Visual Feedback Improves Bimanual Force Control Performances at Planning and Execution Levels

Abstract The purpose of this study was to determine whether altered interlimb coordination patterns across trials improved bimanual force control capabilities within a trial. Fourteen healthy young participants completed bimanual force control tasks at 5%, 25%, and 50% of maximum voluntary contraction with and without visual feedback. To estimate synergetic coordination patterns between hands across multiple trials, we analyzed our primary outcome measure by performing an uncontrolled manifold analysis. In addition, we calculated force accuracy, variability, and regularity within a trial to quantify task stabilization. Using Pearson’s correlation analyses, we determined the relation between the changes in bilateral motor synergies (i.e., a proportion of good variability relative to bad variability) and bimanual force control performance from no-vision to vision conditions. The findings revealed that the presence of visual feedback significantly increased bilateral motor synergies with a reduction of bad variability components across multiple trials, and decreased force error, variability, and regularity within a trial. Further, we observed significant positive correlations between higher bilateral motor synergies and increased improvements in force control capabilities. These findings suggested that bimanual synergetic coordination behaviors at the planning level modulated by external sensory feedback may be related to advanced task stabilization patterns at the execution level.

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Visual feedback improves bimanual force control performances at planning and execution levels

Scientific Reports ◽

10.1038/s41598-021-00721-9 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Hyun Joon Kim ◽

Joon Ho Lee ◽

Nyeonju Kang ◽

James H. Cauraugh

Keyword(s):

Visual Feedback ◽

Force Control ◽

Maximum Voluntary Contraction ◽

Correlation Coefficients ◽

Uncontrolled Manifold ◽

Force Variability ◽

Motor Synergies ◽

Multiple Trials ◽

Motor Synergy ◽

Force Accuracy

AbstractThe 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.

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Effects of force level and task difficulty on force control performance in elderly people

Experimental Brain Research ◽

10.1007/s00221-020-05864-1 ◽

2020 ◽

Vol 238 (10) ◽

pp. 2179-2188

Author(s):

Caren Strote ◽

Christian Gölz ◽

Julia Kristin Stroehlein ◽

Franziska Katharina Haase ◽

Dirk Koester ◽

...

Keyword(s):

Elderly People ◽

Force Control ◽

Task Difficulty ◽

Negative Impact ◽

Maximum Voluntary Contraction ◽

Real Life ◽

Voluntary Contraction ◽

Fine Motor ◽

Force Level ◽

Control Performance

Abstract As the proportion of people over 60 years of age rises continuously in westernized societies, it becomes increasingly important to better understand aging processes and how to maintain independence in old age. Fine motor tasks are essential in daily living and, therefore, necessary to maintain. This paper extends the existing literature on fine motor control by manipulating the difficulty of a force maintenance task to characterize performance optima for elderly. Thirty-seven elderly (M = 68.00, SD = 4.65) performed a force control task at dynamically varying force levels, i.e. randomly changing every 3 s between 10%, 20%, and 30% of the individual’s maximum voluntary contraction (MVC). This task was performed alone or with one or two additional tasks to increase task difficulty. The force control characteristics accuracy, variability, and complexity were analyzed. Lowest variability was observed at 20%. Accuracy and complexity increased with increasing force level. Overall, increased task difficulty had a negative impact on task performance. Results support the assumption, that attention control has a major impact on force control performance in elderly people. We assume different parameters to have their optimum at different force levels, which remain comparably stable when additional tasks are performed. The study contributes to a better understanding of how force control is affected in real-life situations when it is performed simultaneously to other cognitive and sensory active and passive tasks.

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Role of Post-Trial Visual Feedback on Unintentional Force Drift During Isometric Finger Force Production Tasks

Motor Control ◽

10.1123/mc.2020-0031 ◽

2021 ◽

pp. 1-14

Author(s):

S. Balamurugan ◽

Rachaveti Dhanush ◽

S.K.M. Varadhan

Keyword(s):

Visual Feedback ◽

Maximum Voluntary Contraction ◽

Control Variable ◽

Force Production ◽

Voluntary Contraction ◽

Central Controller ◽

The Difference ◽

Post Trial ◽

Fingertip Forces

A reduction in fingertip forces during a visually occluded isometric task is called unintentional drift. In this study, unintentional drift was studied for two conditions, with and without “epilogue.” We define epilogue as the posttrial visual feedback in which the outcome of the just-concluded trial is shown before the start of the next trial. For this study, 14 healthy participants were recruited and were instructed to produce fingertip forces to match a target line at 15% maximum voluntary contraction. The results showed a significant reduction in unintentional drift in the epilogue condition. This reduction is probably due to the difference in the shift in λ, the threshold of the tonic stretch reflex, the hypothetical control variable that the central controller can set.

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Motor control differs for increasing and releasing force

Journal of Neurophysiology ◽

10.1152/jn.00715.2015 ◽

2016 ◽

Vol 115 (6) ◽

pp. 2924-2930 ◽

Cited By ~ 14

Author(s):

Seoung Hoon Park ◽

MinHyuk Kwon ◽

Danielle Solis ◽

Neha Lodha ◽

Evangelos A. Christou

Keyword(s):

Older Adults ◽

Force Control ◽

Discharge Rate ◽

Maximum Voluntary Contraction ◽

Motor Units ◽

Voluntary Contraction ◽

Force Variability ◽

Force Output ◽

Force Increase ◽

Change In Mean

Control of the motor output depends on our ability to precisely increase and release force. However, the influence of aging on force increase and release remains unknown. The purpose of this study, therefore, was to determine whether force control differs while increasing and releasing force in young and older adults. Sixteen young adults (22.5 ± 4 yr, 8 females) and 16 older adults (75.7 ± 6.4 yr, 8 females) increased and released force at a constant rate (10% maximum voluntary contraction force/s) during an ankle dorsiflexion isometric task. We recorded the force output and multiple motor unit activity from the tibialis anterior (TA) muscle and quantified the following outcomes: 1) variability of force using the SD of force; 2) mean discharge rate and variability of discharge rate of multiple motor units; and 3) power spectrum of the multiple motor units from 0–4, 4–10, 10–35, and 35–60 Hz. Participants exhibited greater force variability while releasing force, independent of age ( P < 0.001). Increased force variability during force release was associated with decreased modulation of multiple motor units from 35 to 60 Hz ( R2 = 0.38). Modulation of multiple motor units from 35 to 60 Hz was further correlated to the change in mean discharge rate of multiple motor units ( r = 0.66) and modulation from 0 to 4 Hz ( r = −0.64). In conclusion, these findings suggest that force control is altered while releasing due to an altered modulation of the motor units.

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Age-related deficits in bilateral motor synergies and force coordination

BMC Geriatrics ◽

10.1186/s12877-019-1285-x ◽

2019 ◽

Vol 19 (1) ◽

Cited By ~ 1

Author(s):

Nyeonju Kang ◽

Lisa M. Roberts ◽

Clara Aziz ◽

James H. Cauraugh

Keyword(s):

Older Adults ◽

Young Adults ◽

Standard Deviation ◽

Visual Feedback ◽

Dominant Hand ◽

Adult Group ◽

Motor Synergies ◽

Force Coordination ◽

Age Related ◽

Multiple Trials

Abstract Background Ageing may cause impairments in executing bilateral movement control. This study investigated age-related changes in interlimb force coordination across multiple trials by quantifying bilateral motor synergies based on the uncontrolled manifold hypothesis. Participants completed the trials with and without visual feedback. Methods Twenty healthy individuals (10 older adults and 10 young adults) performed 12 isometric force control trials for the two vision conditions at 5% of maximal voluntary contraction. All dependent variables were analyzed in two-way mixed model (Group × Vision Condition; 2 × 2) ANOVAs with repeated measures on the last factor. Results The analyses revealed that older adults had greater mean force produced by two hands in both vision conditions (i.e., yes and no visual feedback). Across both vision conditions, the older adult group showed greater asymmetrical force variability (i.e., standard deviation of non-dominant hand > standard deviation of dominant hand) and revealed more positive correlation coefficients between forces produced by two hands as compared with the young adult group. Finally, an index of bilateral motor synergies was significantly greater in young adults than older adults when visual feedback was available. Conclusion The current findings indicate that deficits in interlimb force coordination across multiple trials appeared in older adults.

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Force control of quadriceps muscle is bilaterally impaired in subacute stroke

Journal of Applied Physiology ◽

10.1152/japplphysiol.00462.2011 ◽

2011 ◽

Vol 111 (5) ◽

pp. 1290-1295 ◽

Cited By ~ 22

Author(s):

John W. Chow ◽

Dobrivoje S. Stokic

Keyword(s):

Force Control ◽

Maximum Voluntary Contraction ◽

Quadriceps Muscle ◽

Knee Extension ◽

Voluntary Contraction ◽

Force Variability ◽

Stroke Patients ◽

Subacute Stroke ◽

Peak Knee ◽

Isometric Knee Extension

We tested the hypothesis that force variability and error during maintenance of submaximal isometric knee extension are greater in subacute stroke patients than in controls and are related to motor impairments. Contralesional (more-affected) and ipsilesional (less-affected) legs of 33 stroke patients with sufficiently high motor abilities (62 ± 13 yr, 16 ± 2 days postinjury) and the dominant leg of 20 controls (62 ± 10 yr) were tested in sitting position. After peak knee extension torque [maximum voluntary contraction (MVC)] was established, subjects maintained 10, 20, 30, and 50% of MVC as steady and accurate as possible for 10 s by matching voluntary force to the target level displayed on a monitor. Coefficient of variation (CV) and root-mean-square error (RMSE) were used to quantify force variability and error, respectively. The MVC was significantly smaller in the more-affected than less-affected leg, and both were significantly lower than in controls. The CV was significantly larger in the more-affected than less-affected leg at 20 and 50% MVC, whereas both were significantly larger compared with controls across all force levels. Both more-affected and less-affected legs of patients showed significantly greater RMSE than controls at 30 and 50% MVC. The CV and RMSE were not related to the Fugl-Meyer motor score or to the Rivermead Mobility Index. The CV negatively correlated with MVC in controls but only in the less-affected leg of patients. It is concluded that isometric knee extension strength and force control are bilaterally impaired soon after stroke but more so in the more-affected leg. Future studies should examine possible mechanisms and the evolution of these changes.

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Real-time slacking as a default mode of grip force control: implications for force minimization and personal grip force variation

Journal of Neurophysiology ◽

10.1152/jn.00700.2017 ◽

2018 ◽

Vol 120 (4) ◽

pp. 2107-2120 ◽

Cited By ~ 2

Author(s):

Brendan W. Smith ◽

Justin B. Rowe ◽

David J. Reinkensmeyer

Keyword(s):

Real Time ◽

Force Control ◽

Motor System ◽

Grip Force ◽

Maximum Voluntary Contraction ◽

Force Production ◽

Arm Movement ◽

Voluntary Contraction ◽

Grip Force Control ◽

Force Variation

During trial-to-trial movement adaptation, the motor system systematically reduces extraneous muscle forces when kinematic errors experienced on previous movements are small, a phenomenon termed “slacking.” There is also growing evidence that the motor system slacks continuously (i.e., in real-time) during arm movement or grip force control, but the initiation of this slacking is not well-characterized, obfuscating its physiological cause. Here, we addressed this issue by asking participants ( n = 32) to track discrete force targets presented visually using isometric grip force, then applying a brief, subtle error-clamp to that visual feedback on random trials. Participants reduced their force in an exponential fashion, on these error-clamp trials, except when the target force was <10% maximum voluntary contraction (MVC). This force drift began <250 ms after the onset of the error-clamp, consistent with slacking being an ongoing process unmasked immediately after the motor system finished reacting to the last veridical feedback. Above 10% MVC, the slacking rate increased linearly with grip force magnitude. Grip force variation was approximately 50–100% higher with veridical feedback, largely due to heightened signal power at ~1 Hz, the band of visuomotor feedback control. Finally, the slacking rate measured for each participant during error-clamp trials correlated with their force variation during control trials. That is, participants who slacked more had greater force variation. These results suggest that real-time slacking continuously reduces grip force until visual error prompts correction. Whereas such slacking is suited for force minimization, it may also account for ~30% of the variability in personal grip force variation.NEW & NOTEWORTHY We provide evidence that a form of slacking continuously conditions real-time grip force production. This slacking is well-suited to promote efficiency but is expected to increase force variation by triggering additional feedback corrections. Moreover, we show that the rate at which a person slacks is substantially correlated with the variation of their grip force. In combination, at the neurophysiological level, our results suggest slacking is caused by one or more relatively smooth neural adaptations.

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Development of a trunk motor paradigm for use in neuroimaging

Translational Neuroscience ◽

10.1515/tnsci-2020-0116 ◽

2020 ◽

Vol 11 (1) ◽

pp. 193-200

Author(s):

Elizabeth Saunders ◽

Brian C. Clark ◽

Leatha A. Clark ◽

Dustin R. Grooms

Keyword(s):

Motor Control ◽

Maximum Voluntary Contraction ◽

Voluntary Contraction ◽

Erector Spinae ◽

Head Motion ◽

Low Back ◽

Cyclic Contraction ◽

Cyclic Contractions ◽

Measurement Units ◽

Healthy Participants

AbstractThe purpose of this study was to quantify head motion between isometric erector spinae (ES) contraction strategies, paradigms, and intensities in the development of a neuroimaging protocol for the study of neural activity associated with trunk motor control in individuals with low back pain. Ten healthy participants completed two contraction strategies; (1) a supine upper spine (US) press and (2) a supine lower extremity (LE) press. Each contraction strategy was performed at electromyographic (EMG) contraction intensities of 30, 40, 50, and 60% of an individually determined maximum voluntary contraction (MVC) (±10% range for each respective intensity) with real-time, EMG biofeedback. A cyclic contraction paradigm was performed at 30% of MVC with US and LE contraction strategies. Inertial measurement units (IMUs) quantified head motion to determine the viability of each paradigm for neuroimaging. US vs LE hold contractions induced no differences in head motion. Hold contractions elicited significantly less head motion relative to cyclic contractions. Contraction intensity increased head motion in a linear fashion with 30% MVC having the least head motion and 60% the highest. The LE hold contraction strategy, below 50% MVC, was found to be the most viable trunk motor control neuroimaging paradigm.

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The Effects of Spinal Manipulation on Motor Unit Behavior

Brain Sciences ◽

10.3390/brainsci11010105 ◽

2021 ◽

Vol 11 (1) ◽

pp. 105

Author(s):

Lucien Robinault ◽

Aleš Holobar ◽

Sylvain Crémoux ◽

Usman Rashid ◽

Imran Khan Niazi ◽

...

Keyword(s):

Motor Unit ◽

Conduction Velocity ◽

Spinal Manipulation ◽

Maximum Voluntary Contraction ◽

Force Production ◽

Movement Control ◽

Position Sense ◽

Joint Position Sense ◽

Voluntary Contraction ◽

Passive Movement

Over recent years, a growing body of research has highlighted the neural plastic effects of spinal manipulation on the central nervous system. Recently, it has been shown that spinal manipulation improved outcomes, such as maximum voluntary force and limb joint position sense, reflecting improved sensorimotor integration and processing. This study aimed to further evaluate how spinal manipulation can alter neuromuscular activity. High density electromyography (HD sEMG) signals from the tibialis anterior were recorded and decomposed in order to study motor unit changes in 14 subjects following spinal manipulation or a passive movement control session in a crossover study design. Participants were asked to produce ankle dorsiflexion at two force levels, 5% and 10% of maximum voluntary contraction (MVC), following two different patterns of force production (“ramp” and “ramp and maintain”). A significant decrease in the conduction velocity (p = 0.01) was observed during the “ramp and maintain” condition at 5% MVC after spinal manipulation. A decrease in conduction velocity suggests that spinal manipulation alters motor unit recruitment patterns with an increased recruitment of lower threshold, lower twitch torque motor units.

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A new visual feedback-based system for the assessment of pinch force, endurance, accuracy and precision. A test-retest reliability study

Hand Therapy ◽

10.1177/17589983211002550 ◽

2021 ◽

pp. 175899832110025

Author(s):

Alberto Dottor ◽

Eleonora Camerone ◽

Mirko Job ◽

Diletta Barbiani ◽

Elisa Frisaldi ◽

...

Keyword(s):

Visual Feedback ◽

Intraclass Correlation ◽

Precision Grip ◽

Voluntary Contraction ◽

Good Reliability ◽

Retest Reliability ◽

Relative Reliability ◽

Time Accuracy ◽

In The Beginning ◽

Test Retest Reliability

Introduction Given that pinch is a precision grip involved in sustained submaximal activities, a Sustained Contraction (SC) task could be associated to Maximal Voluntary Contraction (MVC). To better evaluate the thumb-index system, the test-retest reliability of pinch MVC and SC, measured by a visual feedback-based pinch gauge was assessed. Methods 26 healthy participants performed MVC and SC in two separate sessions. SC required to maintain 40%MVC as long as possible and it was evaluated in terms of time, accuracy (Mean Distance between force trace and target force, MD), precision (Coefficient of Variability of force trace, CV). MD and CV analyses were conducted dividing the SC task into three equivalent time stages (beginning, middle, exhaustion). Relative Reliability (RR) was measured by Intraclass Correlation Coefficient, and Absolute Reliability (AR) was measured by Standard Error of Measurement and by Bland-Altman plot. Results MVC and Time showed high RR and AR in both hands. RR of MD and CV in right hand was excellent in the beginning and middle stages, and fair in the exhaustion one, showing decreasing reliability as fatigue increases. In the left hand RR of MD and CV was generally lower. MD showed excellent reliability in the beginning stage and good reliability in the other stages. CV showed fair relative reliability at both beginning and middle stages, excellent in the last one. Conversely, it was observed high AR of MD and CV in all stages in both hands. Conclusions All indices are reliable to assess motor control of thumb-index pinch in both hands.

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