The Effect of Cognitive Task, Gait Speed, and Age on Cognitive-Motor Interference during Walking.

Dual-tasking can cause cognitive-motor interference (CMI) and affect task performance. This study investigated the effects of age, gait speed, and type of cognitive task on CMI during gait. Ten younger and 10 older adults walked on a pressure-sensitive GAITRite walkway which recorded gait speed and step length. Participants walked at a slow, preferred, or fast speed while simultaneously completing four cognitive tasks: visuomotor reaction time (VMRT), serial subtraction (SS), word list generation (WLG), and visual Stroop (VS). Each combination of task and speed was repeated for two trials. Tasks were also performed while standing. Motor and cognitive costs were calculated with the formula: ((single-dual)/single × 100). Higher costs indicate a larger reduction in performance from single to dual-task. Motor costs were higher for WLG and SS than VMRT and VS and higher in older adults (p < 0.05). Cognitive costs were higher for SS than WLG (p = 0.001). At faster speeds, dual-task costs increased for WLG and SS, although decreased for VMRT. CMI was highest for working memory, language, and problem-solving tasks, which was reduced by slow walking. Aging increased CMI, although both ages were affected similarly by task and speed. Dual-task assessments could include challenging CMI conditions to improve the prediction of motor and cognitive status.

Sex differences in cognitive-motor components of braking in older adults.

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.

Cognitive and motor deficits contribute to longer braking time in stroke.

BACKGROUND: 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. METHODS: 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. RESULTS: 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 (R2 = 0.40, p = 0.01) in stroke survivors. CONCLUSIONS: 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.

Dynamic bimanual force control in chronic stroke: contribution of non-paretic and paretic hands.

Dynamic force modulation is critical for performing skilled bimanual tasks. Unilateral motor impairments after stroke contribute to asymmetric hand function. Here, we investigate the impact of stroke on dynamic bimanual force control and compare the contribution of each hand to a bimanual task. Thirteen chronic stroke and thirteen healthy control participants performed bimanual, isometric finger flexion during visually guided, force tracking of a trapezoidal trajectory with force increment and decrement phases. We quantified the accuracy and variability of total force from both hands. Individual hand contribution was quantified with the proportion of force contributed to total force and force variability of each hand. The total force output was 53.10% less accurate and 56% more variable in the stroke compared with the control group. The variability of total force was 91.10% greater in force decrement than increment phase. In stroke group, the proportion of force and force variability contributed by each hand differed across the two phases. During force decrement, the proportion of force contributed by the non-paretic hand reduced and force variability of the non-paretic hand increased, compared with the increment phase. The control group showed no differences in each hand's contribution across the two force phases. In conclusion, dynamic bimanual force modulation is impaired after stroke, with greater deficits in force decrement than force increment. The non-paretic and paretic hands adapt differentially to dynamic bimanual task constraints. During force decrement, the non-paretic hand preferentially assumes force modulation, while the paretic hand produces steady force to meet the force requirements.

Does severity of motor impairment affect reactive adaptation and fall-risk in chronic stroke survivors?

BACKGROUND: A single-session of slip-perturbation training has shown to induce long-term fall risk reduction in older adults. Considering the spectrum of motor impairments and deficits in reactive balance after a cortical stroke, we aimed to determine if chronic stroke survivors could acquire and retain reactive adaptations to large slip-like perturbations and if these adaptations were dependent on severity of motor impairment. METHODS: Twenty-six chronic stroke participants were categorized into high and low-functioning groups based on their Chedoke-McMaster-Assessment scores. All participants received a pre-training, slip-like stance perturbation at level-III (highest intensity/acceleration) followed by 11 perturbations at a lower intensity (level-II). If in early phase, participants experienced > 3/5 falls, they were trained at a still lower intensity (level-I). Post-training, immediate scaling and short-term retention at 3 weeks post-training was examined. Perturbation outcome and post-slip center-of-mass (COM) stability was analyzed. RESULTS: On the pre-training trial, 60% of high and 100% of low-functioning participants fell. High-functioning group tolerated and adapted at training-intensity level-II but low-functioning group were trained at level-I (all had > 3 falls on level-II). At respective training intensities, both groups significantly lowered fall incidence from 1st through 11th trials, with improved post-slip stability and anterior shift in COM position, resulting from increased compensatory step length. Both groups demonstrated immediate scaling and short-term retention of the acquired stability control. CONCLUSION: Chronic stroke survivors are able to acquire and retain adaptive reactive balance skills to reduce fall risk. Although similar adaptation was demonstrated by both groups, the low-functioning group might require greater dosage with gradual increment in training intensity.

Fall risk during opposing stance perturbations among healthy adults and chronic stroke survivors.

Studies examining recovery from SLIPS and TRIPS indicate higher incidence of falls during SLIPS than TRIPS however, differences in the recovery mechanisms during these opposing perturbations have not been examined. We therefore aimed to compare the reactive balance responses contributing to fall risk during SLIPS and TRIPS at comparable perturbation intensity among community-dwelling healthy adults and chronic stroke survivors. Younger adults (N = 11), age-matched adults (N = 11) and chronic stroke survivors (N = 12) were exposed to a single SLIP and TRIP through a motorized treadmill (16 m/s2, 0.20 m). Center of mass (COM) state stability was measured by recording COM position and velocity relative to base of support, i.e., D COM/BOS and X COM/BOS, respectively. Trunk and compensatory step kinematics were also recorded. During SLIPS, the incidence of falls among stroke survivors was greater than healthy adults (53.83% vs. 0%), however not for TRIPS. All groups showed higher change in postural stability from liftoff to touchdown during TRIPS than SLIPS. Among healthy adults higher change in D COM/BOS during TRIPS was accompanied by the ability to control trunk flexion at step touchdown and lower peak trunk velocity as compared with SLIPS, with no significant differences in compensatory step length between the perturbations (p > 0.05). Chronic stroke survivors increased compensatory step length during TRIPS versus SLIPS (p < 0.05) contributing to greater stability change. They were unable to control trunk excursion and peak trunk velocity as compared with the healthy adults leading to lower stability than healthy younger and age-matched adults during SLIPS and lower stability than younger adults during TRIPS. Difficulty in trunk control during SLIPS among all individuals and compensatory step length  among stroke survivors emphasizes higher fall risk for SLIPS than TRIPS among these populations.

Modulation of reactive response to slip-like perturbations: effect of explicit cues on paretic versus non-paretic side stepping and fall-risk.

This study aimed to examine the effect of explicit cuing on reactive stepping with the paretic limb during slip-like perturbations in stroke survivors and to identify differences in postural stability and fall-risk while stepping with either limb. Eleven chronic hemiparetic stroke survivors received slip-like stance perturbations in no-cue (implicit, no instructions) and cued (explicit, instructions to step with paretic limb) conditions. Frequency of stepping with the paretic limb was recorded. Differences between non-paretic and paretic steps for falls, number of compensatory steps, relative center-of-mass position (X COM/BOS), and velocity (X(COM/BOS)), and vertical limb support (hip descent-Z hip) were analyzed. Stepping with the paretic limb increased from 6% in no-cue condition to 42% in cued condition with no significant difference in number of falls and steps regardless of stepping limb. At liftoff of the compensatory step, stability was greater (anterior X COM/BOS) with paretic than non-paretic limb stepping whereas, at touchdown (TD) of the step, stability with paretic limb reduced (posterior X COM/BOS and X(COM/BOS)) due to a smaller compensatory step taken with the paretic versus non-paretic limb. There was no significant difference in peak Z hip regardless of stepping limb; however, the timing of peak Z hip differed (occuring prior to TD during non-paretic stepping and post-TD during paretic stepping). Thus, fall onset was earlier with non-paretic versus paretic stepping. The results support that explicit cueing can facilitate initiation of reactive step from the paretic limb as compared with the no-cue condition. Stepping with the paretic limb in the cued condition however altered time of fall onset. Regardless of the stepping side, individuals demonstrated a fall risk suggesting the need for interventions focusing on reactive step training with both the limbs.

Task matters: influence of different cognitive tasks on cognitive-motor interference during dual-task walking in chronic stroke survivors.

BACKGROUND: The impact of unilateral brain damage, such as that caused by stroke, on the interaction between higher cognitive functions and walking remains uncertain. We compared cognitive-motor interference (CMI) during dual-task (DT) walking between chronic stroke survivors and young adults performing explicitly different cognitive tasks. METHODS: Ten community-dwelling chronic stroke survivors and 10 young adults performed 3 cognitive tasks - visuomotor reaction time (VMRT), serial subtraction (SS), and Stroop test (STR) - while sitting and walking. Gait velocity was recorded using an electronic walkway. Cognitive variables included reaction time and number of correct responses. Motor and cognitive costs were computed. RESULTS: DT walking led to significant declines in motor and cognitive performance. Significant main effect of task (P < .01) and group (P < .01) was observed for motor cost. The stroke group showed highest motor cost for SS task, whereas the young group showed highest motor cost for STR task (Group × Task interaction, P < .05). Although cognitive costs for both groups was highest for VMRT and lowest for STR tasks, cognitive cost for SS task was significantly greater for the stroke group compared with the young group (Group × Task interaction, P < .05). CONCLUSIONS: CMI pattern in chronic stroke survivors differs significantly with type of cognitive task. Gradual cognitive decline with chronicity of condition might have a role in altering the CMI pattern in this population. Future studies of DT interventions for stroke survivors might benefit from incorporating working memory tasks in their protocols.

Adverse Effects Faced by Healthcare Workers While Using Personal Protective Equipment During the COVID-19 Pandemic in Civil Hospital, Ahmedabad.

Background Healthcare workers (HCWs) were compelled to use personal protective equipment (PPE) during the COVID-19 pandemic to prevent cross-transmission. One of the most significant challenges in responding to the COVID-19 pandemic is the consistent and effective use of PPE to avoid staff exposure and infection. This study aimed to detect and evaluate the adverse effects of PPE and determine the associated risk factors. Methodology This cross-sectional study included 186 randomly selected HCWs at Civil Hospital, Ahmedabad, from May 2022 to July 2022. An anonymous self-administered questionnaire was used for data collection, and data analysis was done using descriptive statistics. Results PPE-related adverse effects were noted among 147 HCWs, with a prevalence of 79.03%. Data analysis showed that factors significantly associated with PPE adverse effects in HCWs were age group 20-40 years (chi-squared (χ2) = 4.119, p = 0.04) and female gender (χ2 = 7.153, p = 0.007). Overall, 30.8% of participants had tested positive while on duty during the pandemic. Similarly, adverse effects were associated with PPE use of more than four hours per day and more than three days per week (χ2 = 5.477, p = 0.02 and χ2 = 6.488, p = 0.01, respectively). The majority of HCWs expressed indentation and pain on the back of the ear (52.7%) and pressure-related injury (39.8%) as adverse effects after wearing masks; skin soaking in sweat (54.83%) due to gloves; profuse sweating due to gown (64.28%); fogging (65.26%) due to googles and face-shield; and discomfort (61.29%). Conclusions The prevalence of adverse effects related to wearing PPE was alarmingly high among HCWs. The major risk factors were age, female sex, and duration of use. Although the majority of healthcare personnel have received vaccinations, the use of PPE has not altered, and severe skin reactions continue to be a global issue with no known solution. To further understand the problem, national data for the impacted healthcare professionals could be helpful. Furthermore, workplace prevention programs are necessary.

Does the contribution of the paretic hand to bimanual tasks change with grip strength capacity following stroke?

INTRODUCTION: The majority of tasks we perform every day require coordinated use of both hands. Following a stroke, the paretic hand contribution to bimanual tasks is often impaired, leading to asymmetric hand use. Grip strength is a commonly used clinical indicator of progress towards stroke motor recovery. The extent to which the paretic hand's contribution to bimanual tasks improves with increasing grip strength is not known. The purpose of this study is to determine how grip strength capacity of the paretic hand influences its contribution to bimanual tasks. METHODS: Twenty-one chronic stroke participants and ten older control participants volunteered to take part in this study. The individuals with stroke were recruited in two distinct groups based on the grip strength capacity of paretic hand, i.e., paretic hand strength/non-paretic hand strength, expressed as a percentage. The low strength-capacity group was identified as individuals with grip strength capacity less than 60% and the high strength-capacity group was individuals with grip strength capacity greater than or equal to 60%. All groups performed isometric, grip force contractions in two bimanual tasks - a maximum force production (MVC) task and a submaximal force control task. We quantified the magnitude of force contributed by the paretic and non-paretic hands during both tasks. Additionally, in the force control task we quantified the amount and structure of force variability using coefficient of variation (CV) and approximate entropy (ApEn) for both hands. RESULTS: The amount of force contributed by the paretic hand increased in bimanual tasks with an increase in its grip strength capacity, (maximal force production: r = 0.85, p < 0.01; submaximal force control: r = 0.62, p < 0.01). In the bimanual MVC task and bimanual force control task, both hands contributed equal magnitudes of force in the high strength-capacity group but unequal forces in low strength-capacity group. Surprisingly, the amount and structure of force variability in bimanual force control tasks did not change with the increase in grip strength capacity, (CV of force: r = - 0.07, p = 0.77; ApEn: r = - 0.23, p = 0.31). Both low and high strength-capacity stroke groups showed significantly higher CV of force and heightened ApEn compared with the control group. CONCLUSION: With the increase in grip strength capacity, the paretic hand contributes greater magnitude of force but continues to show persistent deficits in force modulation in bimanual tasks. Therefore, stroke rehabilitation should emphasize retraining of the paretic hand for force modulation to maximize its use in bimanual tasks.

Motor Training After Stroke: A Novel Approach for Driving Rehabilitation.

Background: A key component of safe driving is a well-timed braking performance. Stroke-related decline in motor and cognitive processes slows braking response and puts individuals with stroke at a higher risk for car crashes. Although the impact of cognitive training on driving has been extensively investigated, the influence of motor interventions and their effectiveness in enhancing specific driving-related skills after stroke remains less understood. We compare the effectiveness of two motor interventions (force-control vs. strength training) to facilitate braking, an essential skill for safe driving. Methods: Twenty-two stroke survivors were randomized to force-control training or strength training. Before and after training, participants performed a braking task during car-following in a driving simulator. We quantified the cognitive and motor components of the braking task with cognitive processing time and movement execution time. Results: The cognitive processing time did not change for either training group. In contrast, the movement execution became significantly faster (14%) following force-control training but not strength training. In addition, task-specific effects of training were found in each group. The force-control group showed improved accuracy and steadiness of ankle movements, whereas the strength training group showed increased dorsiflexion strength following training. Conclusion: Motor intervention that trains ankle force control in stroke survivors improves the speed of movement execution during braking. Driving rehabilitation after stroke might benefit from incorporating force-control training to enhance the movement speed for a well-timed braking response.

Increased temporal stride variability contributes to impaired gait coordination after stroke.

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.

Does stroke-induced sensorimotor impairment and perturbation intensity affect gait-slip outcomes?

People with chronic stroke (PwCS) demonstrate similar gait-slip fall-risk on both paretic and non-paretic side. Compensatory stepping and slipping limb control are crucial to reduce gait-slip fall-risk. Given the unpredictable intensities of real-life perturbations, this study aimed to determine whether recovery from paretic or non-paretic slips vary as a function of perturbation intensity among PwCS. Forty-four PwCS were assigned to non-paretic low intensity slip, non-paretic high intensity slip, paretic low intensity slip, or paretic high intensity slip group. Participants were subjected to a novel overground gait-slip with a distance of 24 cm (low) or 45 cm (high), under either limb. Recovery strategies, center of mass (CoM) state stability and slipping kinematics were analyzed. Both non-paretic high and low intensity groups demonstrated similar percentage of aborted and recovery stepping, however, paretic high intensity group demonstrated greater aborted stepping (p > 0.05). Both high and low intensity paretic slip groups demonstrated reduced post-slip CoM stability relative to the non-paretic slip groups (p < 0.05). Slip displacement was greater in paretic high group compared with non-paretic high group (p < 0.05). Greater slip displacement at higher intensity was noted only in paretic slip group (p < 0.05). The slip velocity was faster in paretic groups compared to non-paretic slip groups (p < 0.05). Paretic slips showed lower stability at both intensities associated with difficulty in modulating slipping kinematics and resorting to an increased aborted stepping strategy compared to non-paretic slip. These findings are suggestive of developing balance interventions for improving both compensatory non-paretic limb stepping and reactive control of slipping paretic limb for fall-risk reduction.

Force-Control vs. Strength Training: The Effect on Gait Variability in Stroke Survivors.

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.

Impaired force control contributes to car steering dysfunction in chronic stroke.

PURPOSE: Precise control of a car steering wheel requires adequate motor capability. Deficits in grip strength and force control after stroke could influence the ability steer a car. Our study aimed to determine the impact of stroke on car steering and identify the relative contribution of grip strength and grip force control to steering performance. METHODS: Twelve chronic stroke survivors and 12 controls performed three gripping tasks with each hand: maximum voluntary contraction, dynamic force tracking, and steering a car on a winding road in a simulated driving environment. We quantified grip strength, grip force variability, and deviation of the car from the center of the lane. RESULTS: The paretic hand exhibited reduced grip strength, increased grip force variability, and increased lane deviation compared with the non-dominant hand in controls. Grip force variability, but not grip strength, significantly predicted (R2 = 0.49, p < 0.05) lane deviation with the paretic hand. CONCLUSION: Stroke impairs the steering ability of the paretic hand. Although grip strength and force control of the paretic hand are diminished after stroke, only grip force control predicts steering accuracy. Deficits in grip force control after stroke contribute to functional limitations in performing skilled tasks with the paretic hand.Implications for rehabilitationDriving is an important goal for independent mobility after stroke that requires motor capability to manipulate hand and foot controls.Two prominent stroke-related motor impairments that may impact precise car steering are reduced grip strength and grip force control.In individuals with mild-moderate impairments, deficits in grip force modulation rather than grip strength contribute to compromised steering performance with the paretic hand.We recommend that driving rehabilitation should consider re-educating grip force modulation for successful driving outcomes post stroke.

Functional implications of impaired bimanual force coordination in chronic stroke.

BACKGROUND: 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. METHODS: Fourteen stroke survivors (63.03 ±â€¯15.33 years) and 14 healthy controls (68.85 ±â€¯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. RESULTS: 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). CONCLUSIONS: 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.

Force control predicts fine motor dexterity in high-functioning stroke survivors.

BACKGROUND AND PURPOSE: High-functioning stroke survivors with mild to moderate motor impairments show greater functional autonomy in activities of daily living, and often return to work or prior activities. Increased functional independence necessitates dexterous use of hands to execute tasks such as typing, using a phone, and driving. Despite the absence of any pronounced motor impairments, high-functioning individuals with stroke report challenges in performing skilled manual tasks. Two prominent motor deficits that limit functional performance after stroke are decline in strength and force control. Here, we quantify the deficits in fine motor dexterity in high-functioning stroke survivors and determine the relative contribution of strength and force control to fine motor dexterity. METHODS: Fifteen high-functioning participants with stroke (upper-limb Fugl-Meyer score ≥43/66) and 15 controls performed following tasks with the paretic and non-dominant hands respectively: i) Nine-hole peg pest, ii) maximum voluntary contraction and iii) dynamic force tracking with isometric finger flexion. RESULTS: High-functioning stroke participants required greater time to complete the pegboard task, showed reduced finger strength, and increased force variability relative to the controls. Importantly, the time to complete pegboard task in high-functioning stroke participants was explained by finger force variability, not strength. DISCUSSION AND CONCLUSIONS: High-functioning stroke survivors show persistent deficits in fine motor dexterity, finger strength, and force control. The ability to modulate forces (control) contributes to fine motor dexterity in high-functioning stroke survivors. Interventions to improve fine motor dexterity in these individuals should include the assessment and training of force control.

Bimanual force control differs between increment and decrement.

BACKGROUND: Everyday bimanual tasks require increasing and decreasing forces to manipulate objects. Optimal bimanual coordination during force increment and decrement is essential to complete a bimanual task. However, little is known about the differences in bimanual control during force increment and decrement. The purpose of this study was to 1) investigate whether task performance and bimanual coordination differ between force increment and force decrement in a bimanual task, and 2) determine the contribution of bimanual coordination to task performance during force increment and force decrement. METHODS: Seventeen right-handed young adults (24.10 ± 3.09 years) performed following tasks involving bimanual isometric index finger flexion: 1) maximum voluntary contractions and 2) visually-guided force tracking involving gradual force increment and decrement. 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 task performance with the accuracy and variability of total force in force increment and decrement phases. We measured bimanual coordination between two hand forces by computing time-series cross-correlation coefficient and amplitude of coherence in 0-1 Hz. RESULTS: We found decreased accuracy and increased variability of the total force in decrement compared with increment phase. Further, the cross-correlation coefficient and coherence amplitude were greater during force decrement than force increment phase. Finally, cross-correlation coefficient and coherence in 0.5-1 Hz predicted the accuracy and variability of total force. CONCLUSIONS: We provide evidence that task performance is reduced during force decrement as compared with force increment, suggesting that force release is more challenging than force generation in bimanual tasks. Further, bimanual coupling of the forces was better during force decrement than force increment. Overall, the coordination of forces from both hands influences the task performance across combined increment and decrement phases. Specifically, decoupling of forces produced by both hands facilitates error compensation strategy to reach the task goal. Together, these findings highlight that the bimanual control of forces is task-dependent and emphasize the importance of collaboration between hands in achieving a common task goal. These results may have implications for understanding changes in bimanual control with aging and neurological disorders.

Endpoint accuracy of goal-directed ankle movements correlates to over-ground walking in stroke.

OBJECTIVES: Goal-directed movements are essential for voluntary motor control. The inability to execute precise goal-directed movements after stroke can impair the ability to perform voluntary functions, learn new skills, and hinder rehabilitation. However, little is known about how the accuracy of single-joint, goal-directed ankle movements relates to multi-joint, lower limb function in stroke. Here, we determined the impact of stroke on the accuracy of goal-directed ankle movements and its relation to over-ground walking. METHODS: Stroke (N = 28) and control (N = 28) participants performed (1) goal-directed ankle dorsiflexion movements to accurately match 9 degrees in 180 ms and (2) over-ground walking. During goal-directed ankle movements, we measured the endpoint error, position error, time error and the activation of the agonist and antagonist muscles. During over-ground walking, we measured the walking speed, paretic stride length, and cadence. RESULTS: The stroke group demonstrated increased endpoint error than the controls. Increased endpoint error was associated with increased co-activation between agonist-antagonist muscles. Endpoint error was a significant predictor of walking speed and paretic stride length in stroke. CONCLUSIONS: Impaired accuracy of goal-directed, ankle movements is correlated to over-ground walking in stroke. SIGNIFICANCE: Quantifying accuracy of goal-directed ankle movements may provide insights into walking function post-stroke.

An analysis of the use of antimicrobial agents in outdoor patients of ophthalmology.

OBJECTIVES: The study was aimed to analyze commonly used antimicrobials in outdoor patients of ophthalmology department. MATERIALS AND METHODS: The study was an observational, cross-sectional study carried out in the Department of Pharmacology and Ophthalmology after approval from the head of departments and Institutional Ethics Committee. All the patients age 18 years and above who were prescribed antimicrobials and gave consent were included in study. Data were recorded in a case study form containing relevant patient information and results of general, ocular, and special examinations along with the details of antimicrobials prescribed. Data were analyzed according to the World Health Organization/International Network for Rational Use of Drugs indicators and appropriate statistical tests. RESULTS: A total of 900 patients who were prescribed antimicrobial agents (AMAs) were included in the study. The most common chief complaint was diminution of vision (25.78%). The most common indication of use of AMAs was for treating ocular infections (50.22%). The most commonly prescribed antimicrobial group was fluoroquinolone (FQ) (63.8%) and the most common drug was moxifloxacin (35.95%). The most common dosage form of AMAs was eye drops (68.55%). The average number of drugs per encounter was 4.41. The percentage of encounters with injectables prescribed was 0.67%. The percentage of use of antibiotics was 100%. The percentage of total drugs and AMAs prescribed by generic name was 41.5 and 11.92, respectively. The percentage of antimicrobial drugs prescribed from essential drugs list was 34.24%. The mean duration of antimicrobial therapy was 7.2 ± 4.54 days. CONCLUSION: More than half of the patients are prescribed multiple AMAs. Moxifloxacin, a newer generation FQ , was the most commonly prescribed AMA in our study. Educational interventions and strict adherence to hospital antimicrobial use policy are needed to restrict the use of AMAs and increase rational prescribing.