Search

The purpose of this study was to determine the effect of different visual conditions and targeted force levels on bilateral motor synergies and bimanual force control performances. Fourteen healthy young participants performed bimanual isometric force control tasks by extending their wrists and fingers under two visual feedback conditions (i.e., vision and no-vision) and three targeted force levels (i.e., 5%, 25%, and 50% of maximum voluntary contraction: MVC). To estimate bilateral motor synergies across multiple trials, we calculated the proportion of good variability relative to bad variability using an uncontrolled manifold analysis. To assess bimanual force control performances within a trial, we used the accuracy, variability, and regularity of total forces produced by two hands. Further, analysis included correlation coefficients between forces from the left and right hands. In addition, we examined the correlations between altered bilateral motor synergies and force control performances from no-vision to vision conditions for each targeted force level. Importantly, our findings revealed that the presence of visual feedback increased bilateral motor synergies across multiple trials significantly with a reduction of bad variability as well as improved bimanual force control performances within a trial based on higher force accuracy, lower force variability, less force regularity, and decreased correlation coefficients between hands. Further, we found two significant correlations in (a) increased bilateral motor synergy versus higher force accuracy at 5% of MVC and (b) increased bilateral motor synergy versus lower force variability at 50% of MVC. Together, these results suggested that visual feedback effectively improved both synergetic coordination behaviors across multiple trials and stability of task performance within a trial across various submaximal force levels.

BackgroundSeveral studies reported the beneficial effects of globus pallidus internus deep brain stimulation (GPi DBS) on health-related quality of life (HRQoL) in patients with inherited or idiopathic isolated dystonia. However, the impact of this intervention on physical and mental/psychological domains and the effects over time remain unclear.MethodsWe conducted a systematic literature review from January 2000 to May 2019 and performed a meta-analysis of HRQoL outcomes based on the Short Form Health Survey-36 (SF-36) after GPi DBS in patients with inherited or idiopathic isolated dystonia to evaluate the effects of DBS on physical and mental QoL.ResultsSeven studies comprising 144 patients with dystonia (78, generalised; 34, segmental; and 32, focal cervical) were included in this comprehensive analysis. The mean (SD) age at DBS implantation was 41.0 (11.4) years, and the follow-up period after implantation was 3.2 (3.8) years. The random effects model meta-analysis revealed that both physical and mental domains of SF-36 improved following DBS with a significantly larger effect size for the physical domains (effect size=0.781; pConclusionsThis is the first meta-analysis that demonstrates significant benefits in HRQoL following DBS in patients with inherited or idiopathic isolated dystonia. The benefits are greater for physical QoL domains compared with mental/psychological QoL. These findings highlight the importance of a comprehensive multidisciplinary approach to improve mental/psychological QoL.

Visual information is a critical component that influences bimanual force control stabilization. The purpose of this study was to determine the effects of altered visual gain levels on bimanual force control strategies between multiple trials and within a trial. Twelve healthy young participants performed bimanual submaximal force control tasks by executing index finger abduction isometric movements across four different visual gain conditions (i.e., 8, 80, 256, and 512 pixels/N). We followed the uncontrolled manifold (UCM) approach to determine synergistic coordination patterns between two hands across multiple trials (i.e., bilateral motor synergies). Within a trial, force accuracy and variability were calculated to quantify bimanual force control capabilities (i.e., task stabilization). Further, we examined correlations between changes in UCM variables and force control performance from the lowest to higher visual gain conditions, respectively. The findings revealed that the values of bilateral motor synergies at 80, 256, and 512 pixels/N were significantly higher than those at 8 pixels/N. Further, force error at 80, 256, and 512 pixels/N were significantly less than those at 8 pixels/N. In UCM terms, as visual gain increased from 8 pixels/N, less amount of bad variability across multiple trials was significantly related to a reduction of force error within a trial. These findings provide supporting evidence that higher values of visual gain contribute to improved bimanual coordination function across multiple trials as well as task stabilization within trials.

Purpose The purpose of this study was to investigate transient bimanual effects on the force control capabilities of the paretic and non-paretic arms in individuals post stroke across submaximal and maximal force control tasks. Methods Fourteen chronic stroke patients (mean age = 63.8 ± 15.9; stroke duration = 38.7 ± 45.2 months) completed two isometric force control tasks: (a) submaximal control and (b) maximal sustained force production. Participants executed both tasks with their wrist and fingers extending across unimanual (paretic and non-paretic arms) and bimanual conditions. Mean force, force variability using coefficient of variation, force regularity using sample entropy were calculated for each condition. Results During the submaximal force control tasks (i.e., 5, 25, and 50% of maximum voluntary contraction), the asymmetrical mean force between the paretic and non-paretic arms decreased from unimanual to bimanual conditions. The asymmetry of force variability and regularity between the two arms while executing unimanual force control tended to decrease in the bimanual condition because of greater increases in the force variability and regularity for the non-paretic arm than those for the paretic arm. During the maximal sustained force production tasks (i.e., 100% of maximum voluntary contraction), the paretic arm increased maximal forces and decreased force variability in the bimanual condition, whereas the non-paretic arm reduced maximal forces and elevated force variability from unimanual to bimanual conditions. Conclusions The current findings support a proposition that repetitive bimanual isometric training with higher execution intensity may facilitate progress toward stroke motor recovery.

OBJECTIVE: To compare subthalamic nucleus (STN) deep brain stimulation (DBS) with globus pallidus interna (GPi) DBS for tremor suppression in Parkinson disease (PD). BACKGROUND: DBS is an effective surgical therapy that has been shown to provide significant benefit for motor symptoms in PD. Currently, two main structures targeted to treat motor complications in PD are the STN and GPi. Although some groups traditionally favor STN over GPi for tremor suppression, evidence demonstrating superiority in long-term tremor control is limited. METHODS: We performed a systematic review for all randomized trials comparing STN vs GPi DBS in PD that were published before March 2017. Five studies were examined in a random effects model meta-analysis. We conducted moderator variable analysis to determine if there was a treatment effect difference for STN versus GPi. RESULTS: We compared DBS ON versus OFF and found a significant overall standardized difference mean effect: Effect Size = 0.36; 95% CI = 0.316–0.395; P < 0.0001. These findings indicate that DBS reduced tremor symptoms in PD patients with a medium effect size. Moderator variable analysis of STN vs GPI revealed two significant standardized effect sizes: STN effect size = 0.38 and GPi effect size = 0.35. A Z-test showed that effect sizes between the STN and GPi were not significantly different (P = 0.56). CONCLUSIONS: DBS is effective in reducing tremor in PD patients regardless of stimulation target. However, the degree of tremor suppression in STN DBS versus GPi DBS was equivalent.

Neural coupling across hemispheres and homologous muscles often appears during bimanual motor control. Force coupling in a specific frequency domain may indicate specific bimanual force coordination patterns. This study investigated coherence on pairs of bimanual isometric index finger force while manipulating visual gain and task asymmetry conditions. We used two visual gain conditions (low and high gain = 8 and 512 pixels/N), and created task asymmetry by manipulating coefficient ratios imposed on the left and right index finger forces (0.4:1.6; 1:1; 1.6:0.4, respectively). Unequal coefficient ratios required different contributions from each hand to the bimanual force task resulting in force asymmetry. Fourteen healthy young adults performed bimanual isometric force control at 20% of their maximal level of the summed force of both fingers. We quantified peak coherence and relative phase angle between hands at 0–4, 4–8, and 8–12 Hz, and estimated a signal-to-noise ratio of bimanual forces. The findings revealed higher peak coherence and relative phase angle at 0–4 Hz than at 4–8 and 8–12 Hz for both visual gain conditions. Further, peak coherence and relative phase angle values at 0–4 Hz were larger at the high gain than at the low gain. At the high gain, higher peak coherence at 0–4 Hz collapsed across task asymmetry conditions significantly predicted greater signal-to-noise ratio. These findings indicate that a greater level of visual information facilitates bimanual force coupling at a specific frequency range related to sensorimotor processing.

Objective: To reveal clinical characteristics of suboptimal responses to deep brain stimulation (DBS) in a multi-country DYT1 dystonia cohort. Methods: In this multi-country multi-center retrospective study, we analyzed the clinical data of DYT1 patients who experienced suboptimal responses to DBS defined as 30% postoperatively; however, secondary worsening of dystonia commenced between 6 months and 3 years following DBS. The improvement at the last follow-up was less than 30% despite optimally-placed leads, a trial of multiple programming settings, and additional DBS surgeries in all patients. The on-/off-stimulation comparison at the long-term follow-up demonstrated beneficial effects of DBS despite missing the threshold of 30% improvement over baseline. Conclusion: Approximately 8% of patients represent a more aggressive phenotype of DYT1 dystonia characterized by younger age at onset, faster disease progression, and cranial involvement, which seems to be associated with long-term suboptimal responses to DBS (e.g., secondary worsening). This information could be useful for both clinicians and patients in clinical decision making and patient counseling before and following DBS implantations. Patients with this phenotype may have different neuroplasticity, neurogenetics, or possibly distinct neurophysiology. ispartof: FRONTIERS IN HUMAN NEUROSCIENCE vol:14 ispartof: location:Switzerland status: published

Dysfunction in bilateral coordination post-stroke is responsible for impaired bilateral movements. This study examined bilateral synergies using the uncontrolled manifold (UCM) approach while individuals in a chronic stage after stroke executed bilateral isometric force control at three submaximal force levels. Nine patients with stroke and nine age-matched healthy controls performed 24 trials of wrist and fingers extension at 5, 25, and 50% of MVC. The UCM findings revealed: (a) decreased bilateral synergies in patients with stroke as compared to controls at 50% of MVC and (b) reduced good variability and increased bad variability components in patients with stroke at 50% of MVC. Moreover, correlation analyses across both groups showed that a reduction of bilateral synergies was related to increased force error at 50% of MVC and an inconsistent force ratio between the two hands across multiple trials correlated with increased good and bad variability at 5% of MVC. Current findings indicate that quantifying bilateral synergies may provide meaningful profiles for estimating impairments as well as improvements of cooperative behaviors between two hands post-stroke.

In Parkinson's disease (PD), slow gait speed is significantly related to clinical ratings of disease severity, impaired performance of daily activities, as well as increased overall disability. Conducting a meta-analysis on gait speed is an objective and quantitative technique to summarize the effectiveness of DBS and to determine the effect sizes for future studies. We conducted a systematic review and meta-analysis that analyzed the effects of deep brain stimulation (DBS) surgery on gait speed in patients with PD to gain fundamental insight into the nature of therapeutic effectiveness. A random effects model meta-analysis on 27 studies revealed a significant overall standardized mean difference medium effect size equal to 0.60 (SE = 0.06; p

A growing body of literature has reported the effects of dual tasks on gait performance in people with Parkinson’s disease (PD). The purpose of this meta-analysis was to synthesize the existing literature and quantify the overall influence of dual tasks on gait performance in PD. A thorough literature search was conducted, and 19 studies met the stringent inclusion criteria. Two moderator variable analyses examined the dual-task effect by: (a) mean single-task gait speed for each study (≥ 1.1 m/s or < 1.1 m/s), and (b) the type of dual task (arithmetic, language, memory, and motor). Three main findings were revealed by a random effects model analysis. First, a strong negative effect of dual tasks on walking performance (SMD = −0.68) confirmed that gait performance is adversely affected by dual tasks in people with PD. Second, the significant negative effect of dual tasks is present regardless of the mean level of single-task gait speed in a study. Third, dual-task walking speed deteriorates regardless of the type of dual task. Together, these results confirm that dual tasks severely affect walking performances in people with PD.

OBJECTIVE The purpose of this systematic review and meta-analysis was to investigate the therapeutic effects of cathodal tDCS (ctDCS) that suppresses the contralesional primary motor cortex (cM1) activity for individuals with stroke in different recovery phases. METHODS Fifteen studies that used ctDCS for suppressing the cM1 activity were included in this meta-analysis. Twenty total comparisons from the qualified studies identified motor function changes between ctDCS and sham protocols. We divided recovery stages into two categories: (a) acute and subacute phases (time since stroke ≤6 months): eight comparisons and (b) chronic phase (time since stroke >6 months): 12 comparisons. RESULTS Random-effects meta-analysis models revealed motor improvements after applying ctDCS on the cM1 as indicated by a significant standardized effect size (ES = 0.61; P

Bimanual force control requiring asymmetrical forces between limbs is more challenging than bimanual force control when the limbs produce symmetrical forces. Previous studies investigated visual information gains between 8 and 80 pixels/N to facilitate asymmetrical force control. Given that previous studies limited visual information gain to 80 pixels/N, the current experiment expanded the range by increasing visual information gains (8, 80, 256, and 512 pixels/N). A second manipulation involved three task constraint coefficients imposed on bimanual force control: (a) left-biased, (b) right-biased, and (c) equal-biased. Analyses of 15 right-handed adult volunteers revealed a decrease in bimanual force variability and more negative correlation coefficient with increased visual information gain in the equal biased condition. Significant reductions in bimanual force variability were found between 8 and 80 pixels/N. In contrast, significant improvements in coordination patterns between hands continued up to 256 pixels/N. These novel findings demonstrate that bimanual force coordination was more sensitive to an increase in visual information gains (>80 pixels/N) than bimanual force variability.

Transcranial direct current stimulation (tDCS) is an attractive protocol for stroke motor recovery. The current systematic review and meta-analysis investigated the effects of tDCS on motor learning post-stroke. Specifically, we determined long-term learning effects by examining motor improvements from baseline to at least 5 days after tDCS intervention and motor practise. 17 studies reported long-term retention testing (mean retention interval=43.8 days; SD=56.6 days) and qualified for inclusion in our meta-analysis. Assessing primary outcome measures for groups that received tDCS and motor practise versus sham control groups created 21 valid comparisons: (1) 16 clinical assessments and (2) 5 motor skill acquisition tests. A random effects model meta-analysis showed a significant overall effect size=0.59 (p

Background Bilateral motor control deficits poststroke may be lateralized by hemisphere damage. This preliminary study investigated bilateral force control between left and right hemisphere-damaged groups at baseline and after coupled bilateral movement training with neuromuscular stimulation. Methods Stroke participants (8 left hemisphere and 6 right hemisphere cerebrovascular accidents) performed a bilateral isometric force control task at 3 submaximal force levels (5%, 25%, and 50% of maximum voluntary contraction [MVC]) before and after training. Force accuracy, force variability, and interlimb force coordination were analyzed in 3-way mixed design ANOVAs (2 × 2 × 3; Group × Test Session × Force Level) with repeated measures on test session and force level. Results The findings indicated that force accuracy and variability at 50% of MVC in the right hemisphere-damaged group were more impaired than lower targeted force levels at baseline, and the impairment at the highest target level was improved after coupled bilateral movement training. However, these patterns were not observed in the left hemisphere-damaged group. Conclusions Current findings support a proposition that the right hemisphere presumably contributes to controlling bilateral force production.

Visual information is critical to producing and controlling force output to achieve targeted levels. This study investigated bimanual force control in chronic stroke individuals while manipulating visual information. Nine chronic stroke individuals and nine age-matched controls executed bimanual wrist and finger extension at 5% of maximum voluntary contraction. Bimanual force control outcome measures included: (a) coefficient of variation, (b) approximate entropy, and (c) bimanual coordination. Without visual information, chronic stroke individuals displayed less force variability and more regular force production in comparison to age-matched controls. These findings suggest that chronic stroke individuals depended on visual information during bimanual force execution.

Muscle weakness in the extensors poststroke is a common motor impairment. Unfortunately, research is unclear on whether bilateral movements increase extensor force production in the paretic arm. This study investigated sustained force production while stroke individuals maximally extended their wrist and fingers on their paretic arm. Specifically, we determined isometric force production in three conditions: (a) unilateral paretic arm, (b) unilateral nonparetic arm, and (c) bilateral (both arms executing the same movement simultaneously).Seventeen chronic stroke patients produced isometric sustained force by executing wrist and fingers extension in unilateral and bilateral contraction conditions. Mean force, force variability (coefficient of variation), and signal-to-noise ratio were calculated for each contraction condition.Analysis of two-way (Arm × Type of Condition: 2 × 2; Paretic or Nonparetic Arm × Unilateral or Bilateral Conditions) within-subjects ANOVAs revealed that the bilateral condition increased sustained force in the paretic arm, but reduced sustained force in the nonparetic arm. Further, although the paretic arm exhibited more force variability and less signal-to-noise ratio than the nonparetic arm during a unilateral condition, there were no differences when participants simultaneously executed isometric contractions with both arms.Our unique findings indicate that bilateral contractions transiently increased extensor force in the paretic arm. Implications for Rehabilitation Bilateral movements increased isometric wrsit extensor force in paretic arms and redcued force in nonparetic arms versus unilateral movements. Both paretic and nonparetic arms produced similar force variability and signal-to-noise ratio during bilateral movements. Increased sustained force in the paretic arm during the bilateral condition indicates that rehabilitation protocols based on bilateral movements may be beneficial for functional recovery.

Background With increasing age motor functions decline. The additional challenges of executing bimanual movements further hinder motor functions in older adults. The current systematic review and meta-analysis determined the effects of healthy aging on performance in bimanual movements as compared to younger adults. Methods Our comprehensive search identified 27 studies that reported bimanual movement performance measures. Each study included a between groups comparison of older (mean age = 68.79 years) and younger adults (mean age = 23.14 years). The 27 qualified studies generated 40 total outcome measure comparisons: (a) accuracy: 18, (b) variability: 14, and (c) movement time: eight. Results Our meta-analysis conducted on a random effects model identified a relatively large negative standardized mean difference effect (ES = − 0.93). This indicates that older adults exhibited more impaired bimanual movement performance in comparison to younger adults in our group of studies. Specifically, a moderator variable analysis revealed large negative effects in both accuracy (ES = − 0.94) and variability (ES = − 1.00), as well as a moderate negative effect (ES = − 0.71) for movement time. These findings indicate that older adults displayed reduced accuracy, greater variability, and longer execution time when executing bimanual movements. Conclusion These meta-analytic findings revealed that aging impairs bimanual movement performance.

Stroke leads to motor asymmetries in the flexor and extensor muscles of the hand. Typically, the strength deficits in the extensors are greater than the flexors. The impact of differential motor abilities of these muscle groups on the execution of bimanual force control tasks in individuals with stroke is unknown. The primary purpose of this study was to determine the influence of task constraints on visually guided bimanual force control in chronic stroke. Stroke survivors and age-matched individuals performed bimanual isometric contractions for 20 s to match target submaximal force levels. Online visual feedback of the total force (sum of the forces produced by both hands) was provided. The task constraints were manipulated by (a) finger extension, and (b) finger flexion (power grip). Force asymmetry was indexed by the proportion of force contributed by the paretic hand to the total force. The stroke group demonstrated task-specific asymmetry in bimanual force control. Specifically, the paretic hand contributed less force than the non-paretic hand in finger extension whereas this relationship was reversed in power grip. Importantly, regardless of the nature of the task, reduction in motor impairments was associated with increased symmetry and coordination in bimanual tasks. Further, bimanual submaximal grip force control revealed asymmetry and coordination deficits that are not identified by investigating bimanual maximal force production alone. The motor control strategy adopted to optimize performance on bimanual tasks revealed the altered force production of the paretic hand due to the combined effect of extensor weakness and enhanced flexor bias following stroke. Bimanual asymmetries in stroke survivors highlight the need for identifying and treating the task-specific impairments for maximizing motor recovery post stroke.

Individual difference measures have been shown to alter emotional arousal and emotional arousal alters force production during force control tasks. In the current study we examined whether individual differences in behavioral inhibition influence force control during emotional image viewing. Subjects who scored high and low in behavioral inhibition (BIS) produced force with visual feedback for 5 s. Feedback was then removed and replaced by a mutilation, attack, erotica, or neutral image for 6 s. The magnitude and direction of error in force production during image presentation was compared between groups and across image type. The high BIS group displayed a relative increase in force production during exposure to attack and mutilation images compared to the low BIS group. Bias scores (i.e., comparison of unpleasant image to neutral or pleasant image) further confirmed these findings by demonstrating a relative increase in force for the high BIS group during attack and mutilation images as compared to erotica images, whereas the low BIS group displayed the reverse effect. Together these findings extend the premise of action readiness to demonstrate that dispositional differences in behavioral inhibition interact with emotional state to alter force production.

The aim of the study was to develop a novel approach for quantifying stair-stepping in a trajectory tracking task with the goal of understanding how age and stroke-related differences in motor control contribute to force control deficits. Nine stroke participants, nine age-matched controls, and nine young healthy adults performed an isometric gripping task while squeezing, holding, and releasing a cylindrical device. The visual tracking task involved three different rates of force production (5, 10, and 20% maximal force/s). Four outcome measures determined force control deficits: (a) root mean square error, (b) standard deviation, (c) step number, and (d) mean pause duration. Our findings indicate that step number, and especially mean pause duration, differentiated force control deficits in the three groups more effectively than the traditional root mean square error. Moreover, stroke participants showed the largest force control deficits during the grip release phase compared to age-matched and young healthy controls. Importantly, step number and mean pause duration quantified stair-stepping while measuring different constructs than root mean square error. Distinct step and duration interruptions in force modulation by persons post-stroke during the grip release phase provide new information with implications for motor recovery during rehabilitation.

The purpose was to conduct a structured review and meta-analysis to determine the cumulative effect of bilateral arm training on motor capabilities post stroke. Forty-eight stroke studies were selected from three databases with 25 comparisons qualifying for inclusion in our meta-analysis. We identified and coded four types of bilateral arm interventions with 366 stroke patients. A random effects model using the standardized mean difference technique determined a large and significant effect size (0.734; SE = 0.125), high fail-safe N (532), and medium variability in the studies (I2 = 63%). Moderator variable analysis on the type of bilateral training revealed two large and significant effects: (a) BATRAC (0.842; SE = 0.155) and (b) coupled bilateral and EMG-triggered neuromuscular stimulation (1.142; SE = 0.176). These novel findings provide strong evidence supporting bilateral arm training with the caveat that two coupled protocols, rhythmic alternating movements and active stimulation, are most effective.

Objective: To conduct a systematic review and meta-analysis using the International Classification of Functioning to determine the summary effect of electrical stimulation on impairment and activity limitations relevant to gait problems of children with cerebral palsy. Methods: We identified 40 cerebral palsy and electrical stimulation studies, and 17 gait studies qualified for inclusion. Applying enablement classification methods to walking abnormalities created two subgroups: impairment (N = 14) and activity limitations (N = 15). Overall, 238 participants experienced electrical stimulation treatments and 224 served as a no stimulation control group. Calculations followed conventional data extraction and meta-analysis techniques: (a) individual standardized mean differences, (b) summary effect size, (c) I 2heterogeneity test, (d) fail-safe N analysis and (e) moderator variable analyses. Results: Common outcome measures associated with impairment (n = 3) and activity limitations (n = 6) were submitted to separate random effects models meta-analyses, and revealed significant cumulative effect sizes: (a) impairment = 0.616 (SE = 0.10) and (b) activity limitations = 0.635 (SE = 0.14). I 2indicated low and medium amounts of dispersion, whereas fail-safe analyses revealed high N-values for both disablement categories. Moderator variable analyses further confirmed the positive treatment effects from both functional and neuromuscular stimulation. Conclusions: The present systematic review and meta-analyses determined medium effect sizes for electrical stimulation on walking impairment and activity limitations of children with cerebral palsy.

Are motor coordination deficits an underlying cardinal feature of Autism Spectrum Disorders (ASD)? Database searches identified 83 ASD studies focused on motor coordination, arm movements, gait, or postural stability deficits. Data extraction involved between-group comparisons for ASD and typically developing controls (N = 51). Rigorous meta-analysis techniques including random effects models, forest and funnel plots, I (2), publication bias, fail-safe analysis, and moderator variable analyses determined a significant standardized mean difference effect equal to 1.20 (SE = 0.144; p

The present study investigated how trait anxiety alters the balance between attentional control systems to impact performance of a discrete preplanned goal-directed motor task. Participants executed targeted force contractions (engaging the goal-directed attentional system) at the offset of emotional and non-emotional distractors (engaging the stimulus-driven attentional system). High and low anxious participants completed the protocol at two target force levels (10% and 35% of maximum voluntary contraction). Reaction time (RT), performance accuracy, and rate of change of force were calculated. Expectations were confirmed at the 10% but not the 35% target force level: (1) high anxiety was associated with slower RTs, and (2) threat cues lead to faster RTs independently of trait anxiety. These new findings suggest that motor efficiency, but not motor effectiveness is compromised in high relative to low anxious individuals. We conclude that increased stimulus-driven attentional control interferes with movements that require greater attentional resources.

Single-blind case-control study.To compare functional performance and self-assessed disability scores among individuals with and without chronic ankle instability (CAI) and uninjured controls.After an acute lateral ankle sprain, CAI develops in 40% to 75% of all individuals. However, some individuals, copers, maintain high-level activities after an ankle sprain and do not develop CAI. Studying differences between copers and those with CAI is the first step in developing a clinical battery of tests that can accurately determine which individuals are more likely to develop CAI after an acute lateral ankle sprain.Participants were 24 active adults with unilateral CAI (mean +/- SD age, 21.7 +/- 2.8 years), 24 copers (20.8 +/- 1.5 years), and 24 uninjured controls (21.8 +/- 2.6 years). Participants completed 3 questionnaires of self-assessed disability: (1) Foot and Ankle Disability Index, (2) Foot and Ankle Disability Index-Sport, and (3) a questionnaire of ankle function. Four hop tests were also completed: (1) figure-8 hop, (2) side-to-side hop, (3) triple-crossover hop, and (4) single-leg hop for distance.Self-assessed disability was significantly different among groups (P.001), but hop test scores (P = .259) were not. Those with CAI had greater self-assessed disability than copers and uninjured controls. Copers and uninjured controls did not differ in self-assessed disability or functional performance.Self-assessed disability is significantly greater in those with CAI than copersand uninjured controls. However, functional performance, measured by hop tests, did not differ among groups.

In control samples, intense acoustic "go" stimuli accelerate the central and peripheral motor processes that compose simple reaction time movements. The goal of the current study was to determine whether movements that are initiated to intense acoustic cues facilitate simple reaction times in (1) adults with chronic stroke as compared to age matched controls and (2) in older as compared to younger adults. EMG and force data were collected from three groups (stroke, older adults, and younger adults) during a ballistic wrist and finger extension task. Movements were made to the onset of 80 dB and 107 dB acoustic cues and simple reaction times were fractionated into premotor and motor components. The present findings offer two important contributions to the literature. First, increases in stimulus intensity led to faster motor times in the impaired limb of stroke subjects. Second, increased stimulus intensity led to faster premotor reaction times across all groups, although an age rather than a stroke-specific motor deficit was evidenced, with the younger control group displaying significantly faster premotor times. Findings are integrated with previous evidence concerning post stroke corticospinal tract integrity and are interpreted via mechanisms which address stroke and age-related changes in motoneurons and activity in motor units.

The aim of the current experiment was to determine the extent to which pleasant and unpleasant emotional states altered the ability of men and women to control force production on a feedback occluded motor task that was not direction specific. Participants produced a precision pinch grip with visual feedback. After 5 s, feedback was occluded and replaced with a pleasant, unpleasant, or neutral image. The amplitude, variability, and structure of force production were calculated. As expected, the removal of visual feedback led to progressive force decay. More important, relative to neutral conditions, pleasant and unpleasant emotional states led to greater force production, resulting in attenuated force decay. The variability and structure of force production were not altered by affective state. In addition, men and women performed similarly across all conditions for all measures. We conclude that when sustained force production is not directed toward or away from the body, pleasant and unpleasant emotional states similarly excite the motor system. Neurobiological mechanisms are proposed to account for these findings. Implications and future research directions are discussed.

Background Non-invasive brain stimulation (NIBS) facilitates motor improvements post stroke. Transcranial direct current stimulation (tDCS) and repetitive transcranial magnetic stimulation (rTMS) are representative NIBS techniques frequently used in stroke motor rehabilitation. Our primary question is: Do these two techniques improve force production capability in paretic limbs? Objective The current systematic review and meta-analysis investigated the effects of tDCS and rTMS on paretic limb force production in stroke survivors. Methods Our comprehensive search identified 23 studies that reported changes in force production following tDCS or rTMS interventions. Each used random assignment and a sham control group. The 23 qualified studies in our meta-analysis generated 29 comparisons: 14 tDCS and 15 rTMS comparisons. Results Random effects models indicated improvements in paretic limb force after tDCS and rTMS rehabilitation. We found positive effects on force production in the two sets of stimulation protocols: (a) increasing cortical activity in the ipsilesional hemisphere and (b) decreasing cortical activity in the contralesional hemisphere. Moreover, across acute, subacute, and chronic phases, tDCS and rTMS improved force production. Conclusion Cumulative meta-analytic results revealed that tDCS and rTMS rehabilitation protocols successfully improved paretic limb force production capabilities.

Purpose: A limited understanding of how functional ankle instability (FAI) affects dynamic postural stability exists because of a lack of reliable and valid measures. Therefore, the purpose of this investigation was to determine whether a new reliable index for dynamic postural stability could differentiate between those with stable ankles and those with FAI. Methods: Data were collected on 108 subjects (54 subjects with stable ankles (STABLE group); 54 subjects with functionally unstable ankles (FAI group)). Subjects performed a single-leg-hop stabilization maneuver in which they stood 70 cm from the center of a force plate, jumped off both legs, touched a designated marker placed at a height equivalent to 50% of their maximum vertical leap, and landed on a single leg. The dynamic postural stability index and directional stability indices (medial/lateral, anterior/posterior, and vertical) were calculated. The raw and normalized (to energy dissipated) indices were compared between groups. Results: Significant differences were noted for the anterior/posterior stability index (FAI = 0.36 ± 0.09, STABLE = 0.30 ± 0.06). Similar results were seen for the vertical stability index (FAI = 0.73 ± 0.17, STABLE = 0.61 ± 0.13), the normalized dynamic postural stability index (FAI = 0.85 ± 0.17, STABLE = 0.73 ± 0.12), the normalized vertical stability index (FAI = 0.007 ± 0.004, STABLE = 0.005 ± 0.001), and the dynamic postural stability index (FAI = 0.008 ± 0.003, STABLE = 0.006 ± 0.001). Conclusions: These results indicate that the dynamic postural stability index is a sensitive measure of dynamic postural stability and is capable of detecting differences between individuals with stable ankles and individuals with functionally unstable ankles.

Evidence indicates that voluntary and involuntary movements are altered by affective context as well as the characteristics of an initiating cue. The purpose of this study was to determine the contribution of central and peripheral mechanisms to this phenomenon. During the presentation of pleasant, unpleasant, neutral, and blank images, participants (N = 33) responded to auditory stimuli (startle, 107 dB startle or 80 dB tone) by initiating a bimanual isometric contraction of the wrist and finger extensor muscles. Analyses of electromyography and force measures supported the hypothesis that exposure to unpleasant images accelerates central processing times and increases the gradient of slope of peripheral movement execution. In addition, startle cues as compared with tone cues accelerated and magnified all temporal and amplitude indices. Collectively, these findings have noteworthy implications for (a) those seeking to facilitate the speed and force of voluntary movement (i.e., movement rehabilitation), (b) understanding the higher incidence of motor difficulty in individuals with affective disorders, and (c) those seeking to regulate emotional input so as to optimize the quality of intended movements.

The use of activity-dependent interventions has shown some success in promoting recovery of upper limb function in chronic stroke patients. This study compared the neurophysiological and behavioural changes associated with two such rehabilitation protocols: unilateral and bilateral movement training. Twelve chronic stroke patients were randomly assigned to the two training protocols involving six daily practice sessions. Each session consisted of 50 trials of a dowel placement task performed either with both impaired and unimpaired arm moving synchronously (bilateral training group) or with only the impaired arm moving (unilateral training). Kinematic measurements of upper limb movements were made in four unilateral test trials performed prior to and following each practice session. Functional assessments of the impaired upper limb and neurophysiological assessments, using transcranial magnetic stimulation (TMS), of the affected and non-affected cortical hemispheres were made prior to and following the intervention sessions. Individuals receiving bilateral training showed a reduction in movement time of the impaired limb and increased upper limb functional ability compared to individuals receiving unilateral training. In some patients changes to upper limb function were associated with changes to the cortical representation of a target muscle in the non-affected hemisphere. Overall, these findings suggest that a short-term bilateral training intervention may be effective in facilitating upper limb motor function in chronic stroke patients.

The use of transcranial direct current stimulation (tDCS) to enhance cognitive and motor functions has enjoyed a massive increase in popularity. Modifying neuroplasticity via non-invasive cortical stimulation has enormous potential to slow or even reverse declines in functions associated with ageing. The current meta-analysis evaluated the effects of tDCS on cognitive and motor performance in healthy older adults. Of the 81 studies identified, 25 qualified for inclusion. A random effects model meta-analysis revealed a significant overall standardized mean difference equal to 0.53 (SE = 0.09; medium heterogeneity: I = 57.08%; and high fail-safe: N = 448). Five analyses on moderator variables indicated significant tDCS beneficial effects: (a) on both cognitive and motor task performances, (b) across a wide-range of cognitive tasks, (c) on specific brain areas, (d) stimulation offline (before) or online (during) the cognitive and motor tasks. Although the meta-analysis revealed robust support for enhancing both cognitive and motor performance, we outline a number of caveats on the use of tDCS.

Stroke interferes with voluntary control of motor actions. Although spontaneous recovery of function can occur, restoration of normal motor function in the hemiplegic upper limb is noted in fewer than 15% of individuals. However, there is increasing evidence to suggest that in addition to injury-related reorganization, motor cortex functions can be altered by individual motor experiences. Such neural plasticity has major implications for the type of rehabilitative training administered post-stroke. This review proposes that noteworthy upper extremity gains toward motor recovery evolve from activity-dependent intervention based on theoretical motor control constructs and interlimb coordination principles. Founded on behavioral and neurophysiological mechanisms, bilateral movement training/practice has shown great promise in expediting progress toward chronic stroke recovery in the upper extremity. Planning and executing bilateral movements post-stroke may facilitate cortical neural plasticity by three mechanisms: (a) motor cortex disinhibition that allows increased use of the spared pathways of the damaged hemisphere, (b) increased recruitment of the ipsilateral pathways from the contralesional or contralateral hemisphere to supplement the damaged crossed corticospinal pathways, and (c) upregulation of descending premotorneuron commands onto propriospinal neurons.

The authors tested the specificity of practice hypothesis on intersegmental dynamics of rapid-aiming limb movements. During acquisition, 20 participants performed an aiming task as quickly and accurately as possible either with or without vision. Following moderate (140 trials) and extensive (560 trials) practice, participants completed 20 transfer test trials in a no-vision condition. Overall, the acquisition-phase findings revealed that vision improved aiming accuracy performance but had only a slight impact on movement time and intersegmental dynamics. After 560 trials of practice, however, withdrawal of vision resulted in specificity of practice effects on intersegmental dynamics at the shoulder as well as on aiming accuracy. Taken together, those findings support and extend the specificity of practice hypothesis.

Active neuromuscular stimulation is an effective behavioral intervention for motor recovery improvements after a stroke. However, the most effective active neuromuscular stimulation durations have not been determined. The present experiment investigated active stimulation durations (0, 5, and 10 s) coupled with bilateral movements on progress toward motor recovery in wrist and finger extension. Twenty-six stroke survivors with chronic hemiparesis were randomly assigned to the stimulation duration groups, and subjects completed 4 days of rehabilitation training over a 2-week period. Mixed design analyses of variance on the Box and Block scores, chronometric reaction times, and force modulation of the sustained muscle contraction task revealed distinct motor recovery improvements for both the 5 and 10 s stimulation duration groups in comparison to the 0 s duration control group. Further, the number of blocks moved by the 10-s duration group exceeded those moved by the 5-s duration group. In conclusion, the 5 and 10 s duration active stimulation/bilateral movement groups decreased residual motor dysfunctions that persisted beyond 12 months post stroke.

Objective: To investigate progress toward motor recovery in patients with chronic hemiparesis (mean time since stroke 3.2 years), comparing different types of practice schedules. Design: To increase voluntary control of the upper extremity, active neuromuscular stimulation was administered during blocked and random practice schedules as patients performed three specific movements: wrist/finger extension, elbow joint extension, and shoulder joint abduction. Methods: 34 stroke subjects volunteered to participate and were randomly assigned to one of three treatment groups: blocked practice (the same movement was repetitively performed on successive trials) combined with active neuromuscular stimulation; random practice (different movements on successive trials) along with active stimulation; or no active stimulation assistance control group. Subjects completed two days of 90 minute training for each of two weeks with at least 24 hours of rest between sessions. A session was three sets of 30 successful active neuromuscular stimulation trials with the three movements executed 10 times/set. Results: Mixed design analyses on three categories of behavioural measures indicated motor improvements for the blocked and random practice/stimulation groups in comparison with the control group during the post-test period, with a larger number of blocks moved, faster premotor and motor reaction times, and less variability in the sustained muscular contraction task. Conclusions: Upper extremity rehabilitation intervention of active stimulation and blocked practice performed as well as stimulation/random practice. Moreover, these purposeful voluntary movement findings support and extend sensorimotor integration theory to both practice schedules.

Epidemiological evidence suggests the incidence of injury in female athletes is greater after the onset of puberty and that landing from a jump is a common mechanism of knee injury. This investigation compared lower extremity joint kinematics and joint resultant forces and moments during three types of stride jump (stride jump followed by a static landing; a ballistic vertical jump; and a ballistic lateral jump) between pre- and postpubescent recreational athletes to provide some insight into the increased incidence of injury. Sixteen recreationally active postpubescent women (ages 18–25 years) and 16 recreationally active prepubescent girls (ages 8–11 years) participated in this study. High speed 3D videography and force plate data were used to record each jumper’s performance of the stride jumps, and an inverse dynamic procedure was used to estimate lower extremity joint resultant forces and moments and power. These dependent variables were submitted to a 2 × 3 (Maturation Level × Landing Sequence) MANOVA with repeated measures on the last factor. The findings indicated that postpubescents landed with the knee more extended (4.4°) and had greater extension moments (approximately 30% greater hip and knee extension moments) and powers (40% greater knee power). Further, the post-pubescent athletes had greater knee anterior/posterior forces as well as medio-lateral resultant forces. The differences found between the two groups suggest there may be anatomical and physiological changes with puberty that lead to differences in strength or neuromuscular control which influence the dynamic restraint system in these recreational athletes. A combination of these factors likely plays a role in the increased risk of injury in postpubescent females.

Chronic cerebrovascular accident individuals with partial paralysis in an upper extremity typically demonstrate difficulty in voluntarily controlling movement initiation. This study investigated patterns of electromyogram (EMG) activation levels while stroke subjects voluntarily initiated their impaired wrist and finger extensor muscles. Twenty subjects were randomly assigned to either a unilateral movement/stimulation group or a bilateral movement/stimulation group. Participants completed 4 days (6 h over 2 weeks) of active neuromuscular stimulation (i.e., 5 s/trial, 90 trials/day, biphasic waveform) on the wrist and finger extensors according to group assignments. The EMG activation levels were analyzed with a three-factor mixed design Motor recovery protocol x Session block x Trial block (2 x 2 x 3) ANOVA with repeated measures on the second and third factors. This robust analysis revealed higher EMG activation levels for the coupled bilateral movement/stimulation group than the unilateral movement/stimulation group. In addition, higher muscle activation levels were found for the second session block as well as trial blocks 2 and 3. Overall, these findings indicated improved motor capabilities of the impaired muscles as evidenced by the higher voluntary EMG activation levels.

Objective . To assess the relationship between foot alignment and transverse plane knee motion during a single leg-landing task. Design . Clinical trial. Setting . Hospital biomechanics laboratory. Participants . Seven healthy young women without excessive forefoot, arch, or rear-foot malalignments. Methods and measures . Varus and valgus foot malalignments were mimicked by placing 8° medial and lateral posted orthotics into the shoes before participants performed three landings from a drop jump off a 43cm high platform. The change in tibiofemoral rotation relative to the no orthotic condition was measured. Results . The medial posted orthotic resulted in 3.1±5.5° less internal tibiofemoral rotation as compared to the nonorthotic condition, while the lateral posting produced 2.6±2.2° more internal tibiofemoral rotation ( t 6 =−2.51, p ≤0.03). Conclusions . Orthotic induced malalignments altered the magnitude of tibiofemoral rotation during a closed kinematic chain activity. Orthotic posting may be used to reduce the rotary stress on the knee during landing activities.