The assistive potential of functional electrical stimulation to support object manipulation in functional upper extremity movements after stroke: A randomized cross-over study.

Background: After standard care, 55%-75% of patients after stroke show a persistent paresis of the upper limb (UL). Assistive devices are developed to increase the patients' level of independence in daily life. Objectives: To investigate the potential of Functional Electrical Stimulation (FES) to assist object manipulation in activities of daily life. Design: Seventeen patients after stroke were tested and analyzed in a randomized cross-over design. Methods: Functional grasping was assessed by means of the Action Research Arm Test (ARAT) and the modified Box and Block Test (mBBT), in one session with and another without FES assistance. The order of sessions was randomized. Patients' motivation was assessed after each session. Task performance and motivation were compared between conditions using the Wilcoxon test and subgroup analyses were performed for impairment severity by distribution-based mixed-factor analyses. Results: When analyzing the total ARAT, FES did not effectively assist the overall performance (P = .142), but did assist the performance of objects of the Grasp category (P = .020). Impairment severity showed an interaction with the orthotic effect (P = .012), as severely impaired patients profited from FES assistance and mild-moderately impaired did not. When focusing on the more functional items of the ARAT (i.e., excluding scores from thumb-middle and thumb-ring finger combinations), there was a significant orthotic effect of FES on task performance (P = .023). Further, there was an orthotic effect for the number of transported blocks in the mBBT (P = .033), exclusively prominent in the group of severely impaired patients. Functional Electrical Stimulation did not increase the patients' motivation (P = .959), which was high after both conditions. Conclusion: Functional Electrical Stimulation has the potential to support object manipulation, but is dependent on impairment severity and object type. To observe a consistent orthotic effect, features of the stimulator should be further developed to generate appropriate grasps and forces across subjects and objects. Trial Registration: The trial was registered with the German Clinical Trials Register (DRKS00025889).

Neuromuscular effects suggest that imagery engages motor components directly - a commentary on Frank et al. (2023).

Not applicable.

A prospective investigation of the effects of soccer heading on cognitive and sensorimotor performances in semi-professional female players.

Introduction: Repetitive head impacts (RHI) from routine soccer (football) heading have been suggested to contribute to the long-term development of neurodegenerative disorders. However, scientific evidence concerning the actual risk of these RHI on brain health remains inconclusive. Moreover, female athletes-despite a presumably increased vulnerability toward the effects of RHI-are largely underrepresented in previous approaches. Therefore, our aim was to prospectively investigate the effects of heading on cognitive and sensorimotor performances, health perception, and concussion symptoms in semi-professional female soccer players. Methods: An extensive test battery was used to assess cognitive and sensorimotor performances as well as health status (SF-36) and concussion symptoms (SCAT3) of a total of 27 female soccer players (22.2 ± 4.2 years) and 15 control subjects (23.2 ± 3.0 years) before and after one-and-a-half years. Throughout this period, soccer players' heading exposure was determined using video analysis. Results: Subgroup comparisons (control [n = 12], low exposure [n = 7], high exposure [n = 8]) showed no time-dependent differences in SF-36 or SCAT3 scores. Similarly, across most behavioral tests, soccer players' performances evolved equally or more favorably as compared to the control subjects. However, there were significant effects pointing toward slightly negative consequences of heading on aspects of fine motor control (p = 0.001), which were confirmed by correlation and multiple regression analyses. The latter, further, yielded indications for a relationship between heading exposure and negative alterations in postural control (p = 0.002). Discussion: Our findings do not provide evidence for negative effects of soccer heading on female players' health perception, concussion symptoms, and cognitive performances over the course of one-and-a-half years. However, we found subtle negative alterations in fine motor and postural control that could be attributed to heading exposure. Other factors, like the number of previous head injuries, were not linked to the observed changes. Given the reduction of our initial sample size due to player fluctuation, the results need to be interpreted with caution and validated in larger-scale studies. These should not only focus on cognitive outcomes but also consider sensorimotor changes as a result of RHI from soccer heading.

The efficacy of hybrid neuroprostheses in the rehabilitation of upper limb impairment after stroke, a narrative and systematic review with a meta-analysis.

BACKGROUND: Paresis of the upper limb (UL) is the most frequent impairment after a stroke. Hybrid neuroprostheses, i.e., the combination of robots and electrical stimulation, have emerged as an option to treat these impairments. METHODS: To give an overview of existing devices, their features, and how they are linked to clinical metrics, four different databases were systematically searched for studies on hybrid neuroprostheses for UL rehabilitation after stroke. The evidence on the efficacy of hybrid therapies was synthesized. RESULTS: Seventy-three studies were identified, introducing 32 hybrid systems. Among the most recent devices (n = 20), most actively reinforce movement (3 passively) and are typical exoskeletons (3 end-effectors). If classified according to the International Classification of Functioning, Disability and Health, systems for proximal support are expected to affect body structures and functions, while the activity and participation level are targeted when applying Functional Electrical Stimulation distally plus the robotic component proximally. The meta-analysis reveals a significant positive effect on UL functions (p < 0.001), evident in a 7.8-point Mdiff between groups in the Fugl-Meyer assessment. This positive effect remains at the 3-month follow-up (Mdiff = 8.4, p < 0.001). CONCLUSIONS: Hybrid neuroprostheses have a positive effect on UL recovery after stroke, with effects persisting at least three months after the intervention. Non-significant studies were those with the shortest intervention periods and the oldest patients. Improvements in UL functions are not only present in the subacute phase after stroke but also in long-term chronic stages. In addition to further technical development, more RCTs are needed to make assumptions about the determinants of successful therapy.

Outside the Laboratory Assessment of Upper Limb Laterality in Patients With Stroke: A Cross-Sectional Study.

BACKGROUND: The rehabilitation of upper limb sensorimotor performance after stroke requires the assessment of daily use, the identification of key levels of impairment, and monitoring the course of recovery. It needs to be answered, how laboratory-based assessments and everyday behavior are connected, which dimension of metrics, that is, volume, intensity, or quality, is most sensitive to reduced function, and what sensor, that is, gyroscope or accelerometer, is best suited to gather such data. METHODS: Performance in laboratory-based sensorimotor tests, as well as smartwatch-derived kinematic data of everyday life relative upper limb activity, during 1 day of inpatient neurorehabilitation (Germany, 2022) of 50 patients with stroke, was cross-sectionally assessed and resulting laterality indices (performance ratios) between the limbs were analyzed using ANCOVAs and principal component analysis. RESULTS: Laboratory-based tests revealed the strongest laterality indices, followed by smartwatch-based (intensity>quality>volume) metrics. Angular velocity-based metrics revealed higher laterality indices than acceleration-based ones. Laterality indices were overall well associated; however, a principal component analysis suggested upper limb impairments to be unidimensional. CONCLUSIONS: Our findings suggest that the use of sensors can deliver valid information of stroke-related laterality. It appeared that commonly used metrics that estimate the volume of use (ie, energy expenditure) are not the most sensitive. Especially reached intensities could be well used for monitoring, because they are more dependent on the performance of the sensorimotor system and less on confounders like age. The unidimensionality of the upper limb laterality suggests that an impaired limb with reduced movement quality and the inability to reach higher intensities will be used less in everyday life, especially when it is the nondominant side.

Corrigendum: Smoothness metrics in complex movement tasks.

[This corrects the article DOI: 10.3389/fneur.2018.00615.].

Investigating the effects of the aging brain on real tool use performance-an fMRI study.

Introduction: Healthy aging affects several domains of cognitive and motor performance and is further associated with multiple structural and functional neural reorganization patterns. However, gap of knowledge exists, referring to the impact of these age-related alterations on the neural basis of tool use-an important, complex action involved in everyday life throughout the entire lifespan. The current fMRI study aims to investigate age-related changes of neural correlates involved in planning and executing a complex object manipulation task, further providing a better understanding of impaired tool use performance in apraxia patients. Methods: A balanced number of sixteen older and younger healthy adults repeatedly manipulated everyday tools in an event-related Go-No-Go fMRI paradigm. Results: Our data indicates that the left-lateralized network, including widely distributed frontal, temporal, parietal and occipital regions, involved in tool use performance is not subjected to age-related functional reorganization processes. However, age-related changes regarding the applied strategical procedure can be detected, indicating stronger investment into the planning, preparatory phase of such an action in older participants.

Going beyond PA: Assessing sensorimotor capacity with wearables in multiple sclerosis-a cross-sectional study.

BACKGROUND: Wearable technologies are currently clinically used to assess energy expenditure in a variety of populations, e.g., persons with multiple sclerosis or frail elderly. To date, going beyond physical activity, deriving sensorimotor capacity instead of energy expenditure, is still lacking proof of feasibility. METHODS: In this study, we read out sensors (accelerometer and gyroscope) of smartwatches in a sample of 90 persons with multiple sclerosis over the course of one day of everyday life in an inpatient setting. We derived a variety of different kinematic parameters, in addition to lab-based tests of sensorimotor performance, to examine their interrelation by principal component, cluster, and regression analyses. RESULTS: These analyses revealed three components of behavior and sensorimotor capacity, namely clinical characteristics with an emphasis on gait, gait-related physical activity, and upper-limb related physical activity. Further, we were able to derive four clusters with different behavioral/capacity patterns in these dimensions. In a last step, regression analyses revealed that three selected smartwatch derived kinematic parameters were able to partially predict sensorimotor capacity, e.g., grip strength and upper-limb tapping. CONCLUSIONS: Our analyses revealed that physical activity can significantly differ between persons with comparable clinical characteristics and that assessments of physical activity solely relying on gait can be misleading. Further, we were able to extract parameters that partially go beyond physical activity, with the potential to be used to monitor the course of disease progression and rehabilitation, or to early identify persons at risk or a sub-clinical threshold of disease severity.

Patients With Dupuytren Disease Use Excessive Grip Force When Lifting and Holding Small Objects, Independent of the Degree of Contracture.

OBJECTIVE: To identify the extent and quality of fine motor skill alteration in patients with Dupuytren disease (DD) using an instrumented device measuring grip forces, beyond the commonly used measurement of contracture. DESIGN: Case-control study. SETTING: University outpatient clinic. PARTICIPANTS: Patients with DD (N=27) and a contracture >45° (Tubiana stage II, III, and IV) were included and compared with age-matched healthy control patients (N=27). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES(S): All individuals were subjected to a set of specific tests using a new instrumented device ("manipulandum"). These included lifting, grasping, and then holding the "manipulandum" with 4 different object characteristics (light and heavy weight, rough and smooth surface) along with a measurement of the precision grip strength. Standard measurements including the Nine-Hole Peg Test, a two-point discrimination, and the Disability of Arm, Shoulder and Hand score were evaluated in comparison. RESULTS: Although the measurements of precision grip, two-point discrimination, Nine-Hole Peg Test, and Disability of Arm, Shoulder and Hand score showed no statistically significant differences between both groups, patients with DD applied significantly greater forces when tested with the different subtests using the "manipulandum." Analysis of the 2-phase movement (lifting and holding the "manipulandum") revealed highly significant differences between the groups. CONCLUSIONS: Patients with DD use excessive grip forces when lifting and holding the "manipulandum" when compared with healthy control patients, independent of the degree of contracture. As no differences in precision grip strength were seen, the presented approach is useful to obtain additional important information about fine motor function in diseased hands.

Effectiveness of an evidence-based care pathway to improve mobility and participation in older patients with vertigo and balance disorders in primary care (MobilE-PHY2): study protocol for a multicentre cluster-randomised controlled trial.

BACKGROUND: Vertigo, dizziness or balance disorders (VDB) are common leading symptoms in older people, which can have a negative impact on their mobility and participation in daily live, yet, diagnosis is challenging and specific treatment is often insufficient. An evidence-based, multidisciplinary care pathway (CPW) in primary care was developed and pilot tested in a previous study. The aim of the present study is to evaluate the effectiveness and safety of the CPW in terms of improving mobility and participation in community-dwelling older people with VDB in primary care. METHODS: For this multicentre cluster randomised controlled clinic trial, general practitioners (GP) will be recruited in two regions of Germany. A total of 120 patients over 60 years old with VDB will be included. The intervention is an algorithmized CPW. GPs receive a checklist for standardise clinical decision making regarding diagnostic screening and treatment of VDB. Physiotherapists (PT) receive a decision tree for evidence-based physiotherapeutic clinical reasoning and treatment of VDB. Implementation strategies comprises educational trainings as well as a workshop to give a platform for exchange for the GPs and PTs, an information meeting and a pocket card for home care nurses and informal caregivers and telephone peer counselling to give all participants the capability, opportunity and the motivation to apply the intervention. In order to ensure an optimised usual care in the control group, GPs get an information meeting addressing the national guideline. The primary outcome is the impact of VDB on participation and mobility of patients after 6 month follow-up, assessed using the Dizziness Handicap Inventory (DHI) questionnaire. Secondary outcomes are physical activity, static and dynamic balance, falls and fear of falling as well as quality of life. We will also evaluate safety and health economic aspects of the intervention. Behavioural changes of the participants as well as barriers, facilitating factors and mechanisms of impact of the implementation will be investigated with a comprehensive process evaluation in a mixed-methods design. DISCUSSION: With our results, we aim to improve evidence-based health care of community-dwelling older people with VDB in primary care. TRIAL REGISTRATION: DRKS, DRKS00028524 retrospectively registered on March 24, 2022.

Handwriting kinematics during learning to write with the dominant left hand in converted left-handers.

Converting left-handers to their non-dominant right hand was previously widespread, particularly for handwriting. The present study aimed to explore the extent to which adult, converted left-handers can learn writing with their dominant left hand during a 2-year training program. Eleven converted left-handers participated in the training. Handwriting kinematics were assessed at regular intervals (seven sessions) and compared to those of 11 innate left-handed controls matched for age, gender, and overall handedness score for basic (Finger, Wrist, Circle) and complex (Sentence, Copy) handwriting tasks. Regarding basic tasks in the training group, we found rapid increases in left and right-hand frequency and no significant differences between both hands at any time point, indicating successful hand transfer. After 24 months, training participants significantly surpassed controls for writing frequency in basic tasks with their left hand. For complex tasks, we identified significant increases in the training groups' left-hand writing frequency and duration between the first and last session. While training participants' left-hand writing remained significantly slower than their right-hand writing, statistics confirmed final differences between hands only for the duration of the Sentence task. Importantly, left-hand writing in the training group was characterized by lower frequency, lower automaticity, and prolonged duration after 24 months compared to innate left-handers. With training participants' left-hand writing skills significantly increasing for complex tasks and no final statistically significant differences between hands for frequency and automaticity, the program was considered effective. Nevertheless, within 2 years, training participants did not reach innate left-handers handwriting proficiency for complex tasks. Underlying reasons may be various, such as a non-optimal training program, a sensitive period for learning to write, irreversible neural changes during conversion in childhood, age-related decline of motor learning capacity, or retrograde interference between right- and left-hand writing.

Writing while walking: The impact of cognitive-motor multi-tasking on collision avoidance in human locomotion.

BACKGROUND: When moving in public space, individuals are challenged with having to master multiple cognitive and motor demands, either simultaneously or in short succession. Empirical evidence suggests that cognitive-motor multi-tasking during walking may impact one or both, cognitive and motor performance. These performance changes may result from unintentional task-interference effects, but also from strategic behavioral changes to cope with the multiple task demands. Strategic changes in human walking behavior have been uncovered in experimental scenarios, in which individuals avoid colliding with other individuals or objects in the environment. However, whether collision avoidance behavior is sensitive to cognitive-motor multi-task demands has remained underexplored, yet. Thus, with this study, we aimed at systematically studying cognitive-motor multi-task effects on collision avoidance during human locomotion. METHODS: Ten healthy participants (23.9 ± 4.3 years, 4 female) were walking at their preferred speed from a predefined start to end position under four experimental conditions: walking only (BL), walking while having to avoid a collision with another person (IO), writing a text message on a mobile phone while walking (cognitive-motor dual-task, DT), and writing while walking with collision avoidance demand (multi-task, MT). Parameters quantifying locomotor as well as collision avoidance behavior (path length, walking speed, minimum distance, path and speed adjustment) were assessed using optical motion tracking. In addition, performance in the writing task (errors, writing speed) was examined. RESULTS: Participants' locomotor behavior was significantly affected by experimental conditions, with additive effects of multi-task demands on both path length (BL = DT < IO < MT) and walking speed (BL > IO > DT > MT). Further, participants showed an increased error rate and writing speed in the writing task when walking as compared to when standing still, independent of the presence of an interferer. Importantly, collision avoidance behavior was selectively influenced by cognitive-motor multi-task demands, with an increased minimum distance to the other person in the MT-condition, but no differences in path or speed adjustment. DISCUSSION: Our results suggest significant multi-tasking effects of writing a message on the mobile phone while walking on both locomotor behavior and writing task performance. Collision avoidance behavior seems to be selectively affected by multi-task demands, reflected in an increased minimum passing distance, without overt changes in path or speed adjustments. This may be indicative for a strategic change in collision avoidance behavior towards a more cautious strategy to account for altered attention allocation and less visual feedback when writing while walking.

The relationship between self-reported physical frailty and sensor-based physical activity measures in older adults - a multicentric cross-sectional study.

BACKGROUND: The decline in everyday life physical activity reflects and contributes to the frailty syndrome. While especially self-reported frailty assessments have the advantage of reaching large groups at low costs, little is known about the relationship between the self-report and objective measured daily physical activity behavior. The main objective was to evaluate whether and to what extent a self-reported assessment of frailty is associated with daily physical activity patterns. METHODS: Daily activity data were obtained from 88 elderly participants (mean 80.6 ± 9.1 years) over up to 21 days. Acceleration data were collected via smartwatch. According to the results of a self-report frailty questionnaire, participants were retrospectively split up into three groups, F (frail, n = 43), P (pre-frail, n = 33), and R (robust, n = 12). Gait- and activity-related measures were derived from the built-in step detector and acceleration sensor and comprised, i.a., standard deviation of 5-s-mean amplitude deviation (MADstd), median MAD (MADmedian), and the 95th percentile of cadence (STEP95). Parameters were fed into a PCA and component scores were used to derive behavioral clusters. RESULTS: The PCA suggested two components, one describing gait and one upper limb activity. Mainly gait related parameters showed meaningful associations with the self-reported frailty score (STEP95: R2 = 0.25), while measures of upper limb activity had lower coefficients (MADmedian: R2 = 0.07). Cluster analysis revealed two clusters with low and relatively high activity in both dimensions (cluster 2 and 3). Interestingly, a third cluster (cluster 1) was characterized by high activity and low extent of ambulation. Comparisons between the clusters showed significant differences between activity, gait, age, sex, number of chronic diseases, health status, and walking aid. Particularly, cluster 1 contained a higher number of female participants, whose self-reports tended towards a low health status, the frequent use of a walking aid, and a higher score related to frailty questions. CONCLUSIONS: The results demonstrate that subjective frailty assessments may be a simple first screening approach. However, especially older women using walking aids may classify themselves as frail despite still being active. Therefore, the results of self-reports may be particularly biased in older women.

A neural network for the detection of soccer headers from wearable sensor data.

To investigate the proposed association between soccer heading and deleterious brain changes, an accurate quantification of heading exposure is crucial. While wearable sensors constitute a popular means for this task, available systems typically overestimate the number of headers by poorly discriminating true impacts from spurious recordings. This study investigated the utility of a neural network for automatically detecting soccer headers from kinematic time series data obtained by wearable sensors. During 26 matches, 27 female soccer players wore head impacts sensors to register on-field impact events (> 8 g), which were labelled as valid headers (VH) or non-headers (NH) upon video review. Of these ground truth data, subsets of 49% and 21% each were used to train and validate a Long Short-Term Memory (LSTM) neural network in order to classify sensor recordings as either VH or NH based on their characteristic linear acceleration features. When tested on a balanced dataset comprising 271 VHs and NHs (which corresponds to 30% and 1.4% of ground truth VHs and NHs, respectively), the network showed very good overall classification performance by reaching scores of more than 90% across all metrics. When testing was performed on an unbalanced dataset comprising 271 VHs and 5743 NHs (i.e., 30% of ground truth VHs and NHs, respectively), as typically obtained in real-life settings, the model still achieved over 90% sensitivity and specificity, but only 42% precision, which would result in an overestimation of soccer players' true heading exposure. Although classification performance suffered from the considerable class imbalance between actual headers and non-headers, this study demonstrates the general ability of a data-driven deep learning network to automatically classify soccer headers based on their linear acceleration profiles.

Object-centered sensorimotor bias of torque control in the chronic stage following stroke.

When lifting objects whose center of mass (CoM) are not centered below the handle one must compensate for arising external torques already at lift-off to avoid object tilt. Previous studies showed that finger force scaling during object lifting may be impaired at both hands following stroke. However, torque control in object manipulation has not yet been studied in patients with stroke. In this pilot study, thirteen patients with chronic stage left hemispheric stroke (SL), nine patients with right hemispheric stroke (SR) and hand-matched controls had to grasp and lift an object with the fingertips of their ipsilesional hand at a handle while preventing object tilt. Object CoM and therewith the external torque was varied by either relocating a covert weight or the handle. The compensatory torque at lift-off (Tcom) is the sum of the torque resulting from (1) grip force being produced at different vertical finger positions (∆CoP × GF) and (2) different vertical load forces on both sides of the handle (∆Fy × w/2). When having to rely on sensorimotor memories, ∆CoP × GF was elevated when the object CoM was on the ipsilesional-, but decreased when CoM was on the contralesional side in SL, whereas ∆Fy × w/2 was biased in the opposite direction, resulting in normal Tcom. SR patients applied a smaller ∆CoP × GF when the CoM was on the contralesional side. Torques were not altered when geometric cues were available. Our findings provide evidence for an object-centered spatial bias of manual sensorimotor torque control with the ipsilesional hand following stroke reminiscent of premotor neglect. Both intact finger force-to-position coordination and visuomotor control may compensate for the spatial sensorimotor bias in most stroke patients. Future studies will have to confirm the found bias and evaluate the association with premotor neglect.

Influence of stance width on standing balance in healthy older adults.

Posturography is an objective way to systematically interpret postural control. Recent evidence suggests self-selected stance width when conducting posturography in healthy young participants, as it is easy to perform yet standardized. It is unclear, if this is similarly applicable to healthy older adults which can better serve as comparison group for persons with specific impairments, like Parkinson's disease, who might have problems with set foot distances. The aim of this study was to investigate the influence of different stance widths on a set of parameters in healthy older adults. Twenty-four healthy elderly (65.6 ± 5.0 years, BMI 26.2 ± 4.5 kg/m2) participated in the study. Posturographic measurement consisted of two tests (body sway, BS; limits of stability, LoS) each assessed in five stance widths on a force platform. A series of time domain and frequency domain parameters, such as BS and LoS range, sample entropy, mean velocity, and balance functional reserve were calculated. Anthropometric parameters and self-selected stance width (mean 17.7 ± 4.7 cm) showed positive correlation. One-way repeated measures MANOVA revealed significant differences between all parameters and foot positions. Except for sample entropy in A-P dimension, univariate analysis showed significant effects of stance widths on the parameters with stronger effects on M-L dimensions. Outcomes acquired in self-selected stance width provide comparable results to standardized stance widths 20 and 30 cm. The recommendation of self-selected stance width can be adopted to older healthy subjects. Furthermore, it reflects a natural stance and includes individual body composition.

Changes in thumb tapping rates and central motor conduction times are associated in persons with multiple sclerosis.

INTRODUCTION: In persons with multiple sclerosis, nerve conductivity can be reduced. The assessment is generally performed via motor evoked potentials (MEP). So far, a strongly associated motor performance surrogate for changes in the extracted central motor conduction time (CMCT) is missing. METHODS: CMCT and performance in the nine-hole peg test and maximum thumb tapping frequencies over 10 s of 12 persons with multiple sclerosis were measured prior to and after training over 5 consecutive days. Each training consisted of 10,000 thumb taps at maximum effort with the dominant upper limb. RESULTS: The dominant upper limb improved in maximum tapping frequency over 10 s (d = 0.79) and 10,000 taps (d = 1.04), the nine-hole peg test (d = 0.60), and CMCT (d = 0.52). The nondominant upper limb only improved in the nine-hole peg test (d = 0.38). Models of multiple linear regression predicted 0.78 (model 1, tapping performance as factors) and 0.87 (model 2, patient baseline characteristics as factors) of the variance in CMCT changes. DISCUSSION: Changes in CMCT were well predictable, although the assessment of those surrogates is either not economic (model 1) or rather describing a potential of change (model 2). However, we were able to show moderate changes in CMCT within 5 days.

Kinematic analysis of activities of daily living performance in frail elderly.

BACKGROUND: Frailty is accompanied by limitations of activities of daily living (ADL) and frequently associated with reduced quality of life, institutionalization, and higher health care costs. Despite the importance of ADL performance for the consequence of frailty, movement analyses based on kinematic markers during the performance of complex upper extremity-based manual ADL tasks in frail elderly is still pending. The main objective of this study was to evaluate if ADL task performance of two different tasks in frail elderlies can be assessed by an activity measurement based on an acceleration sensor integrated into a smartwatch, and further to what degree kinematic parameters would be task independent. METHODS: ADL data was obtained from twenty-seven elderly participants (mean age 81.6 ± 7.0 years) who performed two ADL tasks. Acceleration data of the dominant hand was collected using a smartwatch. Participants were split up in three groups, F (frail, n = 6), P (pre-frail, n = 13) and R (robust, n = 8) according to a frailty screening. A variety of kinematic measures were calculated from the vector product reflecting activity, agility, smoothness, energy, and intensity. RESULTS: Measures of agility, smoothness, and intensity revealed significant differences between the groups (effect sizes combined over tasks η2p = 0.18 - 0.26). Smoothness was particularly affected by frailty in the tea making task, while activity, agility, a different smoothness parameter and two intensity measures were related to frailty in the gardening task. Four of nine parameters revealed good reliability over both tasks (r = 0.44 - 0.69). Multiple linear regression for the data combined across tasks showed that only the variability of the magnitude of acceleration peaks (agility) contributed to the prediction of the frailty score (R2 = 0.25). CONCLUSION: The results demonstrate that ADL task performance can be assessed by smartwatch-based measures and further shows task-independent differences between the three levels of frailty. From the pattern of impaired and preserved performance parameters across the tested tasks, we concluded that in persons with frailty ADL performance was more impaired by physiological deficiencies, i.e., physical power and endurance, than by cognitive functioning or sensorimotor control.

Immediate Effects of Vibrotactile Biofeedback Instructions on Human Postural Control.

Vibrotactile biofeedback can improve balance and consequently be helpful in fall prevention. However, it remains unclear how different types of stimulus presentations affect not only trunk tilt, but also Center of Pressure (CoP) displacements, and whether an instruction on how to move contributes to a better understanding of vibrotactile feedback.Based on lower back tilt angles (L5), we applied individualized multi-directional vibrotactile feedback to the upper torso by a haptic vest in 30 healthy young adults. Subjects were equally distributed to three instruction groups (attractive - move in the direction of feedback, repulsive - move in the opposite direction of feedback & no instruction - with attractive stimuli). We conducted four conditions with eyes closed (feedback on/off, Narrow Stance with head extended, Semi-Tandem stance), with seven trials of 45s each. For CoP and L5, we computed Root Mean Square (RMS) of position/angle and standard deviation (SD) of velocity, and for L5 additionally, the percentage in time above threshold. The analysis consisted of mixed model ANOVAs and t-tests (α-level: 0.05).In the attractive and repulsive groups feedback significantly decreased the percentage above threshold (p<0.05). Feedback decreased RMS of L5, whereas RMS of CoP and SD of velocity in L5 and COP increased (p<0.05). Finally, an instruction on how to move contributed to a better understanding of the vibrotactile biofeedback.

Shared Representations in Athletes: Segmenting Action Sequences From Taekwondo Reveals Implicit Agreement.

How do athletes represent actions from their sport? How are these representations structured and which knowledge is shared among experts in the same discipline? To address these questions, the event segmentation task was used. Experts in Taekwondo and novices indicated how they would subjectively split videos of Taekwondo form sequences into meaningful units. In previous research, this procedure was shown to unveil the structure of internal action representations and to be affected by sensorimotor knowledge. Without specific instructions on the grain size of segmentation, experts tended to integrate over longer episodes which resulted in a lower number of single units. Moreover, in accordance with studies in figure-skating and basketball, we expected higher agreement among experts on where to place segmentation marks, i.e., boundaries. In line with this hypothesis, significantly more overlap of boundaries was found within the expert group as compared to the control group. This was observed even though the interindividual differences in the selected grain size were huge and expertise had no systematic influence here. The absence of obvious goals or objects to structure Taekwondo forms underlines the importance of shared expert knowledge. Further, experts might have benefited from sensorimotor skills which allowed to simulate the observed actions more precisely. Both aspects may explain stronger agreement among experts even in unfamiliar Taekwondo forms. These interpretations are descriptively supported by the participants' statements about features which guided segmentation and by an overlap of the group's agreed boundaries with those of an experienced referee. The study shows that action segmentation can be used to provide insights into structure and content of action representations specific to experts. The mechanisms underlying shared knowledge among Taekwondoists and among experts in general are discussed on the background of current theoretic frameworks.