Capacity Assessment Instrument - Health: Pilot Study of a New Tool for Adults with Dementia.

OBJECTIVES: This research comprises a pilot study of the CAI-Health, a new tool for the evaluation of decision-making capacity in healthcare. It aims to analyze the instrument's indicators of reliability and internal validity to conclude its final version. METHODS: A total of 89 participants were included, of which 22 had Alzheimer's Disease; 32 had mild cognitive impairment, and 35 were controls. Cronbach's alpha and the intercorrelation matrix were used as indicators of reliability and internal validity as well as to identify items for elimination. Repeated-measures ANOVA allowed for the analysis of differences between the vignettes that comprise CAI-Health. RESULTS: The internal consistency results were acceptable, and no items were proposed for elimination. A repeated-measures ANOVA revealed that the vignettes were unexpectedly equivalent. Despite the procedures used to develop clinical vignettes with increased levels of complexity in assessing decision-making capacity, this study showed no differences in the vignettes' level of demand. CONCLUSIONS: The extensive application of CAI-Health compromises its clinical usefulness and viability. To reduce its length while maintaining a thorough assessment of each ability, it was decided to eliminate two vignettes and retain all interview items. The final version of the CAI-Health comprises a clinical vignette and a capacity interview. CLINICAL IMPLICATIONS: CAI-Health was designed for the assessment of medical decision-making capacity in older adults.

Cognitive decline complaints scale (CDCS): validation and normative studies for the adults and older adults Portuguese population.

OBJECTIVES: Subjective Cognitive Complaints, which result from the self-perception of Subjective Cognitive Decline, are frequently reported by older adults. The Cognitive Decline Complaints Scale (CDCS) assesses subjective complaints of cognitive decline in several cognitive domains through three levels of severity. This study aims to psychometrically validate this instrument considering the Classical Test Theory, and to establish preliminary normative data of the CDCS for adults and older adults of the Portuguese population. METHODS: The community-based sample consisted of 199 cognitively healthy Portuguese participants, aged 50 years or older, stratified according to several sociodemographic variables. In addition to the CDCS, all participants responded to an extensive neuropsychological assessment protocol. RESULTS: The psychometric characteristics of the CDCS were generally adequate for this community sample (e.g. Cronbach's alpha = .936). As for the sociodemographic variables analyzed, only the geographic region showed differences in the CDCS scores, which were more significant in the Azores. There were no significant correlations or differences between the CDCS scores and age and educational level and, therefore, normative data were explored considering the total sample. CONCLUSION: As a scale, the CDCS allows for the detailed assessment of subjective cognitive complaints and the determination of whether or not such complaints are considered normative, which will facilitate an empirically based understanding of this dimension of psychological functioning and also provide indications as to the need for a more extensive neuropsychological assessment.

Montreal Cognitive Assessment (MoCA): A validation study among prisoners.

BACKGROUND: There are numerous scales for screening cognitive performance and thus identification of any potential deficits, but in spite of the vulnerability of the prison population to such problems, there has been no adequate validation of screening tools specifically for use with prisoners or others in the criminal justice system. AIM: To validate the Montreal Cognitive Assessment (MoCA) for use with prisoners. METHODS: 100 adult prisoners in one Portuguese prison were randomly invited by clinicians to take part in this study. A same size sample of community-living adult non-offenders of similar age was selected from the MoCA's normative study database in Portugal. For both groups, the key inclusion criterion was fluency in the Portuguese language. All participants completed the Mini Mental State Examination (MMSE) and the MoCA, both in Portuguese translation. Cronbach's alpha coefficient was calculated as an index of internal consistency and Pearson's r correlations calculated. Group performances were compared using independent samples t-test. Covariance analysis (ANCOVA) was computed with level of education as covariate. To measure the magnitude of the effect, η p 2 ${\eta }_{p}^{2}$ was used. A receiver operating characteristics curve analysis was computed to evaluate the discriminatory accuracy of MoCA and MMSE. RESULTS: The MoCA showed a 'reasonable' internal consistency index (α = 0.75) as well as positive and significant correlations with the MMSE. As a cognitive measure, however, the MoCA showed consistently superior psychometric properties and higher discriminatory accuracy (MoCA = 89%) than the MMSE (65%). According to the Youden index, the optimal cut-off point for the MoCA is below 24 points, whereas for the MMSE, it is below 27. CONCLUSIONS: The MoCA is a valid cognitive screening tool for use with prisoners. Further validations against detailed cognitive evaluation would be a useful next step.

Decision-Making Capacity in Healthcare: Instruments Review and Reflections About its Assessment in the Elderly with Cognitive Impairment and Dementia.

The prevalence of neurodegenerative diseases has been significantly increasing in the last decades, and it is expected to continue to grow. These health disorders can impair patients' decision-making capacity in healthcare. The capacity to make healthcare decisions is a fundamental pillar of informed consent, therefore, it should be carefully assessed. Clinicians' assessment, when not supported by a standardized tool, has revealed to be unreliable, so the recourse to an instrument of capacity assessment is crucial. The present paper aims to identify and summarize published instruments of healthcare decision-making capacity. To do so, a search of peer-reviewed articles in English, Portuguese and Spanish was conducted. A total of eighteen articles, detailing seventeen assessment instruments were selected. Instruments differ on format, structure, assessed abilities and psychometric properties. Likewise, instruments' targeted population also varies, with a few being specifically developed for patients with dementia. Although a high number of instruments were found, there is still no gold standard for healthcare decision-making capacity assessment. The lack of a gold standard highlights the need for more research in this field, as well as an effort to develop guidelines and normative data, in order to improve clinical practices.

Effects of restraining measures due to COVID-19: Pre- and post-lockdown cognitive status and mental health.

The COVID-19 pandemic has prompted all countries to adopt restraining measures to mitigate the spread of the disease. Usually, large-scale disasters tend to be accompanied by significant increases of psychological distress, depression and anxiety. Confinement measures imposed during the COVID-19 pandemic are likely to have similar consequences. In the present study we aim to evaluate how COVID-19 affected the overall psychological functioning of Portuguese individuals by providing a comparison of current data with status prior to the COVID-19 pandemic. The study sample was composed of 150 cognitively healthy participants. Results show an overall maintenance of cognitive capacities, although subjective cognitive decline complaints significantly increased during the pandemic. Regarding mental health, restraining measures culminated in an aggravation of depressive and decrease of the perceived quality of life, associated with feelings of loneliness and perceived social isolation. Finally, higher levels of pre-COVID-19 quality of life seem to play a protective role against depression and anxiety and predict less difficulties in emotion regulation, feelings of solitude and cognitive complaints. In sum, confinement due to COVID-19 implied an aggravation of the mental health of the Portuguese population, which appears to have been attenuated in those with higher pre-pandemic levels of perceived quality of life.

Immediate Effects of Arm Reaching Training in Standing on Postural Control Differ between Right and Left Stroke Individuals.

BACKGROUND: Arm reaching training in standing for several weeks affects the postural control of individuals recovering from cerebrovascular accident (CVA). Whether these effects differ with the side of the brain lesion are unknown. OBJECTIVES: To examine the immediate effects of a training session of arm reaching movements on the balance and trunk motion of individuals who suffered a right or left CVA. MATERIALS AND METHODS: Thirty-six adults divided into four groups (i.e., right CVA, left CVA, right control, and left control) performed 120 reaches in a standing position toward one of three target heights. Before and after the reaching trials, participants stood as quiet as possible on two force plates and had their postural sway, trunk motion, and body weight distribution assessed. RESULTS: CVA groups showed greater postural sway regardless of the brain lesion's side compared to the control groups. After the session of reaching movements, the left stroke group reduced the postural sway and trunk displacements. Larger ranges of weight-bearing asymmetry were more frequent after the training session, mainly for the right stroke group. CONCLUSIONS: A single session training of reaching movements affects mostly the postural control of left stroke survivors. More training sessions may be needed for individuals after right stroke to show balance improvements. The current findings support the hemispheric specialization for postural control and suggest that the training involving arm movements in standing can benefit the motor rehabilitation of stroke individuals.

Synergic control of action in levodopa-naïve Parkinson's disease patients: II. Multi-muscle synergies stabilizing vertical posture.

Postural instability is a major disabling feature in Parkinson's disease (PD). We quantified the organization of leg and trunk muscles into synergies stabilizing the center of pressure (COP) coordinate within the uncontrolled manifold hypothesis in levodopa-naïve patients with PD and age-matched control subjects. The main hypothesis was that changes in the synergic control of posture are present early in the PD process even before levodopa exposure. Eleven levodopa-naïve patients with PD and 11 healthy controls performed whole-body cyclical voluntary sway tasks and a self-initiated load-release task during standing on a force plate. Surface electromyographic activity in 13 muscles on the right side of the body was analyzed to identify muscle groups with parallel scaling of activation levels (M-modes). Data were collected both before ("off-drug") and approximately 60 min after the first dose of 25/100 carbidopa/levodopa ("on-drug"). COP-stabilizing synergies were quantified for the load-release task. Levodopa-naïve patients with PD showed no COP-stabilizing synergy "off-drug", whereas controls showed posture-stabilizing multi-M-mode synergy. "On-drug", patients with PD demonstrated a significant increase in the synergy index. There were no significant drug effects on the M-mode composition, anticipatory postural adjustments, indices of motor equivalence, or indices of COP variability. The results suggest that levodopa-naïve patients with PD already show impaired posture-stabilizing multi-muscle synergies that may be used as promising behavioral biomarkers for emerging postural disorders in PD. Moreover, levodopa modified synergy metrics differently in these levodopa-naïve patients compared to a previous study of patients on chronic antiparkinsonian medications (Falaki et al. in J Electromyogr Kinesiol 33:20-26, 2017a), suggesting different neurocircuitry involvement.

Performance of discrete, reciprocal, and cyclic movements of the ipsilesional upper limb in individuals after stroke.

Aiming movements of the upper limbs can be classified either as discrete, or reciprocal, or cyclic. The control of these movements after a stroke can be affected. The aim of this experimental, cross-sectional study was to characterize the performance of these movements after the right and left hemisphere chronic stroke. Thirty-six individuals aged between 40 and 70 years, right-handed, were allocated into three groups (control, right stroke, and left stroke). Participants were asked to perform aiming movements on a tablet. Individuals after stroke performed the tasks only with their ipsilesional limb, while the control group performed movements with both limbs. The reaction and movement times, peak velocity, and the variability and error of the endpoint were analyzed. Individuals after stroke presented a worse performance in all movement classes as expected, but differently depending on the damaged hemisphere. Participants with right hemisphere damage showed larger endpoint errors, while those with left hemisphere damage had longer reaction and movement times. Both differences were seen consistently in discrete and reciprocal, but not in cyclic movements. Cyclic movements presented shorter latencies, were faster, and showed greater endpoint errors when compared to discrete and reciprocal movements. These results suggest that stroke affects differently the performance of discrete and reciprocal movements according to the hemisphere lesion side, but not in cyclic movements. Different levels of motor control among the three classes of movements by the nervous system may justify these results.

Synergic control of action in levodopa-naïve Parkinson's disease patients: I. Multi-finger interaction and coordination.

We explored the origin of the impaired control of action stability in Parkinson's disease (PD) by testing levodopa-naïve PD patients to disambiguate effects of PD from possible effects of long-term exposure to levodopa. Thirteen levodopa-naïve PD patients and 13 controls performed single- and multi-finger force production tasks, including producing a self-paced quick force pulse into a target. A subgroup of patients (n = 10) was re-tested about 1 h after the first dose of levodopa. Compared to controls, PD patients showed lower maximal forces and synergy indices stabilizing total force (reflecting the higher inter-trial variance component affecting total force). In addition, PD patients showed a trend toward shorter anticipatory synergy adjustments (a drop in the synergy index in preparation to a quick action) and larger non-motor equivalent finger force deviations. Lower maximal force, higher unintentional force production (enslaving) and higher inter-trial variance indices occurred in PD patients after one dosage of levodopa. We conclude that impairment in synergies is present in levodopa-naïve patients, mainly in indices reflecting stability (synergy index), but not agility (anticipatory synergy adjustments). A single dose of levodopa, however, did not improve synergy indices, as it did in PD patients on chronic anti-PD medication, suggesting a different mechanism of action. The results suggest that indices of force-stabilizing synergies may be used as an early behavioral sign of PD, although it may not be sensitive to acute drug effects in drug-naïve patients.

Preparation to a quick whole-body action: control with referent body orientation and multi-muscle synergies.

We examined the control of postural stability in preparation to a discrete, quick whole-body sway toward a target and back to the initial position. Several predictions were tested based on the theory of control with referent body orientation and the notion of multi-muscle synergies stabilizing center of pressure (COP) coordinate. Healthy, young adults performed fast, discrete whole-body motion forward-and-back and backward-and-back under visual feedback on the COP. We used two methods to assess COP stability, analysis of inter-trial variance and analysis of motor equivalence in the muscle activation space. Actions were always preceded by COP counter-movements. Backward COP shifts were faster, and the indices of multi-muscle synergies stabilizing COP were higher prior to those actions. Patterns of muscle activation at the motion onset supported the idea of a gradual shift in the referent body orientation. Prior to the backward movements, there was a trend toward higher muscle co-activation, compared to reciprocal activation. We found strong correlations between the sets of indices of motor equivalence and those of inter-trial variance. Overall, the results support the theory of control with referent coordinates and the idea of multi-muscle synergies stabilizing posture by confirming a number of non-trivial predictions based on these concepts. The findings favor using indices of motor equivalence in clinical studies to minimize the number of trials performed by each subject.

Individual preferences in motor coordination seen across the two hands: relations to movement stability and optimality.

The framework of the uncontrolled manifold (UCM) hypothesis was used to explore variables related to stability of task performance in the two hands of young healthy individuals. Fourteen young adults performed four-finger accurate constant force production tasks interrupted by a voluntary quick force pulse production and by an externally imposed displacement of all fingers. Three groups of variables were used to quantify stability of steady force production: (1) indices of the inter-trial variance were computed within the UCM and orthogonal to the UCM; (2) indices of motor equivalence were computed between steady-state intervals separated by the force pulse and by the finger-lifting episode; and (3) referent coordinate and apparent stiffness were computed using the data during the ascending phase of the finger-lifting episode. In another task, the subjects performed accurate constant force production with visual feedback removal after the 8th second, and the drop in the total force after the removal was computed. There were differences between the right and left hand in some outcome variables such as variance within the UCM, and the timing of anticipatory synergy adjustments prior to the force pulse, consistent with the dynamic dominance hypothesis. There were significant correlations between the two hands for indices that were unrelated to accuracy of performance: variance within the UCM, index of motor equivalence, referent coordinate, apparent stiffness, and the drop of total force after visual feedback removal. We interpret these findings within the concept of stability-optimality trade-off. In particular, we conclude that individual subjects select particular, person-specific solutions within the spectrum allowed by the explicit task constraints, and this choice is consistent between the two hands. We conclude with a hypothesis that selecting specific solutions within the stability-optimality trade-off may represent an individual's personal preference consistent between the two hands.

Quantitative analysis of multi-element synergy stabilizing performance: comparison of three methods with respect to their use in clinical studies.

A number of analyses associated with the uncontrolled manifold (UCM) hypothesis have been used recently to investigate stability of actions across populations. We explored whether some of those methods have an advantage for clinical studies because they require fewer trials to achieve consistent findings. We compared the number of trials needed for the analysis of inter-trial variance, analysis of motor equivalence, and analysis in the space of referent coordinates. Young healthy adults performed four-finger accurate force production tasks under visual feedback with the right (dominant) and left hand over three days. Three methods [analytical (M1), experimental (M2), and cumulative mean (M3) methods] were used to define the minimal number of trials required to reach certain statistical criteria. Two of these methods, M1 and M2, showed qualitatively similar results. Fewer trials (M1: 5-13, M2: 4-10) were needed for analysis of motor equivalence compared to inter-trial variance analysis (M1: 14-24, M2: 10-14). The third method (M3) showed no major differences among the outcome variables. The index of synergy in the inter-trial variance analysis required a very small number of trials (M1, M2: 2-4). Variables related to referent coordinates required only a few trials (under 3), whereas the synergy index in this analysis required the largest number of trials (M1: 24-34, M2: 12-16). This is the first study to quantify the number of trials needed for UCM-based methods of assessing motor coordination broadly used in clinical studies. Clinical studies can take advantage of specific recommendations based on the current data regarding the number of trials needed for each analysis thus allowing minimizing the test session duration without compromising data reliability.

Stability of steady hand force production explored across spaces and methods of analysis.

We used the framework of the uncontrolled manifold (UCM) hypothesis and explored the reliability of several outcome variables across different spaces of analysis during a very simple four-finger accurate force production task. Fourteen healthy, young adults performed the accurate force production task with each hand on 3 days. Small spatial finger perturbations were generated by the "inverse piano" device three times per trial (lifting the fingers 1 cm/0.5 s and lowering them). The data were analyzed using the following main methods: (1) computation of indices of the structure of inter-trial variance and motor equivalence in the space of finger forces and finger modes, and (2) analysis of referent coordinates and apparent stiffness values for the hand. Maximal voluntary force and the index of enslaving (unintentional finger force production) showed good to excellent reliability. Strong synergies stabilizing total force were reflected in both structure of variance and motor equivalence indices. Variance within the UCM and the index of motor equivalent motion dropped over the trial duration and showed good to excellent reliability. Variance orthogonal to the UCM and the index of non-motor equivalent motion dropped over the 3 days and showed poor to moderate reliability. Referent coordinate and apparent stiffness indices co-varied strongly and both showed good reliability. In contrast, the computed index of force stabilization showed poor reliability. The findings are interpreted within the scheme of neural control with referent coordinates involving the hierarchy of two basic commands, the r-command and c-command. The data suggest natural drifts in the finger force space, particularly within the UCM. We interpret these drifts as reflections of a trade-off between stability and optimization of action. The implications of these findings for the UCM framework and future clinical applications are explored in the discussion. Indices of the structure of variance and motor equivalence show good reliability and can be recommended for applied studies.

Validity and Clinical Utility of Different Clock Drawing Test Scoring Systems in Multiple Forms of Dementia.

The Clock Drawing Test (CDT) has a known potential for the detection of cognitive impairment in populations with dementia, especially Alzheimer disease (AD). Our aim was to compare the clinical utility of 3 CDT scoring systems (Rouleau, Cahn, and Babins) in several pathologies with cognitive compromise from a tertiary center memory clinic. We selected patients with a clinical diagnosis of mild stage AD, behavioral variant frontotemporal dementia (FTD), vascular dementia (VaD), dementia with Lewy bodies (DLB), and Parkinson disease with dementia (PDD). The results showed significant differences between the several diagnoses with the following pattern of results: AD, DLB < FTD, VaD, PDD. Qualitative analysis of clock drawing errors confirmed the stimulus-bound response as a hallmark of AD, while conceptual deficit was significantly more prevalent in patients with AD and DLB. Our results supported the CDT potential as a cognitive screening measure for mild dementia, particularly sensitive to AD and DLB, especially when we used the Cahn scoring system and its analysis of qualitative errors.

Human predisposition to cognitive impairment and its relation with environmental exposure to potentially toxic elements.

New lines of evidence suggest that less than 10% of neurodegenerative diseases have a strict genetic aetiology and other factors may be prevalent. Environmental exposures to potentially toxic elements appear to be a risk factor for Parkinson's, Alzheimer's and sclerosis diseases. This study proposes a multidisciplinary approach combining neurosciences, psychology and environmental sciences while integrating socio-economic, neuropsychological, environmental and health data. We present the preliminary results of a neuropsychological assessment carried out in elderly residents of the industrial city of Estarreja. A battery of cognitive tests and a personal questionnaire were administered to the participants. Multivariate analysis and multiple linear regression analysis were used to identify potential relationships between the cognitive status of the participants and environmental exposure to potentially toxic elements. The results suggest a relationship between urinary PTEs levels and the incidence of cognitive disorders. They also point towards water consumption habits and profession as relevant factors of exposure. Linear regression models show that aluminium (R 2 = 38%), cadmium (R 2 = 11%) and zinc (R 2 = 6%) are good predictors of the scores of the Mini-Mental State Examination cognitive test. Median contents (µg/l) in groundwater are above admissible levels for drinking water for aluminium (371), iron (860), manganese (250), and zinc (305). While the World Health Organization does not provide health-based reference values for aluminium, results obtained from this study suggest that it may have an important role in the cognitive status of the elderly. Urine proved to be a suitable biomarker of exposure both to elements with low and high excretion rates.

Impairment of social cognition in multiple sclerosis: Amygdala atrophy is the main predictor.

BACKGROUND: Patients with multiple sclerosis (MS) frequently reveal social behavior disturbance. Nevertheless, little is known regarding the impact of MS on social cognition, particularly theory of mind (ToM), and its neural basis. OBJECTIVES: To explore how ToM is affected in MS and its neural correlates. METHODS: Enrolled 60 consecutive MS patients and 60 healthy controls (HC) matched on age, sex, and education. Participants underwent ToM testing (Eyes Test, Videos Test) and 3 T brain magnetic resonance imaging (MRI). Using Freesurfer software, cortical and subcortical gray matter (GM) volumes were calculated. RESULTS: MS patients performed worse on Eyes Test (58.7% ± 13.8% vs 81.9% ± 10.4%, p < 0.001) and Videos Test (75.3% ± 9.3% vs 88.1% ± 7.1%, p < 0.001). Eyes Test performance in MS was positively correlated with the volume of subcortical structures (amygdala, putamen) and cortical regions (entorhinal cortex, fusiform gyrus, superior temporal gyrus, superior parietal gyrus, supramarginal gyrus, medial orbitofrontal cortex, anterior and posterior cingulate gyrus). In regression analysis, amygdala volume was the single predictor of performance ( R2 change = 0.064, p = 0.031), and a mediation analysis indicated that it contributes for the differences observed between MS and HC. CONCLUSION: Patients with MS have impairment on social cognition. Amygdala atrophy was the main predictor probably due to its central position within the "social brain" network.

Muscle Activation During Pilates Exercises in Participants With Chronic Nonspecific Low Back Pain: A Cross-Sectional Case-Control Study.

OBJECTIVE: To determine the amplitude of the electromyographic activity of trunk muscles during Pilates exercises in women with and without chronic low back pain (LBP). DESIGN: Case-control study. SETTING: University physical therapy clinic. PARTICIPANTS: Women (N=60) divided into an LBP group and a control group. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Amplitude of the electromyographic activity (root mean square values) of the gluteus maximus and external oblique muscles collected during 3 Pilates exercises: Shoulder Bridge performed on the mat, and Hip Roll and Breathing performed in equipment. Pain intensity was assessed in the LBP group. RESULTS: The amplitude of the electromyographic activity was similar between groups (P≥.05). For both groups, the amplitude of the gluteus maximus was higher in the Shoulder Bridge exercise compared with the Hip Roll with 2 springs (control group: mean difference [MD]=.18; 95% confidence interval [CI], .05-.41; LBP group: MD=.29; 95% CI, .16-.31) and the Breathing exercise (control group: MD=-.40; 95% CI, -.55 to -.26; LBP group: MD=-.36; 95% CI, -.52 to -.20). The amplitude of the external oblique muscle was higher in the Shoulder Bridge compared with the Hip Roll with 2 springs (control group: MD=.13; 95% CI, .05-.21; LBP group: MD=.18; 95% CI, .03-.33). Pain intensity increased after exercises, but this increase was lower for the mat exercises. CONCLUSIONS: Similar muscle activation between groups was found. The findings suggest that mat exercises caused less pain and a greater difference in the amplitude of muscle activation compared with the equipment-based exercises.

Assessment of the Ipsilesional Hand Function in Stroke Survivors: The Effect of Lesion Side.

BACKGROUND: The aim of this study was to examine the effect of the side of brain lesion on the ipsilesional hand function of stroke survivors. METHODS: Twenty-four chronic stroke survivors, equally allocated in 2 groups according to the side of brain lesion (right or left), and 12 sex- and age-matched healthy controls performed the Jebsen-Taylor Hand Function Test (JTHFT), the Nine-Hole Peg Test (9HPT), the maximum power grip strength (PwGSmax) test, and the maximum pinch grip strength (PnGSmax) test. Only the ipsilesional hand of the stroke survivors and both hands (left and right) of the controls were assessed. RESULTS: PwGS max and PnGS max were similar among all tested groups. Performances in JTHFT and 9HPT were affected by the brain injury. Individuals with left brain damage showed better performance in 9HPT than individuals with right brain damage, but performance in JTHFT was similar. CONCLUSIONS: Individuals after a brain injury have the capacity to produce maximum strength preserved when using their ipsilesional hand. However, the dexterity of their hands and digits is affected, in particular for stroke individuals with right brain lesion.

Relationship of diminished interjoint coordination after stroke to hand path consistency.

Differences between 12 left-brain (LCVA, 65.4 ± 11.7 years old) and 10 right-brain (RCVA, 61 ± 12.1 years old) chronic stroke survivors and 10 age-matched control adults in coordinating specific joint motions of the arm to stabilize hand path when reaching to a central target were investigated in this study. The importance of coordinating joints to stabilize hand path was tested by comparing results from uncontrolled manifold (UCM) analysis performed on experimental data versus simulated data where the covariation (coordination) between particular joint motions was removed from the original data set. UCM analysis allowed estimation of the joint configuration variance magnitude that led to hand path variability (V ORT), where the extent of increase in V ORT after removing a joint's covariation indicated how well coordinated its motion actually was with those of the other joints. The more strongly coordinated a joint was with other joints, the greater effect removal of its covariance should have on indices of hand path stability. For the paretic arm of stroke survivors, simulated removal of a joint's covariation, mainly that of shoulder with elbow and wrist, led to less change in the magnitude of V ORT compared to the same arm of control subjects. These findings confirm a reduced ability of the motion of proximal joint from paretic arm to combine flexibly with motions of the distal joints to stabilize hand path.

Synergic control of the minimum toe clearance in young and older adults during foot swing on treadmill walking in different speeds.

BACKGROUND: The vertical toe position at minimum toe clearance (MTC) in the swing phase is critical for walking safety. Consequently, the joints involved should be strictly controlled and coordinated to stabilize the foot at MTC. The uncontrolled manifold (UCM) hypothesis framework has been used to determine the existence of synergies that stabilize relevant performance variables during walking. However, no study investigated the presence of a multi-joint synergy stabilizing the foot position at MTC and the effects of age and walking speed on this synergy. RESEARCH QUESTIONS: Is there a multi-joint synergy stabilizing MTC during treadmill walking? Does it depend on the persons' age and walking speed? METHODS: Kinematic data from 23 young and 15 older adults were analyzed using the UCM approach. The participants walked on a treadmill at three speeds: slow, self-selected, and fast. The sagittal and frontal joint angles from the swing and stance legs and pelvis obliquity were used as motor elements and the vertical toe position at MTC was the performance variable. The variances in the joint space that affected (VORT, 'bad' variance) and did not affect (VUCM, 'good' variance) the toe position at MTC and the synergy index (ΔV) were computed. RESULTS: The ΔV>0 was revealed for all subjects. Walking speed did not affect ΔV in older adults, whereas ΔV reduced with speed in young adults. ΔV was higher for older than for young adults at self-selected and fast speeds, owing to a lower VORT in the older group. SIGNIFICANCE: The vertical toe position at MTC was stabilized by a strong multi-joint synergy. In older adults, this synergy was stronger, as they were better at limiting VORT than young adults. Reduced VORT in older adults could be caused by more constrained walking, which may be associated with anxiety due to walking on a treadmill.