Publications by authors named "Cheng-Ya Huang"

20 Publications

  • Page 1 of 1

Glenohumeral internal rotation deficit on pitching biomechanics and muscle activity.

Int J Sports Med 2021 Oct 12. Epub 2021 Oct 12.

School & Graduate Institute of Physical Therapy, College of Medicine, National Taiwan University, Taipei, Taiwan.

To characterize the scapular pitching biomechanics in symptomatic GIRD pitchers (SG) compared to asymptomatic GIRD (ASG) and healthy pitchers. The scapular kinematics and associated muscle activities during pitching were recorded in 33 high school pitchers. Compared to healthy, GIRD pitchers had less scapular posterior tilt in each pitching event (average difference, AD = 14.4°, p < 0.01) and ASG demonstrated less scapular upward rotation at ball release (AD = 12.8°, p < 0.01) and greater muscle activity in the triceps brachii in the early-cocking phase (AD = 9.9%, p = 0.015) and in the serratus anterior in the late-cocking phase (AD = 30.8%, p < 0.01). Additionally, SG had less muscular activity on triceps brachii in the acceleration phase and serratus anterior in the cocking phase (AD = 37.8%, p = 0.016; AD = 15.5%, p < 0.01, respectively) compared to ASG. GIRD pitchers exhibited less scapular posterior tilt during pitching, which may cause impingement. Since tightness of the anterior shoulder is a common cause of inadequacy of posterior tilt during arm elevation, stretching exercise of the anterior shoulder is recommended. Given the inadequate recruitment during pitching in the GIRD pitchers, symptoms may develop following potential impingement.
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http://dx.doi.org/10.1055/a-1667-6080DOI Listing
October 2021

Effects of Conscious Control of Scapular Orientation in Oral Cancer Survivors With Scapular Dyskinesis: A Randomized Controlled Trial.

Integr Cancer Ther 2021 Jan-Dec;20:15347354211040827

National Taiwan University, Taipei.

Objectives: Spinal accessory nerve dysfunction is one of the complications of neck dissection in patients with oral cancer. This study aimed to explore the effects of long-term scapular-focused exercises and conscious control of scapular orientation on scapular movement and quality of life (QoL).

Methods: This study was a randomized controlled trial with concealed allocation, assessor blinding, and intention-to-treat analysis. Thirty-six patients with oral cancer were randomly allocated to the motor-control group (scapular-focused exercise + conscious control of scapular orientation) or the regular-exercise group (scapular-focused exercises only). Both groups received conventional physical therapy after neck dissection for 3 months. Shoulder pain intensity, active range of motion (AROM) of shoulder abduction, scapular muscle strength and activity under maximal voluntary isometric contraction (MVIC), scapular muscle activity when performing scapular movements, and QoL were measured at baseline, 1 month after the start of the intervention, and the end of the intervention.

Results: Both groups showed significant improvement in all outcomes except shoulder pain intensity. After the 3-month intervention, the motor-control group had more significant improvement in AROM of shoulder abduction with a 19° difference (95% CI: 10-29,  < .001), muscle strength of upper trapezius with an 11 N difference (95% CI: 2-20;  = .021), and QoL than the regular-exercise group. When performing shoulder horizontal adduction and flexion, the relative value (%MVIC) of serratus anterior was smaller in the motor-control group with a 106%MVIC difference (95% CI: 7-205,  = .037).

Conclusions: Scapular-focused exercises have promising effects on spinal accessory nerve dysfunction. Combining scapular-focused exercises with conscious control of scapular orientation has more remarkable benefits on AROM of shoulder abduction, UT muscle strength, and muscle activation pattern than the scapular-focused exercises alone. Conscious control of scapular orientation should be considered to integrate into scapular-focused exercises in patients with oral cancer and scapular dyskinesis.Trial registry name and URL, and registration number: ClinicalTrials.gov (URL: https://clinicaltrials.gov; Approval No: NCT03545100).
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http://dx.doi.org/10.1177/15347354211040827DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8381416PMC
October 2021

Attentional Resource Associated With Visual Feedback on a Postural Dual Task in Parkinson's Disease.

Neurorehabil Neural Repair 2020 10 24;34(10):891-903. Epub 2020 Aug 24.

Physical Therapy Center, National Taiwan University Hospital, Taipei, Taiwan.

Background: Restricted attentional resource and central processing in patients with Parkinson's disease (PD) may reduce the benefit of visual feedback in a dual task.

Objectives: Using brain event-related potentials (ERPs), this study aims to investigate the neural mechanisms of posture visual feedback and supraposture visual feedback during performing of a posture-motor dual task.

Methods: Eighteen patients with PD and 18 healthy controls stood on a mobile platform (postural task) and executed a manual force-matching task (suprapostural task) concurrently with provided visual feedback of platform movement (posture-feedback condition) or force output (force-feedback condition). The platform movement, force-matching performance, and ERPs (P1, N1, and P2 waves) were recorded.

Results: Both PD and control groups had superior force accuracy in the force-feedback condition. Decreased postural sway by posture-feedback was observed in healthy controls but not in PD. Force-feedback led to a greater frontal area N1 peak in PD group but smaller N1 peaks in control group. In addition, force-feedback led to smaller P2 peaks of the frontal and sensorimotor areas among PD patients but greater P2 peaks of the sensorimotor and parietal-occipital areas among healthy controls. However, P1 modulations was present only in healthy controls.

Conclusions: Force-feedback had positive effect on force accuracy in both PD and healthy individuals; however, the beneficial effect of posture-feedback on posture balance is not observed in PD. These findings are the first to suggest that PD could recruit more attentional resources in dual-task preparation to enhance suprapostural accuracy and avoid degrading postural stability by supraposture visual feedback.
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http://dx.doi.org/10.1177/1545968320948071DOI Listing
October 2020

Motor control integrated into muscle strengthening exercises has more effects on scapular muscle activities and joint range of motion before initiation of radiotherapy in oral cancer survivors with neck dissection: A randomized controlled trial.

PLoS One 2020 6;15(8):e0237133. Epub 2020 Aug 6.

School and Graduate Institute of Physical Therapy, College of Medicine, National Taiwan University, Taipei, Taiwan.

Background: Accessory nerve shoulder dysfunction is common after neck dissection in oral cancer survivors. This study aimed to investigate the short-term effects of scapular muscle strengthening exercises with motor-control techniques on neck dissection-related shoulder dysfunction in oral cancer survivors before the initiation of radiotherapy.

Methods: Thirty-eight participants were randomly allocated into the motor-control and regular-exercise groups. Each group received conventional physical therapy and specific scapular muscle strengthening exercises for 1 month immediately after neck dissection. Motor control techniques were integrated with scapular strengthening exercises for the motor-control group. Shoulder pain, active range of motion (AROM) of shoulder abduction, and scapular muscle activities including upper trapezius (UT), middle trapezius (MT), lower trapezius (LT), and serratus anterior (SA) when performing maximal voluntary isometric contraction (MVIC) and scapular muscle exercises were evaluated at baseline and after 1 month of training.

Results: Both groups reduced shoulder pain and increased muscle activity of maximum voluntary isometric contraction (MVIC) of each muscle after the intervention. Increased AROM of shoulder abduction was only observed in the motor-control group (95% CI 3.80 to 20.51, p = 0.004). Relative to baseline evaluation, muscle activities of UT decreased in the motor-control group when performing shoulder shrug with 1-kg weight (95% CI -33.06 to -1.29, p = 0.034). Moreover, the SA activity decreased in the motor-control group (95% CI -29.73 to -27.68, p<0.001) but increased in the regular-exercise group (95% CI 28.16 to 30.05, p<0.001) when performing shoulder horizontal adduction and flexion.

Conclusion: Early strengthening exercise with motor control techniques has greater benefits for improving AROM of shoulder abduction, muscle economy, and reducing compensatory scapular muscle activities in patients with neck dissection-related shoulder dysfunction before the initiation of radiotherapy.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0237133PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7410307PMC
October 2020

The Effects of Task Prioritization on Dual-Tasking Postural Control in Patients With Parkinson Disease Who Have Different Postural Impairments.

Arch Phys Med Rehabil 2020 07 28;101(7):1212-1219. Epub 2020 Mar 28.

School and Graduate Institute of Physical Therapy, College of Medicine, National Taiwan University, Taipei, Taiwan; Physical Therapy Center, National Taiwan University Hospital, Taipei, Taiwan. Electronic address:

Objective: To investigate the effect of task prioritization on dual-task control in Parkinson disease (PD) associated with different postural impairments.

Design: Cross-sectional study. Participants were instructed to keep 2 interlocking rings apart and maintain balance in a tandem stance. Attention was focused on either stance stability (posture-focus strategy) or the interlocking rings (supraposture-focus strategy).

Setting: University research laboratory.

Participants: Fifteen patients with PD and less postural impairment and 15 patients with PD and more postural impairment (N=30).

Interventions: Not applicable.

Main Outcome Measures: Postural sway, postural determinism (%DET), ankle co-contraction, and ring-touching time.

Results: In the less-impairment group, the supraposture-focus strategy provided smaller postural sway and postural %DET compared with the posture-focus strategy. In the more-impairment group, task prioritization showed lower effect on both postural sway and postural %DET. The supraposture-focus strategy led to less ankle co-contraction than the posture-focus strategy in the more-impairment group, but task prioritization did not affect ankle co-contraction in the less-impairment group. In both groups, the supraposture-focus strategy led to less ring-touching time than the posture-focus strategy.

Conclusions: The supraposture-focus strategy provided better dual-task control than the posture-focus strategy in both PD groups. In the less-impairment group, the supraposture-focus strategy enhanced postural automaticity and postural stability. In the more-impairment group, the supraposture-focus strategy reduced ankle stiffness, owing to reduced muscle co-contraction.
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http://dx.doi.org/10.1016/j.apmr.2020.02.014DOI Listing
July 2020

H-reflex in abductor hallucis and postural performance between flexible flatfoot and normal foot.

Phys Ther Sport 2019 May 19;37:27-33. Epub 2019 Feb 19.

School and Graduate Institute of Physical Therapy, College of Medicine, National Taiwan University, Floor 3, No.17, Xuzhou Rd., Zhongzheng District, Taipei City, 100, Taiwan, ROC; Department of Physical Education, Fu Jen Catholic University, No.510, Zhongzheng Rd., Xinzhuang Dist., New Taipei City, 24205, Taiwan, ROC. Electronic address:

Objective: Morphological changes of the abductor hallucis muscle (AbH) in flexible flatfoot (FF) individuals influence regulations of the medial longitudinal arch (MLA). Prolonged and repeated stretching of AbH in flexible flatfoot may cause changes in muscle reflex properties and further influence postural performance. However, AbH muscle reflex under different postural conditions have never been examined. The purpose of this study was to investigate differences in AbH H-reflex and postural performance between individuals with normal foot (NF) alignment and FF under prone, double-leg stance (DLS), and single-leg stance (SLS) conditions.

Design: Cross-sectional study.

Setting: University laboratory.

Participants: Individuals with FF (n = 12) and NF (n = 12).

Main Outcome Measures: AbH H-reflex, AbH EMG and center of pressure (CoP) displacement.

Results: Under all postural conditions, AbH H-reflex was significantly lower in the FF group (P < .05). Under the SLS condition, AbH EMG was significantly higher in the FF group (P < .05), and CoP displacement for the medial-lateral and anterior-posterior directions were significantly higher in the FF group (P < .05).

Conclusions: With increased postural demand, FF individuals maintained their postural stability by recruiting greater AbH activities than through automatic stretch reflex, but FF individuals still showed inferior posture stability.
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http://dx.doi.org/10.1016/j.ptsp.2019.02.004DOI Listing
May 2019

Neuronal Responses to a Postural Dual-Task With Differential Attentional Prioritizations: Compensatory Resource Allocation With Healthy Aging.

J Gerontol B Psychol Sci Soc Sci 2019 10;74(8):1326-1334

School and Graduate Institute of Physical Therapy, College of Medicine, National Taiwan University, Taipei, Taiwan.

Objectives: Restricted central processing in older adults prevents optimization of a dual task with a flexible prioritization strategy. This study investigated the neural mechanisms of task-priority in young and older adults when performing a posture-motor dual-task.

Method: Sixteen healthy young and 16 older adults performed a force-matching task on a mobile-platform under posture-focus (PF) and supraposture-focus (SF) conditions. The platform movement, force-matching performance, and event-related potentials in the preparatory period were recorded.

Results: For the elders, the postural stability and force-matching accuracy using the PF strategy were inferior to those using the SF strategy; whereas, the dual-task performances of the young adults were less affected by the prioritization. Only the elders exhibited the P1 wave, with the PF strategy associated with a smaller P1 and larger P1 than the SF strategy in the sensorimotor-parietal and right frontotemporal areas, respectively. The PF strategy also led to a larger P2 wave in the right frontotemporal area of elders, but a greater P2 wave in the sensorimotor-parietal area of young adults.

Discussion: For both prioritization strategies, older adults entailed a longer preparatory process than younger adults. Dual-task performance of older adults was more vulnerable to PF strategy, underlying compensatory resource allocation in the preparatory period for resolution of dual-task interference due to degenerated frontal function.
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http://dx.doi.org/10.1093/geronb/gby073DOI Listing
October 2019

Progressive conscious control of scapular orientation with video feedback has improvement in muscle balance ratio in patients with scapular dyskinesis: a randomized controlled trial.

J Shoulder Elbow Surg 2018 Aug 6;27(8):1407-1414. Epub 2018 Jun 6.

School and Graduate Institute of Physical Therapy, College of Medicine, National Taiwan University, Taipei, Taiwan; Division of Physical Therapy, Department of Physical Medicine and Rehabilitation, National Taiwan University Hospital, Taipei, Taiwan. Electronic address:

Background: Video feedback (VF) can guide patients to consciously control scapular orientation without inappropriate substitution. This study investigated whether progressive conscious control with VF improves scapular muscle activation and movements during arm elevation in patients with subacromial impingement and scapular dyskinesis.

Methods: The study recruited 38 amateur overhead athletes with subacromial impingement and scapular medial border prominence who were randomly assigned to the VF or control group. The participants in both groups controlled the scapular position and progressively practiced from 0° to 45° and from 0° to 90° of arm elevation. Participants in the VF group also controlled the scapular position with a video presentation of the scapula on a screen. We investigated the scapular kinematics, muscle activation, and balance ratio for outcome collection in the preintervention and postintervention conditions with and without VF conditions.

Results: Decreased upper trapezius (UT) activation (3%-13%, P < .0083), increased lower trapezius (LT) activation (3%-17%, P < .0083), restored UT/LT ratios (0.67-3.13, P < .0083), and decreased scapular internal rotation (1.8°-6.1°, P < .003) relative to the preintervention condition were demonstrated in the 2 postintervention conditions in both groups. The VF group also demonstrated decreased UT/serratus anterior ratios (0.21-0.30, P < .0083) in 2 postintervention conditions relative to the preintervention condition.

Conclusions: The progressive control of scapular orientation with or without VF can be used to reduce the UT/LT ratio and improve scapular internal rotation during arm elevation. Control training with VF can further decrease the UT/serratus anterior ratio.
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http://dx.doi.org/10.1016/j.jse.2018.04.006DOI Listing
August 2018

Improving Dual-Task Control With a Posture-Second Strategy in Early-Stage Parkinson Disease.

Arch Phys Med Rehabil 2018 08 31;99(8):1540-1546.e2. Epub 2018 Mar 31.

Department of Neurology, National Taiwan University Hospital, College of Medicine, National Taiwan University, Taipei, Taiwan. Electronic address:

Objective: To examine the task prioritization effects on postural-suprapostural dual-task performance in patients with early-stage Parkinson disease (PD) without clinically observed postural symptoms.

Design: Cross-sectional study. Participants performed a force-matching task while standing on a mobile platform, and were instructed to focus their attention on either the postural task (posture-first strategy) or the force-matching task (posture-second strategy).

Setting: University research laboratory.

Participants: Individuals (N=16) with early-stage PD who had no clinically observed postural symptoms.

Interventions: Not applicable.

Main Outcome Measures: Dual-task change (DTC; percent change between single-task and dual-task performance) of posture error, posture approximate entropy (ApEn), force error, and reaction time (RT). Positive DTC values indicate higher postural error, posture ApEn, force error, and force RT during dual-task conditions compared with single-task conditions.

Results: Compared with the posture-first strategy, the posture-second strategy was associated with smaller DTC of posture error and force error, and greater DTC of posture ApEn. In contrast, greater DTC of force RT was observed under the posture-second strategy.

Conclusions: Contrary to typical recommendations, our results suggest that the posture-second strategy may be an effective dual-task strategy in patients with early-stage PD who have no clinically observed postural symptoms in order to reduce the negative effect of dual tasking on performance and facilitate postural automaticity.
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http://dx.doi.org/10.1016/j.apmr.2018.02.013DOI Listing
August 2018

Age-Related Differences in Reorganization of Functional Connectivity for a Dual Task with Increasing Postural Destabilization.

Front Aging Neurosci 2017 12;9:96. Epub 2017 Apr 12.

Institute of Allied Health Sciences, College of Medicine, National Cheng Kung UniversityTainan, Taiwan.

The aged brain may not make good use of central resources, so dual task performance may be degraded. From the brain connectome perspective, this study investigated dual task deficits of older adults that lead to task failure of a suprapostural motor task with increasing postural destabilization. Twelve younger (mean age: 25.3 years) and 12 older (mean age: 65.8 years) adults executed a designated force-matching task from a level-surface or a stabilometer board. Force-matching error, stance sway, and event-related potential (ERP) in the preparatory period were measured. The force-matching accuracy and the size of postural sway of the older adults tended to be more vulnerable to stance configuration than that of the young adults, although both groups consistently showed greater attentional investment on the postural task as sway regularity increased in the stabilometer condition. In terms of the synchronization likelihood (SL) of the ERP, both younger and older adults had net increases in the strengths of the functional connectivity in the whole brain and in the fronto-sensorimotor network in the stabilometer condition. Also, the SL in the fronto-sensorimotor network of the older adults was greater than that of the young adults for both stance conditions. However, unlike the young adults, the older adults did not exhibit concurrent deactivation of the functional connectivity of the left temporal-parietal-occipital network for postural-suprapostural task with increasing postural load. In addition, the older adults potentiated functional connectivity of the right prefrontal area to cope with concurrent force-matching with increasing postural load. In conclusion, despite a universal negative effect on brain volume conduction, our preliminary results showed that the older adults were still capable of increasing allocation of neural sources, particularly via compensatory recruitment of the right prefrontal loop, for concurrent force-matching under the challenging postural condition. Nevertheless, dual-task performance of the older adults tended to be more vulnerable to postural load than that of the younger adults, in relation to inferior neural economy or a slow adaptation process to stance destabilization for scant dissociation of control hubs in the temporal-parietal-occipital cortex.
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http://dx.doi.org/10.3389/fnagi.2017.00096DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5388754PMC
April 2017

Improving posture-motor dual-task with a supraposture-focus strategy in young and elderly adults.

PLoS One 2017 2;12(2):e0170687. Epub 2017 Feb 2.

Physical Therapy Center, National Taiwan University Hospital, Taipei City, Taiwan.

In a postural-suprapostural task, appropriate prioritization is necessary to achieve task goals and maintain postural stability. A "posture-first" principle is typically favored by elderly people in order to secure stance stability, but this comes at the cost of reduced suprapostural performance. Using a postural-suprapostural task with a motor suprapostural goal, this study investigated differences between young and older adults in dual-task cost across varying task prioritization paradigms. Eighteen healthy young (mean age: 24.8 ± 5.2 years) and 18 older (mean age: 68.8 ± 3.7 years) adults executed a designated force-matching task from a stabilometer board using either a stabilometer stance (posture-focus strategy) or force-matching (supraposture-focus strategy) as the primary task. The dual-task effect (DTE: % change in dual-task condition; positive value: dual-task benefit, negative value: dual-task cost) of force-matching error and reaction time (RT), posture error, and approximate entropy (ApEn) of stabilometer movement were measured. When using the supraposture-focus strategy, young adults exhibited larger DTE values in each behavioral parameter than when using the posture-focus strategy. The older adults using the supraposture-focus strategy also attained larger DTE values for posture error, stabilometer movement ApEn, and force-matching error than when using the posture-focus strategy. These results suggest that the supraposture-focus strategy exerted an increased dual-task benefit for posture-motor dual-tasking in both healthy young and elderly adults. The present findings imply that the older adults should make use of the supraposture-focus strategy for fall prevention during dual-task execution.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0170687PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5289460PMC
September 2017

An Increase in Postural Load Facilitates an Anterior Shift of Processing Resources to Frontal Executive Function in a Postural-Suprapostural Task.

Front Hum Neurosci 2016 19;10:420. Epub 2016 Aug 19.

Institute of Allied Health Sciences, College of Medicine, National Cheng Kung UniversityTainan City, Taiwan; Department of Physical Therapy, College of Medicine, National Cheng Kung UniversityTainan City, Taiwan.

Increase in postural-demand resources does not necessarily degrade a concurrent motor task, according to the adaptive resource-sharing hypothesis of postural-suprapostural dual-tasking. This study investigated how brain networks are organized to optimize a suprapostural motor task when the postural load increases and shifts postural control into a less automatic process. Fourteen volunteers executed a designated force-matching task from a level surface (a relative automatic process in posture) and from a stabilometer board while maintaining balance at a target angle (a relatively controlled process in posture). Task performance of the postural and suprapostural tasks, synchronization likelihood (SL) of scalp EEG, and graph-theoretical metrics were assessed. Behavioral results showed that the accuracy and reaction time of force-matching from a stabilometer board were not affected, despite a significant increase in postural sway. However, force-matching in the stabilometer condition showed greater local and global efficiencies of the brain networks than force-matching in the level-surface condition. Force-matching from a stabilometer board was also associated with greater frontal cluster coefficients, greater mean SL of the frontal and sensorimotor areas, and smaller mean SL of the parietal-occipital cortex than force-matching from a level surface. The contrast of supra-threshold links in the upper alpha and beta bands between the two stance conditions validated load-induced facilitation of inter-regional connections between the frontal and sensorimotor areas, but that contrast also indicated connection suppression between the right frontal-temporal and the parietal-occipital areas for the stabilometer stance condition. In conclusion, an increase in stance difficulty alters the neurocognitive processes in executing a postural-suprapostural task. Suprapostural performance is not degraded by increase in postural load, due to (1) increased effectiveness of information transfer, (2) an anterior shift of processing resources toward frontal executive function, and (3) cortical dissociation of control hubs in the parietal-occipital cortex for neural economy.
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http://dx.doi.org/10.3389/fnhum.2016.00420DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4990564PMC
September 2016

Neural Correlates of Task Cost for Stance Control with an Additional Motor Task: Phase-Locked Electroencephalogram Responses.

PLoS One 2016 24;11(3):e0151906. Epub 2016 Mar 24.

School and Graduate Institute of Physical Therapy, College of Medicine, National Taiwan University, Taipei 100, Taiwan.

With appropriate reallocation of central resources, the ability to maintain an erect posture is not necessarily degraded by a concurrent motor task. This study investigated the neural control of a particular postural-suprapostural procedure involving brain mechanisms to solve crosstalk between posture and motor subtasks. Participants completed a single posture task and a dual-task while concurrently conducting force-matching and maintaining a tilted stabilometer stance at a target angle. Stabilometer movements and event-related potentials (ERPs) were recorded. The added force-matching task increased the irregularity of postural response rather than the size of postural response prior to force-matching. In addition, the added force-matching task during stabilometer stance led to marked topographic ERP modulation, with greater P2 positivity in the frontal and sensorimotor-parietal areas of the N1-P2 transitional phase and in the sensorimotor-parietal area of the late P2 phase. The time-frequency distribution of the ERP primary principal component revealed that the dual-task condition manifested more pronounced delta (1-4 Hz) and beta (13-35 Hz) synchronizations but suppressed theta activity (4-8 Hz) before force-matching. The dual-task condition also manifested coherent fronto-parietal delta activity in the P2 period. In addition to a decrease in postural regularity, this study reveals spatio-temporal and temporal-spectral reorganizations of ERPs in the fronto-sensorimotor-parietal network due to the added suprapostural motor task. For a particular set of postural-suprapostural task, the behavior and neural data suggest a facilitatory role of autonomous postural response and central resource expansion with increasing interregional interactions for task-shift and planning the motor-suprapostural task.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0151906PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4807025PMC
August 2016

Neural basis of postural focus effect on concurrent postural and motor tasks: phase-locked electroencephalogram responses.

Behav Brain Res 2014 Nov 6;274:95-107. Epub 2014 Aug 6.

Department of Physical Therapy, College of Medicine, National Cheng Kung University, Tainan 701, Taiwan; Institute of Allied Health Sciences, College of Medicine, National Cheng Kung University, Tainan 701, Taiwan. Electronic address:

Dual-task performance is strongly affected by the direction of attentional focus. This study investigated neural control of a postural-suprapostural procedure when postural focus strategy varied. Twelve adults concurrently conducted force-matching and maintained stabilometer stance with visual feedback on ankle movement (visual internal focus, VIF) and on stabilometer movement (visual external focus, VEF). Force-matching error, dynamics of ankle and stabilometer movements, and event-related potentials (ERPs) were registered. Postural control with VEF caused superior force-matching performance, more complex ankle movement, and stronger kinematic coupling between the ankle and stabilometer movements than postural control with VIF. The postural focus strategy also altered ERP temporal-spatial patterns. Postural control with VEF resulted in later N1 with less negativity around the bilateral fronto-central and contralateral sensorimotor areas, earlier P2 deflection with more positivity around the bilateral fronto-central and ipsilateral temporal areas, and late movement-related potential commencing in the left frontal-central area, as compared with postural control with VIF. The time-frequency distribution of the ERP principal component revealed phase-locked neural oscillations in the delta (1-4Hz), theta (4-7Hz), and beta (13-35Hz) rhythms. The delta and theta rhythms were more pronounced prior to the timing of P2 positive deflection, and beta rebound was greater after the completion of force-matching in VEF condition than VIF condition. This study is the first to reveal the neural correlation of postural focusing effect on a postural-suprapostural task. Postural control with VEF takes advantage of efficient task-switching to facilitate autonomous postural response, in agreement with the "constrained-action" hypothesis.
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http://dx.doi.org/10.1016/j.bbr.2014.07.054DOI Listing
November 2014

Rate control and quality assurance during rhythmic force tracking.

Behav Brain Res 2014 Feb 20;259:186-95. Epub 2013 Nov 20.

Department of Physical Therapy, College of Medicine, National Cheng Kung University, Tainan, Taiwan; Institute of Allied Health Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan. Electronic address:

Movement characteristics can be coded in the single neurons or in the summed activity of neural populations. However, whether neural oscillations are conditional to the frequency demand and task quality of rhythmic force regulation is still unclear. This study was undertaken to investigate EEG dynamics and behavior correlates during force-tracking at different target rates. Fourteen healthy volunteers conducted load-varying isometric abduction of the index finger by coupling the force output to sinusoidal targets at 0.5 Hz, 1.0 Hz, and 2.0 Hz. Our results showed that frequency demand significantly affected EEG delta oscillation (1-4 Hz) in the C3, CP3, CPz, and CP4 electrodes, with the greatest delta power and lowest delta peak around 1.5 Hz for slower tracking at 0.5 Hz. Those who had superior tracking congruency also manifested enhanced alpha oscillation (8-12 Hz). Alpha rhythms of the skilled performers during slow tracking spread through the whole target cycle, except for the phase of direction changes. However, the alpha rhythms centered at the mid phase of a target cycle with increasing target rate. In conclusion, our findings clearly suggest two advanced roles of cortical oscillation in rhythmic force regulation. Rate-dependent delta oscillation involves a paradigm shift in force control under different time scales. Phasic organization of alpha rhythms during rhythmic force tracking is related to behavioral success underlying the selective use of bimodal controls (feedback and feedforward processes) and the timing of attentional focus on the target's peak velocity.
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http://dx.doi.org/10.1016/j.bbr.2013.11.019DOI Listing
February 2014

Behavioral data and neural correlates for postural prioritization and flexible resource allocation in concurrent postural and motor tasks.

Hum Brain Mapp 2013 Mar 23;34(3):635-50. Epub 2011 Nov 23.

Institute of Allied Health Sciences, College of Medicine, National Cheng Kung University, Tainan 701, Taiwan.

This study was undertaken to investigate the reciprocity effect between postural and suprapostural performances and its underlying neural mechanisms wherein subjects executed a perceptual-motor suprapostural task and maintained steady upright postures. Fourteen healthy individuals conducted force-matching maneuvers (static vs. dynamic) under two stance conditions (bipedal stance vs. unipedal stance); meanwhile, force-matching error, center of pressure dynamics, event-related potentials (ERPs), and the movement-related potential (MRP) were monitored. The behavioral results showed that force-matching error and postural sway were differently modulated by variations in stance pattern and force-matching version. Increase in postural challenge undermined the precision of static force-matching but facilitated a dynamic force-matching task. Both static and dynamic force-matching tasks improved postural control of unipedal stance but not of bipedal stance, in reference to the control conditions. ERP results revealed a stance-dependent N1 response, which was greater around the parietal cortex in the unipedal stance conditions. Instead, P2 was modulated by the effect of the suprapostural motor task, with a smaller P2 in the right parietal cortex for dynamic force-matching. Spatiotemporal evolution of the MRP commenced at the left frontal-central area and spread bilaterally over the frontal-central and parietal cortex. MRP onset was subject to an analogous interaction effect on force-matching performance. Our findings suggest postural prioritization and a structural alternation effect of stance pattern on postural performance, relevant to implicit expansion and selective allocation of central resources for relative task-loads of a postural-suprapostural task.
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http://dx.doi.org/10.1002/hbm.21460DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6870496PMC
March 2013

Reciprocal influences on performances of a postural-suprapostural task by manipulating the level of task-load.

J Electromyogr Kinesiol 2010 Jun 27;20(3):413-9. Epub 2009 Aug 27.

Institute of Allied Health Sciences, College of Medicine, National Cheng Kung University, Tainan 701, Taiwan.

The objective of this study was to investigate the reciprocal influences of stance pattern (bilateral stance vs. unilateral stance) and thumb-index precision grip task (static target vs. dynamic target) on postural-suprapostural tasks by manipulating task-load. Fifteen healthy volunteers participated in four postural-suprapostural tasks, including static force-matching in bilateral/unilateral stance (BS_static; US_static), dynamic force-matching in bilateral/unilateral stance (BS_dynamic; US_dynamic), and two control tasks in bilateral and unilateral stances without a finger task. The normalized force error (NFE), reaction time (RT) of the finger tasks, and normalized change in center of pressure sway (Delta NCoP) were measured. For suprapostural task performance, a significant interaction effect between postural and suprapostural tasks on NFE of the finger tasks was noted (static: BSUS), but RT was not different among the four tasks. For postural task performance, negative Delta NCoP during unilateral stance indicated a spontaneous reduction in postural sway due to added force-matching. In contrast, addition of force-matching tended to increase postural sway during bilateral stance, but postural fluctuations decreased as task-load of suprapostural task increased (BS_dynamic
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http://dx.doi.org/10.1016/j.jelekin.2009.06.003DOI Listing
June 2010

Assessment of H reflex sensitivity with M wave alternation consequent to fatiguing contractions.

Int J Neurosci 2008 Sep;118(9):1317-30

School of Physical Therapy, National Cheng Kung University, Tainan, Taiwan.

The objective of this study was to examine the changes in H reflex sensitivity after neuromuscular fatigue associated with fluctuations of the M wave. In the maximal and submaximal voluntary contraction (MVC and SMVC) paradigms, subjects performed voluntary plantarflexion at 100% MVC and 40% MVC respectively until the limit of torque maintenance was reached. In the submaximal electrical stimulation (SMES) paradigm, the tricep surae was exhausted with sustained electrical stimulation of 40% of the maximal tolerable intensity at a 40-Hz stimulus rate. The H reflexes and maximal M waves (M(max)) of the soleus were recorded before and after the three fatigue paradigms, and the H reflex was standardized with M(max) to minimize possible bias due to fatigue-induced M wave fluctuation. The results showed a significant increase in the standardized H reflex due to the SMES paradigm in spite of M(max) potentiation. The SMVC paradigm led to a reduction in size of the standardized H reflex without modification of M(max), whereas the standardized H reflex was not mediated by the MVC paradigm, which contributed to a noticeable M(max) potentiation. The present study underscored the fact that the H reflex sensitivity and M wave amplitude were not necessarily suppressed consequent to neuromuscular fatigue, but varied with the activation history of a muscle for size-dependent efficacy of the Ia transmission pathways and postactivation potentiation.
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http://dx.doi.org/10.1080/00207450802055606DOI Listing
September 2008

Modulation of soleus H reflex due to stance pattern and haptic stabilization of posture.

J Electromyogr Kinesiol 2009 Jun 21;19(3):492-9. Epub 2007 Sep 21.

Institute of Allied Health Sciences, College of Medicine, National Cheng Kung University, Tainan 701, Taiwan.

The quiet stance is a complicated motor act requiring sophisticated sensorimotor integration to balance an artificial inverted pendulum with the ankle musculature. The objective of this study was to characterize the effects of stance pattern (bilateral stance vs. unilateral stance) and directional influence of light finger touch (medial-lateral vs. anterior-posterior) in unilateral stance upon responsiveness of the soleus H reflex. Sixteen healthy volunteers (mean age, 24.25+/-1.77 years) participated in four postural tasks with the eyes open, including the bilateral stance (BS), the unilateral stance without finger touch (USNT), and with finger touch in the medial-lateral direction (USML) and anterior-posterior direction (USAP). Meanwhile, the soleus H reflex, the pre-stimulus background activity of ankle antagonist pairs, and center of pressure (CoP) sway were measured. In reference to the BS, the USNT resulted in a significant stance effect on suppression of the soleus H reflex (H/M(max)) associated with enhancement of CoP sway. Among the conditions of unilateral stance, there was a marked directional effect of finger touch on modulation of the H/M(max). A greater disinhibition of the H/M(max) in consequence to light touch in the ML direction than in the AP direction was noted (H/M(max): USML>USAP>USNT). This directional modulation of the soleus H reflex concurred with haptic stabilization of posture in unilateral stance, showing a more pronounced reduction in CoP sway in the USML condition than in the USAP condition. However, alteration in postural sway and modulation of the soleus H reflex were not mutually correlated when stance pattern or touch vector varied. In conclusion, gating of the soleus H reflex indicated adaptation of an ankle strategy to stance pattern and haptic stabilization of posture. Relative to bilateral stance, postural maintenance in unilateral stance relied less on reflexive correction of the soleus. When finger touch was provided in line with prevailing postural threat in the lateral direction, postural stability in unilateral stance was better secured than finger touch in anterior-posterior direction, resulting in more pronounced disinhibition of the monosynaptic reflex pathway.
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http://dx.doi.org/10.1016/j.jelekin.2007.07.014DOI Listing
June 2009

Characterization of the mechanical and neural components of spastic hypertonia with modified H reflex.

J Electromyogr Kinesiol 2006 Aug 25;16(4):384-91. Epub 2005 Oct 25.

Institute of Allied Health Sciences, National Cheng Kung University, Tainan 701, Taiwan.

As the H reflex remains unable to assess mechanical changes intrinsic to a muscle, the aim of this study was to modify the H reflex techniques and to characterize the neural and mechanical components of muscle spasticity, relating the two components to clinical observations. Thirty-four patients featuring either a spinal-cord lesion (n=15) or stroke (n=19) and 23 neurologically normal subjects were recruited. Soleus H reflex and maximal M response (M(max)) were measured with electromyography and mechanomyography (MMG). The motoneuronal excitability was represented with the adjusted ratio of the H reflex to the M(max) (H/M(max)) and the ratio of the paired H reflexes (H(2)/H(1)). Muscle mechanical properties were characterized by the amplitude and median frequency of maximal M response recorded with MMG (MMG(Mmax)). The results showed that spastic patients exhibited a larger H/M(max), H(2)/H(1) and amplitude of MMG(Mmax) than the control group. H/M(max) and amplitude of MMG(Mmax) accounted for 55.7% of the variance in the Modified Ashworth Scale, the clinical hypertonia assessment. The amplitude of MMG(Mmax) correlated with functional impairments, as assessed with the Barthel index and Fugl-Meyer motor-assessment scale. It was concluded that spastic hypertonia involved an atypical increase in motoneuronal excitability and muscle mechanical properties, while impairment of functional performance and daily activity was attributable primarily to altered mechanical properties of a spastic muscle.
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http://dx.doi.org/10.1016/j.jelekin.2005.09.001DOI Listing
August 2006
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