Kohei Watanabe

Chukyo University, Koromo, Aichi, Japan

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Publications (34)88.66 Total impact

  • Kohei Watanabe · Motoki Kouzaki · Toshio Moritani
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    ABSTRACT: Recently, we demonstrated region-specific electromyography (EMG) responses along the rectus femoris (RF) muscle during gait in healthy young men (Watanabe et al., 2014b). For the RF muscle, regional EMG response should be tested to characterize neuromuscular control and/or to assess its dysfunction and/or pathology during gait. We aimed to identify spatial distribution of EMG pattern within the RF muscle in elderly during gait. Seven young men (age: 20.4±1.0 years) and 8 elderly men (age: 73.8±5.9 years) walked on treadmill with three different speed: slow (preferred -1km/h), preferred, and fast (preferred +1km/h). The spatial distribution of surface EMG was tested by central locus activation (CLA), which is calculated from 18 surface electrodes along the longitudinal line of the muscle. CLA were not different between the groups for slow and preferred gait speed (p>0.05) during a gait cycle. In fast gait speed, CLA at 80% of a gait cycle (swing phase) for the elderly were significantly located at more distal site than the young group (p<0.05) (13.0±2.1cm and 10.2±2.2cm from most proximal electrodes for the elderly and young). This difference in CLA reflected a significantly lower EMG activity at the proximal regions in the elderly group (p<0.05). These results suggest the elderly manifest characteristic regional EMG responses within the RF muscle for leg swing movement of fast speed gait.
    No preview · Article · Nov 2015 · Journal of Biomechanics
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    Aya Tomita · Ryosuke Ando · Akira Saito · Kohei Watanabe · Hiroshi Akima
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    ABSTRACT: We previously developed a novel technique to record surface electromyography (EMG) of the vastus intermedius (VI) in men. The purpose of the present study was to assess whether this technique can be applied to women in the same way. We measured the subcutaneous fat thickness at the site of electrode placement on VI using ultrasonography. Nine men and ten women performed isometric knee extensions at 25%, 50%, 75%, and 100% of the maximal voluntary contraction. During the tasks, surface EMG signals were recorded from the superficial region of VI with interelectrode distances (IEDs) of 10 mm (IED-10) and 20 mm (IED-20). The subcutaneous fat thickness in women was significantly greater than in men (women: 8.7 ± 2.1 mm; men: 5.6 ± 1.6 mm, p < 0.01). However, the amplitude and frequency of the EMG signal of VI at the different force levels were not affected by IEDs in either sex. These results suggest that surface EMG recording of VI with both IED-10 and IED-20 would be applicable to relatively lean women with a similar sensitivity to that in men.
    Full-text · Article · Oct 2015 · Journal of Electromyography and Kinesiology
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    ABSTRACT: Introduction This study examined changes in fascicle length and pennation of vastus intermedius (VI) and vastus lateralis (VL) from rest to isometric contraction.Methods Fourteen healthy men performed submaximal (30% and 50% of maximum voluntary contraction; MVC) isometric knee extensions at 60° and 110° knee flexion (0 = full extension). Panoramic images of VL and VI were obtained at rest and during contractions to measure fascicle length and pennation using extended field-of-view ultrasonography, after confirmation that the technique could be used reliably during sustained submaximal isometric contractions.Results The relative change in fascicle length from rest to 50% MVC was greater in VI than VL at 110° (P<0.05). Pennation increased during contraction at 60° for VL (P<0.05), but not for VI.Conclusion Muscle-dependent fascicle behaviors were observed during contraction. These findings may provide a mechanistic underpinning for differences in sarcomere length changes, relative force contribution, and blood flow during contraction. This article is protected by copyright. All rights reserved.
    No preview · Article · Sep 2015 · Muscle & Nerve
  • Kohei Watanabe · Motoki Kouzaki · Toshio Moritani
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    ABSTRACT: We investigated the effect of resistance training and detraining on the spatial distribution pattern of surface electromyography (SEMG) of the biceps brachii. Ten male subjects completed 6 weeks of resistance training of one arm and 8 weeks of detraining. During training and detraining periods, spatial distribution patterns of SEMG were measured and quantified with 64 two-dimensional electrodes. MVC, muscle thickness, and SEMG amplitude of the trained arm were significantly greater than those of the untrained arm after the 6 weeks of resistance training (p < 0.05), but these differences were no longer observed after 2 months of detraining. On the other hand, no significant differences in the spatial distribution pattern of SEMG were observed between the arms. Spatial distribution pattern of SEMG was not changed during resistance training and detraining periods. This suggests that detectable adaptations in the motor unit recruitment pattern do not occur during regular resistance training.
    No preview · Article · Aug 2015 · Arbeitsphysiologie
  • Kohei Watanabe · Motoki Kouzaki · Toshio Moritani
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    ABSTRACT: In some muscles, non-uniform surface electromyography (EMG) responses have been demonstrated within a muscle, meaning that the electrode location could be critical in the results of surface EMG. The present study investigated possible region-specific EMG responses within the human biceps femoris (BF) muscle. Surface EMG was recorded from various regions along the longitudinal axis of the BF muscle with 20 electrodes. Ten healthy men performed maximal isometric contractions of hip extension and knee flexion, which involve the BF muscle. The ratio of the EMG amplitude between hip extension and knee flexion tasks (HE/KF) was calculated and compared among the regions. There were no significant differences in HE/KF among the regions along the BF muscle (p > 0.05). This suggests that the entire superficial region of the BF muscle is equally regulated in the two different tasks. We suggest that the electrode location is not critical on estimating the activation properties and/or functional role of the superficial region, which corresponds with approximately 50% of the muscle length, of the BF muscle using surface EMG during maximal contraction.
    No preview · Article · Aug 2015 · Journal of applied biomechanics
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    ABSTRACT: To test the hypothesis that motor units with different axonal excitability levels are localized in specific portions of the rectus femoris (RF) muscle using transcutaneous electrical nerve stimulation. M-waves were elicited by transcutaneous electrical nerve stimulation and detected from 24 sites along longitudinal line of the muscle. The stimulation was applied to the femoral nerve, and the current level was gradually increased. The central locus activation, which is calculated from the spatial distribution of M-waves, appeared at the proximal regions at low stimulation level and then moved to the middle site of the muscle with an increase in the stimulation level. The results reveal that groups of motor units activated at different stimulation levels are located in different positions in the proximal-distal muscle direction. Our results suggest that motor unit properties in proximal and other regions are not uniform within the RF muscle.
    Full-text · Article · Jun 2015 · Arbeitsphysiologie
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    Akira Saito · Kohei Watanabe · Hiroshi Akima
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    ABSTRACT: Although many studies have been focused on muscle synergies in the lower limbs, synergies of the thigh muscles during cycling have not been investigated in detail. We examined synergies of the thigh muscles including the vastus intermedius (VI) and adductor magnus (AM) while cycling. Eight healthy men pedaled at 20%, 40%, 60%, 80% and 100% of maximal aerobic power output at a constant cadence of 60rpm. Surface electromyography (EMG) recorded signals from the deep VI and the three superficial quadriceps femoris (QF) muscles, the two hamstrings and the AM. The root mean square of the EMG signal was averaged every 2° of crank rotation and normalized by the peak value for each muscle. We used factor analysis to assess normalized EMG recordings while cycling and to identify thigh muscle synergies. The VI, the superficial QF muscles and the AM dominated the first muscle synergy at all power output levels. The AM also formed a second synergy with the two hamstrings at all power output levels. These results suggest that the VI coordinates with the other QF and AM muscles, and that the AM coordinates with the QF and hamstring muscles while cycling. Copyright © 2014 Elsevier B.V. All rights reserved.
    Full-text · Article · Dec 2014 · Human Movement Science
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    Kohei Watanabe · Motoki Kouzaki · Toshio Moritani
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    ABSTRACT: Introduction: We investigated the effect of workload and the use of pedal straps on the spatial distribution of neuromuscular activation within the rectus femoris (RF) muscle during pedaling movements. Methods: Eleven healthy men performed submaximal pedaling exercises on an electrically braked ergometer at different workloads and with or without pedal straps. During these tasks, surface electromyograms (SEMGs) were recorded from the RF using 36 electrode pairs, and central locus activation (CLA) was calculated along the longitudinal line of the muscle. Results: CLA moved markedly, indicating changes in spatial distribution of SEMG within the muscle, during a crank cycle under all conditions (P < 0.05). There were significant differences in CLA among different workloads and between those with and without pedal straps (P < 0.05). Conclusion: These results suggest that neuromuscular activation within the RF is regulated regionally by changes in workload and the use of pedal straps during pedaling. Muscle Nerve 52:404-411, 2015.
    Full-text · Article · Dec 2014 · Muscle & Nerve
  • Kohei Watanabe · Motoki Kouzaki · Toshio Moritani
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    ABSTRACT: Introduction: Our recent studies have demonstrated region-specific neural activation within the rectus femoris (RF) muscle. However, these studies involved a fixed joint angle or posture. In this study we investigated the effect of hip and knee joint angles on neural activation within RF using multichannel surface electromyography (SEMG). Methods: Eleven healthy men performed isometric maximal voluntary contraction (MVC) during knee extension and hip flexion at different hip or joint angles. During the contractions, SEMG of the RF was recorded using 46 electrode pairs covering most of the superficial area of the muscle. Results: During knee extension MVC, an increase in the hip joint angle was associated with a significant increase in SEMG amplitude in the proximal region and a decrease in the distal region (P < 0.05). Higher SEMG amplitude during hip flexion MVC compared with knee extension MVC was observed in proximal regions with the flexed knee and hip joint angles. This task-dependent spatial distribution of SEMG amplitude was seen at the extended hip, but not at the extended knee. Conclusions: SEMG amplitudes within the RF muscle are not modified uniformly with changes in joint position.
    No preview · Article · Nov 2014 · Muscle & Nerve
  • Kohei Watanabe · Motoki Kouzaki · Toshio Moritani
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    ABSTRACT: The spatial distribution pattern of neuromuscular activation within the human rectus femoris (RF) muscle was investigated during gait by multi-channel surface electromyography (surface EMG). Eleven healthy men walked on a treadmill with three gait speeds (4, 5, and 6km/h) and gradients (0°, 12.5°, and 25°). The spatial distribution of surface EMG was tested by central locus activation (CLA), which is calculated from 2-D multi-channel surface EMG with 46 surface electrodes. For all conditions, CLA was around the middle regions during the swing-to-stance transition and moved in a proximal direction during the stance phase and stance-to-swing transition (p<0.05). CLA during the stance-to-swing transition and early swing phase significantly moved to proximal site with increasing gait speed (p<0.05). During the early stance and swing phases, with increasing grade, CLA significantly moved distally (p<0.05). These results suggest that the RF muscle is regionally activated during a gait cycle and is non-uniformly regulated longitudinally.
    No preview · Article · Sep 2014 · Journal of Biomechanics
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    ABSTRACT: Objective The aim of this study was to examine whether or not there is a gender difference in metabolic responses to surface electrical muscle stimulation (sEMS) in type 2 diabetes (T2DM). Methods Ten men and eight women with T2DM participated in two sessions; in both sessions the subjects were investigated after a breakfast and that in one occasion they underwent 30-min sEMS while in the other they were followed while resting. Blood and gas exchange data were compared between genders as to the extent of blood glucose and non-esterified fatty acids responses to sEMS. Results The time course change of blood glucose concentration after sEMS did not statistically differ between genders while sEMS could attenuate postprandial blood glucose level regardless of gender (p < 0.05). Women had a lower respiratory quotient and lactate concentration during sEMS when compared with men (p < 0.05). Conclusions This study indicated that sEMS might have resulted in lower anaerobic glycolysis in women as compared to men with T2DM. sEMS is expected to be a new exercise method in T2DM. Determining the possible gender differences and precise mechanisms might further shed some light for the efficacy of sEMS use for clinical practice.
    Full-text · Article · Jul 2014 · Journal of Electromyography and Kinesiology
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    Kohei Watanabe · Yoshiki Taniguchi · Toshio Moritani
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    ABSTRACT: Purpose: We aimed to test the effect of additional electrical muscle stimulation (EMS) during moderate-intensity voluntary pedaling exercise on metabolic and cardiovascular responses. Methods: Eleven healthy male subjects performed moderate-intensity pedaling exercise at a constant workload (80% of ventilatory threshold) for 20 min while EMS was applied to thigh muscles from 5 to 10 min and from 15 to 20 min during the exercise. Results: A significantly higher oxygen uptake (VO₂), heart rate, and respiratory gas exchange ratio were observed during the exercise periods with EMS despite the constant workload. These changes were accompanied by an elevated blood lactate concentration, suggesting the existence of additional fast-twitch motor unit (MU) recruitment during the exercise with EMS. Conclusion: Our data suggest that the use of intermittent EMS during a constant load exercise mimics the high-intensity interval training, possibly due to additional fast-twitch MU recruitment and co-contractions of the quadriceps and hamstrings muscles, leading to higher anaerobic metabolism and a lower mechanical efficiency.
    Full-text · Article · May 2014 · Arbeitsphysiologie
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    ABSTRACT: Introduction: We investigated the motor unit (MU) firing pattern in type 2 diabetes mellitus (T2DM) patients by means of multichannel surface electromyography (SEMG). Methods: Eight T2DM patients and 8 age-matched, healthy men performed a ramp-up contraction to 20% of maximal voluntary contraction (MVC). They also performed a sustained contraction at 10% of MVC during isometric knee extension. Multichannel SEMG signals recorded from the vastus lateralis muscle were decomposed with the convolution kernel compensation technique to extract individual MU firing patterns. Results: During the ramp contraction, the extent of MU firing modulation was significantly attenuated in T2DM. Variability of MU firing rate was significantly higher in T2DM at later periods during the sustained contraction. Conclusions: Our findings suggest that T2DM patients manifest characteristic MU activity patterns due possibly to some degree of neuromuscular impairment affecting the integrity of MU firing modulation.
    Full-text · Article · Nov 2013 · Muscle & Nerve
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    Kohei Watanabe · Motoki Kouzaki · Toshio Moritani
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    ABSTRACT: Introduction: Anatomical properties between proximal and other regions within the human rectus femoris (RF) muscle are nonuniform. We aimed to clarify the possible region-specific myoelectric manifestations of fatigue within the RF muscle by using an advanced surface electromyography (SEMG) technique. Methods: Nine healthy men performed sustained contractions at 50% of maximal voluntary contraction until exhaustion during isometric knee extension and hip flexion. During these contractions, multi-channel SEMG was recorded from the RF by using 46 electrode pairs which cover most of the superficial area of the muscle. Results: Fatigue-induced SEMG, i.e., an increase in root mean square and a decrease in median frequency, was not uniform within the muscle during both tasks and was greater in proximal regions. Conclusions: Our findings suggest that myoelectric manifestations of fatigue within the human RF muscle are localized, and proximal regions are more fatigable than other regions within this muscle.
    Full-text · Article · Aug 2013 · Muscle & Nerve
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    Akira Saito · Kohei Watanabe · Hiroshi Akima
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    ABSTRACT: Although the possibility that the vastus intermedius (VI) muscle contributes to flexion of the knee joint has been suggested previously, the detail of its functional role in knee flexion is not well understood. The purpose of this study was to examine the antagonist coactivation of VI during isometric knee flexion. Thirteen men performed 25-100% of maximal voluntary contraction (MVC) at 90°, 120°, and 150° knee joint angles. Surface electromyography (EMG) of the four individual muscles in the quadriceps femoris (QF) was recorded and normalized by the EMG signals during isometric knee extension at MVC. Cross-talk on VI EMG signal was assessed based on the median frequency response to selective cooling of hamstring muscles. Normalized EMG of the VI was significantly higher than that of the other synergistic QF muscles at each knee joint angle (all P<0.05) with minimum cross-talk from the hamstrings to VI. There were significant correlations between the EMG signal of the hamstrings and VI (r=0.55-0.85, P<0.001). These results suggest that VI acts as a primary antagonistic muscle of QF during knee flexion, and that VI is presumably a main contributor to knee joint stabilization.
    Full-text · Article · Mar 2013 · Journal of electromyography and kinesiology: official journal of the International Society of Electrophysiological Kinesiology
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    Hiroshi Akima · Akira Saito · Kohei Watanabe · Motoki Kouzaki
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    ABSTRACT: We quantified the alternate muscle activity among four synergists of the quadriceps femoris (QF), including the vastus intermedius (VI), during low-level sustained contraction. Surface electromyograms (EMGs) were recorded from the VI, vastus lateralis (VL), vastus medialis (VM), and rectus femoris (RF) in 11 healthy men during isometric knee extension at 2.5% maximum voluntary contraction for 60 min to determine alternate muscle activity among the four synergists of the QF. Alternate activity was primarily found between the RF and VI, VL, or VM, and rarely found among the vasti muscles. Multiple muscle comparison revealed the duration of alternate activity in the RF/VI+VL+VM combination remained high throughout the experiment, although the frequency of that combination did not. These results suggested that there is a fixed muscle combination, i.e., RF and the 3 vasti muscles, to perform low-intensity sustained contraction in the human QF.
    Full-text · Article · Jul 2012 · Muscle & Nerve
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    ABSTRACT: The purpose of the present study is to investigate spatial surface electromyography (SEMG) potential distribution pattern in type 2 diabetes mellitus (T2DM) patients. Nine T2DM patients and nine age-matched healthy men (CON) performed a sustained isometric knee extension at 10% of maximal voluntary contraction for 120s. Multi-channel SEMG was recorded from the vastus lateralis muscle by means of 64 electrodes. To characterize spatial SEMG potential distribution pattern, modified entropy and correlation coefficients between same electrode locations were calculated at 15, 60 and 120s for the root mean square values. At 60 and 120s, modified entropy in T2DM was significantly lower than those in CON (p<0.05). Correlation coefficients for T2DM were significantly higher than those for CON at 60 and 120s (p<0.05). From these results, we suggested that T2DM patients continue to recruit limited and same motor units during the sustained contraction at low force level.
    Full-text · Article · Apr 2012 · Diabetes research and clinical practice
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    ABSTRACT: The aim of the present study was to compare spatial electromyographic (EMG) potential distribution during force production between elderly and young individuals using multi-channel surface EMG (SEMG). Thirteen elderly (72-79years) and 13 young (21-27years) healthy male volunteers performed ramp submaximal contraction during isometric knee extension from 0% to 65% of maximal voluntary contraction. During contraction, multi-channel EMG was recorded from the vastus lateralis muscle. To evaluate alteration in heterogeneity and pattern in spatial EMG potential distribution, coefficient of variation (CoV), modified entropy and correlation coefficients with initial torque level were calculated from multi-channel SEMG at 5% force increment. Increase in CoV and decrease in modified entropy of RMS with increase of exerted torque were significantly smaller in elderly group (p<0.05) and correlation coefficients with initial torque level were significantly higher in elderly group than in young group at moderate torque levels (p<0.05). These data suggest that the increase of heterogeneity and the change in the activation pattern are smaller in elderly individuals than in young individuals. We speculated that multi-channel SEMG pattern in elderly individual reflects neuromuscular activation strategy regulated predominantly by clustering of similar type of muscle fibers in aged muscle.
    Full-text · Article · Feb 2012 · Journal of electromyography and kinesiology: official journal of the International Society of Electrophysiological Kinesiology
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    Kohei Watanabe · Motoki Kouzaki · Toshio Moritani
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    ABSTRACT: Compartmentalization of skeletal muscle by multiple motor nerve branches, named as neuromuscular compartment (NMC), has been demonstrated in animals as well as humans. While different functional roles among individual NMCs were reported in the animal studies, no studies have clarified the region-specific functional role within a muscle related with NMCs arrangement in human skeletal muscle. It was reported that the rectus femoris (RF) muscle is innervated by two nerve branches attached at proximal and distal parts of the muscle. The purpose of the present study is to clarify the possible region-specific functional role in the human RF muscle. Multi-channel surface electromyography (SEMG) were recorded from the RF muscle by using 128 electrodes during two different submaximal isometric contractions that the muscle contributes, i.e. isometric knee extension and hip flexion, at 20%, 40%, 60% and 80% of maximal voluntary contraction (MVC). Results indicated that the central locus activation for the amplitude map of SEMG during hip flexion located at more proximal region compared with that during knee extension. Significant higher normalized root mean square (RMS) values were observed at the proximal region during the hip flexion in comparison to those at middle and distal regions at 60% and 80% of MVC (p<0.05). In while, significant higher normalized RMS values were demonstrated at the distal region comparing with that at the proximal region at 80% of MVC (p<0.05). The results of the present study suggest possible region-specific functional role in the human RF muscle.
    Full-text · Article · Dec 2011 · Journal of electromyography and kinesiology: official journal of the International Society of Electrophysiological Kinesiology
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    Akira Saito · Kohei Watanabe · Hiroshi Akima

    Full-text · Article · May 2011 · Medicine & Science in Sports & Exercise

Publication Stats

223 Citations
88.66 Total Impact Points

Institutions

  • 2013-2015
    • Chukyo University
      Koromo, Aichi, Japan
  • 2012
    • Kyoto University
      • Graduate School of Human and Environmental Studies
      Kioto, Kyōto, Japan
  • 2011-2012
    • Japan Society for the Promotion of Science
      Edo, Tōkyō, Japan
  • 2008-2010
    • Nagoya University
      • Graduate School of Education and Human Development
      Nagoya, Aichi, Japan