Kohei Watanabe

Chukyo University, Koromo, Aichi, Japan

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Publications (23)36.72 Total impact

  • 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.
    Journal of biomechanics. 09/2014;
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    ABSTRACT: We aimed to test the effect of additional electrical muscle stimulation (EMS) during moderate-intensity voluntary pedaling exercise on metabolic and cardiovascular responses.
    Arbeitsphysiologie 05/2014; · 2.66 Impact Factor
  • Kohei Watanabe, Motoki Kouzaki, Toshio Moritani
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    ABSTRACT: Introduction Our recent studies demonstrated region-specific neural activation within the rectus femoris (RF) muscle. However, these studies involved a fixed joint angle or posture. Here, we investigated the effect of hip and knee joint angles on neural activation within RF using multi-channel surface electromyography (SEMG). Methods Eleven healthy men performed isometric maximal voluntary contractions (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 the 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. Conclusion SEMG amplitudes within the RF muscle are not modified uniformly with changes in joint position. © 2014 Wiley Periodicals, Inc.
    Muscle & Nerve 03/2014; · 2.31 Impact Factor
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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.
    Journal of Electromyography and Kinesiology. 01/2014;
  • 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.
    Journal of electromyography and kinesiology: official journal of the International Society of Electrophysiological Kinesiology 03/2013; · 2.00 Impact Factor
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    ABSTRACT: Introduction We investigated the motor unit (MU) firing pattern in type 2 diabetes mellitus (T2DM) patients by means of multi-channel surface electromyography (SEMG). Methods Eight T2DM patients and 8 age-matched healthy men performed a ramp-up contraction up to 20% of maximal voluntary contraction (MVC). They also performed a sustained contraction at 10% of MVC during isometric knee extension. Multi-channel 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. Discussion 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. © 2013 Wiley Periodicals, Inc.
    Muscle & Nerve 02/2013; · 2.31 Impact Factor
  • 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. Muscle Nerve, 2013.
    Muscle & Nerve 11/2012; · 2.31 Impact Factor
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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.
    Muscle & Nerve 07/2012; 46(1):86-95. · 2.31 Impact Factor
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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.
    Diabetes research and clinical practice 04/2012; 97(3):468-73. · 2.74 Impact Factor
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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.
    Journal of electromyography and kinesiology: official journal of the International Society of Electrophysiological Kinesiology 02/2012; 22(1):74-9. · 2.00 Impact Factor
  • 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.
    Journal of electromyography and kinesiology: official journal of the International Society of Electrophysiological Kinesiology 12/2011; 22(2):251-8. · 2.00 Impact Factor
  • Kohei Watanabe, Hiroshi Akima
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    ABSTRACT: Recently, a new recording technique for surface electromyography (EMG) of the deeper muscle component of the quadriceps femoris muscle group, i.e., vastus intermedius (VI) muscle, from the distal portion of the VI muscle has been developed; however, the effect of electrode location on EMG signal of the VI muscle remains unclear. The aim of this study is to compare neuromuscular activation detected at the middle and distal portions of the VI muscle, in order to clarify whether the surface EMG of the VI muscle can be used to assess the neuromuscular activation of the entire muscle. Six healthy men participated in this study. During incremental ramp contraction of isometric knee extension (~30% of maximal voluntary contraction), needle EMG was recorded from the middle and distal regions of the VI muscle and surface EMG was performed at the distal region of the VI muscle. Excellent correlation was observed between needle EMG at the middle and distal regions (r=0.897-0.984, p<0.001). No significant difference was observed between correlation coefficient of surface EMG detected at the distal versus needle EMG detected at the middle and that of surface EMG detected at distal versus needle EMG detected at distal (p<0.05). These results suggest that surface EMG at the distal portion of the VI muscle, which is the only region available for surface EMG, can be used to evaluate global neuromuscular activation of the VI muscle during isometric contraction at a low force level.
    Journal of neuroscience methods 04/2011; 198(2):332-5. · 2.30 Impact Factor
  • Kohei Watanabe, Hiroshi Akima
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    ABSTRACT: The purpose of this study was to investigate neuromuscular activation of the vastus intermedius (VI) muscle during fatiguing contraction. Seven healthy men performed sustained isometric knee extension exercise at 50% of maximal voluntary contraction until exhaustion. During the fatiguing task, surface electromyograms (EMGs) were recorded from four muscle components of the quadriceps femoris muscle group: VI; vastus lateralis (VL); vastus medialis (VM); and rectus femoris (RF) muscles. For the VI muscle, our recently developed technique was used. Root mean square (RMS) and median frequency (MF) of the surface EMG signal were calculated and these variables were then normalized by the value at the beginning of the task. Normalized RMS of the VI muscle resembled those of the other three muscles at all given times. At 95% of exhaustion time, normalized MF of the VI muscle was significantly higher than that of the VL muscle (p<0.05). These results suggested that neuromuscular activation is not consistent between the VI and VL muscles at the exhaustion for isometric submaximal contraction and this could reflect the dissimilar intramuscular metabolism between these muscles.
    Journal of electromyography and kinesiology: official journal of the International Society of Electrophysiological Kinesiology 08/2010; 20(4):661-6. · 2.00 Impact Factor
  • Medicine and Science in Sports and Exercise - MED SCI SPORT EXERCISE. 01/2010; 42.
  • Kohei Watanabe, Hiroshi Akima
    Medicine &amp Science in Sports &amp Exercise 01/2010; 42:579-580. · 4.48 Impact Factor
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    ABSTRACT: It is reported that the rate of locomotor muscle fatigue development during intermittent isometric exercise in hypoxia is accelerated compared with normoxia. In contrast, when sustained isometric contractions are used, some studies do not show any effect of hypoxia on fatigue development. Increased intramuscular pressure during sustained isometric exercise causes substantial and sustained ischemia, even in normoxia. Therefore, we hypothesized that the difference in muscle deoxygenation between normoxia and hypoxia would be small during sustained exercise compared with intermittent exercise and that this may contribute to the inconsistent findings. Subjects performed sustained and intermittent isometric, unilateral, and submaximal knee-extension exercises (60% maximal voluntary contraction to exhaustion) while breathing normoxic (inspired O2 fraction = 0.21) or hypoxic gas mixtures (inspired O2 fraction = 0.10-0.12). Muscle oxygenation (deoxyhemoglobin/myoglobin and tissue oxygenation index) using near-infrared spectroscopy and surface EMG were measured from the left vastus lateralis. During intermittent isometric exercise in hypoxia, increases in deoxyhemoglobin/myoglobin and reductions of tissue oxygenation index were larger (P < 0.05) than those in normoxia. The rate of rise in integrated EMG during intermittent exercise was accelerated (P < 0.05) in hypoxia. In contrast, there were no significant differences in changes in near-infrared spectroscopy variables and integrated EMG during sustained isometric exercise between normoxia and hypoxia. These results suggest that muscle deoxygenation is exaggerated during intermittent isometric exercise in hypoxia compared with normoxia, whereas during sustained isometric exercise, the extent of muscle deoxygenation is the same between normoxia and hypoxia. The different extent of muscle deoxygenation during sustained and intermittent isometric exercise in normoxia and hypoxia could affect muscle fatigability, which results from the varied rate of accumulation of metabolites.
    Medicine and science in sports and exercise 12/2009; 42(7):1269-78. · 4.48 Impact Factor
  • Kohei Watanabe, Hiroshi Akima
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    ABSTRACT: The purposes of this study were to attempt to record surface electromyography (EMG) from the superficial region of vastus intermedius (VI) and to investigate the influence of adjacent muscle activity on surface EMG of VI. First, serial axial magnetic resonance imaging of the thigh was performed for 45 healthy young men to determine morphological characteristics of the VI. Second, surface EMG activity of the VI and other quadriceps femoris (QF) muscle group components were recorded in maximum voluntary contraction during isometric knee extension from 11 healthy young men. To test cross-talk of EMG signals between VI and the nearest adjacent muscle, vastus lateralis (VL), we applied cooling for 20-min on VL to selectively alter activity. Cooling the skin above a muscle is known to decrease median frequency (MF) of EMG signal of the muscle. All subjects displayed a superficial region in VI sufficiently large (14 cm(2)) to record surface EMG. Surface EMG of VI could be detected in the same scale as other QF muscle group components. Cooling induced a significant MF decrease only in VL (from 92.5 to 44.2 Hz, p<0.001), but no significant change was observed in VI (from 63.8 to 61.7 Hz). From this result, we concluded the muscle activity of VL is negligible on surface EMG detected from VI during isometric contraction.
    Journal of electromyography and kinesiology: official journal of the International Society of Electrophysiological Kinesiology 08/2009; 19(4):e280-9. · 2.00 Impact Factor
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    ABSTRACT: The purpose of this study was to investigate activity of hip adductor muscles over time and during a representative crank cycle in fatiguing pedaling. Sixteen healthy men performed incremental pedaling exercise until exhaustion. During the exercise, surface electromyogram (EMG) was detected from adductor magnus (AM), adductor longus (AL), and selected thigh muscles. Temporal changes to normalized EMG in AM muscle resembled those in vastus lateralis (VL) muscle, whereas those in AL muscle showed later onset of increase from baseline compared with AM and VL muscles. During a representative crank cycle, the same level of normalized EMG was found between propulsive and pulling phases for AM muscle, whereas muscle activation of AL muscle during the pulling phase was statistically significant higher than that during the propulsive phase. We concluded that AM and AL muscles were gradually recruited over time during fatiguing pedaling exercise, but their temporal change and activation phases were not completely the same.
    Arbeitsphysiologie 06/2009; 106(6):815-25. · 2.66 Impact Factor
  • Kohei Watanabe, Hiroshi Akima
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    ABSTRACT: The purpose of the present study was to investigate the electromyography (EMG) to torque relationship of the vastus intermedius (VI) muscle. Thirteen healthy men performed maximal voluntary contraction (MVC) and submaximal contraction during isometric knee extension at 10% of the MVC to 90% of the MVC at intervals of 10% of the MVC level. Surface EMG was detected from four muscle components of the QF muscle group, i.e., VI, vastus lateralis (VL), vastus medialis, and rectus femoris (RF) muscles. Normalized muscle activation in the VI muscle was significantly lower than in the VL muscle at a lower torque level (20 and 40% of MVC) and significantly lower compared to the RF muscle at a higher torque level (from 60 to 90% of MVC). These results suggest that neuromuscular activation in the VI muscle is not consistent with the other components of QF muscle group during submaximal knee extension contractions.
    Arbeitsphysiologie 05/2009; 106(5):665-73. · 2.66 Impact Factor
  • Medicine and Science in Sports and Exercise - MED SCI SPORT EXERCISE. 01/2009; 41.

Publication Stats

92 Citations
36.72 Total Impact Points

Institutions

  • 2012–2014
    • Chukyo University
      Koromo, Aichi, Japan
    • Japan Society for the Promotion of Science
      Edo, Tōkyō, Japan
  • 2011–2014
    • Kyoto University
      • Graduate School of Human and Environmental Studies
      Kioto, Kyōto, Japan
  • 2009–2013
    • Nagoya University
      • Graduate School of Education and Human Development
      Nagoya, Aichi, Japan