Advances in mobility aid use reporting: situational context and objective measurement improve understanding of daily aid use in older adults.

BACKGROUND: Understanding mobility aid use has implications for falls risk reduction and aid prescription. However, aid use in daily life is understudied and more complex than revealed by commonly used yes/no self-reporting. AIMS: To advance approaches for evaluating mobility aid use among older adults using a situational (context-driven) questionnaire and wearable sensors. METHODS: Data from two cross-sectional observational studies of older adults were used: (1) 190 participants (86 ± 5 years) completed tests of standing, sit-to-stand, walking, grip strength, and self-reported fear of falling and (2) 20 participants (90 ± 4 years) wore two body-worn and one aid-mounted sensors continuously for seven days to objectively quantify aid use during walking. Situational and traditional binary reporting stratified participants into aid dependency levels (0-4) and aid-user groups, respectively. Physical performance and fear of falling were compared between aid users, and dependency levels and sensor-derived walking behaviors were compared to reported aid use. RESULTS: Physical performance and fear of falling differed between aid-user groups (P < 0.05). Sensor-derived outputs revealed differences in walking behaviors and aid use when categorized by dependency level and walking bout length (P < 0.05). Walking bout frequency (rho(18) = - 0.47, P = 0.038) and aid use time (rho(13) = .72, P = 0.002) were associated with dependency level. DISCUSSION: Comparisons of situational aid dependency revealed heterogeneity between aid users suggesting binary aid use reporting fails to identify individual differences in walking and aid use behaviors. CONCLUSIONS: Enhanced subjective aid use reporting and objective measurements of walking and aid use may improve aid prescription and inform intervention to support safe and effective mobility in older adults.

Detecting accelerometer non-wear periods using change in acceleration combined with rate-of-change in temperature.

BACKGROUND: Accelerometery is commonly used to estimate physical activity, sleep, and sedentary behavior. In free-living conditions, periods of device removal (non-wear) can lead to misclassification of behavior with consequences for research outcomes and clinical decision making. Common methods for non-wear detection are limited by data transformations (e.g., activity counts) or algorithm parameters such as minimum durations or absolute temperature thresholds that risk over- or under-estimating non-wear time. This study aimed to advance non-wear detection methods by integrating a 'rate-of-change' criterion for temperature into a combined temperature-acceleration algorithm. METHODS: Data were from 39 participants with neurodegenerative disease (36% female; age: 45-83 years) who wore a tri-axial accelerometer (GENEActiv) on their wrist 24-h per day for 7-days as part of a multi-sensor protocol. The reference dataset was derived from visual inspection conducted by two expert analysts. Linear regression was used to establish temperature rate-of-change as a criterion for non-wear detection. A classification and regression tree (CART) decision tree classifier determined optimal parameters separately for non-wear start and end detection. Classifiers were trained using data from 15 participants (38.5%). Outputs from the CART analysis were supplemented based on edge cases and published parameters. RESULTS: The dataset included 186 non-wear periods (85.5% < 60 min). Temperature rate-of-change over the first five minutes of non-wear was - 0.40 ± 0.17 °C/minute and 0.36 ± 0.21 °C/minute for the first five minutes following device donning. Performance of the DETACH (DEvice Temperature and Accelerometer CHange) algorithm was improved compared to existing algorithms with recall of 0.942 (95% CI 0.883 to 1.0), precision of 0.942 (95% CI 0.844 to 1.0), F1-Score of 0.942 (95% CI 0.880 to 1.0) and accuracy of 0.996 (0.994-1.000). CONCLUSION: The DETACH algorithm accurately detected non-wear intervals as short as five minutes; improving non-wear classification relative to current interval-based methods. Using temperature rate-of-change combined with acceleration results in a robust algorithm appropriate for use across different temperature ranges and settings. The ability to detect short non-wear periods is particularly relevant to free-living scenarios where brief but frequent removals occur, and for clinical application where misclassification of behavior may have important implications for healthcare decision-making.

Can we use peripheral vision to create a visuospatial map for compensatory reach-to-grasp reactions?

Perturbation-induced reach-to-grasp reactions are dependent on vision to capture environmental features of potential support surfaces. Previous research proposed the use of an intrinsic visuospatial map of the environment to reduce delays in motor responses (e.g., stepping, grasping a handrail). Forming such a map from foveal vision would be challenging during movement as it would require constant foveal scanning. The objective of this study was to determine if compensatory reach-to-grasp reactions could be successfully executed while relying on a visuospatial map acquired using peripheral vision. Subjects were instructed to respond to a perturbation by grasping a handle randomly located at 0°, 20° or 40° in their field of view under three visual conditions: full vision throughout the entire trial (FV), vision available prior to perturbation only (MAP), and vision available post-perturbation only (ONLINE). Electromyography was used to determine reaction time and kinematic data were collected to determine initial reach angle. Overall, participants were successful in arresting whole-body motion across all visual conditions and handle locations. Initial reach angles were target specific when vision was available prior to perturbation onset (FV and MAP). However, the 40° handle location produced a greater initial reach angle in MAP, suggesting some limitations for mapping in the further visual periphery. These findings suggest that peripheral vision contributes to the ability to spatially locate targets by building an a priori visuospatial map, which benefits the control of rapid compensatory reach-to-grasp reactions evoked in the response to unpredictable events of instability.

Standing, Transition, and Walking Ability in Older Adults: The Case for Independently Evaluating Different Domains of Mobility Function.

BACKGROUND: Independent mobility is a complex behavior that relies on the ability to walk, maintain stability, and transition between postures. However, guidelines for assessment that details what elements of mobility to evaluate and how they should be measured remain unclear. METHODS: Performance on tests of standing, sit-to-stand, and walking were evaluated in a cohort of 135 complex, comorbid, and older adults (mean age 87 ± 5.5 years). Correlational analysis was conducted to examine the degree of association for measures within and between mobility domains on a subset of participants (n = 83) able to complete all tasks unaided. Participants were also grouped by the presence of risk markers for frailty (gait speed and grip strength) to determine if the level of overall impairment impacted performance scores and if among those with risk markers, the degree of association was greater. RESULTS: Within-domain relationships for sit-to-stand and walking were modest (rho = 0.01-0.60). Associations either did not exist or relationships were weak for measures reflecting different domains (rho = -0.35 to 0.25, p > 0.05). As expected, gait speed differed between those with and without frailty risk markers (p < 0.001); however, balance and sit-to-stand measures did not (p ≥ 0.05). CONCLUSIONS: This study highlights the need to independently evaluate different mobility domains within an individual as a standard assessment approach. Modest within-domain relationships emphasize the need to account for multiple, unique control challenges within more complex domains. These findings have important implications for standardized mobility assessment and targeted rehabilitation strategies for older adults.

Dual-Task Elderly Gait of Prospective Fallers and Non-Fallers: A Wearable-Sensor Based Analysis.

Wearable sensors could facilitate point of care, clinically feasible assessments of dynamic stability and associated fall risk through an assessment of single-task (ST) and dual-task (DT) walking. This study investigated gait changes between ST and DT walking and between older adult prospective fallers and non-fallers. The results were compared to a study based on retrospective fall occurrence. Seventy-five individuals (75.2 ± 6.6 years; 47 non-fallers, 28 fallers; 6 month prospective fall occurrence) walked 7.62 m under ST and DT conditions while wearing pressure-sensing insoles and accelerometers at the head, pelvis, and on both shanks. DT-induced gait changes included changes in temporal measures, centre of pressure (CoP) path stance deviations and coefficient of variation, acceleration descriptive statistics, Fast Fourier Transform (FFT) first quartile, ratio of even to odd harmonics, and maximum Lyapunov exponent. Compared to non-fallers, prospective fallers had significantly lower DT anterior⁻posterior CoP path stance coefficient of variation, DT head anterior⁻posterior FFT first quartile, ST left shank medial⁻lateral FFT first quartile, and ST right shank superior maximum acceleration. DT-induced gait changes were consistent regardless of faller status or when the fall occurred (retrospective or prospective). Gait differences between fallers and non-fallers were dependent on retrospective or prospective faller identification.

The Ontario Neurodegenerative Disease Research Initiative (ONDRI).

Because individuals develop dementia as a manifestation of neurodegenerative or neurovascular disorder, there is a need to develop reliable approaches to their identification. We are undertaking an observational study (Ontario Neurodegenerative Disease Research Initiative [ONDRI]) that includes genomics, neuroimaging, and assessments of cognition as well as language, speech, gait, retinal imaging, and eye tracking. Disorders studied include Alzheimer's disease, amyotrophic lateral sclerosis, frontotemporal dementia, Parkinson's disease, and vascular cognitive impairment. Data from ONDRI will be collected into the Brain-CODE database to facilitate correlative analysis. ONDRI will provide a repertoire of endophenotyped individuals that will be a unique, publicly available resource.

Gaze shifts during dual-tasking stair descent.

To investigate the role of vision in stair locomotion, young adults descended a seven-step staircase during unrestricted walking (CONTROL), and while performing a concurrent visual reaction time (RT) task displayed on a monitor. The monitor was located at either 3.5 m (HIGH) or 0.5 m (LOW) above ground level at the end of the stairway, which either restricted (HIGH) or facilitated (LOW) the view of the stairs in the lower field of view as participants walked downstairs. Downward gaze shifts (recorded with an eye tracker) and gait speed were significantly reduced in HIGH and LOW compared with CONTROL. Gaze and locomotor behaviour were not different between HIGH and LOW. However, inter-individual variability increased in HIGH, in which participants combined different response characteristics including slower walking, handrail use, downward gaze, and/or increasing RTs. The fastest RTs occurred in the midsteps (non-transition steps). While gait and visual task performance were not statistically different prior to the top and bottom transition steps, gaze behaviour and RT were more variable prior to transition steps in HIGH. This study demonstrated that, in the presence of a visual task, people do not look down as often when walking downstairs and require minimum adjustments provided that the view of the stairs is available in the lower field of view. The middle of the stairs seems to require less from executive function, whereas visual attention appears a requirement to detect the last transition via gaze shifts or peripheral vision.

Reactive Stepping After Stroke: Determinants of Time to Foot Off in the Paretic and Nonparetic Limb.

BACKGROUND AND PURPOSE: Impaired features of reactive stepping, specifically delays in the early time to foot off (TFO) phase, are associated with increased fall rates after stroke. This study aimed to determine differences in, and determinants of, paretic and nonparetic limb TFO, and to determine whether both paretic and nonparetic TFO were associated with perturbation-evoked falls. METHODS: Retrospective chart review of 105 individuals with stroke was performed within an inpatient rehabilitation setting; each had received a standardized assessment of reactive balance control (in response to a perturbation) at time of discharge. RESULTS: There were no significant differences in paretic (351 ms) and nonparetic (365 ms) TFO. The capacity to maximally load the nonparetic limb, the amplitude of the perturbation, and the capacity to load the paretic limb were all negatively associated with paretic step TFO, explaining 23.8% of the variance. The amplitude of the perturbation and the preperturbation load under the nonparetic stepping limb were, respectively, negatively and positively associated with nonparetic step TFO, explaining 22.7% of the variance. The likelihood of a perturbation-evoked fall was associated with mean nonparetic limb TFO but not paretic limb TFO. DISCUSSION AND CONCLUSIONS: Unique stroke-related impairments of dynamic balance control and limb-load asymmetry may differentially influence paretic and nonparetic reactive step TFO, in response to a loss of balance. The amplitude of the perturbation influences reactive step TFO in both limbs. The results of the current study have implications for the future development of standardized clinical assessment methodologies and training strategies to evaluate and remediate reactive stepping and reduce fall risk.Video Abstract available for more insights from the authors (see Supplemental Digital Content 1, http://links.lww.com/JNPT/A133).

Perturbation training to promote safe independent mobility post-stroke: study protocol for a randomized controlled trial.

BACKGROUND: Falls are one of the most common medical complications post-stroke. Physical exercise, particularly exercise that challenges balance, reduces the risk of falls among healthy and frail older adults. However, exercise has not proven effective for preventing falls post-stroke. Falls ultimately occur when an individual fails to recover from a loss of balance. Thus, training to specifically improve reactive balance control could prevent falls. Perturbation training aims to improve reactive balance control by repeatedly exposing participants to postural perturbations. There is emerging evidence that perturbation training reduces fall rates among individuals with neurological conditions, such as Parkinson disease. The primary aim of this work is to determine if perturbation-based balance training can reduce occurrence of falls in daily life among individuals with chronic stroke. Secondary objectives are to determine the effect of perturbation training on balance confidence and activity restriction, and functional balance and mobility. METHODS/DESIGN: Individuals with chronic stroke will be recruited. Participants will be randomly assigned to one of two groups: 1) perturbation training, or 2) 'traditional' balance training. Perturbation training will involve both manual perturbations (e.g., a push or pull from a physiotherapist), and rapid voluntary movements to cause a loss of balance. Training will occur twice per week for 6 weeks. Participants will record falls and activity for 12 months following completion of the training program. Standardized clinical tools will be used to assess functional balance and mobility, and balance confidence before and after training. DISCUSSION: Falls are a significant problem for those with stroke. Despite the large body of work demonstrating effective interventions, such as exercise, for preventing falls in other populations, there is little evidence for interventions that prevent falls post-stroke. The proposed study will investigate a novel and promising intervention: perturbation training. If effective, this training has the potential to not only prevent falls, but to also improve safe independent mobility and engagement in daily activities for those with stroke. TRIAL REGISTRATION: Current Controlled Trials: ISRCTN05434601 .

Patient characteristics that influence enrollment and attendance in aerobic exercise early after stroke.

OBJECTIVE: To identify patient characteristics that influence physiotherapist's decisions on enrollment and attendance in a structured aerobic exercise program early after stroke. DESIGN: Retrospective chart review. SETTING: Rehabilitation hospital. PARTICIPANTS: Consecutive sample of people (N=345) admitted to inpatient stroke rehabilitation over a 2-year period. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Patient demographic characteristics, preexisting medical conditions, and poststroke outcome variables (neurological deficit, physical impairment, balance control, and functional mobility and independence) were compared between individuals enrolled and not enrolled in a structured aerobic exercise program. The rate of attendance was calculated for the enrolled group. RESULTS: One hundred twenty-nine patients (38%) were enrolled in the structured aerobic exercise program. Patients who were older (P=.0093) and had cardiac disease (P=.012), cardioembolic sources (P=.0094), and arthritis (P=.031) were less likely to be enrolled in the structured aerobic exercise program. Poststroke outcome variables were not associated with enrollment. Among those enrolled, the rate of attendance was positively correlated with the FIM cognitive rating (r=.27; P=.0031). CONCLUSIONS: Enrollment in structured aerobic exercise programs during inpatient stroke rehabilitation can be limited by safety concerns related to patients' cardiovascular and musculoskeletal status. Barriers associated with the perception of cardiovascular risk factors should be confronted because they do not preclude participation in cardiac rehabilitation. In addition, poststroke deficits do not limit participation in adapted aerobic exercise early after stroke. It is likely that the characteristics of the structured aerobic exercise program were integral to accommodate the breadth of poststroke deficits encountered in this study. Future research investigating physiotherapist and practice environment factors that influence the decision to prescribe and implement aerobic exercise is warranted.

Localizing evoked cortical activity associated with balance reactions: does the anterior cingulate play a role?

The ability to correct balance disturbances is essential for the maintenance of upright stability. Although information about how the central nervous system controls balance reactions in humans remains limited, recent literature highlights a potentially important role for the cerebral cortex. The objective of this study was to determine the neural source of the well-reported balance-evoked N1 response. It was hypothesized that the N1 is associated with an "error-detection" event in response to the induced perturbation and therefore may be associated with activity within the anterior cingulate cortex (ACC). The localized source of the N1 evoked by perturbations to standing balance was compared, within each participant, to the location of an error-related negativity (ERN) known to occur within the ACC while performing a flanker task. In contrast to the main hypotheses, the results revealed that the location of the N1 was not within the ACC. The mean Talairach coordinates for the ERN were (6.47, -4.41, 41.17) mm, corresponding to the cingulate gyrus [Brodmann area (BA) 24], as expected. However, coordinates for the N1 dipole were (5.74, -11.81, 53.73) mm, corresponding to the medial frontal gyrus (BA 6), specifically the supplementary motor area. This may suggest the N1 is linked to the planning and execution of elements of the evoked balance reactions rather than being associated with error or event detection. Alternatively, it is possible that the N1 is associated with variation in the cortical representation due to task-specific differences in the activation of a distributed network of error-related processing. Subsequent work should focus on disentangling these two possible explanations as they relate to the cortical processing linked to reactive balance control.

Autonomic contributions in postural control: a review of the evidence.

The ability to maintain balance is critical for daily activities such as walking and fall avoidance. The contemporary models of postural control emphasize the central and somatic interactions engaged in maintaining balance; however, there is emerging evidence that the autonomic nervous system (ANS) - the sympathetic division, in particular - routinely participates in postural control. The purpose of this paper is to review the evidence demonstrating the autonomic interactions in postural control. These interactions are presented in two broad categories: those that conceptualize the maintenance of postural equilibrium as a component of bodily homeostasis and those that illustrate how changes in affective states link cognitive perceptions and physiological responses (in this case, balance). The shared commonalities between postural and autonomic pathways are presented, pointing to the areas of overlap and the potential sources of the interaction. Although the specific function of autonomic engagement in postural control remains unknown, the potential roles are explored and highlight the directions for continued study.

Spatial-temporal gait variability poststroke: variations in measurement and implications for measuring change.

OBJECTIVE: To determine the responsiveness to change of spatial-temporal gait parameters among stroke survivors for 3 different variability measures: SD, coefficient of variation (CV), and median absolute deviation (MAD). DESIGN: Retrospective chart review. SETTING: Clinical laboratory in a Canadian hospital. PARTICIPANTS: Stroke survivors (N=74) receiving inpatient rehabilitation. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Spatial-temporal gait variability was calculated for step length, step width, stance time, swing time, and double support time. Responsiveness to change was determined by comparing (1) trials without versus trials with a concurrent cognitive task and (2) admission to discharge from rehabilitation. RESULTS: Variability estimators (SD, CV, and MAD) increased with the addition of a cognitive task and decreased from admission to discharge of rehabilitation. However, these changes were not statistically significant when change in gait velocity was included as a covariate. The effect size values were similar for all variability estimators with a trend toward a greater SD response to temporal parameters. The CV displayed a larger response to change for step length than did the SD and MAD. Although gait variability decreased between admission and discharge, the effect size was larger for the condition without the cognitive task than for the condition with the cognitive task. CONCLUSIONS: Our results show that gait variability estimators demonstrate a similar responsiveness to a concurrent cognitive task and improved walking ability with recovery from stroke. Future work may focus on evaluating the clinical utility of these measures in relation to informing therapy and response to gait-specific training protocols.

Does participation in standardized aerobic fitness training during inpatient stroke rehabilitation promote engagement in aerobic exercise after discharge? A cohort study.

OBJECTIVE: To determine whether attending an aerobic fitness program during inpatient stroke rehabilitation is associated with increased participation in physical activity after discharge. DESIGN: This was a prospective cohort study. Patients who received inpatient stroke rehabilitation and were discharged into the community (n = 61; mean age, 65 years) were recruited. Thirty-five participants attended a standardized aerobic fitness program during inpatient rehabilitation, whereas 26 did not. The Physical Activity Scale for Individuals with Physical Disabilities (PASIPD) and adherence to the American College of Sports Medicine (ACSM) guidelines were assessed up to 6 months after discharge. RESULTS: Participants in the fitness group had PASIPD scores and adherence to ACSM guidelines similar to those of participants in the nonfitness group up to 6 months after discharge. There was no significant correlation between volume of exercise performed during the inpatient program and amount of physical activity after discharge. CONCLUSION: Participation in an inpatient fitness program did not increase participation in physical activity after discharge in individuals with stroke. A new model of care that encourages patients to pursue physical activity after discharge and reduces the potential barriers to participation should be developed.

Upper limb contributions to frontal plane balance control in rollator-assisted walking.

While assisting with balance is a primary reason for rollator use, few studies have examined how the upper limbs are used for balance. This study examines upper limb contributions to balance control during rollator-assisted walking. We hypothesized that there would be an increased upper limb contribution, measured by mean vertical loading (Fz) and variation in frontal plane center-of-pressure (COPhigh), when walking balance is challenged/impaired. Experiment 1 compared straight-line and beam-walking in young adults (n = 11). As hypothesized, Fz and COPhighincreased in beam-walking compared to baseline (mean Fz: 13.7 vs. 9.1% body weight (BW), p < 0.001, RMS COPhigh: 1.35 vs. 1.07 cm, p < 0.001). Experiment 2 compared older adults who regularly use rollators (RU, n = 10) to older adult controls (CTL, n = 10). The predicted higher upper limb contribution in the RU group was not supported. However, when individuals were grouped by balance impairment, those with the lowest Berg Balance scores (< 45) demonstrated greater speed-adjusted COPhigh than those with higher scores (p = 0.013). Furthermore, greater COPhigh and Fz were correlated to greater reduction in step width, supporting the role of upper limb contributions to frontal plane balance. This work will guide studies assessing reliance on rollators by providing a basis for measurement of upper limb balance contributions.

Using wireless technology in clinical practice: does feedback of daily walking activity improve walking outcomes of individuals receiving rehabilitation post-stroke? Study protocol for a randomized controlled trial.

BACKGROUND: Regaining independent ambulation is the top priority for individuals recovering from stroke. Thus, physical rehabilitation post-stroke should focus on improving walking function and endurance. However, the amount of walking completed by individuals with stroke attending rehabilitation is far below that required for independent community ambulation. There has been increased interest in accelerometer-based monitoring of walking post-stroke. Walking monitoring could be integrated within the goal-setting process for those with ambulation goals in rehabilitation. The feedback from these devices can be downloaded to a computer to produce reports. The purpose of this study is to determine the effect of accelerometer-based feedback of daily walking activity during rehabilitation on the frequency and duration of walking post-stroke. METHODS: Participants will be randomly assigned to one of two groups: feedback or no feedback. Participants will wear accelerometers daily during in- and out-patient rehabilitation and, for participants in the feedback group, the participants' treating physiotherapist will receive regular reports of walking activity. The primary outcome measures are the amount of daily walking completed, as measured using the accelerometers, and spatio-temporal characteristics of walking (e.g. walking speed). We will also examine goal attainment, satisfaction with progress towards goals, stroke self-efficacy, and community-integration. DISCUSSION: Increased walking activity during rehabilitation is expected to improve walking function and community re-integration following discharge. In addition, a focus on altering walking behaviour within the rehabilitation setting may lead to altered behaviour and increased activity patterns after discharge. TRIAL REGISTRATION: ClinicalTrials.gov NCT01521234.

'Priming' the brain to generate rapid upper-limb reactions.

Evoked autonomic nervous system (ANS) activity may be an important modulator of rapid reactions, generated in the face of urgency and may serve to augment the parallel somatosensory processing to adjust speed of processing. The primary objective of the current study was to temporally pair auditory stimuli with whole body perturbations to determine if conditioning could 'prime' the central nervous system (CNS) to respond faster and with greater ANS reactivity to the auditory stimulus alone. Healthy young participants (n = 19) were seated in a custom chair, which tilted backwards upon the release of an electromagnet and were instructed to reach to grasp a handle located in front of their arm as fast as possible following an auditory cue. Three conditions were completed in the following order: (1) baseline-auditory cue alone (5 trials); (2) paired-auditory cue, followed by a chair tilt 110 ms later (20 trials); and (3) post-pairing-auditory cue alone (5 trials). Participants were not informed of the switch from paired to auditory-only stimuli in the first trial of the post-pairing task condition. Reaction time was measured using electromyography, and autonomic nervous system activity was monitored via the electrodermal response (EDR). The first trial post-pairing had significantly faster reaction time (Δ = 21 ms) and significantly greater EDR amplitude compared to the last trial prior to pairing (baseline). The amplitude of contraction and overall time to handle contact were not significantly different between the first trial post-pairing and the last trial prior to pairing. This study demonstrates that the CNS can be 'primed' to generate rapid reactions and an elevated autonomic response in the absence of whole body instability. This indicates that afferent volume generated following whole body instability is not the only determinant of rapid reactions and emphasizes the importance of physiologic measures of autonomic activity with respect to stimulus-evoked reaction time.

Role of peripheral vision in rapid perturbation-evoked reach-to-grasp reactions.

Onset and execution of compensatory reaches are faster than the most rapid voluntary reaches. With onset latencies near 100 ms, it is proposed that initial control of compensatory reaches cannot rely on visual information obtained after perturbation onset; rather, they rely on a visuospatial map acquired prior to instability. In natural conditions, it is not practical to direct gaze toward every potential support surface in preparation for a perturbation, suggesting that peripheral vision may be uniquely important. This study aimed to determine whether visuospatial mapping achieved using only peripheral visual information could be used to control reach-to-grasp reactions. Participants sat in an unstable chair. Whole body perturbations were used to evoke rapid reach-to-grasp reactions. A handle was positioned at midline or to the right of the participant. Gaze was directed toward the center or right to view the handle in peripheral or central visual fields. Electromyographic and kinematic data were recorded. Peripheral information acquired prior to perturbation was sufficient for successful execution of reach-to-grasp without delay. Differences in reach kinematics, however, did exist between vision conditions (e.g., maximum lateral wrist displacement and magnitude of hand overshoot relative to the handle were greater for peripheral vs. central vision). Handle location led to target-specific differences in initial muscle recruitment revealing information acquired prior to perturbation were used to guide initial limb trajectory. Results reveal the capacity to rely on a visuospatial map constructed from peripheral visual information for compensatory reaching but also highlight limitations leading to more conservative reach trajectories.

Emotional state as a modulator of autonomic and somatic nervous system activity in postural control: a review.

Advances in our understanding of postural control have highlighted the need to examine the influence of higher brain centers in the modulation of this complex function. There is strong evidence of a link between emotional state, autonomic nervous system (ANS) activity and somatic nervous system (somatic NS) activity in postural control. For example, relationships have been demonstrated between postural threat, anxiety, fear of falling, balance confidence, and physiological arousal. Behaviorally, increased arousal has been associated with changes in velocity and amplitude of postural sway during quiet standing. The potential links between ANS and somatic NS, observed in control of posture, are associated with shared neuroanatomical connections within the central nervous system (CNS). The influence of emotional state on postural control likely reflects the important influence the limbic system has on these ANS/somatic NS control networks. This narrative review will highlight several examples of behaviors which routinely require coordination between the ANS and somatic NS, highlighting the importance of the neurofunctional link between these systems. Furthermore, we will extend beyond the more historical focus on threat models and examine how disordered/altered emotional state and ANS processing may influence postural control and assessment. Finally, this paper will discuss studies that have been important in uncovering the modulatory effect of emotional state on postural control including links that may inform our understanding of disordered control, such as that observed in individuals living with Parkinson's disease and discuss methodological tools that have the potential to advance understanding of this complex relationship.

Wrist Accelerometer Estimates of Physical Activity Intensity During Walking in Older Adults and People Living With Complex Health Conditions: Retrospective Observational Data Analysis Study.

BACKGROUND: Accurate measurement of daily physical activity (PA) is important as PA is linked to health outcomes in older adults and people living with complex health conditions. Wrist-worn accelerometers are widely used to estimate PA intensity, including walking, which composes much of daily PA. However, there is concern that wrist-derived PA data in these cohorts is unreliable due to slow gait speed, mobility aid use, disease-related symptoms that impact arm movement, and transient activities of daily living. Despite the potential for error in wrist-derived PA intensity estimates, their use has become ubiquitous in research and clinical application. OBJECTIVE: The goals of this work were to (1) determine the accuracy of wrist-based estimates of PA intensity during known walking periods in older adults and people living with cerebrovascular disease (CVD) or neurodegenerative disease (NDD) and (2) explore factors that influence wrist-derived intensity estimates. METHODS: A total of 35 older adults (n=23 with CVD or NDD) wore an accelerometer on the dominant wrist and ankle for 7 to 10 days of continuous monitoring. Stepping was detected using the ankle accelerometer. Analyses were restricted to gait bouts ≥60 seconds long with a cadence ≥80 steps per minute (LONG walks) to identify periods of purposeful, continuous walking likely to reflect moderate-intensity activity. Wrist accelerometer data were analyzed within LONG walks using 15-second epochs, and published intensity thresholds were applied to classify epochs as sedentary, light, or moderate-to-vigorous physical activity (MVPA). Participants were stratified into quartiles based on the percent of walking epochs classified as sedentary, and the data were examined for differences in behavioral or demographic traits between the top and bottom quartiles. A case series was performed to illustrate factors and behaviors that can affect wrist-derived intensity estimates during walking. RESULTS: Participants averaged 107.7 (SD 55.8) LONG walks with a median cadence of 107.3 (SD 10.8) steps per minute. Across participants, wrist-derived intensity classification was 22.9% (SD 15.8) sedentary, 27.7% (SD 14.6) light, and 49.3% (SD 25.5) MVPA during LONG walks. All participants measured a statistically lower proportion of wrist-derived activity during LONG walks than expected (all P<.001), and 80% (n=28) of participants had at least 20 minutes of LONG walking time misclassified as sedentary based on wrist-derived intensity estimates. Participants in the highest quartile of wrist-derived sedentary classification during LONG walks were significantly older (t16=4.24, P<.001) and had more variable wrist movement (t16=2.13, P=.049) compared to those in the lowest quartile. CONCLUSIONS: The current best practice wrist accelerometer method is prone to misclassifying activity intensity during walking in older adults and people living with complex health conditions. A multidevice approach may be warranted to advance methods for accurately assessing PA in these groups.