scholarly journals Improvements in force variability and structure from vision- to memory-guided submaximal isometric knee extension in subacute stroke

2018 ◽  
Vol 124 (3) ◽  
pp. 592-603 ◽  
Author(s):  
John W. Chow ◽  
Dobrivoje S. Stokic
Keyword(s):  
Visual Feedback ◽  
Memory Retrieval ◽  
Spectral Power ◽  
Maximum Voluntary Contraction ◽  
Knee Extension ◽  
Force Variability ◽  
Median Frequency ◽  
Subacute Stroke ◽  
Isometric Knee Extension ◽  
Force Signal

We examined changes in variability, accuracy, frequency composition, and temporal regularity of force signal from vision-guided to memory-guided force-matching tasks in 17 subacute stroke and 17 age-matched healthy subjects. Subjects performed a unilateral isometric knee extension at 10, 30, and 50% of peak torque [maximum voluntary contraction (MVC)] for 10 s (3 trials each). Visual feedback was removed at the 5-s mark in the first two trials (feedback withdrawal), and 30 s after the second trial the subjects were asked to produce the target force without visual feedback (force recall). The coefficient of variation and constant error were used to quantify force variability and accuracy. Force structure was assessed by the median frequency, relative spectral power in the 0–3-Hz band, and sample entropy of the force signal. At 10% MVC, the force signal in subacute stroke subjects became steadier, more broadband, and temporally more irregular after the withdrawal of visual feedback, with progressively larger error at higher contraction levels. Also, the lack of modulation in the spectral frequency at higher force levels with visual feedback persisted in both the withdrawal and recall conditions. In terms of changes from the visual feedback condition, the feedback withdrawal produced a greater difference between the paretic, nonparetic, and control legs than the force recall. The overall results suggest improvements in force variability and structure from vision- to memory-guided force control in subacute stroke despite decreased accuracy. Different sensory-motor memory retrieval mechanisms seem to be involved in the feedback withdrawal and force recall conditions, which deserves further study. NEW & NOTEWORTHY We demonstrate that in the subacute phase of stroke, force signals during a low-level isometric knee extension become steadier, more broadband in spectral power, and more complex after removal of visual feedback. Larger force errors are produced when recalling target forces than immediately after withdrawing visual feedback. Although visual feedback offers better accuracy, it worsens force variability and structure in subacute stroke. The feedback withdrawal and force recall conditions seem to involve different memory retrieval mechanisms.

Force control of quadriceps muscle is bilaterally impaired in subacute stroke

2011 ◽  
Vol 111 (5) ◽  
pp. 1290-1295 ◽  
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.

Intermittency in the Control of Continuous Force Production

2000 ◽  
Vol 84 (4) ◽  
pp. 1708-1718 ◽  
Author(s):  
Andrew B. Slifkin ◽  
David E. Vaillancourt ◽  
Karl M. Newell
Keyword(s):  
Visual Feedback ◽  
Visual Information ◽  
Spectral Power ◽  
Force Production ◽  
Motor Output ◽  
Force Variability ◽  
Force Output ◽  
Feedback Information ◽  
Information Processes ◽  
Feedback Frequency

The purpose of the current investigation was to examine the influence of intermittency in visual information processes on intermittency in the control continuous force production. Adult human participants were required to maintain force at, and minimize variability around, a force target over an extended duration (15 s), while the intermittency of on-line visual feedback presentation was varied across conditions. This was accomplished by varying the frequency of successive force-feedback deliveries presented on a video display. As a function of a 128-fold increase in feedback frequency (0.2 to 25.6 Hz), performance quality improved according to hyperbolic functions (e.g., force variability decayed), reaching asymptotic values near the 6.4-Hz feedback frequency level. Thus, the briefest interval over which visual information could be integrated and used to correct errors in motor output was approximately 150 ms. The observed reductions in force variability were correlated with parallel declines in spectral power at about 1 Hz in the frequency profile of force output. In contrast, power at higher frequencies in the force output spectrum were uncorrelated with increases in feedback frequency. Thus, there was a considerable lag between the generation of motor output corrections (1 Hz) and the processing of visual feedback information (6.4 Hz). To reconcile these differences in visual and motor processing times, we proposed a model where error information is accumulated by visual information processes at a maximum frequency of 6.4 per second, and the motor system generates a correction on the basis of the accumulated information at the end of each 1-s interval.

scholarly journals Post-Activation Potentiation and Fatigue of Quadriceps Muscle after Continuous Isometric Contractions at Maximal and Submaximal Intensities

2018 ◽  
Vol 4 (67) ◽  
Author(s):  
Nerijus Masiulis ◽  
Albertas Skurvydas ◽  
Sigitas Kamandulis ◽  
Jūratė Kudirkaitė ◽  
Vytautas Sukockas ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Recovery Period ◽  
Maximum Voluntary Contraction ◽  
Isometric Exercise ◽  
Quadriceps Muscle ◽  
Knee Extension ◽  
Voluntary Contraction ◽  
Contractile Properties ◽  
Contraction Time ◽  
Isometric Knee Extension

The dominance of fatigue or post-activation potentiation (PAP) depends on the type, intensity, and duration of exercise and duration of the recovery before contractility is tested. Although the decrease in PAP magnitude with decreased exercise intensity is well documented (Vandervoort et al., 1983; Behm et al., 2004), it is not clear how PAP and fatigue influences the contractile properties of skeletal muscle when exercise is of different intensity but with the same amount of work performed. Thus it is important to understand the manifestation of PAP and fatigue of skeletal muscle after continuous maximal and submaximal contractions but with the same amount of work performed. Eight healthy untrained men (age 23—27 years, mass 83.5 ± 5.4 kg) performed maximal sustained isometric knee extension for 30 s (MVC-30 s) and on the other occasion the same subject performed sustained isometric knee extension for 60 s at 50% of maximal (50% MVC-60 s). We assumed that the amount of performed work was the same during both MVC-30 s and 50% MVC-60 s exercises. The experimental order was randomized. The contractile properties of quadriceps muscle evoked by electrical stimulation at 1 Hz (P 1), 10 Hz (P 10), 20 Hz (P 20), and 50 Hz (P 50) as well as contraction time (CT) and relaxation time (RT) of single twitch (P 1) and EMGrms of v. lateralis muscle were recorded before and immediately after the exercises (0 min) and 1, 2, and 3 min following the exercises. A significantly greater potentiation (p < 0.05) of P1 was observed after 30-s MVC (MVC-30 s) compared with the 60-s MVC (50% MVC-60 s) immediately after exercise and at 1 min of recovery. No changes in P 1 contraction time (CT) were observed during 3 min recovery period, however half relaxation of P 1 (½ RT) was more prolonged (p < 0.05) immediately after 50% MVC-60 s exercises. Moreover, immediately and 1 min post exercise the P 10 force after MVC-30 s exercise was higher (p < 0.05) compared to 50% MVC-60 s exercise. No differences between MVC-30 s and 50% MVC-60 s exercises were observed at high stimulation frequencies, maximal voluntary contraction force (MVC) as well as for EMGrms values during 3 min recovery period. The main finding of the present study was that PAP was observed after both maximal and submaximal intensity exercises when the same amount of work was performed. The more intensively exercise is performed, the more PAP offsets fatigue straight after exercise (maximal intensity); while after submaximal exercise PAP becomes more evident only during the recovery period.Keywords: skeletal muscle, isometric exercise, maximum voluntary contraction, recovery.

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

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.

scholarly journals Gear Shifting of Quadriceps during Isometric Knee Extension Disclosed Using Ultrasonography

2018 ◽  
Vol 2018 ◽  
pp. 1-7 ◽  
Author(s):  
Shu Zhang ◽  
Weijian Huang ◽  
Yu Zeng ◽  
Wenxiu Shi ◽  
Xianfen Diao ◽  
...  
Keyword(s):  
Video Processing ◽  
Morphological Changes ◽  
Knee Extension ◽  
Voluntary Contraction ◽  
Spatial Distance ◽  
Video Sequences ◽  
Motion Pattern ◽  
Isometric Knee Extension ◽  
Force Signal ◽  
Processing Techniques

Ultrasonography has been widely employed to estimate the morphological changes of muscle during contraction. To further investigate the motion pattern of quadriceps during isometric knee extensions, we studied the relative motion pattern between femur and quadriceps under ultrasonography. An interesting observation is that although the force of isometric knee extension can be controlled to change almost linearly, femur in the simultaneously captured ultrasound video sequences has several different piecewise moving patterns. This phenomenon is like quadriceps having several forward gear ratios like a car starting from rest towards maximal voluntary contraction (MVC) and then returning to rest. Therefore, to verify this assumption, we captured several ultrasound video sequences of isometric knee extension and collected the torque/force signal simultaneously. Then we extract the shapes of femur from these ultrasound video sequences using video processing techniques and study the motion pattern both qualitatively and quantitatively. The phenomenon can be seen easier via a comparison between the torque signal and relative spatial distance between femur and quadriceps. Furthermore, we use cluster analysis techniques to study the process and the clustering results also provided preliminary support to the conclusion that, during both ramp increasing and decreasing phases, quadriceps contraction may have several forward gear ratios relative to femur.

scholarly journals Effects of expiratory effort on force variability in isometric knee extension

2021 ◽  
Vol 70 (5) ◽  
pp. 315-325
Author(s):  
Kazuki Shirakawa ◽  
Yoshinori Ohtsuka ◽  
Takahiro Yunoki
Keyword(s):  
Knee Extension ◽  
Force Variability ◽  
Isometric Knee Extension

scholarly journals Opponens pollicis silent period during a precision motor task with the isometric contraction of the ipsilateral knee extension.

2018 ◽  
Vol 7 (2) ◽  
pp. 9-14
Author(s):  
Shinichi Daikuya ◽  
Yumi Okayama
Keyword(s):  
Central Nervous System ◽  
Visual Feedback ◽  
Motor Task ◽  
Silent Period ◽  
Knee Extension ◽  
System Function ◽  
Central Nervous System Function ◽  
Task Order ◽  
Isometric Knee Extension ◽  
Nervous System Function

Objectives: To clarify the excitability of the central nervous system function via a difference in the feedback method, we examined the alterations in the duration of the silent period recorded from the opponens pollicis muscle during a precision motor task. This task involved isometric knee extension using visual feedback and verbal conduction. Design: Cross-sectional study with an A-B-A task-order design. Methods: 12 healthy adults (7 males and 5 females; mean age: 23.7 ± 2.1 years) participated in this study. SP was recorded from the opponens pollicis muscle during a precision motor task involving with isometric contraction during ipsilateral knee extension with constant torque by two kinds of feedback. The precision motor task was carried out as follows; Subjects maintained knee extension torque at a constant strength using the BIODEX SYSTEM 3 with 60° of knee flexion. The knee extension torque was set at 25% of individual maximum effort. We monitored the torque using two methods. The first method used subjects’ own visual feedback with gazing at the BIODEX screen (Task A). The second task featured torque adjustment by the examiner’s verbal instruction. Subjects’ eyes were bandaged to eliminate visual feedback (Task B). Silent period was recorded from the opponens pollicis muscle while subjects maintained ipsilateral isometric knee extension during an A-B-A task order. As a stimulus condition, a constant current rectangular wave with a frequency of 0.5 Hz and a duration of 0.2 ms, was added 16 times in the median nerve at the wrist with the intensity of supra-maximum, which maximal M wave was evoked. We compared the duration of silent period between tasks in each dominant and non-dominant side. Results: The duration of silent period on the dominant leg was 109.1 ± 5.2 ms (Task A), 105.2 ± 7.2 ms (Task B), and 107.6 ± 6.7 ms (Task A). And that on the non-dominant leg was 111.3 ± 6.1 ms (Task A), 105.9 ± 4.4 ms (Task B), and 109.3 ± 4.4 ms (Task A). There was no significant difference on the dominant leg side. However, during Task B on the non-dominant leg side, the duration of silent period was shortened (Tukey’s test, p = 0.01, 0.08). Conclusion: During less-skilled motor adjustment using the non-dominant leg, the motor control with verbal conduction and no visual feedback requires more afferent activation. In these cases, central nervous system function excitability associated with ipsilateral upper extremity increases, even if the task involves the lower extremity.

scholarly journals Characterizing rapid-onset vasodilation to single muscle contractions in the human leg

2015 ◽  
Vol 118 (4) ◽  
pp. 455-464 ◽  
Author(s):  
Daniel P. Credeur ◽  
Seth W. Holwerda ◽  
Robert M. Restaino ◽  
Phillip M. King ◽  
Kiera L. Crutcher ◽  
...  
Keyword(s):  
Maximum Voluntary Contraction ◽  
Knee Extensor ◽  
Rapid Onset ◽  
Knee Extension ◽  
Voluntary Contraction ◽  
Muscle Contractions ◽  
Isometric Contractions ◽  
Single Muscle ◽  
Isometric Knee Extension ◽  
Mechanical Factors

Rapid-onset vasodilation (ROV) following single muscle contractions has been examined in the forearm of humans, but has not yet been characterized in the leg. Given known vascular differences between the arm and leg, we sought to characterize ROV following single muscle contractions in the leg. Sixteen healthy men performed random ordered single contractions at 5, 10, 20, 40, and 60% of their maximum voluntary contraction (MVC) using isometric knee extension made with the leg above and below heart level, and these were compared with single isometric contractions of the forearm (handgrip). Single thigh cuff compressions (300 mmHg) were utilized to estimate the mechanical contribution to leg ROV. Continuous blood flow was determined by duplex-Doppler ultrasound and blood pressure via finger photoplethysmography (Finometer). Single isometric knee extensor contractions produced intensity-dependent increases in peak leg vascular conductance that were significantly greater than the forearm in both the above- and below-heart level positions (e.g., above heart level: leg 20% MVC, +138 ± 28% vs. arm 20% MVC, +89 ± 17%; P < 0.05). Thigh cuff compressions also produced a significant hyperemic response, but these were brief and smaller in magnitude compared with single isometric contractions in the leg. Collectively, these data demonstrate the presence of a rapid and robust vasodilation to single muscle contractions in the leg that is largely independent of mechanical factors, thus establishing the leg as a viable model to study ROV in humans.

scholarly journals EARLY STRENGTH TESTING AFTER ACL RECONSTRUCTION IMPACTS ISOKINETIC STRENGTH PERFORMANCE AT TIME OF RETURN TO SPORT

2021 ◽  
Vol 9 (7_suppl3) ◽  
pp. 2325967121S0011
Author(s):  
Adam Weaver ◽  
Dylan Roman ◽  
Maua Mosha ◽  
Nicholas Giampetruzzi
Keyword(s):  
Test Performance ◽  
Knee Extension ◽  
Strength Test ◽  
Strength Testing ◽  
Isokinetic Strength ◽  
Rehabilitation Process ◽  
Strength Performance ◽  
Knee Extension Strength ◽  
Isometric Knee Extension ◽  
Strength Tests

Background: The standard of care in ACL reconstruction (ACLR) typically involves standardized strength testing at 6 months or later to assess a patient’s readiness to return to play (RTP) using isokinetic and isometric testing, and functional strength testing. Recent literature suggests that isokinetic knee extension strength should demonstrate 89% limb symmetry index (LSI) or greater prior to returning to sport. However, there is little known on the effects of strength testing early in the rehabilitation process and the relationship to strength test performance at time of RTP. Purpose: The purpose of this study was to examine how early post-operative strength test performance impacts isokinetic strength outcomes at RTP testing in adolescents. Methods: The retrospective cohort study included patients undergoing primary ACLR between 12 and 18 years of age, early post-operative strength measures, and isokinetic dynamometer strength at RTP from July 2017 and April 2019. Data was dichotomized into desired outcomes at 3 months: >70% isometric knee extension LSI, > 20 repetitions on anterior stepdown test (AST), > 90% LSI Y Balance. At RTP testing, isokinetic knee extension strength data was categorized into >89% LSI at 3 speeds (300, 180, 60°/sec). Chi square testing and odds ratio statistics were used to examine association and its magnitude. Results: 63 patients met inclusion criteria (38 females; 15.37±1.66 years old). >70% LSI isometric knee extension strength at 3 months showed a significant association (Table 2) and demonstrated the strongest odds of having >89% LSI on isokinetic strength tests at all 3 speeds at RTP with 180°/sec being the highest (OR=14.5; 95% CI=4.25,49.43; p= <0.001). Performance on AST showed a significant association (χ2 (1, n=63) = 17.00, p <0.001), and highest odds at 180°/sec (OR=4.61; 95% CI = 1.59, 13.39, p=<0.001) and 60°/sec (OR= 3.07; 95% CI = 1.10, 8.63, p= 0.04). Combination of performance on isometric strength tests and AST showed a significant association to isokinetic strength at all three speeds, but less predictive then isometrics in isolation. (Table 2). There was no significant relationship between YBR LSI at 3 months and isokinetic strength at 6 months. Conclusion: Standardized strength testing early in rehabilitation can help identify patients that will successfully complete RTP testing. Our results suggest that isometric knee extension strength and timed anterior stepdown test provide meaningful clinical information early in the rehabilitation process. This data also suggests that the use of YBAL for predicting isokinetic strength performance is limited. [Table: see text][Table: see text]

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