ultra-complex random (simulated by surrogating the Lorenz attractor) pattern. The degree of coupling between performance (posture and gaze) and the target motion was quantified in the spectral coherence, gain, phase and cross-approximate entropy (cross-ApEn) between signals. Sway-target coherence decreased as a function of target complexity and was lower for the older compared to the young participants when tracking the chaotic target. On the other hand, gaze-target coherence was not affected by either target complexity or age. Yet, a lower cross-ApEn value when tracking the chaotic stimulus motion revealed a more synchronous gaze-target relationship for both age groups. Results suggest limitations in online visuo-motor processing of complex motion cues and a less efficient exploitation of the body sway dynamics with age. Complex visual motion cues may provide a suitable training stimulus to improve visuo-motor integration and restore sway variability in older adults.

Association between vestibulo-ocular reflex suppression, balance, gait, and fall risk in ageing and neurodegenerative disease: protocol of a one-year prospective follow-up study

Background

Falls frequency increases with age and particularly in neurogeriatric cohorts. The interplay between eye movements and locomotion may contribute substantially to the occurrence of falls, but is hardly investigated. This paper provides an overview of current approaches to simultaneously measure eye and body movements, particularly for analyzing the association of vestibulo-ocular reflex (VOR) suppression, postural deficits and falls in neurogeriatric risk cohorts. Moreover, VOR suppression is measured during head-fixed target presentation and during gaze shifting while postural control is challenged. Using these approaches, we aim at identifying quantitative parameters of eye-head-coordination during postural balance and gait, as indicators of fall risk.

Methods/Design

Patients with Progressive Supranuclear Palsy (PSP) or Parkinson’s disease (PD), age- and sex-matched healthy older adults, and a cohort of young healthy adults will be recruited. Baseline assessment will include a detailed clinical assessment, covering medical history, neurological examination, disease specific clinical rating scales, falls-related self-efficacy, activities of daily living, neuro-psychological screening, assessment of mobility function and a questionnaire for retrospective falls. Moreover, participants will simultaneously perform eye and head movements (fixating a head-fixed target vs. shifting gaze to light emitting diodes in order to quantify vestibulo-ocular reflex suppression ability) under different conditions (sitting, standing, or walking). An eye/head tracker synchronized with a 3-D motion analysis system will be used to quantify parameters related to eye-head-coordination, postural balance, and gait. Established outcome parameters related to VOR suppression ability (e.g., gain, saccadic reaction time, frequency of saccades) and motor related fall risk (e.g., step-time variability, postural sway) will be calculated. Falls will be assessed prospectively over 12 months via protocols and monthly telephone interviews.

Discussion

This study protocol describes an experimental setup allowing the analysis of simultaneously assessed eye, head and body movements. Results will improve our understanding of the influence of the interplay between eye, head and body movements on falls in geriatric high-risk cohorts.

Electronic supplementary material

The online version of this article (doi:10.1186/s12883-015-0447-5) contains supplementary material, which is available to authorized users.

Visuo-locomotor coordination for direction changes in a manual wheelchair as compared to biped locomotion in healthy subjects

The visual system during walking provides travel path and environmental information. Although the manual wheelchair (MWC) is also a frequent mode of locomotion, its underlying visuo-locomotor control is not well understood. This study begins to understand the visuo-locomotor coordination for MWC navigation in relation to biped gait during direction changes in healthy subjects. Eight healthy male subjects (26.9±6.4 years) were asked to walk as well as to propel a MWC straight ahead and while changing direction by 45° to the right guided by a vertical pole. Body and MWC movement (speed, minimal clearance, point of deviation, temporal body coordination, relative timing of body rotations) and gaze behavior were analysed. There was a main speed effect for direction and a direction by mode interaction with slower speeds for MWC direction change. Point of deviation was later for MWC direction change and always involved a counter movement (seen for vehicular control) with greater minimal distance from the vertical pole as compared to biped gait. In straight ahead locomotion, subjects predominantly fixed their gaze on the end target for both locomotor modes while there was a clear trend for subjects to fixate on the vertical pole more for MWC direction change. When changing direction, head movement always preceded gaze changes, which was followed by trunk movement for both modes. Yet while subjects turned the trunk at the same time during approach regardless of locomotor mode, head movement was earlier for MWC locomotion. These results suggest that MWC navigation combines both biped locomotor and vehicular-based movement control. Head movement to anticipate path deviations and lead steering for locomotion appears to be stereotypic across locomotor modes, while specific gaze behavior predominantly depends on the environmental demands.

The effect of stationary walking on the quality of life of the elderly women: a randomized controlled trial

INTRODUCTION

Aging has a profound effect on all the body organs and quality of life. One of the appropriate interventions is exercises such as walking. Nevertheless, the risk of falling and its complications are lower in stationary walking than walking on ground. Due to the higher life expectancy in women than men, the increasing number of elderly, and the low quality of life of women compared to men, this study aimed to assess the impact of stationary walking on the quality of life of the elderly women.

METHODS

In this clinical trial, 66 household elderly women covered by health centers of Maragheh were randomly selected and divided into experimental and control groups. Six weeks exercise intervention was conducted. The participants completed the quality of life questionnaire of the elderly, before and after the intervention. SPSS software was used to analyze the data.

RESULTS

Mean scores of quality of life, in various aspects of the experimental group, before and after intervention, showed significant difference; there was no statistically significant difference in the control group. In addition, there was a significant difference in the mean and standard deviation of different aspects of quality of life in pre- and post-test of experiment and control groups.

CONCLUSION

Using regular and constant exercise program such as stationary walking can increase the quality of life of the elderly women. It can improve healthy aging and having a healthy life at this age, too. Therefore, it is recommended to have stationary walking program in daily lives of the elderly.

Dynamic control of posture across locomotor tasks

Successful locomotion depends on postural control to establish and maintain appropriate postural orientation of body segments relative to one another and to the environment and to ensure dynamic stability of the moving body. This article provides a framework for considering dynamic postural control, highlighting the importance of coordination, consistency, and challenges to postural control posed by various locomotor tasks, such as turning and backward walking. The impacts of aging and various movement disorders on postural control are discussed broadly in an effort to provide a general overview of the field and recommendations for assessment of dynamic postural control across different populations in both clinical and research settings. Suggestions for future research on dynamic postural control during locomotion also are provided and include discussion of opportunities afforded by new and developing technologies, the need for long-term monitoring of locomotor performance in everyday activities, gaps in our knowledge of how targeted intervention approaches modify dynamic postural control, and the relative paucity of literature regarding dynamic postural control in movement disorder populations other than Parkinson's disease.

Head-eye movement control tests in patients with chronic neck pain; inter-observer reliability and discriminative validity

Background

Head-eye movement control deficit is an identified problem in patients with chronic neck pain, particularly in cases of whiplash associated disorders (WAD). To date, there is no evidence concerning the reliability and validity of visually assessed active head-eye movement control tests. Therefore, the objectives of the present cross-sectional study were, a) to develop a test battery; and b) to investigate inter-observer reliability and discriminative validity in patients with chronic neck pain compared to healthy controls.

Methods

The study was conducted at two physiotherapy clinics in Switzerland. Ethics Committee approval was obtained. Ten active head-eye coordination tests, on 23 patients with chronic neck pain and associated symptoms and 19 healthy controls, were videotaped. The tests included eye movements in the neutral head position and 45° relative neck rotation, gaze stability and sequential head-eye movements. All tests were performed in the sitting and standing positions. Two blinded physiotherapists independently rated the randomized videos. Performance was rated as "negative", "moderately positive" or "clearly positive". Weighted kappa (wK) and 95% confidence intervals (CI) were calculated to investigate inter-observer reliability. Good reliability was defined as wK >0.5 with a lower boundary of 95% CI >0.2. Odds ratios (to define cut-off points) and the distribution of the classificator, numbers of positive tests, were calculated.

Results

Three out of ten tests showed "excellent" (wK 0.82 to 0.86), five out of ten tests showed "substantial" (wK 0.69 to 0.79) and two out of ten tests showed "moderate" (wK 0.54 to 0.59) reliability. Results were comparable in the sitting and standing positions. On average, three out of five tests were rated positive in patients and one out of five tests was rated positive in healthy controls. An odds ratio of 13.3 to 18.6 was obtained using ≥2/5 tests as a cut-off point.

Conclusion

Visual assessment by physiotherapists of head-eye movement control tests is reliable. The test battery is able to discriminate between patients with chronic neck pain and healthy controls. There were no differences in performance between the sitting and standing positions. The test battery can therefore be reduced to five tests. Further research is needed to identify the test-retest stability and responsiveness.

Action strategies of older adults walking through apertures

The current study aimed to determine if the action strategies (i.e. Critical Point) of older adults when walking through apertures are different from those previously reported in young adults. Older adults (N=9) walked at a self selected pace along a 6-m path passing through a static door aperture (45-80 cm in 5 cm increments). Results showed that older adults rotate their shoulders more at apertures less than 1.6 times their shoulder width, indicating a more cautious approach. However, rotation magnitudes were highly variable at all aperture widths, but was not related to differences in stability. Therefore it appears that older adults use a body-scaled locomotor control strategy when passing through apertures.

Old age affects gaze and postural coordination

Visual tracking of the surrounding environment is an important daily task, often executed simultaneously with the regulation of upright balance. Visual and postural coordination may be affected by aging which is associated with a decline in sensory and motor functions. The aim of the present study was to assess the effects of aging on the control of saccadic and smooth pursuit eye movements when standing on a moving surface. Nineteen young and 12 elderly subjects tracked a visual target presented as unpredictable smooth pursuit or saccadic displacements. Subjects were instructed to maintain gaze on target during quiet stance with or without yaw surface rotations. Elderly subjects followed both saccadic and pursuit targets with less accuracy than young subjects. Moreover, elderly subjects responded with longer time lags during saccadic target shifts and executed more catch-up saccades during smooth pursuits than younger subjects. Standing on a moving surface induced larger target-gaze errors. Catch-up saccades during pursuit occurred more frequently during surface perturbations. Our results suggest that visual tracking abilities decline with age and that postural challenge affects accuracy but not timing of gaze responses. Such declines observed with aging may result from multiple but minor sensory and motor deficits.

Relação entre cognição (função executiva e percepção espacial) e equilíbrio de idosos de baixa escolaridade

O objetivo deste estudo foi investigar se défices na percepção visuoespacial e nas funções executivas apresentariam relação com o equilíbrio em idosos de baixa escolaridade. Participaram deste estudo 38 idosos (com média de idade 69,1±6,8 anos), com um a seis anos de escolaridade formal. Os testes aplicados foram: o teste de seqüência alfa-numérica - partes A, que avalia escaneamento visual e seqüenciamento (TSA-A), B, que avalia flexibilidade mental e memória operacional (TSA-B), considerando-se ainda o delta, que avalia função executiva (TSA-D); teste de cancelamento de estrelas (TCE), que avalia percepção espacial; a escala de equilíbrio de Berg (EEB) e a escala de eficácia de quedas (falls efficacy scale - international, FES-I), que avaliam equilíbrio e risco de quedas. As correlações foram verificadas pelo teste de Spearman, com p<0,05. Foram encontradas fortes correlações significativas entre as escalas de equilíbrio (EEB e FES-I) e o TSA-B (r=-0,61 e r=0,60, respectivamente); e correlações moderadas entre a EEB e o TSA-A (r=-0,51) e entre a FES-I e o TSA-D (r=0,55). Também houve correlações significativas entre as escalas de equilíbrio (EEB e FES-I) e o TCE (r=0,45 e r=-0,45, respectivamente). A função executiva e a percepção espacial apresentaram relação com o equilíbrio e com o medo de cair em idosos de baixa escolaridade. Quanto melhores forem a função executiva e a percepção espacial, melhor tenderá a ser o equilíbrio e menor tenderá a ser o medo de cair.