記述言語：英語   掲載種別：研究論文（学術雑誌）

© The Author(s) 2020. The execution of cognitive tasks is known to alter postural sway during standing, but the underlying mechanisms are still debated. This study investigated how performing a mental task modified balance control during standing. We required 15 healthy adult males to maintain an upright stance under conditions of simply relaxing and maintaining normal quiet standing (control condition) or while performing a secondary cognitive task (mental arithmetic). Under each condition, we measured the participants’ center of pressure and used kinematic measurements for a quantitative evaluation of postural control modulation. We calculated the standard deviation of the joint angles (ankle, knee, and hip) and the estimated joint stiffness to measure joint mobility changes in postural control. To estimate the kinematic pattern of covariation among these joints, we used uncontrolled manifold analysis, an assessment of the strength of multijoint coordination. Compared to normal standing, executing the cognitive task while standing led to reduced movements of the ankle and hip joints. There were no significant differences in ankle stiffness or uncontrolled manifold ratios between the conditions. Our results suggest that when performing a secondary cognitive task during standing, neither changes in the modification of stiffness nor the strength of multijoint coordination (both of which preserve the center of mass position) explains changes in postural sway.

DOI： 10.1177/0031512520919543

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記述言語：英語   掲載種別：研究論文（学術雑誌）

DOI： 10.3390/sports8040046

記述言語：英語   掲載種別：研究論文（学術雑誌）

The present study was a cross-sectional comparison of probabilistic structure in the distribution of pitching location among baseball pitchers of various age groups (25 elementary school (ES), 20 junior high school (JH), 15 high school (HS), and 18 college students (CL)). In the results, despite the general age-dependent variations in pitching precision, the difference was reflected not only in error ‘size’ but also in the ‘shape’ of error as it was shown by fitting 95% confidence ellipse to the two dimensional distribution of pitch location. While the precision measure as a reflection of trial-by-trial variability of release timing (major axis length of the ellipse) was constant, minor axis length of the ellipse as a reflection of variability in the pitching form of each participant demonstrated significant differences among the groups. In the ES group particularly, the trial-by-trial variability in the trajectory angle of the throwing arm was significantly correlated with the minor axis length; this correlation was far greater than those in older groups. The present study is the first to demonstrate the detailed structure of the variability of pitching location of baseball dependent on age.

DOI： 10.1080/14763141.2020.1822908

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

© 2019, Springer-Verlag GmbH Germany, part of Springer Nature. Pole walking (PW), a form of locomotion in which a person holds a pole in each hand, enhances the involvement of alternating upper-limb movement. While this quadruped-like walking increases postural stability for bipedal conventional walking (CW), in terms of the neural controlling mechanisms underlying the two locomotion forms (PW and CW), the similarities and differences remain unknown. The purpose of this study was to compare the neural control of PW and CW from the perspective of locomotor adaptation to a novel environment on a split-belt treadmill. We measured the anterior component of the ground reaction (braking) force during and after split-belt treadmill walking in 12 healthy subjects. The results demonstrated that (1) PW delayed locomotor adaptation when compared with CW; (2) the degrees of transfer of the acquired movement pattern to CW and PW were not different, regardless of whether the novel movement pattern was learned in CW or PW; and (3) the movement pattern learned in CW was washed out by subsequent execution in PW, whereas the movement pattern learned in PW was not completely washed out by subsequent execution in CW. These results suggest that the neural control mechanisms of PW and CW are not independent, and it is possible that PW could be a locomotor behavior built upon a basic locomotor pattern of CW.

DOI： 10.1007/s00221-019-05541-y

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記述言語：英語   掲載種別：研究論文（学術雑誌）

© 2019 Saito et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Transcutaneous electrical stimulation is a relatively new technique to evoke spinal reflexes in lower limb muscles. The advantage of this technique is that the spinal reflex responses can be obtained from multiple lower limb muscles simultaneously. However, repeatability of spinal reflexes evoked by transcutaneous spinal cord stimulation between days has not been evaluated. We aimed to examine repeatability of recruitment properties of the spinal reflexes evoked by transcutaneous spinal cord stimulation. Recruitment curves of the spinal reflexes evoked by transcutaneous spinal cord stimulation of 8 lower limb muscles (i.e., foot, lower leg, and thigh muscles) of 20 males were measured on two consecutive days. To confirm that responses were caused by activation of the sensory fiber, a double-pulse stimulation with 50 ms inter-pulse interval was delivered. Peak-to-peak amplitude of the first response was calculated for each muscle when no response was observed in the second response owing to post-activation depression. For comparison with the spinal reflexes evoked by transcutaneous spinal cord stimulation, the recruitment curves of the H-reflex amplitude of the soleus of 9 males were measured. Threshold intensity and maximal slope of the recruitment curves were calculated, and inter-day repeatability of the properties was quantified using intraclass correlation coefficients. For the spinal reflexes evoked by transcutaneous spinal cord stimulation, the intraclass correlation coefficient values of threshold intensity and maximal slope for each muscle ranged from 0.487 to 0.874 and from 0.471 to 0.964, respectively. Regarding the soleus H-reflex, the intraclass correlation coefficients of threshold intensity and maximal slope were 0.936 and 0.751, respectively. The present data showed that repeatability of the recruitment properties of the spinal reflexes evoked by transcutaneous spinal cord stimulation in the lower limb was moderate to high. Measurement of the spinal reflexes evoked by transcutaneous spinal cord stimulation would be useful for longitudinal neurophysiological studies.

DOI： 10.1371/journal.pone.0214818

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記述言語：英語   掲載種別：研究論文（学術雑誌）

© 2018, Springer-Verlag GmbH Germany, part of Springer Nature. Neuromuscular electrical stimulation (NMES) of lower limbs elicits muscle contractions through the activation of efferent fibers and concomitant recruitment of afferent fibers, which can modulate excitability of the central nervous system. However, neural mechanisms of NMES and how unilateral stimulation of the soleus affects spinal reflexes in multiple lower limb muscles bilaterally remains unknown. Twelve able-bodied participants were recruited, and spinal reflex excitability changes were tested after four interventions, each applied for 60 s, on the right plantar flexors: (1) motor-level NMES; (2) sensory-level NMES; (3) voluntary contraction; (4) rest. Spinal reflexes were elicited using single-pulse transcutaneous spinal cord stimulation applied on the lumbar level of the spinal cord to evoke bilateral responses in multiple lower limb muscles, while maximum motor response (M max ) was tested in the soleus by stimulating the posterior tibial nerve. Spinal reflexes and M max before each intervention were compared to immediately after and every 5 min subsequently, for 15 min. Results showed that motor-level NMES inhibited spinal reflexes of the soleus and other studied muscles of the ipsilateral leg, but not the contralateral leg (except vastus medialis) for 15 min, while not affecting soleus muscle properties (M max ). Voluntary contraction effect lasted less than 5 min, while sensory-level NMES and rest did not produce an effect. Short-term spinal reflex excitability was likely affected because antidromic impulses during motor-level NMES coincided in the spinal cord with afferent inputs to induce spinal neuroplasticity, whereas afferent input alone did not produce short-term effects. Such activation of muscles with NMES could reduce spasticity in individuals with neurological impairments.

DOI： 10.1007/s00221-018-5437-6

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記述言語：英語   掲載種別：研究論文（学術雑誌）

© 2019, Springer-Verlag GmbH Germany, part of Springer Nature. Although no damage occurs in the brains of individuals with spinal cord injury, structural and functional reorganization occurs in the sensorimotor cortex because of the deafferentation of afferent signal input from below the injury level. This brain reorganization that is specific to individuals with spinal cord injury is speculated to contribute to the improvement of the motor function of the remaining upper limbs. However, no study has investigated in detail the motor function above the injury level. To clarify this, we designed an experiment using the handgrip force steadiness task, which is a popular technique for evaluating motor function as the index of the variability of common synaptic input to motoneurons. Fourteen complete spinal cord injury (cSCI) individuals in the chronic phase, fifteen individuals with lower limb disabilities, and twelve healthy controls participated in the study. We clarified that the force steadiness in the cSCI group was significantly higher than that in the control groups, and that sports years were significantly correlated with this steadiness. Furthermore, multiple analyses revealed that force steadiness was significantly predicted by sports years. These results suggest that brain reorganization after spinal cord injury can functionally affect the remaining upper limb motor function. These findings may have implications in the clinical rehabilitation field, such as occupational rehabilitation of the upper limbs. They also indicate that individuals with complete spinal cord injury, based on their enhanced force adjustment skills, would excel at fine motor tasks such as manufacturing and handicrafts.

DOI： 10.1007/s00221-019-05656-2

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記述言語：英語   掲載種別：研究論文（学術雑誌）

© 2018 Hagio et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. An execution of cognitive processing interferes with postural sway during quiet standing. It reduces sway variability in young adults, but the mechanism is not clear. To elucidate the mechanisms, we focused on breathing in the present study. The purpose of this study was to clarify whether a decrease in postural sway amplitude during a postural–cognitive task is related to the change in breathing movement. The center of pressure (COP) was recorded via a force plate and the motion of leg joints (ankle, knee, and hip), and breathing movements were measured with a 3D motion capture system in quiet standing and standing with cognitive (mental arithmetic) task conditions. The change ratios of each variable from the quiet standing condition to the cognitive task were also calculated. It was shown that the MASt condition produced a significantly smaller RMS of COP displacement as compared to the QSt condition (p < 0.01). The results revealed that the breathing rate was faster and the amplitude of breathing movement smaller when subjects performed the cognitive task. A significant positive correlation (r = 0.75, p < 0.01) was found between the change ratio of breathing amplitude and the COP amplitude. The present results suggest that reduced standing postural sway during a cognitive task is related, at least in part, to a decrease in breathing amplitude.

DOI： 10.1371/journal.pone.0197385

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記述言語：英語   掲載種別：研究論文（学術雑誌）

© 2018 Elsevier B.V. The effects of motor imagery on spinal reflexes such as the H-reflex are unclear. One reason for this is that the muscles that can be used to record spinal reflexes are limited to traditional evoking methods Recently, transcutaneous spinal cord stimulation has been used for inducing spinal reflexes from multiple muscles and we aimed to examine the effect of motor imagery on spinal reflexes from multiple muscles. Spinal reflexes evoked by transcutaneous spinal cord stimulation were recorded from six muscles from lower limbs during motor imagery of right wrist extension and ankle plantarflexion with maximum isometric contraction. During both imaginary tasks, facilitation of spinal reflexes was detected in the ankle ipsilateral plantarflexor and dorsiflexor muscles, but not in thigh, toe or contralateral lower limb muscles. These results suggest that motor imagery of isometric contraction facilitates spinal reflex excitability in muscles of the ipsilateral lower leg and the facilitation does not correspond to the imaginary involved muscles.

DOI： 10.1016/j.neulet.2018.01.015

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

© 2018 Fujio, Obata, Kitamura, Kawashima and Nakazawa. Recent studies demonstrated that the corticospinal pathway is one of the key nodes for the feedback control of human standing and that the excitability is flexibly changed according to the current state of posture. However, it has been unclear whether this pathway is also involved in a predictive control of human standing. Here, we investigated whether the corticospinal excitability of the soleus (SOL) and tibialis anterior (TA) muscles during standing would be modulated anticipatorily when perturbation was impending. We measured the motor-evoked potential (MEP) induced by transcranial magnetic stimulation over the motor cortex at six stimulus intensities. Three experimental conditions were set depending on predictabilities about perturbation occurrence and onset: No perturbation, No Cue, and Cue conditions. In the Cue condition, an acoustic signal was given as timing information of perturbation. The slope of the stimulus– response relation curve revealed that the TA-MEP was enhanced when postural perturbation was expected compared to when the perturbation was not expected (No Perturbation vs. No Cue, 0.023 ± 0.004 vs. 0.042 ± 0.007; No Perturbation vs. Cue, 0.023 ± 0.004 vs. 0.050 ± 0.009; Bonferroni correction, p = 0.01, respectively). In addition, two-way analysis of variance (intensity × condition) revealed the main effect of condition (F (1,13) = 6.31, p = 0.03) but not intensity and interaction when the MEP amplitude of the Cue and No Cue conditions was normalized by that in No Perturbation, suggesting the enhancement more apparent when timing information was given. The SOL-MEP was not modulated even when perturbation was expected, but it slightly reduced due to the timing information. The results of an additional experiment confirmed that the acoustic cue by itself did not affect the TA- and SOL-MEPs. Our findings suggest that a prediction of a future state of standing balance modulates the corticospinal excitability in the TA, and that the additional timing information facilitates this modulation. The corticospinal pathway thus appears to be involved in mechanisms of the predictive control as well as feedback control of standing posture.

DOI： 10.3389/fnhum.2018.00068

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記述言語：英語   掲載種別：研究論文（学術雑誌）

© 2017, Springer-Verlag GmbH Germany, part of Springer Nature. The study aimed to compare the ability of dance and non-dance subjects to perform fine control of a simple heel-raising/lowering movement, and to determine if there are any differences in motor unit activity in the primary plantar flexor muscles during the movement. Subjects were instructed to accurately track a sinusoidal trace with a heel-raising and lowering movement at four controlled frequencies (1, 0.5, 0.25, and 0.125 Hz). The ankle joint angle was used to characterize movement errors from the target. Surface electromyography was recorded from the soleus and medial gastrocnemius muscles. One trial including five sinusoidal traces was divided into two phases: an up phase and a down phase. To characterize motor unit activity of the plantar flexor muscles, a wavelet transform was applied to electromyographic signals recorded in each phase. For both phases, errors in movement accuracy were lower in dancers than in controls (8.7 ± 4.6 vs. 11.5 ± 6.8%, P < 0.05) regardless of the frequency of the sinusoidal wave traced. During the down phase, peak power of soleus electromyographic signals at ~ 10 Hz was statistically larger in control subjects than in dancers (10.4 ± 0.7 vs. 6.3 ± 0.4% total power, P < 0.05). These results indicate that dancers have a higher degree of motor skill in a heel raise tracking task and exhibit adaptations in the motor unit activity during skilled dynamic movements.

DOI： 10.1007/s00221-017-5131-0

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

© 2017 A combination of electrical nerve stimulation (ENS) and passive or active cyclic movements (i.e., pedaling and stepping) has been suggested to induce stronger short-term effects in spinal circuits as compared to either intervention alone. The purpose of the present study is to determine whether the effects of ENS during passive stepping are dependent on the timing of the stimulation during the stepping cycle. A total of 10 able-bodied participants were recruited for the study. Two interventions were assessed during passive ground stepping: (1) ENS of the common peroneal nerve (CPN) during the swing phase (ENSswing) and (2) stance phase (ENSstance). ENS was applied at the motor threshold intensity on the tibialis anterior muscle for a total of 30 min. Spinal reciprocal inhibition (RI) was assessed by conditioning the H-reflex in the soleus muscle with electrical stimulation to the CPN before (baseline), as well as 5, 15, and 30 min after each intervention. Compared to the baseline, the amount of RI was increased 5 and 15 min after the ENSswing intervention, whereas it was decreased after the ENSstance intervention. This suggests that ENS has a phase-dependent effect on RI during passive stepping. Overall, the results imply that phase-dependent timing of ENS is essential for guiding plasticity in the spinal circuits.

DOI： 10.1016/j.jelekin.2017.12.007

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

© 2017 IEEE. The purpose of this study was to investigate the effect of anode position on the spinal reflex responses evoked by transcutaneous spinal cord stimulation. Healthy males participated in two experiments. In Experiment 1 (Exp. 1, n = 3), we investigated the effect of anode position on the spinal reflex responses in multiple lower-limb muscles. Experiment 2 (Exp. 2, n = 8) focused on the effect of anode position on the spinal reflex response in the vastus medialis (VM) muscle. In each experiment, electromyographic signals were recorded in the right leg muscle(s). The cathode was placed over the area between the spinous processes of the L1 and L2 vertebrae. The anode was placed over (1) the abdomen (ABD), (2) the ipsilateral (right) anterior superior iliac spine (iASIS), or (3) the contralateral (left) anterior superior iliac spine (cASIS). A double pulse stimulation test was conducted to confirm that the response was due to activation of sensory fibers (i.e. spinal reflex). The results showed that the anode position was critical for inducing the spinal reflex in the VM (Exp. 1). The ratio of second to first responses was smaller when the anode was placed over the ABD or cASIS than when the anode was placed over the iASIS (Exp. 2). In addition, the onset latency of the first response was longer when the anode was placed over the ABD or cASIS than when the anode was placed over the iASIS (Exp. 2). These results showed that the anode should be placed over the ABD or cASIS to effectively elicit spinal reflexes in lower-limb muscles.

DOI： 10.1109/EMBC.2017.8037024

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記述言語：英語   掲載種別：研究論文（学術雑誌）

© 2017 Informa UK Limited, trading as Taylor & Francis Group. This study evaluated baseball pitching accuracy using a variety of parameters to quantify pitching errors and analysed the validity of the accuracy measurements by comparing the outcomes of two small groups of pitchers. Several professional (n = 5) and high school (n = 8) pitchers threw 30 pitches each, including 20 fastballs and 10 breaking balls. To assess pitching accuracy, pitch locations relative to the catcher’s mitt (as the target) were evaluated with various parameters, including major/minor radius, an area of 95% confidence ellipse, absolute error, constant error and pitch location trajectory. Compared to the high school pitchers, the professional pitchers exhibited shorter major and minor radii in their 20 fastball pitches (p  <  0.05), more accurate control in the lateral direction (p  <  0.05), and shorter pitch location trajectories (p  <  0.05). The evaluation methods presented in this study can objectively assess pitching accuracy and may thus provide useful coaching feedback with visual information.

DOI： 10.1080/14763141.2017.1332236

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記述言語：英語   掲載種別：研究論文（学術雑誌）

© 2017 Masugi et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. While previous studies have shown that muscle stretching suppresses monosynaptic spinal reflex excitability in stretched muscles, its effects on non-stretched muscles is still largely unknown. The purpose of this study was to examine the effects of muscle stretching on monosynaptic spinal reflex in non-stretched muscles. Ten healthy male subjects participated in this study. Muscle stretching of the right triceps surae muscle was performed using a motor torque device for 1 minute. Three different dorsiflexion torques (at approximately 5, 10, and 15 Nm) were applied during muscle stretching. Spinal reflexes evoked by transcutaneous spinal cord stimulation were recorded in both the lower-limb muscles before, during, and at 0 and 5 min following muscle stretching. The amplitudes of the spinal reflexes in both the stretched and non-stretched muscles in the right (ipsilateral) leg were smaller during stretching compared to before, and at 0 and 5 min after stretching. Furthermore, the degree of reduction in the amplitude of the spinal reflexes in the right (ipsilateral) leg muscles increased significantly as the dorsiflexion torque (i.e., stretching of the right triceps surae muscles) increased. In contrast, reduction in the amplitude of the spinal reflexes with increasing dorsiflexion torque was not seen in the left (contralateral) leg muscles. Our results clearly indicate that muscle stretching has inhibitory effects on monosynaptic spinal reflexes, not only in stretched muscles, but also in non-stretched muscles of the ipsilateral leg.

DOI： 10.1371/journal.pone.0180275

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記述言語：日本語   掲載種別：研究論文（その他学術会議資料等）

<p>【はじめに，目的】</p><p></p><p>運動野から脊髄運動ニューロンに下降する皮質脊髄路（CST）は，ヒト二足立位の制御に関わる神経経路の一つである。これまでの研究で，足関節底背屈筋CSTの興奮性は，不安定な環境に暴露された際に上昇することが報告されており，フィードバック情報に応じて，姿勢要求に見合うように変調していると考えられる。</p><p></p><p>一方，姿勢外乱により不安定な環境が予測される時，CSTがどのように調節されるかは明らかではない。CSTが予測情報を利用して興奮性を調節しているのであれば，予測される外乱に応じてあらかじめ応答を設定していると考えられる。</p><p></p><p>本研究の目的は，足関節底背屈筋CSTの興奮性が，外乱の方位・強度の予測情報に応じて，先行して変調するかを明らかにすることであった。</p><p></p><p></p><p>【方法】</p><p></p><p>対象は健常な成人男性12名（27.3±5.6歳）であった。経頭蓋磁気刺激装置（TMS）を用い，姿勢外乱が印加される50ms前の運動誘発電位（MEP）を計測した。参加者には，プラットフォーム上（Motion-Base MB-150）で立位姿勢を保持するように指示した。外乱は，足底支持面の前後方向への水平移動を負荷した。今回の研究では，強度および方位を変えた3種類の外乱を用いた。実験条件は，それぞれの外乱が単独で加わる①前方・弱（3.5cm，10cm/s），②前方・強（7.0cm，25cm/s），③後方（7.0cm，25cm/s）と，3種の外乱が順不同に加わる④ランダム，さらに，外乱を負荷しない⑤外乱なし，を設けた。筋活動応答を，前脛骨筋（TA），ヒラメ筋（SOL）から導出した。統計処理は，各条件で得られたMEPの差を一元配置分散分析により比較した。統計的有意水準は5%とした。</p><p></p><p></p><p>【結果】</p><p></p><p>前脛骨筋MEPは，外乱なし，後方，前方・弱，ランダム，前方・強条件の順に増大していた。分散分析の結果，前脛骨筋MEPには条件間の主効果が認められた（F_2.2 _24.7=14.9，p＜0.001）。事後解析において，後方以外の他の条件で外乱なし条件よりも有意に増大していた。またこれは外乱の強度・方位の影響を受け，前方・強条件で前方・弱および後方条件よりも有意な増大を示した。一方，ヒラメ筋MEPについては，条件間の主効果が認められなかった（F_{4 44}=2.2，p=0.09）。</p><p></p><p></p><p>【結論】</p><p></p><p>本研究の結果から，外乱の予測によってTAのCSTの興奮性が事前に変調することが明らかとなった。また，この変調は，外乱の強度および方位に応じてスケーリングされることが分かった。このことは，無意識・無自覚に調節される立位の制御においても，随意運動と同じように，予測情報を利用して中枢神経系の応答が事前設定されていることを示唆している。また，TAとSOLの間で予測の効果が異なっており，このことは立位姿勢における両筋の役割の違いや，皮質脊髄路との連絡の強さの違いを反映していると考えられる。</p>

DOI： 10.14900/cjpt.2016.0476

CiNii Article

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記述言語：英語   掲載種別：研究論文（学術雑誌）

© 2016 Fujio et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.The purpose of the present study was to investigate how stretch reflex (SR) responses in the ankle extensor (soleus: SOL) and flexor (tibialis anterior: TA) muscles would be modulated with temporal and/or spatial predictions of external perturbations and whether their effects are specific to the standing posture. SR responses in the SOL/TA were elicited by imposing quick ankle toes-up/toes-down rotations while standing upright and in the supine position. We designed four experimental conditions based on pre-information about perturbations: no information (No Cue), the timing of the perturbation onset (TIM), the direction of the perturbation (DIR), and both the timing and direction of the perturbation (TIM/DIR). Each condition was separated and its order was counterbalanced. In the SR of TA evoked by toes-down rotation, integrated electromyography activities of the late component were significantly reduced in the TIM and TIM/DIR conditions as compared with those in the No Cue and DIR conditions. The occurrence rate of late SR components that reflects how often the reflex response was observed was also lower in the TIM and TIM/DIR conditions as compared with that in the No Cue and DIR conditions. On the other hand, no significant changes were seen among the four conditions in the early SR component in the TA and both SR components in the SOL. The same results in the occurrence rate were found in the supine position. The present results suggest (1) only temporal predictions have a remarkable effect on the SR excitability of the TA, and (2) this effect is independent of posture.

DOI： 10.1371/journal.pone.0158721

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

This study examined the effect of different joint angle on the sensitivity of short- and long-latency stretch reflex responses in ankle flexor and ankle extensor muscles. The B-mode echo image of each muscle in individual subject was used to estimate the change of muscle fiber length. The stretch reflex sensitivity of short- and long-latency components was evaluated by the multiple linear regression analysis with two independent variables, muscle fiber stretching velocity (MSV) and background EMG activity (BGA). The reflex sensitivity of short-latency component (M1) in soleus (SOL) muscle is dependent on the ankle joint angle and initial muscle fiber length. However, the reflex sensitivity of short- and long-latency components (M1 and M2) in gastrocnemius (GAS) muscle is not always dependent on initial muscle fiber length. Moreover, the reflex sensitivity of Ml in SOL is dependent on knee joint angle. On the other hand, in all conditions the reflex sensitivity of ankle flexor muscle: tibialis anterior (TA) was significantly lower than that of ankle extensor muscles. These results indicated that the joint angle dependency of the standardized sensitivity of short- and long-latency stretch reflex responses was different in different muscles.

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記述言語：英語   掲載種別：研究論文（学術雑誌）

Excitability of both stretch reflex (SR) and motor evoked potential (MEP) elicited in the tibialis anterior (TA) muscle by transcranial magnetic stimulation were tested in standing humans. The results demonstrated significantly greater values for both SR and MEP in the TA while standing than while in the supine posture, although background electromyographic activity was silent in the two conditions. Taken together with previous reports that both pathways are facilitated in the TA at the early stance phase of human walking, our findings suggest that a common neural mechanism underlies both observations, one that might be functionally relevant for securing ankle joint stabilization during upright standing. © 2002 Elsevier Science Ireland Ltd. All rights reserved.

DOI： 10.1016/S0304-3940(02)01353-8

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