•We examined the role of bimanual force coordination in bimanual dexterity after stroke.•Stroke group showed impaired dexterity in a bimanual task with a shared goal.•Stroke group had poor bimanual ...coordination of forces during dynamic force modulation.•Reduced bimanual force coordination predicted impaired dexterity in a bimanual task.
The ability to coordinate forces with both hands is crucial for manipulating objects in bimanual tasks. The purpose of this study was to determine the influence of bimanual force coordination on collaborative hand use for dexterous tasks in chronic stroke survivors.
Fourteen stroke survivors (63.03 ± 15.33 years) and 14 healthy controls (68.85 ± 8.16) performed two bimanual tasks: 1) Pegboard assembly task, and 2) dynamic force tracking task using bilateral index fingers. The Pegboard assembly task required collaborative use of both hands to construct a structure with pins, collars, and washers. We quantified bimanual dexterity with Pegboard assembly score as the total number of pins, collars, and washers assembled in one minute. The force tracking task involved controlled force increment and decrement while tracking a trapezoid trajectory. The task goal was to match the target force with the total force, i.e., sum of forces produced by both hands as accurately as possible. We quantified bimanual force coordination by computing time-series cross-correlation coefficient, time-lag, amplitude of coherence in 0 – 0.5 Hz, and 0.5–1 Hz for force increment and decrement phases.
In the Pegboard assembly task, the stroke group assembled fewer items relative to the control group (p = 0.004). In the bimanual force tracking task, the stroke group showed reduced cross-correlation coefficient (p = 0.01), increased time-lag (p = 0.00), and reduced amplitude of coherence in 0–0.5 Hz (p = 0.03) and in 0.5–1 Hz (p = 0.00). Multiple regression analysis in the stroke group revealed that performance on Pegboard assembly task was explained by cross-correlation coefficient and coherence in 0.5–1 Hz during force increment (R2 = 0.52, p = 0.00).
Individuals with stroke show impaired bimanual dexterity and diminished bimanual force coordination. Importantly, stroke-related deterioration in bimanual force coordination was associated with poor performance on dexterous bimanual tasks that require collaboration between hands. Re-training bimanual force coordination in stroke survivors could facilitate a higher degree of participation in daily activities through improved bimanual dexterity.
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
< 0.0001;
Z
= 10.49). This large effect indicated substantial motor coordination deficits in the ASD groups across a wide range of behaviors. The current overall findings portray motor coordination deficits as pervasive across diagnoses, thus, a cardinal feature of ASD.
A less precise force output impairs our ability to perform movements, learn new motor tasks, and use tools. Here we show that low-frequency oscillations in force are detrimental to force precision. ...We summarize the recent evidence that low-frequency oscillations in force output represent oscillations of the spinal motor neuron pool from the voluntary drive, and can be modulated by shifting power to higher frequencies. Further, force oscillations below 0.5 Hz impair force precision with increased voluntary drive, aging, and neurological disease. We argue that the low-frequency oscillations are (1) embedded in the descending drive as shown by the activation of multiple spinal motor neurons, (2) are altered with force intensity and brain pathology, and (3) can be modulated by visual feedback and motor training to enhance force precision. Thus, low-frequency oscillations in force provide insight into how the human brain regulates force precision.
Abstract
Heightened motor variability is a prominent impairment after stroke. During walking, stroke survivors show increased spatial and temporal variability; however, the functional implications of ...increased gait variability are not well understood. Here, we determine the effect of gait variability on the coordination between lower limbs during overground walking in stroke survivors. Ambulatory stroke survivors and controls walked at a preferred pace. We measured stride length and stride time variability, and accuracy and consistency of anti-phase gait coordination with phase coordination index (PCI). Stroke survivors showed increased stride length variability, stride time variability, and PCI compared with controls. Stride time variability but not stride length variability predicted 43% of the variance in PCI in the stroke group. Stride time variability emerged as a significant predictor of error and consistency of phase. Despite impaired spatial and temporal gait variability following stroke, increased temporal variability contributes to disrupted accuracy and consistency of gait coordination. We provide novel evidence that decline in gait coordination after stroke is associated with exacerbated stride time variability, but not stride length variability. Temporal gait variability may be a robust indicator of the decline in locomotor function and an ideal target for motor interventions that promote stable walking after stroke.
Fast and accurate braking is essential for safe driving and relies on efficient cognitive and motor processes. Despite the known sex differences in overall driving behavior, it is unclear whether sex ...differences exist in the objective assessment of driving-related tasks in older adults. Furthermore, it is unknown whether cognitive-motor processes are differentially affected in men and women with advancing age. We aimed to determine sex differences in the cognitive-motor components of the braking performance in older adults. Fourteen men (63.06 ± 8.53 years) and 14 women (67.89 ± 11.81 years) performed a braking task in a simulated driving environment. Participants followed a lead car and applied a quick and controlled braking force in response to the rear lights of the lead car. We quantified braking accuracy and response time. Importantly, we also decomposed response time in its cognitive (pre-motor response time) and motor (motor response time) components. Lastly, we examined whether sex differences in the activation and coordination of the involved muscles could explain differences in performance. We found sex differences in the cognitive-motor components of braking performance with advancing age. Specifically, the cognitive processing speed is 27.41% slower in women, while the motor execution speed is 24.31% slower in men during the braking task. The opposite directions of impairment in the cognitive and motor speeds contributed to comparable overall braking speed across sexes. The sex differences in the activation of the involved muscles did not relate to response time differences between men and women. The exponential increase in the number of older drivers raises concerns about potential effects on traffic and driver safety. We demonstrate the presence of sex differences in the cognitive-motor components of braking performance with advancing age. Driving rehabilitation should consider differential strategies for ameliorating sex-specific deficits in cognitive and motor speeds to enhance braking performance in older adults.
The functional declines with aging relate to deficits in motor control and strength. In this study, we determine whether older adults exhibit impaired driving as a consequence of declines in motor ...control or strength.
Young and older adults performed the following tasks: (i) maximum voluntary contractions of ankle dorsiflexion and plantarflexion; (ii) sinusoidal tracking with isolated ankle dorsiflexion; and (iii) a reactive driving task that required responding to unexpected brake lights of the car ahead. We quantified motor control with ankle force variability, gas position variability, and brake force variability. We quantified reactive driving performance with a combination of gas pedal error, premotor and motor response times, and brake pedal error.
Reactive driving performance was ~30% more impaired (t = 3.38; p < .01) in older adults compared with young adults. Older adults exhibited greater motor output variability during both isolated ankle dorsiflexion contractions (t = 2.76; p < .05) and reactive driving (gas pedal variability: t = 1.87; p < .03; brake pedal variability: t = 4.55; p < .01). Deficits in reactive driving were strongly correlated to greater motor output variability (R
= .48; p < .01) but not strength (p > .05).
This study provides novel evidence that age-related declines in motor control but not strength impair reactive driving. These findings have implications on rehabilitation and suggest that interventions should focus on improving motor control to enhance driving-related function in older adults.
Purpose:
Increased gait variability in stroke survivors indicates poor dynamic balance and poses a heightened risk of falling. Two primary motor impairments linked with impaired gait are declines in ...movement precision and strength. The purpose of the study is to determine whether force-control training or strength training is more effective in reducing gait variability in chronic stroke survivors.
Methods:
Twenty-two chronic stroke survivors were randomized to force-control training or strength training. Participants completed four training sessions over 2 weeks with increasing intensity. The force-control group practiced increasing and decreasing ankle forces while tracking a sinusoid. The strength group practiced fast ankle motor contractions at a percentage of their maximal force. Both forms of training involved unilateral, isometric contraction of the paretic, and non-paretic ankles in plantarflexion and dorsiflexion. Before and after the training, we assessed gait variability as stride length and stride time variability, and gait speed. To determine the task-specific effects of training, we measured strength, accuracy, and steadiness of ankle movements.
Results:
Stride length variability and stride time variability reduced significantly after force-control training, but not after strength training. Both groups showed modest improvements in gait speed. We found task-specific effects with strength training improving plantarflexion and dorsiflexion strength and force control training improving motor accuracy and steadiness.
Conclusion:
Force-control training is superior to strength training in reducing gait variability in chronic stroke survivors. Improving ankle force control may be a promising approach to rehabilitate gait variability and improve safe mobility post-stroke.
Abstract Research indicates that balance is impaired in the involved limb following an ankle injury. However, bilateral balance impairments are a viable reason for previous non-significant findings ...between involved and uninvolved limbs. The purpose of this investigation was to conduct a meta-analysis on studies reporting the effects of lateral ankle trauma on balance of the involved and uninvolved limb after acute ankle injury and chronic ankle instability. Twelve studies qualified for inclusion and assessed static balance for both the involved and uninvolved limbs post-injury and a control group. Meta-analyses calculated standardized mean difference effects and explored moderating variables for the involved and uninvolved limbs relative to controls. A significant cumulative effect size (ES = 0.448, p < 0.00001) indicated that balance of the involved limb is impaired after a history of ankle injury. Moderator variable analysis revealed that both acute (ES = 0.529, p < 0.0002) and chronic (ES = 0.338, p < 0.001) lateral ankle trauma negatively affected balance. Analysis of the uninvolved limb also revealed postural stability impairments (ES = 0.275, p < 0.003). Additional, moderator analysis showed a significant acute effect (ES = 0.564, p < 0.0001), but failed to find significance for individuals with chronic ankle instability (ES = 0.070, p = 0.552). These findings provide strong evidence that balance is bilaterally impaired after an acute lateral ankle sprain. However, these findings suggest that bilateral balance deficits are not present in patients with chronic ankle instability. Based on these findings, the uninvolved limb should not be used as a reference for “normal balance” following an acute lateral ankle sprain. Further, patients with acute lateral ankle sprains should undergo balance training on both limbs.
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 (
I
2
=
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.
Braking is a critical determinant of safe driving that depends on the integrity of cognitive and motor processes. Following stroke, both cognitive and motor capabilities are impaired to varying ...degrees. The current study examines the combined impact of cognitive and motor impairments on braking time in chronic stroke.
Twenty stroke survivors and 20 aged-matched healthy controls performed cognitive, motor, and simulator driving assessments. Cognitive abilities were assessed with processing speed, divided attention, and selective attention. Motor abilities were assessed with maximum voluntary contraction (MVC) and motor accuracy of the paretic ankle. Driving performance was examined with the braking time in a driving simulator and self-reported driving behavior.
Braking time was 16% longer in the stroke group compared with the control group. The self-reported driving behavior in stroke group was correlated with braking time (r = - 0.53, p = 0.02). The stroke group required significantly longer time for divided and selective attention tasks and showed significant decrease in motor accuracy. Together, selective attention time and motor accuracy contributed to braking time (R
= 0.40, p = 0.01) in stroke survivors.
This study provides novel evidence that decline in selective attention and motor accuracy together contribute to slowed braking in stroke survivors. Driving rehabilitation after stroke may benefit from the assessment and training of attentional and motor skills to improve braking during driving.
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