Cognitive motor interference while walking: A systematic review and meta-analysis

Trait anxiety increases the attentional cost of walking in young adults: A cross-sectional study

BACKGROUND

Anxiety is a prevalent mental health disorder, with debilitating symptoms causing avoidance and decreased quality of life. Balance impairments during standing and walking are common in anxiety. However, understanding of gait control mechanisms in people with trait anxiety, particularly when walking requires increased attention (dual-task), is still limited. This work examined the attentional cost of walking in people with varying levels of trait anxiety. Since people with anxiety are often prone to Space and Motion Discomfort (SMD), this work also evaluated the potential role of SMD in the attentional cost of walking.

METHODS

Fifty-six participants, aged 18-51, classified as anxious and non-anxious, were asked to walk under single- and two dual-task conditions (cognitive: counting backwards; visuomotor: texting on a mobile phone). Task performance (walking, counting and texting) was measured. Prefrontal cortex (PFC) activation was recorded using functional near infrared spectroscopy (fNIRS) for a subset of participants (n = 29).

RESULTS

Anxious individuals walked slower under dual-task conditions, with smaller increases in PFC activation from single to dual-task conditions in the cognitive task. Dual-task walking was unrelated to SMD.

LIMITATIONS

sample size was limited, particularly for fNIRS data.

CONCLUSIONS

To the best of our knowledge, this study is the first to identify anxiety-related deficits in attentional gait control in the general population, including during the everyday task of texting on a mobile phone. Since decrements in dual-task walking are linked to poor health outcomes, results from this work may have functional implications for people with anxiety.

Increased dual-task interference during upper limb movements in stroke exceeding that found in aging - a systematic review and meta-analysis

Objective

To determine whether dual-task interference during upper limb tasks is increased in patients after stroke compared to healthy older subjects and to compare magnitude of stroke-induced change in interference to that explained by aging.

Methods

We conducted a systematic literature search in MEDLINE, CINAHL, Google Scholar and PEDro databases up to October 2023 for studies on upper limb dual-tasks in stroke and elderly healthy subjects. Eleven upper limb dual-task studies in stroke patients and 11 studies in healthy older subjects were identified and systematically reviewed. A meta-analysis was performed on seven stroke studies and on five studies in healthy older subjects that included control groups.

Results

Most stroke studies investigated proximal arm movements with kinematic measures, but few studies evaluated manual dexterity. In contrast, studies in healthy older subjects used more distal (finger tapping) tasks. The meta-analysis showed that stroke patients had on average a 19% (CI 95% = 1.0-37.3) increase in dual-task interference compared to age-matched healthy controls (Z = 2.06, p = 0.04). Older healthy subjects showed greater dual-task interference compared to younger subjects (19% greater, CI 95% = 6.5-31.2, Z = 2.98, p = 0.003).

Conclusion

Meta-analysis revealed an increase in dual-task interference during upper limb movements in stroke patients, exceeding age-related changes, supporting the presence of subclinical impairments in divided attention post-stroke that may impede motor recovery.

Comparing the effects of dual-task training and single-task training on walking, balance and cognitive functions in individuals with Parkinson's disease: A systematic review

BACKGROUND

This systematic review aimed to examine whether dual-task (DT) training was superior to single-task (ST) training in improving DT walking, balance and cognitive functions for individuals with Parkinson's disease (PD).

METHODS

Literature search was performed in the following electronic databases: PubMed, the Cochrane Library, Web of Science, and Metstr covering inception to May 10, 2023. And in order to facilitate comparison across trials, we calculated the effect size (Hedges' g) of gait, balance, cognitive, and other parameters under both ST and DT conditions, using the mean change score and standard deviation (SD) of change score of the experimental and control groups. Randomized controlled trials that examined the effects of DT motor and cognitive training in individuals with Parkinson's disease were included for this systematic review.

RESULTS

A total of 214 participants recruited from six articles (actually five trials) were involved in this review. In terms of walking ability, only double support time and stride time variability showed significant between-group difference (Hedges' g = 0.34, 0.18, respectively). Compared to ST training group, DT training group had a more improvement effect in laboratory balance measurement (Hedges' g = 0.18, 1.25), but no significant improvement in clinical balance measurement. No significant between-group differences were observed, thus its training effect on cognitive function was inconclusive.

CONCLUSIONS

The DT training failed to achieve promising results better than ST training in improving DT walking and balance functions for individuals with PD. Any firm conclusion cannot be drawn at present, due to the limited number of eligible publications. Larger sample size and high-quality studies are needed to investigate the effectiveness of DT training in individuals with PD.

Cognitive-motor dual task to reveal gait impairments in multiple sclerosis patients at an early stage: A systematic review

BACKGROUND

Multiple sclerosis can cause locomotor and cognitive impairments even at lower levels of disability, which can impact daily life. The cognitive-motor dual task is commonly used to assess everyday locomotion. Thus, this study aimed to examine the effect of cognitive-motor dual tasks on gait parameters among patients with multiple sclerosis in the early disease stages and to determine whether dual tasks could be used as a clinical test to detect locomotion impairments.

METHODS

A systematic search of five databases was conducted in May 2024. The population of interest was patients with multiple sclerosis with an Expanded Disability Status Scale score of 4 or less. The following outcome measures were examined: spatiotemporal and kinematic parameters. The Newcastle-Ottawa Scale was used to assess the quality of the studies.

FINDINGS

Eleven studies including 270 patients with multiple sclerosis and 221 healthy controls. Three spatiotemporal parameters were modified both in patients with multiple sclerosis and healthy controls during dual-task performance: gait speed, stride length and the double support phase. No spatiotemporal parameter was affected during dual-task performance in patients with multiple sclerosis alone.

INTERPRETATION

Dual-task performance could be useful for assessing gait impairments in patients with multiple sclerosis provided that assessments and protocols are standardized. Nevertheless, the spatiotemporal parameters did not allow discrimination between patients with multiple sclerosis at an early stage and healthy controls. Three-dimensional gait analysis during dual-task performance could be a useful approach for detecting early gait impairments in patients with multiple sclerosis, assessing their progression and adjusting rehabilitation programs.

The impact of cognitive-motor interference on balance and gait in hearing-impaired older adults: a systematic review

BACKGROUND

Hearing impairments are a rising burden in our aging society. Hearing loss is associated with reduced cognitive performance as well as decrements in balance and gait. Therefore, impaired hearing affects also dual tasking (DT). The aim of this review is to summarize the evidence for DT performance decrements of older adults with hearing impairments during maintaining balance or walking.

METHODS

The systematic literature research according to PRISMA guidelines was conducted using MEDLINE, APA Psych-Info, and Web of Science. Inclusion criteria were: Independent living older people ≥ 60 years with hearing impairments, use of a DT paradigm to test hearing impaired older adults within a balance or walking condition.

RESULTS

N = 57 studies were found within the databases. Eight studies were included (N = 456 participants (58% women), including n = 200 older hearing-impaired persons with different levels of hearing loss). Most of the included studies oriented their inclusion criteria for hearing-impairments at thresholds for mild hearing loss with Pure Tone Average (0.5-4 kHz) ≥ 25 and < 40 dB. Three of the studies focused on DT balance performance and five used DT walking comparing participants with and without hearing loss. For DT balance and gait performance, higher decrements for the hearing-impaired group were observed compared to healthy older adults. Performance decrements were accompanied by reduced compensatory strategies in balance performance.

CONCLUSION

More pronounced decrements in DT performance were observed for participants with hearing impairments compared to those without. This implies that hearing-impaired older adults might need specific interventions to reduce the cognitive-motor interference (CMI) to maintain balance control or walking stability in daily situations that require managing of cognitive and motor tasks simultaneously. However, taking all results into account the underlying mechanisms of CMI for this target group needs to be further examined.

TRIAL REGISTRATION

This review was registered at Prospero with the ID CRD42022340232.

Translating the Interplay of Cognition and Physical Performance in COPD and Interstitial Lung Disease: Meeting Report and Literature Review

TOPIC IMPORTANCE

Cognitive and physical limitations are common in individuals with chronic lung diseases, but their interactions with physical function and activities of daily living are not well characterized. Understanding these interactions and potential contributors may provide insights on disability and enable more tailored rehabilitation strategies.

REVIEW FINDINGS

This review summarizes a 2-day meeting of patient partners, clinicians, researchers, and lung associations to discuss the interplay between cognitive and physical function in people with chronic lung diseases. This report covers four areas: (1) cognitive-physical limitations in patients with chronic lung diseases; (2) cognitive assessments; (3) strategies to optimize cognition and motor control; and (4) future research directions. Cognitive and physical impairments have multiple effects on quality of life and daily function. Meeting participants acknowledged the need for a standardized cognitive assessment to complement physical assessments in patients with chronic lung diseases. Dyspnea, fatigue, and age were recognized as important contributors to cognition that can affect motor control and daily physical function. Pulmonary rehabilitation was highlighted as a multidisciplinary strategy that may improve respiratory and limb motor control through neuroplasticity and has the potential to improve physical function and quality of life.

SUMMARY

There was consensus that cognitive function and the cognitive interference of dyspnea in people with chronic lung diseases contribute to motor control impairments that can negatively affect daily function, which may be improved with pulmonary rehabilitation. The meeting generated several key research questions related to cognitive-physical interactions in individuals with chronic lung diseases.

Multimodal training with dual-task enhances immediate and retained effects on dual-task effects of gait speed not by cognitive-motor trade-offs in stroke survivors: a randomized controlled trial

PURPOSE

Individuals who have experienced stroke may benefit from dual-task related training to improve gait speed performance. Whether noted improvements reflect true effects on gait or cognitive-motor trade-offs still remains unclear. Therefore, this study aimed to investigate the effects of dual-task training on dual-task effects of both walking and cognitive domains in stroke survivors.

MATERIALS AND METHODS

Forty-four individuals with stroke were randomized to dual-task or single-task training groups. Both groups exercised three 60-minute sessions per week for 4 weeks. The primary outcomes were dual-task effects on gait speed and cognitive score. Outcomes were assessed before and after the intervention and 1-month follow-up.

RESULTS

While both groups exhibited improvement in absolute gait speed under dual-task conditions, the dual-task training group demonstrated superior results by providing an additional gain on dual-task effects of gait speed. Compared to single-task training, dual-task training exhibited a significant improvement in dual-task effects of gait speed at post-treatment and follow-up. Regarding the dual-task effects on cognitive scores, no significant differences within and between groups after training were observed.

CONCLUSION

Dual-task training enhances immediate and retained effects on the dual-task effects of gait speed in individuals with stroke, not by cognitive-motor trade-offs.

TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov.

CLINICALTRIALS.GOV IDENTIFIER

NCT02686515.

Effects of a dual-task activity on gait parameters of people with and without intellectual disabilities

BACKGROUND

The main objective of this study was to evaluate gait parameters in people with intellectual disability (ID) and without intellectual disability (WID) in two different walking conditions [single task vs. dual task (DT)]. A secondary aim was to evaluate the dual-task cost (DTC) that the DT causes in each group.

METHODS

A total of 119 participants joined in this study: 56 ID (30 men) and 63 WID (30 men). The OptoGait system was used to assess gait. In addition, Witty photocells were added to assess gait under the DT condition.

RESULTS

Single support time was lower for participants with ID (P < 0.01), while double support time was higher (P < 0.05). All coefficients of variation for gait parameters were higher in participants with ID. Additionally, changes in gait were observed in both groups during the DT condition compared with the single-task condition. These changes were larger for participants with ID in step length, double support time and gait speed (P < 0.001), resulting in a higher DTC in these variables in the ID group (P < 0.01).

CONCLUSIONS

Both groups reduced gait performance in the DT condition. However, greater gait variability occurred in the ID group. In addition, DTC was higher for the ID group in all variables analysed. Therefore, people with ID show worse gait performance during a DT than people WID.

Functional near-infrared spectroscopy evidence of cognitive-motor interference in different dual tasks

Dual tasks (DTs) combining walking with a cognitive task can cause various levels of cognitive-motor interference, depending on which brain resources are recruited in each case. However, the brain activation and functional connectivity underlying cognitive-motor interferences remain to be elucidated. Therefore, this study investigated the neural correlation during different DT conditions in 40 healthy young adults (mean age: 27.53 years, 28 women). The DTs included walking during subtraction or N-Back tasks. Cognitive-motor interference was calculated, and brain activation and functional connectivity were analysed. Portable functional near-infrared spectroscopy was utilized to monitor haemodynamics in the prefrontal cortex (PFC), motor cortex and parietal cortex during each task. Walking interference (decrease in walking speed during DT) was greater than cognitive interference (decrease in cognitive performance during DT), regardless of the type of task. Brain activation in the bilateral PFC and parietal cortex was greater for walking during subtraction than for standing subtraction. Furthermore, brain activation was higher in the bilateral motor and parietal and PFCs for walking during subtraction than for walking alone, but only increased in the PFC for walking during N-Back. Coherence between the bilateral lateral PFC and between the left lateral PFC and left motor cortex was significantly greater for walking during 2-Back than for walking. The PFC, a critical brain region for organizing cognitive and motor functions, played a crucial role in integrating information coming from multiple brain networks required for completing DTs. Therefore, the PFC could be a potential target for the modulation and improvement of cognitive-motor functions during neurorehabilitation.

The moving wave: Applications of the mobile EEG approach to study human attention

Although historically confined to traditional research laboratories, electroencephalography (EEG) paradigms are now being applied to study a wide array of behaviors, from daily activities to specialized tasks in diverse fields such as sports science, neurorehabilitation, and education. This transition from traditional to real-world mobile research can provide new tools for understanding attentional processes as they occur naturally. Early mobile EEG research has made progress, despite the large size and wired connections. Recent developments in hardware and software have expanded the possibilities of mobile EEG, enabling a broader range of applications. Despite these advancements, limitations influencing mobile EEG remain that must be overcome to achieve adequate reliability and validity. In this review, we first assess the feasibility of mobile paradigms, including electrode selection, artifact correction techniques, and methodological considerations. This review underscores the importance of ecological, construct, and predictive validity in ensuring the trustworthiness and applicability of mobile EEG findings. Second, we explore studies on attention in naturalistic settings, focusing on replicating classic P3 component studies in mobile paradigms like stationary biking in our lab, and activities such as walking, cycling, and dual-tasking outside of the lab. We emphasize how the mobile approach complements traditional laboratory paradigms and the types of insights gained in naturalistic research settings. Third, we discuss promising applications of portable EEG in workplace safety and other areas including road safety, rehabilitation medicine, and brain-computer interfaces. In summary, this review explores the expanding possibilities of mobile EEG while recognizing the existing challenges in fully realizing its potential.

Investigating cognitive-motor effects during slacklining using mobile EEG

Balancing is a very important skill, supporting many daily life activities. Cognitive-motor interference (CMI) dual-tasking paradigms have been established to identify the cognitive load of complex natural motor tasks, such as running and cycling. Here we used wireless, smartphone-recorded electroencephalography (EEG) and motion sensors while participants were either standing on firm ground or on a slackline, either performing an auditory oddball task (dual-task condition) or no task simultaneously (single-task condition). We expected a reduced amplitude and increased latency of the P3 event-related potential (ERP) component to target sounds for the complex balancing compared to the standing on ground condition, and a further decrease in the dual-task compared to the single-task balancing condition. Further, we expected greater postural sway during slacklining while performing the concurrent auditory attention task. Twenty young, experienced slackliners performed an auditory oddball task, silently counting rare target tones presented in a series of frequently occurring standard tones. Results revealed similar P3 topographies and morphologies during both movement conditions. Contrary to our predictions we observed neither significantly reduced P3 amplitudes, nor significantly increased latencies during slacklining. Unexpectedly, we found greater postural sway during slacklining with no additional task compared to dual-tasking. Further, we found a significant correlation between the participant's skill level and P3 latency, but not between skill level and P3 amplitude or postural sway. This pattern of results indicates an interference effect for less skilled individuals, whereas individuals with a high skill level may have shown a facilitation effect. Our study adds to the growing field of research demonstrating that ERPs obtained in uncontrolled, daily-life situations can provide meaningful results. We argue that the individual CMI effects on the P3 ERP reflects how demanding the balancing task is for untrained individuals, which draws on limited resources that are otherwise available for auditory attention processing. In future work, the analysis of concurrently recorded motion-sensor signals will help to identify the cognitive demands of motor tasks executed in natural, uncontrolled environments.

The effect of visual sensory interference during multitask obstacle crossing in younger and older adults

When older adults step over obstacles during multitasking, their performance is impaired; the impairment results from central and/or sensory interference. The purpose was to determine if sensory interference alters performance under low levels of cognitive, temporal, and gait demand, and if the change in performance is different for younger versus older adults. Participants included 17 younger adults (20.9±1.9 years) and 14 older adults (69.7±5.4 years). The concurrent task was a single, simple reaction time (RT) task: depress button in response to light cue. The gait task was stepping over an obstacle (8 m walkway) in three conditions: (1) no sensory interference (no RT task), (2) low sensory interference (light cue on obstacle, allowed concurrent foveation of cue and obstacle), or (3) high sensory interference (light cue away from obstacle, prevented concurrent foveation of cue and obstacle). When standing, the light cue location was not relevant (no sensory interference). An interaction (sensory interference by task, p<0.01) indicated that RT was longer for high sensory interference during walking, but RT was not altered for standing, confirming that sensory interference increased RT during obstacle approach. An interaction (sensory interference by age, p<0.01) was observed for foot placement before the obstacle: With high sensory interference, younger adults placed the trail foot closer to the obstacle while older adults placed it farther back from the obstacle. The change increases the likelihood of tripping with the trail foot for younger adults, but with the lead limb for older adults. Recovery from a lead limb trip is more difficult due to shorter time for corrective actions. Overall, visual sensory interference impaired both RT and gait behavior with low levels of multitask demand. Changes in foot placement increased trip risk for both ages, but for different limbs, reducing the likelihood of balance recovery in older adults.

Perturbation-based dual task assessment in older adults with mild cognitive impairment

Background

Dual tasking (i.e., concurrent performance of motor and cognitive task) is significantly impaired in older adults with mild cognitive impairment (OAwMCI) compared to cognitively intact older adults (CIOA) and has been associated with increased fall risk. Dual task studies have primarily examined volitionally driven events, and the effects of mild cognitive impairment on reactive balance control (i.e., the ability to recover from unexpected balance threats) are unexplored. We examined the effect of cognitive tasks on reactive balance control in OAwMCI compared to CIOA.

Methods

Adults >55 years were included and completed the Montreal Cognitive Assessment (MoCA) to categorize them as OAwMCI (MoCA: 18-24, n = 15) or CIOA (MoCA: ≥25, n = 15). Both OAwMCI [MoCA: 22.4 (2.2), 65.4 (6.1) years, 3 females] and CIOA [MoCA: 28.4 (1.3), 68.2 (5.5) years, 10 females] responded to large magnitude stance slip-like perturbations alone (single task) and while performing perceptual cognitive tasks targeting the visuomotor domain (target and tracking game). In these tasks, participants rotated their head horizontally to control a motion mouse and catch a falling target (target game) or track a moving object (track). Margin of stability (MOS) and fall outcome (harness load cell >30% body weight) were used to quantify reactive balance control. Cognitive performance was determined using performance error (target) and sum of errors (tracking). A 3 × 2 repeated measures ANOVA examined the effect of group and task on MOS, and generalized estimating equations (GEE) model was used to determine changes in fall outcome between groups and tasks. 2 × 2 repeated measures ANOVAs examined the effect of group and task on cognitive performance.

Results

Compared to CIOA, OAwMCI exhibited significantly deteriorated MOS and greater number of falls during both single task and dual task (p < 0.05), and lower dual task tracking performance (p < 0.01). Compared to single task, both OAwMCI and CIOA exhibited significantly deteriorated perceptual cognitive performance during dual task (p < 0.05); however, no change in MOS or fall outcome between single task and dual task was observed.

Conclusion

Cognitive impairment may diminish the ability to compensate and provide attentional resources demanded by sensory systems to integrate perturbation specific information, resulting in deteriorated ability to recover balance control among OAwMCI.

Development and External Validation of a Gait Test Based Diagnostic Model for Detecting Mild Cognitive Impairment

OBJECTIVE

To address the lack of large-scale screening tools for mild cognitive impairment (MCI), this study aimed to assess the discriminatory ability of several gait tests for MCI and develop a screening tool based on gait test for MCI.

DESIGN

A diagnostic case-control test.

SETTING

The general community.

PARTICIPANTS

We recruited 134 older adults (≥65 years) for the derivation sample, comprising -69 individuals in the cognitively normal group and -65 in the MCI group (N=134). An additional 70 participants were enrolled for the validation sample.

INTERVENTIONS

All participants completed gait tests consisting of a single task (ST) and 3 dual tasks (DTs): counting backwards, serial subtractions 7, and naming animals.

MAIN OUTCOME MEASURES

Binary logistic regression analyses were used to develop models, and the efficacy of each model was assessed using receiver operating characteristic (ROC) curve and area under the curve (AUC). The best effective model was the final diagnostic model and validated using ROC curve and calibration curve.

RESULTS

The DT gait test incorporating serial subtractions 7 as the cognitive task demonstrated the highest efficacy with the AUC of 0.906 and the accuracy of 0.831 in detecting MCI with "years of education" being adjusted. Furthermore, the model exhibited consistent performance across different age and sex groups. In external validation, the model displayed robust discrimination (AUC=0.913) and calibration (calibrated intercept=-0.062, slope=1.039).

CONCLUSIONS

The DT gait test incorporating serial subtractions 7 as the cognitive task demonstrated robust discriminate ability for MCI. This test holds the potential to serve as a large-scale screening tool for MCI, aids in the early detection and intervention of cognitive impairment in older adults.

Effects of combined cognitive and resistance training on physical and cognitive performance and psychosocial well-being of older adults ≥65: study protocol for a randomised controlled trial

INTRODUCTION

With increasing life expectancy of older adult population, maintaining independence and well-being in later years is of paramount importance. This study aims to investigate the impact of three distinct interventions: cognitive training, resistance training and a combination of both, compared with an inactive control group, on cognitive performance, mobility and quality of life in adults aged ≥65 years.

METHODS AND ANALYSIS

This trial will investigate healthy older adults aged ≥65 years living independently without cognitive impairments. Participants will be randomly assigned to one of four groups: (1) cognitive training, (2) resistance training, (3) combined cognitive and resistance training, and (4) control group (n=136 participants with 34 participants per group). The interventions will be conducted over 12 weeks. The cognitive training group will receive group-based activities for 45-60 min two times a week. The resistance training group exercises will target six muscle groups and the combined group will integrate cognitive tasks into the resistance training sessions. Primary outcomes are: Short Physical Performance Battery, Sit-to-Stand Test, Montreal Cognitive Assessment, Trail Making Test and Stroop Test combined with gait on a treadmill (dual task). Life satisfaction will be measured by the Satisfaction With Life Scale. Secondary outcomes encompass hand grip strength and the Functional Independence Measure.

ETHICS AND DISSEMINATION

Ethical approval was provided by the local Ethics Committee at the University of Hamburg (no. 2023_009). Informed consent will be obtained from all study participants. The results of the study will be distributed for review and discussion in academic journals and conferences.

TRIAL REGISTRATION NUMBER

DRKS00032587.

Cognitive-motor interference during walking with modified leg mechanics: a dual-task walking study

Background

The use of mobile exoskeletons as assistive walking devices has the potential to affect the biomechanics of the musculoskeletal system due to their weight and restricted range of motion. This may result in physical and cognitive load for the user. Understanding how lower extremity loading affects cognitive-motor interference is crucial for the design of wearable devices, including powered exoskeletons, and the development of effective training interventions.

Objective

This study aims to examine the effects of modified leg mechanics on cognitive-motor interference in dual-task walking. Gait variability, as an indicator of motor control, was analyzed to investigate its relation to cognitive task difficulty and to determine whether lower extremity loading modifies this relationship. Additionally, the impact on the gait pattern, as represented by the mean values of spatio-temporal gait parameters were investigated.

Method

Fifteen healthy young adults walked on a treadmill with and without weight cuffs bilaterally attached to their thighs and shanks while performing a visual-verbal Stroop test (simple task) and a serial subtraction task (difficult task). Dependent variables include mean values and variability (coefficients of variation) of step length, step width, stride time and double support time. Additionally, secondary task performance as correct response rates and perceived workload were assessed.

Results

Double support time variability decreased during dual-task walking, but not during walking with modified leg mechanics while performing the difficult secondary task. Walking with modified leg mechanics resulted in increased gait variability compared to normal walking, regardless of cognitive load. During walking with modified leg mechanics, step length, step width, and stride time increased, while double support time decreased. The secondary tasks did not affect the gait pattern.

Conclusion

The interplay between an external focus of attention and competition for attentional resources may influence the variability of double support time. The findings suggest that walking with modified leg mechanics could increase cognitive-motor interference for healthy young adults in demanding dual-task situations. Therefore, it is important to analyze the underlying mechanisms of cognitive-motor interference in the context of human-exoskeleton interaction.

Risk of using smartphones while walking for digital natives in realistic environments: Effects of cognitive-motor interference

The effect of using smartphones while walking on the cognitive and physical abilities of the "digital native" generation, i.e., individuals who have grown up in a digital media-centric environment, remains poorly understood. This study evaluated the effects of cognitive-motor interference on the use of smartphones while walking in children and young adults. The study involved 50 individuals from the digital age generation, including 24 children and 26 young adults. The study encompassed three experimental conditions, in which participants were instructed to traverse a distance of 60 m. The initial condition functioned as a control, wherein the participants walked without supplementary stimuli. In the second condition, the participants were provided with explicit instructions to grasp the smartphone device and position it in front of their chest by using both hands. This manipulation introduced a postural component into the experimental setup. The third condition required participants to be ambulatory while concurrently engaging in a cognitive task, namely, participating in a game that necessitated focused attention. Gait parameters were obtained by using inertial measurement unit sensors. Subsequently, the acquired gait characteristics were converted into dual-task costs (DTC). In the cognitive condition, children exhibited significantly greater DTC values for gait speed (76%), stride length (79%), stride time (102%), and stride length coefficient of variation (CV) than the young adults (p < 0.025). Moreover, as shown by the increased CV, a significant association exists between poor performance in smartphone games among children and increased variability in stride length. In children, the DTC of stride time CV decreased as smartphone game scores increased (R2 = 16.5%), and the DTC of stride length CV decreased more markedly as smartphone game scores increased (R2 = 28.2%). In conclusion, children are at a higher risk of pedestrian accidents when using smartphones while walking compared to young adults.

Effect of mental fatigue on hand force production capacities

Mental fatigue is common in society, but its effects on force production capacities remain unclear. This study aimed to investigate the impact of mental fatigue on maximal force production, rate of force development-scaling factor (RFD-SF), and force steadiness during handgrip contractions. Fourteen participants performed two randomized sessions, during which they either carried out a cognitively demanding task (i.e., a visual attention task) or a cognitively nondemanding task (i.e., documentary watching for 62 min). The mental fatigue was evaluated subjectively and objectively (performances and electroencephalography). Maximal voluntary contraction (MVC) force, RFD-SF, and force steadiness (i.e., force coefficient of variation at submaximal intensities; 25, 50, and 75% of MVC) were recorded before and after both tasks. The feeling of mental fatigue was much higher after completing the cognitively demanding task than after documentary watching (p < .001). During the cognitively demanding task, mental fatigue was evidenced by increased errors, missed trials, and decreased N100 amplitude over time. While no effect was reported on force steadiness, both tasks induced a decrease in MVC (p = .040), a force RFD-SF lower slope (p = .011), and a reduction in the coefficient of determination (p = .011). Nevertheless, these effects were not explicitly linked to mental fatigue since they appeared both after the mentally fatiguing task and after watching the documentary. The study highlights the importance of considering cognitive engagement and mental load when optimizing motor performance to mitigate adverse effects and improve force production capacities.

How Does Postural Control in Patients with Functional Motor Disorders Adapt to Multitasking-Based Immersive Virtual Reality?

BACKGROUND

Motor symptoms in functional motor disorders (FMDs) refer to involuntary, but learned, altered movement patterns associated with aberrant self-focus, sense of agency, and belief/expectations. These conditions commonly lead to impaired posture control, raising the likelihood of falls and disability. Utilizing visual and cognitive tasks to manipulate attentional focus, virtual reality (VR) integrated with posturography is a promising tool for exploring postural control disorders.

OBJECTIVES

To investigate whether postural control can be adapted by manipulating attentional focus in a 3D immersive VR environment.

METHODS

We compared postural parameters in 17 FMDs patients and 19 age-matched healthy controls over a single session under four increasingly more complex and attention-demanding conditions: simple fixation task (1) in the real room and (2) in 3D VR room-like condition; complex fixation task in a 3D VR city-like condition (3) avoiding distractors and (4) counting them. Dual-task effect (DTE) measured the relative change in performance induced by the different attention-demanding conditions on postural parameters.

RESULTS

Patients reduced sway area and mediolateral center of pressure displacement velocity DTE compared to controls (all, P < 0.049), but only under condition 4. They also showed a significant reduction in the sway area DTE under condition 4 compared to condition 3 (P = 0.025).

CONCLUSIONS

This study provides novel preliminary evidence for the value of a 3D immersive VR environment combined with different attention-demanding conditions in adapting postural control in patients with FMDs. As supported by quantitative and objective posturographic measures, our findings may inform interventions to explore FMDs pathophysiology.

Lower limb prosthesis users' perceptions of everyday life-A phenomenographic study

INTRODUCTION

A lack of understanding of personal experiences related to limb amputation and prosthetic use limits the extent to which clinicians involved in rehabilitation can support and advise their clients in a person-centered consultation. The objective of this qualitative study was to explore the personal experience of daily life as a lower limb prosthesis user.

METHODS

Fifteen lower limb prosthesis users participated in individual semistructured interviews. Transcripts were analyzed using a phenomenographic approach.

RESULTS

The extent to which prosthesis users were able to adjust to their impairment and move on with their life was influenced by social interactions with other prosthesis users, access to relevant information about prosthetic solutions that may benefit them, and finding a balance between desired activities and their physical and/or cognitive capacity.

CONCLUSIONS

After a period of existential adjustment, prosthesis users described themselves as living active, fulfilling lives. This was facilitated to a large extent by social interactions with other prosthesis users and access to information they perceived as relevant. Social media plays a particularly important role in establishing connections with other prosthesis users and is perceived as a useful source of information.

Stand up to better pay attention, sit down to better subtract: a new perspective on the advantage of cognitive-motor interactions

The Stroop task and subtraction rely on the different cognitive processes and cerebral regions, but both these cognitive functions interact with posture. The study of cognitive-motor interactions falls under the concept of sharing resources, implying that resources for processing are limited. Researchers try to understand this interaction by constructing dual task (DT) paradigms. None have investigated the Stroop and subtraction tasks in three inherently simple postures in two groups of young adults. This study aimed to test whether a given posture benefits a given cognitive function when cognitive and postural tasks are not overly demanding and are underpinned by common cerebral structures. This study presents the results of 60 healthy young adults performing a subtraction task in three postures (sitting, standing, and walking) and 57 healthy young adults performing the Stroop task in the same three postures. Our results showed that performance at the Stroop task, in terms of number of correct answers and interference, are better while standing or even walking compared to sitting while subtraction is better sitting compared to standing and walking. Moreover, static postural parameters did not vary when in DT compared to single task. This means that there was no additional cost on posture when achieving the cognitive activity simultaneously. The absence of impact of the DT on postural parameters in static postures and the changes in the gait pace when walking suggest that cognitive tasks can be achieved in various postures, without being too costly on posture.

Dual-tasking modulates movement speed but not value-based choices during walking

Value-based decision-making often occurs in multitasking scenarios relying on both cognitive and motor processes. Yet, laboratory experiments often isolate these processes, thereby neglecting potential interactions. This isolated approach reveals a dichotomy: the cognitive process by which reward influences decision-making is capacity-limited, whereas the influence of motor cost is free of such constraints. If true, dual-tasking should predominantly impair reward processing but not affect the impact of motor costs. To test this hypothesis, we designed a decision-making task in which participants made choices to walk toward targets for rewards while navigating past an obstacle. The motor cost to reach these rewards varied in real-time. Participants either solely performed the decision-making task, or additionally performed a secondary pitch-recall task. Results revealed that while both reward and motor costs influenced decision-making, the secondary task did not affect these factors. Instead, dual-tasking slowed down participants' walking, thereby reducing the overall reward rate. Hence, contrary to the prediction that the added cognitive demand would affect the weighing of reward or motor cost differentially, these processes seem to be maintained at the expense of slowing down the motor system. This slowdown may be indicative of interference at the locomotor level, thereby underpinning motor-cognitive interactions during decision-making.

Walking modulates visual detection performance according to stride cycle phase

Walking is among our most frequent and natural of voluntary behaviours, yet the consequences of locomotion upon perceptual and cognitive function remain largely unknown. Recent work has highlighted that although walking feels smooth and continuous, critical phases exist within each step for the successful coordination of perceptual and motor function. Here, we test whether these phasic demands impact upon visual perception, by assessing performance in a visual detection task during natural unencumbered walking. We finely sample visual performance over the stride cycle as participants walk along a smooth linear path at a comfortable speed in a wireless virtual reality environment. At the group-level, accuracy, reaction times, and response likelihood show strong oscillations, modulating at approximately 2 cycles per stride (~2 Hz) with a marked phase of optimal performance aligned with the swing phase of each step. At the participant level, Bayesian inference of population prevalence reveals highly prevalent oscillations in visual detection performance that cluster in two idiosyncratic frequency ranges (2 or 4 cycles per stride), with a strong phase alignment across participants.

Performance during attention-demanding walking conditions in older adults

BACKGROUND

Conventional balance and gait assessments for fall risk screening are often conducted under unperturbed conditions. However, older adults can allocate their attention to motor tasks (balance or walking) without revealing performance deficiencies, posing a challenge in identifying those with compromised gait and balance.

RESEARCH QUESTIONS

Do community-dwelling older adults exhibit greater changes in cognitive and/or walking performance under balance-challenging conditions compared to typical dual-task walking conditions?

METHODS

Twenty-nine healthy, community-dwelling older adults performed four cognitive tasks (visual and auditory Stroop tasks, Clock task, and Paced Auditory Serial Addition Test) while walking with and without lateral treadmill sways (Perturbed vs. Unperturbed) and during standing. We calculated dual-task costs (DTC) and walking perturbation effects (WPE) as the percentage of change in cognitive and walking performance between dual and single-task conditions and between Perturbed and Unperturbed conditions, respectively.

RESULTS

Older adults exhibited similar DTC and WPE on cognitive task performance. However, in walking performance, they demonstrated significantly greater WPE than DTC across all gait and stability measures (p < 0.01), including the mean and variability of stride and margins of stability (MOS) measures, the variability of trunk movement and lower-limb joint angles, and the local stability measures. Older adults took shorter but wider steps, exhibited shorter MOSAP but greater MOSML, and experienced increased movement variability and walking instability to a greater extent than during dual-task walking. Overall, changes in variability and stability measures were more pronounced than those in mean gait measures.

SIGNIFICANCE

Introducing destabilizing perturbations to increase the task demands of balance and gait assessments is a more effective method to challenge older adults compared to simply adding a concurrent cognitive task. Fall screening assessments for community-dwelling older adults should incorporate balance-challenging conditions, such as introducing gait perturbations.

Benign Prostatic Hyperplasia and the Risk of Falls in Older Men: Insights From a Population-Based Study on Geriatric Morbid Conditions

PURPOSE

The purpose of this study was to explore the association between benign prostatic hyperplasia (BPH) and the incidence of falls from the perspective of geriatric morbid conditions.

METHODS

Data were sourced from the triennial National Survey of Older Koreans conducted by the Ministry of Health and Welfare (2017-2020). In total, 8,135 male participants aged 65 and older were included, and information was gathered through questionnaires and physical measurements. Logistic regression analysis was utilized to determine the impact of BPH on the risk of falls, and subgroup analyses were conducted to examine the influence of BPH on specific types of falls.

RESULTS

Of the participants, 15.2% (1,238 of 8,135) reported that their BPH treatment exceeded 3 months, and 8.0% (648 of 8,135) reported experiencing falls, with 61.4% (398/648) of these falls resulting in injuries. A significant association was identified between BPH and both falls (odds ratio [OR], 1.798; 95% confidence interval [CI], 1.479-2.185) and falls with injuries (OR, 2.133; 95% CI, 1.689-2.694). A subgroup analysis indicated a correlation between BPH and falls in groups having one (OR, 1.912; 95% CI, 1.356-2.694) and 2 or more conditions (OR, 1.856; 95% CI, 1.455-2.367) involving visual and auditory impairments, cognitive decline, depression, lower motor weakness, and limitations in daily activities.

CONCLUSION

The findings indicate that BPH contributes to the incidence of falls among older men, particularly those with comorbid conditions. Considering the heightened fall risk among elderly individuals suffering from multiple morbidities, particularly those with BPH, targeted interventions are essential for mitigating the risk of falls in this vulnerable group.

Is an 8-Week Regimen of Nordic Walking Training Sufficient to Benefit Cognitive Performance in Healthy Older Adults? A Pilot Study

Nordic walking requires the association of walking and coordination of limbs while orienteering in a natural environment. It has been shown to improve functional capacities more than normal walking. However, its cognitive benefits are less clear. The main hypothesis was that this training improves visuospatial capacities and inhibition functions. A total of 14 healthy older adults were included. The training was performed in three sessions of 75 min a week for 8 weeks. Pre-, intermediate, and post-tests were carried out. Cognitive functions including global cognition (MoCA), executive functions (Color-Word Stroop test), speed of information processing, switching capacities (Trail Making Test A and B), and visuospatial capacities (Rey Complex Figure Copy Task) were assessed. Motor functions including balance control (Unipedal Balance Test), functional mobility (Timed Up and Go), hamstring flexibility (Chair Sit and Reach test), and motor coordination (Four-Square Stepping Test) were evaluated. Physical function, including lower limb strength (Timed Sit-To-Stand) and cardiovascular capacities (Incremental Shuttle Walking Test), was measured. Cardiovascular capacity, strength of lower limbs, and motor coordination were positively affected by training. With respect to cognition, training improved visuospatial capacities, while switching capacities, information processing speed, and executive functions did not improve. A possible explanation is that they needed a longer program duration to show benefits. However, analyses of responders suggested that NW positively affected cognitive functioning in a subset of participants. Eight weeks of NW training produced physical, motor, and cognitive improvements. A longer training duration could be necessary to extend the benefits to executive functions in all participants.

Brain activation during standing balance control in dual-task paradigm and its correlation among older adults with mild cognitive impairment: a fNIRS study

BACKGROUND

This study aimed to compare the balance ability and functional brain oxygenation in the prefrontal cortex (PFC) among older adults with mild cognitive impairment (MCI) under single and dual tasks, and also investigate their relationship. Neural regulatory mechanisms of the brain in the MCI were shed light on in balance control conditions.

METHODS

21 older adults with MCI (female = 12, age: 71.19 ± 3.36 years) were recruited as the experimental group and 19 healthy older adults (female = 9, age: 70.16 ± 4.54 years) as the control group. Participants completed balance control of single task and dual task respectively. Functional near-infrared spectroscopy (fNIRS) and force measuring platform are used to collect hemodynamic signals of the PFC and center of pressure (COP) data during the balance task, respectively.

RESULTS

The significant Group*Task interaction effect was found in maximal displacement of the COP in the medial-lateral (ML) direction (D-ml), 95% confidence ellipse area (95%AREA), root mean square (RMS), the RMS in the ML direction (RMS-ml), the RMS in the anterior-posterior (AP) direction (RMS-ap), sway path (SP), the sway path in the ML direction (SP-ml), and the sway path in the AP direction (SP-ap). The significant group effect was detected for five regions of interest (ROI), namely the left Brodmann area (BA) 45 (L45), the right BA45 (R45), the right BA10 (R10), the left BA46 (L46), and the right BA11 (R11). Under single task, maximal displacement of the COP in the AP direction (D-ap), RMS, and RMS-ap were significantly negatively correlated with R45, L45, and R11 respectively. Under dual task, both RMS and 95%AREA were correlated positively with L45, and both L10 and R10 were positively correlated with RMS-ap.

CONCLUSION

The MCI demonstrated worse balance control ability as compared to healthy older adults. The greater activation of PFC under dual tasks in MCI may be considered a compensatory strategy for maintaining the standing balance. The brain activation was negatively correlated with balance ability under single task, and positively under dual task.

TRIAL REGISTRATION

ChiCTR2100044221 , 12/03/2021.

Beyond traditional training: Integrating data from semi-immersive VR dual-task intervention in Parkinsonian Syndromes. A study protocol

Completing cognitive and motor tasks simultaneously requires a high level of cognitive control in terms of executive processes and attentional abilities. Most of the daily activities require a dual-task performance. While walking, for example, it may be necessary to adapt gait to obstacles of the environment or simply participate in a conversation; all these activities involve more than one ability at the same time. This parallel performance may be critical in the cognitive or motor load, especially for patients with neurological diseases such as Parkinsonian Syndromes. Patients are often characterized by a crucial impairment in performing both tasks concurrently, showing a decrease in attention skills and executive functions, thus leading to increased negative outcomes. In this scenario, the accurate assessment of the components involved in dual-task performance is crucial, and providing an early specific training program appears to be essential. The objective of this protocol is to assess cognitive and motor components involved in dual-task performance and create a training program based on ecological activities focusing on executive and motor functions. Thus, we will employ Virtual Reality to provide semi-immersive, multisensory, ecological, standardized, and realistic experiences for rehabilitative purposes in patients with Parkinsonian Syndromes, considering its high prevalence in aging and the incidence of motor and cognitive dysfunctions in this population. Moreover, we propose to integrate the great amount of different data provided by dual-task and Virtual Reality system, using machine learning techniques. These integrations may increase the treatment's reliability in terms of better prognostic indexes and individualized training.

Biological and Physical Performance Markers for Early Detection of Cognitive Impairment in Older Adults

Dementia is a major cause of poor quality of life, disability, and mortality in old age. According to the geroscience paradigm, the mechanisms that drive the aging process are also involved in the pathogenesis of chronic degenerative diseases, including dementia. The dissection of such mechanisms is therefore instrumental in providing biological targets for interventions and new sources for biomarkers. Within the geroscience paradigm, several biomarkers have been discovered that can be measured in blood and that allow early identification of individuals at risk of cognitive impairment. Examples of such markers include inflammatory biomolecules, markers of neuroaxonal damage, extracellular vesicles, and DNA methylation. Furthermore, gait speed, measured at a usual and fast pace and as part of a dual task, has been shown to detect individuals at risk of future dementia. Here, we provide an overview of available biomarkers that may be used to gauge the risk of cognitive impairment in apparently healthy older adults. Further research should establish which combination of biomarkers possesses the highest predictive accuracy toward incident dementia. The implementation of currently available markers may allow the identification of a large share of at-risk individuals in whom preventive interventions should be implemented to maintain or increase cognitive reserves, thereby reducing the risk of progression to dementia.

Reduced Proactive and Reactive Cognitive Flexibility in Older Adults Underlies Performance Costs During Dual-Task Walking: A Mobile Brain/Body Imaging (MoBI) Study

Age-related reductions in cognitive flexibility may limit modulation of control processes during systematic increases to cognitive-motor demands, exacerbating dual-task costs. In this study, behavioral and neurophysiologic changes to proactive and reactive control during progressive cognitive-motor demands were compared across older and younger adults to explore the basis for age-differences in cognitive-motor interference (CMI). 19 younger (19 - 29 years old, mean age = 22.84 +/- 2.75 years, 6 male, 13 female) and 18 older (60 - 77 years old, mean age = 67.89 +/- 4.60 years, 9 male, 9 female) healthy adults completed cued task-switching while alternating between sitting and walking on a treadmill. Gait kinematics, task performance measures, and brain activity were recorded using electroencephalography (EEG) based Mobile Brain/Body Imaging (MoBI). Response accuracy on easier trial types improved in younger, but not older adults when they walked while performing the cognitive task. As difficulty increased, walking provoked accuracy costs in older, but not younger adults. Both groups registered faster responses and reduced gait variability during dual-task walking. Older adults exhibited lower amplitude modulations of proactive and reactive neural activity as cognitive-motor demands systematically increased, which may reflect reduced flexibility for progressive preparatory and reactive adjustments over behavioral control.

Executive Functions Assessment Based on Wireless EEG and 3D Gait Analysis During Dual-Task: A Feasibility Study

Executive functions (EFs) are neurocognitive processes planning and regulating daily life actions. Performance of two simultaneous tasks, requiring the same cognitive resources, lead to a cognitive fatigue. Several studies investigated cognitive-motor task and the interference during walking, highlighting an increasing risk of falls especially in elderly and people with neurological diseases. A few studies instrumentally explored relationship between activation-no-activation of two EFs (working memory and inhibition) and spatial-temporal gait parameters. Aim of our study was to detect activation of inhibition and working memory during progressive difficulty levels of cognitive tasks and spontaneous walking using, respectively, wireless electroencephalography (EEG) and 3D-gait analysis. Thirteen healthy subjects were recruited. Two cognitive tasks were performed, activating inhibition (Go-NoGo) and working memory (N-back). EEG features (absolute and relative power in different bands) and kinematic parameters (7 spatial-temporal ones and Gait Variable Score for 9 range of motion of lower limbs) were analyzed. A significant decrease of stride length and an increase of external-rotation of foot progression were found during dual task with Go-NoGo. Moreover, a significant correlation was found between the relative power in the delta band at channels Fz, C4 and progressive difficulty levels of Go-NoGo (activating inhibition) during walking, whereas working memory showed no correlation. This study reinforces the hypothesis of the prevalent involvement of inhibition with respect to working memory during dual task walking and reveals specific kinematic adaptations. The foundations for EEG-based monitoring of cognitive processes involved in gait are laid. Clinical and Translational Impact Statement: Clinical and instrumental evaluation and training of executive functions (as inhibition), during cognitive-motor task, could be useful for rehabilitation treatment of gait disorder in elderly and people with neurological disease.

Classification and Definitions of Compensatory Protective Step Strategies in Older Adults: A Scoping Review

BACKGROUND

The risk for an unexpected fall can be due to increasing age, health conditions, and loss of cognitive, sensory, or musculoskeletal functions. Falls have personal and economic consequences in many countries. Different disturbances can occur during gait, such as tripping, slipping, or other unexpected circumstances that can generate a loss of balance. The strategies used to recover balance depend on many factors, but selecting a correct response strategy influences the success of balance recovery.

OBJECTIVES

(1) To collect and clarify the definitions of compensatory protective step strategies to recover balance in older adults; (2) to identify the most used methods to induce loss of balance; and (3) to identify the most used spatiotemporal variables in analyzing these actions.

METHODS

The present review has followed the PRISMA guideline extension for Scoping Review (PRISMA-ScR) and the phases proposed by Askery and O'Malley. The search was conducted in three databases: PubMed, Web of Science, and Scopus.

RESULTS

A total of 525 articles were identified, and 53 studies were included. Forty-five articles were quasi-experimental studies, six articles were randomized controlled trials, and two studies had an observational design. In total, 12 compensatory protective step strategies have been identified.

CONCLUSIONS

There are 12 compensatory protective step strategies: lowering and elevating strategy, short- and long-step strategy, backward and forward stepping for slip, single step, multiple steps, lateral sidesteps or loaded leg sidestep unloaded leg sidestep, crossover step (behind and front), and medial sidestep. To standardize the terminology applied in future studies, we recommend collecting these strategies under the term of compensatory protective step strategies. The most used methods to induce loss of balance are the tether-release, trip, waist-pull, and slip methods. The variables analyzed by articles are the number of steps, the acceleration phase and deceleration phase, COM displacement, the step initiation or step duration, stance phase time, swing phase time and double-stance duration, stride length, step length, speed step, speed gait and the type of step.

Cortical thickness and white matter microstructure predict freezing of gait development in Parkinson's disease

The clinical applications of the association of cortical thickness and white matter fiber with freezing of gait (FoG) are limited in patients with Parkinson's disease (PD). In this retrospective study, using white matter fiber from diffusion-weighted imaging and cortical thickness from structural-weighted imaging of magnetic resonance imaging, we investigated whether a machine learning-based model can help assess the risk of FoG at the individual level in patients with PD. Data from the Parkinson's Disease Progression Marker Initiative database were used as the discovery cohort, whereas those from the Fujian Medical University Union Hospital Parkinson's Disease database were used as the external validation cohort. Clinical variables, white matter fiber, and cortical thickness were selected by random forest regression. The selected features were used to train the support vector machine(SVM) learning models. The median area under the receiver operating characteristic curve (AUC) was calculated. Model performance was validated using the external validation cohort. In the discovery cohort, 25 patients with PD were defined as FoG converters (15 men, mean age 62.1 years), whereas 60 were defined as FoG nonconverters (38 men, mean age 58.5 years). In the external validation cohort, 18 patients with PD were defined as FoG converters (8 men, mean age 66.9 years), whereas 37 were defined as FoG nonconverters (21 men, mean age 65.1 years). In the discovery cohort, the model trained with clinical variables, cortical thickness, and white matter fiber exhibited better performance (AUC, 0.67-0.88). More importantly, SVM-radial kernel models trained using random over-sampling examples, incorporating white matter fiber, cortical thickness, and clinical variables exhibited better performance (AUC, 0.88). This model trained using the above mentioned features was successfully validated in an external validation cohort (AUC, 0.91). Furthermore, the following minimal feature sets that were used: fractional anisotropy value and mean diffusivity value for right thalamic radiation, age at baseline, and cortical thickness for left precentral gyrus and right dorsal posterior cingulate gyrus. Therefore, machine learning-based models using white matter fiber and cortical thickness can help predict the risk of FoG conversion at the individual level in patients with PD, with improved performance when combined with clinical variables.

Heterogeneity of Tasks and Outcome Measures in Dual Tasking Studies in Children With Cerebral Palsy: A Scoping Review

OBJECTIVE

The aims of this scoping review are to examine the available literature regarding dual tasking in children with cerebral palsy (CP) and to identify and categorize both the motor and cognitive tasks and outcome measures used primarily through the International Classification of Functioning, Disability, and Health model.

METHODS

Five electronic databases were searched. Studies were included if they: (1) were published in English; (2) included at least 1 group of children or adolescents with a diagnosis of CP; (3) assessed dual tasking as part of the study; (4) reported the method for performing the dual task; and (5) reported the outcome measures utilized.

RESULTS

Twenty-three studies with 439 children with CP were included. All studies utilized motor activities as the primary task, including walking, balance, and a functional transition. Motor secondary tasks occurred in 10 studies, cognitive secondary tasks in 12 studies, and 1 study used both. Forty-one outcome measures over 23 studies assessed the body structure and function domain, 7 measures over 6 studies assessed activity limitations, and 2 outcomes over 2 studies assessed participation.

CONCLUSION

The 23 included studies demonstrated heterogeneity in the age and function of participants, secondary tasks, and outcome measures. Future studies on dual tasking in children with CP should consider the difficulty of the primary motor or cognitive task and compare secondary tasks to establish this contribution to motor performance. Studies should incorporate activity and participation measures to assess meaningful functional outcomes.

IMPACT

Children with CP experience challenges when exposed to dual task situations. This scoping review highlights the importance of considering multiple factors when designing dual tasking studies involving children with CP to facilitate results translation, improved participation, and enhanced function. Similarly, studies should utilize activity and participation outcomes to assess quality of life.

Association of Age with Dual-Task Objective Cognitive Indicators and Gait Parameters in Older Adults

Background

Early recognition of dementia like Alzheimer's disease is crucial for disease diagnosis and treatment, and existing objective tools for early screening of cognitive impairment are limited.

Objective

To investigate age-related behavioral indicators of dual-task cognitive performance and gait parameters and to explore potential objective markers of early cognitive decline.

Methods

The community-based cognitive screening data was analyzed. Hierarchical cluster analysis and Pearson correlation analysis were performed on the 9-item subjective cognitive decline (SCD-9) scores, walking-cognitive dual-task performance, walking speed, and gait parameters of 152 participants. The significant differences of indicators that may related to cognitive decline were statistically analyzed across six age groups. A mathematical model with age as the independent variable and motor cognition composite score as the dependent variable was established to observe the trend of motor cognition dual-task performance with age.

Results

Strong correlation was found between motor cognitive scores and SCD and age. Gait parameters like the mean value of ankle angle, the left-right difference rate of ankle angle and knee angle and the coefficient of variation of gait cycle showed an excellent correlation with age. Motor cognition scores showed a decreasing trend with age. The slope of motor cognition scores with age after 50 years (k = -1.06) was six times higher than that before 50 years (k = -0.18).

Conclusions

Cognitive performance and gait parameters in the walking-cognitive dual-task state are promising objective markers that could characterize age-related cognitive decline.

Transcranial direct current stimulation facilitates backward walking training

Backward walking training presents a great challenge to the physical and neural systems, which may result in an improvement in gait performance. Transcranial direct current electrical stimulation (tDCS), which can non-invasively enhance cortical activity, has been reported to strengthen corticomotor plasticity. We investigated whether excitatory tDCS over the primary motor cortex (M1) or the dorsolateral prefrontal cortex (DLPFC) enhances the effects of backward walking training in healthy participants. Thirty-six healthy participants (16 men and 20 women, mean age 21.3 ± 1.4 years) participated in this study. The participants were randomly assigned to one of the three tDCS groups (M1, DLPFC, and sham). They performed 5 min of backward walking training during 15 min of tDCS. We evaluated dual-task forward and backward walking performance before and after training. Both tDCS groups increased walking speed in the backward condition, but the DLPFC group increased the dual-task backward walking speed more than the M1 group. The M1 group showed decreased gait variability in dual-task backward walking, whereas the DLPFC group showed increased gait variability. Backward walking training combined with M1 stimulation may increase the backward walking speed by reducing gait variability. Backward walking training combined with DLPFC stimulation may prioritize walking speed over gait stability. Our results indicate that backward walking training combined with tDCS may be extended to other rehabilitation methods to improve gait performance.

The effect of different types of cognitive tasks on postural sway fluctuations in older and younger adults: A nonlinear study

BACKGROUND

There are numerous types of cognitive tasks classified as mental tracking (MT), working memory (WM), reaction time (RT), discrimination and decision-making and verbal fluency (VF). However, limited studies have investigated the effects of cognitive task type on postural control in older adults.

PURPOSE

s: The aim of this study was to investigate the effect of aging and several types of cognitive tasks on postural control in terms of nonlinear analysis.

METHOD

Postural control was investigated under 6 conditions (single task and dual-task with RT; easy and difficult VF; easy and difficult WM; easy and difficult MT. Outcome measurements were the max Lyapunov, entropy, and correlation dimension at anteroposterior (AP) and mediolateral (ML) directions.

RESULTS

The results revealed that within the older group, the AP & ML max Lyapunov at dual-task with difficult WM and MT was significantly higher than all other conditions. In addition, the older group had lower AP entropy at dual-task with easy VF, difficult WM, and easy as well as difficult MT.

CONCLUSION

The results can be useful to understand the postural control mechanisms and to detect the alterations following aging and applying different types of cognitive tasks. In addition, the investigated parameters can be a basis for identifying postural control deficiencies.

Association of impaired cognitive function with balance confidence, static balance, dynamic balance, functional mobility, and risk of falls in older adults with depression

Objectives

Increased depression severity has been linked to cognitive impairment (CI). Importantly, CI is a known risk factor for impaired balance and falls. Therefore, this study aims to explore the relationship between CI and neuromuscular functions and secondarily it aims to find out if CI is a potential predictor for neuromuscular functions deficits in depressed elderly.

Methods

Eighty-four depressed elderly participated in the study. Assessment for CI symptoms were done using Mini Mental Status Examination (MMSE) in subjects having confirmed depression. Neuromuscular functions such as balance confidence, static and dynamic balance, functional mobility, and fall risk were subjectively assessed using Activities-specific Balance Confidence (ABC) Scale, Berg Balance Scale (BBS), Timed Up and Go (TUG) Test, and Performance Oriented Mobility Assessment (POMA), respectively.

Results

Pearson's analysis revealed that there was moderate positive linear-correlation between MMSE and BBS (R = 0.382, p = <0.001) and between MMSE and ABC (R = 0.229, p = 0.036*). Further, regression analysis (R 2) revealed that MMSE significantly predicted the neuromuscular functions using BBS [F(1, 82) = 14.013, p < 0.001, with an R 2 of 0.146] and ABC [F(1, 82) = 4.545, p= 0.036*, with an R 2 of 0.053].

Conclusion

Results of this study points to an impaired CI as a possible factor in development of neuromuscular function impairment in depressed elderly.

Concurrent Validity of Dual-Task Walking Speed With CERAD-NP Assessment Battery in Community-Dwelling Older Adults

Objective

To explore the concurrent validity of the dual-task walking speed assessments in older adults using the Consortium to Establish a Registry for Alzheimer's Disease Neuro-Psychological (CERAD-NP) Assessment Battery.

Design

Cross-sectional design.

Setting

Welfare care centers, Senior complex centers, and Dementia prevention care centers.

Participants

A total of 163 community-dwelling older adults (N=163) were recruited using consecutive sampling. Participants were composed of 65 older adults with cognitive decline and 98 without cognitive decline.

Interventions

Not applicable.

Main Outcome Measures

This study assessed the concurrent validity between dual-task walking speed assessments and the Total II score of CERAD-NP using Spearman's rank order correlations. The effect of the dual-task walking speed assessments on the Total II score was further investigated through multiple linear regression analysis.

Results

There was a moderate and statically significant association between the Total II score and all 8 dual-task walking speed assessments (P<.05). The Total II score was strongly associated with the dual tasks of walking on a straight path while counting backward and crossing over an obstacle (r=0.698, r=0.697, respectively; P<.05). According to multiple linear regression, only the dual task of walking while counting backward was significantly associated with the Total II score (P<.05).

Conclusion

The dual-task walking speed assessments, which involved walking and performing a secondary task such as counting backward or crossing an obstacle on a straight path, were highly indicative of cognitive decline. The combination of results from both tasks may provide a more comprehensive evaluation of cognitive decline compared with relying solely on a single-task assessment.

Does listening to audiobooks affect gait behavior?

BACKGROUND

The effect of listening to audiobooks, podcasts, and other audio files while walking on gait performance has not been well studied. Although the number of audio users is growing annually. Evidence suggests that a posture-first strategy contributes to gait stability in healthy individuals during dual-task conditions, but this effect may be diminished when the cognitive task is consciously prioritized.

OBJECTIVES

To study the effect of listening to an audiobook while walking, as a daily life-like dual-task, on spatiotemporal gait parameters.

METHODS

Forty young healthy (24.05 ± 3.66) subjects participated in the study. Spatiotemporal gait parameters were measured for 5 min on a treadmill once without (single-task) and once while listening to an audiobook through over-ear headphones (dual-task). Measured parameters included spatiotemporal parameters, gait phases, maximum pressure, and dual-task cost. Data were statistically analyzed using SPSS software.

RESULTS

There were no significant differences in any of the studied parameters between the single- and dual-task conditions, even though the subjective cognitive load of listening to audiobooks while walking was high. However, participants with different habits had significant differences in gait phases and maximum pressure. Rare listeners had a shorter stance phase, a longer swing phase, and a higher maximum pressure on the dominant heel. They also had significant differences in dual-task costs.

CONCLUSION

No differences in the spatiotemporal gait parameters for walking with and without listening to audiobooks, as a daily life-like dual-task, were observed. However, the difference between participants who listened rarely and participants who listened often may confirm the "posture first" strategy in young healthy people.

TRIAL REGISTRATION

DRKS00025837, retrospectively registered on 23.11.2021.

Spatiotemporal gait characteristics during single- and dual-task walking are associated with the burden of cerebral small vessel disease

Introduction

Gait impairment is a common symptom among individuals with cerebral small vessel disease (CSVD). However, performance differences between single-task walking (STW) and dual-task walking (DTW) among individuals with CSVD remain unclear. Therefore, we aimed to examine differences in gait characteristics during STW and DTW as well as the association between gait performance and neuroimaging markers.

Methods

We enrolled 126 older individuals with CSVD. The speed, cadence, stride length, stride time, and their dual-task cost (DTC) or variability were measured under the STW, motor-cognitive DTW (cognitive DTW), and motor-motor DTW (motor DTW) conditions. We examined neuroimaging features such as white matter hyperintensities (WMHs), lacunes, microbleeds, and total burden. Further, we analysed the association of neuroimaging markers with gait performance, including gait variability and DTC.

Results

Almost all spatiotemporal characteristics, as well as their DTCs or variabilities, showed significant among-group differences according to disease severity in the cognitive DTW condition; however, relatively lesser differences were observed in the STW and motor DTW conditions. The total CSVD burden score was moderately correlated with all the spatial parameters, as well as their DTCs or variabilities, in the cognitive DTW condition. Moreover, WMHs showed a correlation with speed, stride time, and cadence, as well as their DTCs, in the cognitive DTW condition. Furthermore, lacunes showed a moderate correlation with speed, stride length, and the DTC of speed, whilst microbleeds were only related to the DTC of stride length in the cognitive DTW condition. Neuroimaging biomarkers were not correlated with spatiotemporal parameters in STW and motor DTW conditions after Bonferroni correction. Moreover, the correlation coefficient between the total CSVD burden score and gait parameters was greater than those of other biomarkers.

Discussion

Parameters in the cognitive DTW condition are more appropriate than those in the motor DTW condition for the evaluation of gait abnormalities in patients with CSVD. Moreover, the total CSVD burden score might have better predictive utility than any single neuroimaging marker. Patients with CSVD, especially those with moderate-to-severe disease, should concentrate more on their gait patterns and reduce the load of secondary cognitive tasks whilst walking in daily life.

Neuromuscular assessment of force development, postural, and gait performance under cognitive-motor dual-tasking in healthy older adults and people with early Parkinson's disease: Study protocol for a cross-sectional Mobile Brain/Body Imaging (MoBI) study

Background

Neuromuscular dysfunction is common in older adults and more pronounced in neurodegenerative diseases. In Parkinson's disease (PD), a complex set of factors often prevents the effective performance of activities of daily living that require intact and simultaneous performance of the motor and cognitive tasks.

Methods

The cross-sectional study includes a multifactorial mixed-measure design. Between-subject factor grouping the sample will be Parkinson's Disease (early PD vs. healthy). The within-subject factors will be the task complexity (single- vs. dual-task) in each motor activity, i.e., overground walking, semi-tandem stance, and isometric knee extension, and a walking condition (wide vs. narrow lane) will be implemented for the overground walking activity only. To study dual-task (DT) effects, in each motor activity participants will be given a secondary cognitive task, i.e., a visual discrimination task for the overground walking, an attention task for the semi-tandem, and mental arithmetic for the isometric extension. Analyses of DT effects and underlying neuronal correlates will focus on both gait and cognitive performance where applicable. Based on an a priori sample size calculation, a total N = 42 older adults (55-75 years) will be recruited. Disease-specific changes such as laterality in motor unit behavior and cortical control of movement will be studied with high-density surface electromyography and electroencephalography during static and dynamic motor activities, together with whole-body kinematics.

Discussion

This study will be one of the first to holistically address early PD neurophysiological and neuromuscular patterns in an ecologically valid environment under cognitive-motor DT conditions of different complexities. The outcomes of the study aim to identify the biomarker for early PD either at the electrophysiological, muscular or kinematic level or in the communication between these systems.

Clinical Trial Registration

ClinicalTrials.Gov, NCT05477654. This study was approved by the Medical Ethical Committee (106/2021).

Effects of Whole-Body Vibration Training on Lower Limb Muscle Strength and Physical Performance Among Older Adults: A Systematic Review and Meta-analysis

OBJECTIVE

To evaluate the effects of whole-body vibration training (WBVT) on lower limb muscle strength and physical performance in older adults.

DATA SOURCES

Web of Science, PubMed, Cochrane Library, and MEDLINE databases were searched for papers published in English, from January 1, 2000, to May 30, 2022.

STUDY SELECTION

Randomized controlled trials of WBVT in older adults (mean age, 65 years or older) published in English. The Physiotherapy Evidence Database Scale was used to assess the quality of the selected studies.

DATA EXTRACTION

Two investigators independently assessed articles according to the evaluation criteria. Differences between investigator assessments were resolved by consulting a third investigator before reassessment.

DATA SYNTHESIS

Systematic review of 18 randomized controlled studies found that WBVT produced significant improvements in lower limb muscle strength and physical performance among older adults. We used the Cochrane Collaboration method to assess risk of bias and RevMan version 5.4a to extract means and calculate SDs. WBVT significantly improved knee strength (standard mean difference [SMD]=0.72, 95% confidence interval [CI] [0.38, 1.07], P<.0001, I2=58%) and explosive power (SMD=0.47, 95% CI [0.10, 0.83], P=.01, I2=0%) among older adults. Significant improvements in each physical performance were observed in the sit-to-stand test (SMD=0.57, 95% CI [0.30, 0.84], P<.0001, I2=35%), the subgroup of studies that evaluated balance with timed Up and Go test, SMD was 0.53 (95% CI [0.19, 0.88], P=.002, I2=56%) and the Tinetti total score, SMD was 0.72 (95% CI [0.04, 1.41], P=.04, I2=81%), walking speed (SMD=0.46, 95% CI [0.14, 0.77], P=.005, I2=49%), and walking endurance (SMD=0.43, 95% CI [0.02, 0.85], P=.04, I2=24%).

CONCLUSIONS

WBVT may be an effective intervention to improve lower limb muscle strength and physical performance in older adults. Tinetti total score remains controversial and warrants assessment in future high-quality randomized controlled trials.

High-velocity resistance training improves executive function in mobility-limited older adults

OBJECTIVES

To examine the effect of high-velocity resistance training (HVRT) on the executive function of middle-aged and older adults with and without mobility limitations.

METHODS

Participants (n = 41, female: 48.9%) completed a supervised 12-week HVRT intervention (2 sessions/week; at 40-60% of one-repetition maximum). The sample included 17 middle-aged adults (40-55 years); 16 older adults (>60 years) and 8 mobility-limited older adults (LIM). Executive function was assessed before and after the intervention period and was reported as z-scores. Maximal dynamic strength, peak power, quadriceps muscle thickness, maximal isometric voluntary contraction (MVIC), and functional performance were also measured pre and post intervention. Training-related adaptations in cognitive measures were calculated using a Generalized Estimating Equation model.

RESULTS

HVRT improved executive function in LIM (adjusted marginal mean differences [AMMD]: 0.21; 95%CI: 0.04, 0.38; p = 0.040) although no effect on middle-aged (AMMD: 0.04; 95%CI: -0.09; 0.17; p = 0.533) and older (AMMD: -0.11; 95%CI: -0.25; 0.02; p = 0.107) participants was observed. Improvements in maximal dynamic strength, peak power, MVIC, quadriceps muscle thickness, and functional performance were all associated with changes in executive function, and changes in the first four also seem to mediate the association between changes in functional performance and executive function.

CONCLUSIONS

HVRT-induced improvement in executive function of mobility-limited older adults were mediated by changes in lower-body muscle strength, power, and muscle thickness. Our findings reinforce the relevance of muscle-strengthening exercises to preserve cognition and mobility in older adults.

An Exploratory Study of Walking, Listening, and Remembering in Younger and Middle-Aged Adults

PURPOSE

The purpose of this study was to assess how needing to listen and remember information while walking affects speech perception, memory task performance, and gait in younger and middle-aged adults.

METHOD

Four gait parameters (stride duration, step variability, whole-body center of mass acceleration, and mediolateral head acceleration) were measured when younger and middle-aged participants stood or walked on a treadmill while they simultaneously completed a speech-on-speech perception task and a preload memory task, singly and in combination.

RESULTS

Speech perception was significantly poorer for middle-aged than for younger participants. Performance on the speech perception measure did not differ significantly between walking and standing for either group of participants, but the additional cognitive load of the memory task reduced performance on the speech perception task. Memory task performance was significantly poorer when combined with the speech perception task than when measured in isolation for both participant groups, but no further declines were noted when participants were also walking. Mediolateral head acceleration, which has been linked to loss of balance, was significantly greater during multitask trials, as compared to when participants were only walking without being required to listen or remember. Post hoc analysis showed that dual- and multitask influences on mediolateral head acceleration were more prominent for middle-aged than for younger participants. Stride duration was longer in the multitask condition than when participants were only walking.

CONCLUSIONS

Results of this exploratory study indicate that gait may be impacted when individuals (both younger and middle-aged) are listening and remembering while walking. Data also substantiate prior findings of early age-related declines in the perception of speech in the presence of understandable speech maskers.

Spatiotemporal gait parameter fluctuations in older adults affected by mild cognitive impairment: comparisons among three cognitive dual-task tests

BACKGROUNDS

Gait disorder is associated with cognitive functional impairment, and this disturbance is more pronouncedly when performing additional cognitive tasks. Our study aimed to characterize gait disorders in mild cognitive impairment (MCI) under three dual tasks and determine the association between gait performance and cognitive function.

METHODS

A total of 260 participants were enrolled in this cross-sectional study and divided into MCI and cognitively normal control. Spatiotemporal and kinematic gait parameters (31 items) in single task and three dual tasks (serial 100-7, naming animals and words recall) were measured using a wearable sensor. Baseline characteristics of the two groups were balanced using propensity score matching. Important gait features were filtered using random forest method and LASSO regression and further described using logistic analysis.

RESULTS

After matching, 106 participants with MCI and 106 normal controls were recruited. Top 5 gait features in random forest and 4 ~ 6 important features in LASSO regression were selected. Robust variables associating with cognitive function were temporal gait parameters. Participants with MCI exhibited decreased swing time and terminal swing, increased mid stance and variability of stride length compared with normal control. Subjects walked slower when performing an extra dual cognitive task. In the three dual tasks, words recall test exhibited more pronounced impact on gait regularity, velocity, and dual task cost than the other two cognitive tests.

CONCLUSION

Gait assessment under dual task conditions, particularly in words recall test, using portable sensors could be useful as a complementary strategy for early detection of MCI.

Implicit Motor Learning Strategies Benefit Dual-Task Performance in Patients with Stroke

Background and Objectives: In stroke rehabilitation, the use of either implicit or explicit learning as a motor learning approach during dual tasks is common, but it is unclear which strategy is more beneficial. This study aims to determine the benefits of implicit versus explicit motor learning approaches in patients with stroke. Materials and Methods: Seventeen patients with stroke and 21 control participants were included. Motor learning was evaluated using the Serial Reaction Time Task (SRTT) in the context of dual-task conditions. The SRTT was conducted on two separate days: one day for implicit learning conditions and the other day for explicit learning conditions. Under the explicit learning conditions, a task rule was given to the participants before they started the task, but not under the implicit learning conditions. Learning scores were calculated for both implicit and explicit learning, and these scores were then compared within groups for patients with stroke and controls. We calculated the difference in learning scores between implicit and explicit learning and conducted a correlation analysis with the Trail Making Test (TMT) Parts A and B. Results: Learning scores on the SRTT were not different between implicit and explicit learning in controls but were significantly greater in patients with stroke for implicit learning than for explicit learning. The difference in learning scores between implicit and explicit learning in patients with stroke was correlated with TMT-A and showed a correlation trend with TMT-B. Conclusions: Implicit learning approaches may be effective in the acquisition of motor skills with dual-task demands in post-stroke patients with deficits in attention and working memory.

"PNP slows down" - linearly-reduced whole body joint velocities and altered gait patterns in polyneuropathy

Introduction

Gait disturbances are a common consequence of polyneuropathy (PNP) and a major factor in patients' reduced quality of life. Less is known about the underlying mechanisms of PNP-related altered motor behavior and its distribution across the body. We aimed to capture whole body movements in PNP during a clinically relevant mobility test, i.e., the Timed Up and Go (TUG). We hypothesize that joint velocity profiles across the entire body would enable a deeper understanding of PNP-related movement alterations. This may yield insights into motor control mechanisms responsible for altered gait in PNP.

Methods

20 PNP patients (61 ± 14 years) and a matched healthy control group (CG, 60 ± 15 years) performed TUG at (i) preferred and (ii) fast movement speed, and (iii) while counting backward (dual-task). We recorded TUG duration (s) and extracted gait-related parameters [step time (s), step length (cm), and width (cm)] during the walking sequences of TUG and calculated center of mass (COM) velocity [represents gait speed (cm/s)] and joint velocities (cm/s) (ankles, knees, hips, shoulders, elbows, wrists) with respect to body coordinates during walking; we then derived mean joint velocities and ratios between groups.

Results

Across all TUG conditions, PNP patients moved significantly slower (TUG time, gait speed) with prolonged step time and shorter steps compared to CG. Velocity profiles depend significantly on group designation, TUG condition, and joint. Correlation analysis revealed that joint velocities and gait speed are closely interrelated in individual subjects, with a 0.87 mean velocity ratio between groups.

Discussion

We confirmed a PNP-related slowed gait pattern. Interestingly, joint velocities in the rest of the body measured in body coordinates were in a linear relationship to each other and to COM velocity in space coordinates, despite PNP. Across the whole body, PNP patients reduce, on average, their joint velocities with a factor of 0.87 compared to CG and thus maintain movement patterns in terms of velocity distributions across joints similarly to healthy individuals. This down-scaling of mean absolute joint velocities may be the main source for the altered motor behavior of PNP patients during gait and is due to the poorer quality of their somatosensory information.

Clinical Trial Registration

https://drks.de/search/de, identifier DRKS00016999.

Continuous peripersonal tracking accuracy is limited by the speed and phase of locomotion

Recent evidence suggests that perceptual and cognitive functions are codetermined by rhythmic bodily states. Prior investigations have focused on the cardiac and respiratory rhythms, both of which are also known to synchronise with locomotion-arguably our most common and natural of voluntary behaviours. Compared to the cardiorespiratory rhythms, walking is easier to voluntarily control, enabling a test of how natural and voluntary rhythmic action may affect sensory function. Here we show that the speed and phase of human locomotion constrains sensorimotor performance. We used a continuous visuo-motor tracking task in a wireless, body-tracking virtual environment, and found that the accuracy and reaction time of continuous reaching movements were decreased at slower walking speeds, and rhythmically modulated according to the phases of the step-cycle. Decreased accuracy when walking at slow speeds suggests an advantage for interlimb coordination at normal walking speeds, in contrast to previous research on dual-task walking and reach-to-grasp movements. Phasic modulations of reach precision within the step-cycle also suggest that the upper limbs are affected by the ballistic demands of motor-preparation during natural locomotion. Together these results show that the natural phases of human locomotion impose constraints on sensorimotor function and demonstrate the value of examining dynamic and natural behaviour in contrast to the traditional and static methods of psychological science.