Updated on 2025/06/26

写真a

 
MIYAMOTO, Naokazu
 
Affiliation
Faculty of Sport Sciences, School of Sport and Sciences
Job title
Professor
Degree
博士（人間・環境学） ( 京都大学 )
Homepage URL
https://www.miyamotolab.net/

Research Experience

  • 2020.04
    -
    2025.03

    順天堂大学 スポーツ健康科学部   先任准教授

  • 2022.04
    -
    2024.03

    JAPAN SPORT COUNCIL

  • 2018
    -
    2020

    Juntendo University   Faculty of Health and Sports Science

  • 2013
    -
    2018

    National Institute of Fitness and Sports in Kanoya   Sports and Life Science

  • 2012
    -
    2013

    Waseda University   Faculty of Sport Sciences

  • 2010
    -
    2012

    Waseda University   Faculty of Sport Sciences

  • 2007
    -
    2010

    Waseda University   Faculty of Sport Sciences

  • 2005
    -
    2007

    Kyoto Institute of Technology

▼display all

Education Background

  • 　
    -
    2005

    京都大学大学院   人間・環境学研究科（博士後期課程）  

  • 　
    -
    2002

    京都大学大学院   人間・環境学研究科（修士課程）  

  • 　
    -
    2000

    Kyoto University  

Professional Memberships

  • 　
    　
    　

    日本運動生理学会

  • 　
    　
    　

    日本バイオメカニクス学会

  • 　
    　
    　

    日本体力医学会

  • 　
    　
    　

    日本体育学会

Research Areas

  • Sports sciences

Research Interests

  • 神経筋生理学

  • 運動生理学

  • バイオメカニクス

  • トレーニング科学

Awards

  • 若手研究奨励賞大賞

    2024   日本トレーニング科学会   （共同研究者）

  • 大塚スポーツ医・科学賞 奨励賞

    2017   日本体力医学会   （共同研究者）

  • 奨励賞

    2012   日本トレーニング科学会   （共同研究者）

  • 奨励賞

    2011   日本トレーニング科学会   （共同研究者）

 

Papers

  • Adaptive walking performance is related to the hip joint position sense during active hip flexion rather than during passive hip flexion

    Taishi Matsui, Kosuke Hirata, Naokazu Miyamoto, Ryota Akagi

    Frontiers in Sports and Active Living   7   1510447  2025.02  [Refereed]

    　View Summary

    The purpose of this study was to investigate the relationship between hip joint position sense during active or passive hip flexion and adaptive walking performance across obstacles. After screening, 30 young men with the right dominant leg (age, 21 ± 2 years) participated in the experiment. To measure adaptive walking performance on the first day, the participants stepped over an obstacle underfoot with the left leg just high enough to avoid touching the obstacle. The difference between the height of the knee joint at the moment of crossing the obstacle and the height of the obstacle was normalized to the lower limb length and used to evaluate performance. To measure hip joint position sense on the second day, the participants adjusted their left hip joint angle to the target angle (range of joint motion: 80° of hip flexion) by active or passive hip flexion using a dynamometer. Although the absolute error in hip joint position sense during active hip flexion (6.3° ± 4.4°) significantly correlated with that during passive hip flexion (23.2° ± 11.0°) (r = 0.507, P < 0.001), a notable difference was observed between the two (P < 0.001). The normalized knee joint height was significantly correlated with the absolute error of hip joint position sense during active hip flexion (r = 0.477, P < 0.001) but not during passive hip flexion. The results of this study suggest a strong association between hip joint position sense under conditions that closely resemble actual walking behavior and adaptive walking performance, such as crossing over obstacles.

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    Scopus

  • Age-dependence of semitendinosus tendon properties used for anterior cruciate ligament reconstruction differs in males and females

    Naokazu Miyamoto, Eri Miyamoto-Mikami, Mayuko Kinoshita, Takuto Akazawa, Noriko Kimura, Hirofumi Nishio, Yohei Kobayashi, Masashi Nagao, Yuji Takazawa

    Clinical Biomechanics     106329 - 106329  2024.08  [Refereed]

    Authorship：Lead author, Corresponding author

    DOI

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    1
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  • Biceps femoris long head stiffens after 2 weeks of training cessation in highly trained sprinters.

    Naokazu Miyamoto, Kazuhiko Yamazaki, Takafumi Iwasaki, Iñigo Mujika, Daichi Yamashita, Kosuke Hirata

    European journal of applied physiology   124 ( 11 ) 3317 - 3323  2024.06  [Refereed]  [International journal]

    Authorship：Lead author, Corresponding author

    　View Summary

    PURPOSE: Most athletes experience short-term training cessation because of illness, injury, post-season vacation, or other reasons. Passive muscle stiffness is a potential risk factor for a sprint-type hamstring strain injury, but limited information is available about the effect of short-term training cessation on passive muscle stiffness. The present study aimed to identify whether and how passive muscle stiffness of the biceps femoris long head (BFlh) would vary due to 2 weeks of training cessation in sprinters. METHODS: Passive BFlh shear-wave speed (a proxy for stiffness) was measured using ultrasound shear-wave elastography in 28 male sprinters, before and after 2 weeks of intervention. During the 2 weeks, the participants in the training-cessation group (n = 14) were allowed to maintain their normal daily activities but not to perform any physical training, including stretching and resistance exercises. The participants in the training continuation group (n = 14) performed the training (including maximum speed sprint, plyometric, and weight training) prescribed by their coaches 5 days per week. RESULTS: In the training-cessation group, passive BFlh shear-wave speed increased after the 2 weeks of training cessation (4.75 ± 0.77 to 5.00 ± 0.88 m/s, P < 0.001). In contrast, there was no significant difference before and after the 2 weeks of training continuation (4.90 ± 0.85 to 4.93 ± 0.85 m/s, P = 0.521). CONCLUSIONS: The present findings indicate that muscles stiffen by training cessation in sprinting athletes.

    DOI PubMed

    Scopus

  • Relationship between jump height and lower limb joint kinetics and kinematics during countermovement jump in elite male athletes.

    Kotaro Shinchi, Daichi Yamashita, Takaki Yamagishi, Kazuhiro Aoki, Naokazu Miyamoto

    Sports biomechanics   23 ( 12 ) 3454 - 3465  2024.05  [Refereed]  [International journal]

    Authorship：Last author

    　View Summary

    This study aims to identify the relationship between jump height and the kinetic and kinematic parameters of the hip, knee, and ankle joints during countermovement jump (CMJ) in elite male athletes. Sixty-six elite male athletes from various sports (strength and power, winter downhill, combat, ball game, and aquatic) performed maximal effort CMJs with hands and arms crossed against their chests on force platforms. Jumping motion in the sagittal plane was recorded using video analysis and the peak torque, power, and angular velocity of the right hip, knee, and ankle joints were calculated during the propulsive phase. Correlations between the CMJ height and kinetic and kinematic parameters were investigated using Pearson's product-moment coefficient (r) and Spearman's rank correlation coefficient (ρ). CMJ height was highly correlated with peak hip power (ρ = 0.686, p < 0.001) and peak knee angular velocity (r = 0.517, p < 0.001), and moderately correlated with peak hip angular velocity (r = 0.438, p < 0.001) and peak hip torque (r = 0.398, p = 0.001). These results indicate that notable hip torque and power can contribute to increased angular velocity in both the knee and hip joints, ultimately increasing the CMJ height in elite male athletes.

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  • Observing an expert's action swapped with an observer's face increases corticospinal excitability during combined action observation and motor imagery.

    Hironori Watanabe, Sohei Washino, Shigehiko Ogoh, Naokazu Miyamoto, Hiroaki Kanehisa, Hirokazu Kato, Yasuhide Yoshitake

    European Journal of Neuroscience   59 ( 5 ) 1016 - 1028  2024.05  [Refereed]  [International journal]

    　View Summary

    This study aimed to examine whether observing an expert's action swapped with an observer's face increases corticospinal excitability during combined action observation and motor imagery (AOMI). Twelve young males performed motor imagery of motor tasks with different difficulties while observing the actions of an expert performer and an expert performer with a swapped face. Motor tasks included bilateral wrist dorsiflexion (EASY) and unilateral two-ball rotating motions (DIFF). During the AOMI of EASY and DIFF, single-pulse transcranial magnetic stimulation was delivered to the left primary motor cortex, and motor-evoked potentials (MEPs) were obtained from the extensor carpi ulnaris and first dorsal interosseous muscles of the right upper limb, respectively. Visual analogue scale (VAS) assessed the subjective similarity of the expert performer with the swapped face in the EASY and DIFF to the participants themselves. The MEP amplitude in DIFF was larger in the observation of the expert performer with the swapped face than that of the expert performer (P = 0.012); however, the corresponding difference was not observed in EASY (P = 1.000). The relative change in the MEP amplitude from observing the action of the expert performer to that of the expert performer with the swapped face was positively correlated with VAS only in DIFF (r = 0.644, P = 0.024). These results indicate that observing the action of an expert performer with the observer's face enhances corticospinal excitability during AOMI, depending on the task difficulty and subjective similarity between the expert performer being observed and the observer.

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  • Changes in consciousness during the training process of an elite athlete performing “Cassina” (Kovacs straight or piked with 1/1 turn) on high bar in gymnastics event.

    Kaya Kazuma, Naito Hisashi, Miyamoto Naokazu, Harada Mutsumi, Tomita Hiroyuki

    Research Journal of Sports Performance   16   92 - 105  2024  [Refereed]

    　View Summary

    The purpose of this study is to describe in detailed examples of the practice process leading up to the implementation of “Cassina” in a competition and exploring effective consciousness. The subject is an athlete who won a silver medal in the gymnastics team final at the Tokyo 2020 Olympic Games. It became clear that practicing with an awareness of the giant in the preparation phase is important to catch the bar in “Cassina”. Especially, in the acceleration phase, it is important to maintain straight body and the toes go through as far as possible. In the preflight phase, it is crucial to arch outwards.

    DOI

  • Effect of two weeks of training cessation on concentric and eccentric knee muscle strength in highly trained sprinters

    Daichi Yamashita, Kosuke Hirata, Kazuhiko Yamazaki, Iñigo Mujika, Naokazu Miyamoto

    PLOS ONE   18 ( 7 ) e0288344  2023.07  [Refereed]

    Authorship：Last author, Corresponding author

    DOI

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  • Association between order during first upwind leg and finishing place of race in sailing event of Tokyo 2020 Olympic Games

    Masahiro Hagiwara, Naokazu Miyamoto, Jiei Michishita

    Journal of High Performance Sport   11   79 - 89  2023.06  [Refereed]

  • Genetic polymorphisms related to muscular strength and flexibility are associated with artistic gymnastic performance in the Japanese population.

    Hiroshi Kumagai, Tomoko Kaneko, Yuko Shintake, Eri Miyamoto-Mikami, Hiroyuki Tomita, Makoto Fukuo, Wataru Kawai, Mutsumi Harada, Naoki Kikuchi, Nobuhiro Kamiya, Kosuke Hirata, Hirofumi Zempo, Seiji Maeda, Naokazu Miyamoto, Noriyuki Fuku

    European journal of sport science   23 ( 6 ) 955 - 963  2023.06  [Refereed]  [International journal]

    　View Summary

    This study aimed to examine how genetic polymorphisms related to muscular strength and flexibility influence artistic gymnastic performance in an attempt to identify a novel polymorphism associated with flexibility. In study 1, the passive straight-leg-raise (PSLR) score and aromatase gene CYP19A1 rs936306 polymorphism, a key enzyme for estrogen biosynthesis, were assessed in 278 individuals. In study 2, athletes (281 gymnasts and 1908 other athletes) were asked about their competition level, and gymnasts were assessed using the difficulty score (D-score) for each event. Muscular strength- (ACTN3 R577X rs1815739 and ACE I/D rs4341) and flexibility-related (ESR1 rs2234693 T/C and CYP19A1 rs936306 C/T) genetic polymorphisms were analyzed. In study 1, males with the CYP19A1 CT + TT genotype showed significantly higher PSLR scores than those with the CC genotype. In study 2, male gymnasts with the R allele of ACTN3 R577X showed a correlation with the floor, rings, vault, and total D-scores. In addition, male gymnasts with the C allele of ESR1 T/C and T allele of CYP19A1 C/T polymorphisms were correlated with the pommel horse, parallel bars, horizontal bar, and total D-scores. Furthermore, genotype scores of these three polymorphisms correlated with the total D-scores and competition levels in male gymnasts. In contrast, no such associations were observed in female gymnasts. Our findings suggest that muscular strength- and flexibility-related polymorphisms play important roles in achieving high performance in male artistic gymnastics by specifically influencing the performance of events that require muscular strength and flexibility, respectively. HighlightsEstrogen-related CYP19A1 polymorphism is a novel determinant of flexibility in males.Muscular strength- and flexibility-related polymorphisms play important roles in high performance in male artistic gymnastics.Genotypes of ACTN3 R577X, ESR1 rs2234693, and CYP19A1 rs936306 may contribute to training plan optimization and event selection in artistic gymnastics.

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  • Greater task difficulty during unilateral motor tasks changes intracortical inhibition and facilitation in the ipsilateral primary motor cortex in young men

      808   137293  2023.05  [Refereed]

    DOI

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  • Passive muscle stiffness of biceps femoris is acutely reduced after eccentric knee flexion

    Lei Zhi, Naokazu Miyamoto, Hisashi Naito

    Journal of Sports Science and Medicine   21   487 - 492  2022.12  [Refereed]

    Authorship：Corresponding author

  • Age-related changes in mechanical properties of semitendinosus tendon used for anterior cruciate ligament reconstruction.

    Takuto Akazawa, Naokazu Miyamoto, Hirofumi Nishio, Eri Miyamoto-Mikami, Mayuko Kinoshita, Yohei Kobayashi, Masashi Nagao, Yuji Takazawa

    Journal of orthopaedic surgery and research   17 ( 1 ) 501 - 501  2022.11  [Refereed]  [International journal]

    Authorship：Corresponding author

    　View Summary

    BACKGROUND: Hamstring tendons are a popular choice for autografts in anterior cruciate ligament (ACL) reconstruction. However, there is increasing evidence that hamstring tendon autografts carry a high risk of revision and residual instability in young patients. To elucidate the reasons for the inferior outcome of the reconstructed ACL with hamstring tendon autografts in young patients, we investigated the Young's modulus and the extent of cyclic loading-induced slackening of the semitendinosus tendon used for ACL reconstruction across a broad range of ages. METHODS: Twenty-six male patients (aged 17-53 years), who were scheduled for ACL reconstruction surgery using the semitendinosus tendon autograft, participated in this study. The distal portion of the harvested semitendinosus tendon, which was not used to construct the autograft, was used for cyclic tensile testing to calculate the Young's modulus and the extent of slackening (i.e., increase in slack length). RESULTS: Spearman correlation analysis revealed that the Young's modulus of the semitendinosus tendon was positively correlated with the patient's age (ρ = 0.559, P = 0.003). In contrast, the extent of tendon slackening did not correlate with the patient's age. CONCLUSIONS: We demonstrated that the Young's modulus of the semitendinosus tendon increases with age, indicating that the semitendinosus tendon used for ACL reconstruction is compliant in young patients.

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  • Effects of Quercetin Glycoside Supplementation Combined With Low-Intensity Resistance Training on Muscle Quantity and Stiffness: A Randomized, Controlled Trial

    Yuta Otsuka, Naokazu Miyamoto, Akitoshi Nagai, Takayuki Izumo, Masaaki Nakai, Masahiro Fukuda, Takuma Arimitsu, Yosuke Yamada, Takeshi Hashimoto

    Frontiers in Nutrition   9   912217  2022.07  [Refereed]

  • Effects of resistance training intensity on muscle quantity/quality in middle-aged and older people: a randomized controlled trial

    Yuta Otsuka, Yosuke Yamada, Akifumi Maeda, Takayuki Izumo, Tomohiro Rogi, Hiroshi Shibata, Masahiro Fukuda, Takuma Arimitsu, Naokazu Miyamoto, Takeshi Hashimoto

    Journal of cachexia, sarcopenia and muscle   13 ( 2 ) 894 - 908  2022.04  [Refereed]  [International journal]

    　View Summary

    BACKGROUND: A sarcopenia diagnosis is confirmed by the presence of low muscle quantity or quality under the 2018 revised definition by the European Working Group on Sarcopenia in Older People 2. Imaging methods [i.e. magnetic resonance imaging (MRI)], dual-energy X-ray absorptiometry (DXA), and bioelectrical impedance analysis are tools to evaluate muscle quantity or quality. The present study aimed to investigate whether and how low-intensity and moderate-intensity resistance training improved both muscle quantity and quality measured by MRI, DXA, and segmental bioelectrical impedance spectroscopy (S-BIS) in middle-aged and older people. METHODS: A single-blind, randomized, controlled trial was conducted. Community-dwelling people aged 50-79 years were randomly allocated to no exercise (no-Ex), low-intensity exercise (low-Ex), and moderate-intensity exercise (moderate-Ex) groups. Participants in the exercise groups performed resistance training for 24 weeks, with loads of 40% and 60% of one repetition maximum in the low-Ex and moderate-Ex groups, respectively. Cross-sectional area (CSA), lean mass, and muscle electrical properties on S-BIS were used to determine the effects of training interventions on muscle quantity and quality of the lower limbs. RESULTS: Fifty participants (no-Ex 17, age 63.5 ± 8.5 years, women 47.1%; low-Ex 16, age 63.6 ± 8.1 years, women 50.0%; moderate-Ex 17, age 63.5 ± 8.3 years, women 52.9%) completed the 24 week exercise intervention. For the primary outcome, significant intervention effects were found in thigh muscle CSA on MRI between the moderate-Ex and no-Ex groups (+6.8 cm2 , P < 0.01). Low-Ex for 24 weeks only increased quadriceps CSA (+2.3 cm2 , P < 0.05). The per cent change of thigh muscle CSA (+7.0%, P < 0.01) after 24 week moderate-Ex was higher than that of leg lean mass on DXA (+2.3%, P = 0.088). Moderate-Ex for 24 weeks also improved S-BIS electrical properties related to muscle quantity and quality, including the intracellular resistance index (+0.1 cm2 /Ω, P < 0.05), membrane capacitance (+0.7 nF, P < 0.05), and phase angle (+0.3 deg, P < 0.05); their changes were positively correlated with that of thigh muscle CSA (P < 0.01). CONCLUSIONS: Resistance exercise with moderate intensity improved muscle quantity and quality measured by MRI and S-BIS, whereas that with low intensity only increased muscle quantity in middle-aged and older people. The comparisons among the responses to exercise between the assessment methods indicate the greater value of MRI and S-BIS to measure changes of muscle quantity and quality than of lean mass measured by DXA for assessing the local effects of resistance training.

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    53
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  • Passive and active muscle elasticity of medial gastrocnemius is related to performance in sprinters

    Kazuhiko Yamazaki, Kakeru Inoue, Naokazu Miyamoto

    European Journal of Applied Physiology   122 ( 2 ) 447 - 457  2022.02  [Refereed]

    Authorship：Corresponding author

  • Characteristics of the passive muscle stiffness of the vastus lateralis: a feasibility study to assess muscle fibrosis

    Maeda A, Yamagishi M, Otsuka Y, Izumo T, Rogi T, Shibata H, Fukuda M, Arimitsu T, Yamada Y, Miyamoto N, Hashimoto T

    International Journal of Environmental Research and Public Health   18 ( 17 ) 8947  2021  [Refereed]

  • Site‐specific features of active muscle stiffness and proximal aponeurosis strain in biceps femoris long head

    Naokazu Miyamoto, Kosuke Hirata

    Scandinavian Journal of Medicine & Science in Sports   31 ( 8 ) 1666 - 1673  2021  [Refereed]

    Authorship：Lead author, Corresponding author

    DOI

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    7
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  • No association of plantar aponeurosis stiffness with medial longitudinal arch stiffness

      42 ( 10 ) 945 - 949  2021  [Refereed]

    Authorship：Corresponding author

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    3
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  • Female Athletes Genetically Susceptible to Fatigue Fracture Are Resistant to Muscle Injury: Potential Role of COL1A1 Variant

    ERI MIYAMOTO-MIKAMI, HIROSHI KUMAGAI, KUMPEI TANISAWA, YUKI TAGA, KOSUKE HIRATA, NAOKI KIKUCHI, NOBUHIRO KAMIYA, RYOKO KAWAKAMI, TAISHI MIDORIKAWA, TAKUJI KAWAMURA, RYO KAKIGI, TOSHIHARU NATSUME, HIROFUMI ZEMPO, KOYA SUZUKI, YOSHIMITSU KOHMURA, KAZUNORI MIZUNO, SUGURU TORII, SHIZUO SAKAMOTO, KOICHIRO OKA, MITSURU HIGUCHI, HISASHI NAITO, NAOKAZU MIYAMOTO, NORIYUKI FUKU

    Medicine & Science in Sports & Exercise   53 ( 9 ) 1855 - 1864  2021  [Refereed]

    DOI

  • Association between medial gastrocnemius muscle-tendon unit architecture and ankle dorsiflexion range of motion with and without consideration of slack angle

    Kosuke Hirata, Hiroaki Kanehisa, Naokazu Miyamoto

    PLOS ONE   16 ( 3 ) e0248125 - e0248125  2021  [Refereed]

    Authorship：Last author, Corresponding author

    　View Summary

    Joint flexibility is theoretically considered to associate with muscle-tendon unit (MTU) architecture. However, this potential association has not been experimentally demonstrated in humans in vivo. We aimed to identify whether and how MTU architectural parameters are associated with joint range of motion (RoM), with a special emphasis on slack angle. The fascicle length, pennation angle, tendinous tissue length, MTU length, and shear modulus of the medial gastrocnemius (MG) were assessed during passive ankle dorsiflexion using ultrasound shear wave elastography in 17 healthy males. During passive dorsiflexion task, the ankle joint was rotated from 40° plantar flexion to the maximal dorsiflexion joint angle at which each subject started experiencing pain. From the ankle joint angle-shear modulus relationship, the angle at which shear modulus began to rise (slack angle) was calculated. Two dorsiflexion RoMs were determined as follows; 1) range from the anatomical position to maximal angle (RoManat-max) and 2) range from the MG slack angle to maximal angle (RoMslack-max). The MTU architectural parameters were analyzed at the anatomical position and MG slack angle. The resolved fascicle length (fascicle length × cosine of pennation angle) and ratios of resolved fascicle or tendinous tissue length to MTU length measured at the MG slack angle significantly correlated with the RoMslack-max(r = 0.491, 0.506, and -0.506, respectively). Any MTU architectural parameters assessed at the anatomical position did not correlate with RoManat-maxor RoMslack-max. These results indicate that MTUs with long fascicle and short tendinous tissue are advantageous for joint flexibility. However, this association cannot be found unless MTU architecture and joint RoM are assessed with consideration of muscle slack.

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  • Does intra-abdominal pressure have a causal effect on muscle strength of hip and knee joints?

    Tayashiki K, Kanehisa H, Miyamoto N

    Journal of Strength and Conditioning Research   35 ( 1 ) 41 - 46  2021  [Refereed]

    Authorship：Corresponding author

  • Non-uniform distribution of passive muscle stiffness within hamstring

    Naokazu Miyamoto, Noriko Kimura, Kosuke Hirata

    Scandinavian Journal of Medicine and Science in Sports   30 ( 9 ) 1729 - 1738  2020.09

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  • Moderate hypoxia promotes skeletal muscle cell growth and hypertrophy in C2C12 cells

    Sakushima K, Yoshikawa M, Osaki T, Miyamoto N, Hashimoto T

    Biochemical and Biophysical Research Communications   525 ( 4 ) 921 - 927  2020  [Refereed]

  • eQTL variants in COL22A1 are associated with muscle injury in athletes

    Miyamoto-Mikami E, Kumagai H, Kikuchi N, Kamiya N, Miyamoto N, Fuku​ N

    Physiological Genomics   52 ( 12 ) 588 - 589  2020  [Refereed]

  • Nonuniform distribution of passive muscle stiffness within hamstring

    Miyamoto N, Kimura N, Hirata K

    Scandinavian Journal of Medicine and Science in Sports   30 ( 9 ) 1729 - 1738  2020  [Refereed]

    Authorship：Lead author, Corresponding author

  • COL5A1 rs12722 polymorphism is not associated with passive muscle stiffness and sports-related muscle injury in Japanese athletes.

    Eri Miyamoto-Mikami, Naokazu Miyamoto, Hiroshi Kumagai, Kosuke Hirata, Naoki Kikuchi, Hirofumi Zempo, Noriko Kimura, Nobuhiro Kamiya, Hiroaki Kanehisa, Hisashi Naito, Noriyuki Fuku

    BMC Medical Genetics   20 ( 1 ) 192 - 192  2019.12  [Refereed]  [International journal]

    　View Summary

    BACKGROUND: Poor joint flexibility has been repeatedly proposed as a risk factor for muscle injury. The C-to-T polymorphism (rs12722) in the 3'-untranslated region of the collagen type V α1 chain gene (COL5A1) is reportedly associated with joint flexibility. Flexibility of a normal joint is largely determined by passive muscle stiffness, which is influenced by intramuscular collagenous connective tissues including type V collagen. The present study aimed to test the hypothesis that the COL5A1 rs12722 polymorphism influences joint flexibility via passive muscle stiffness, and is accordingly associated with the incidence of muscle injury. METHODS: In Study 1, we examined whether the rs12722 polymorphism is associated with joint flexibility and passive muscle stiffness in 363 healthy young adults. Joint flexibility was evaluated by passive straight-leg-raise and sit-and-reach tests, and passive muscle stiffness was measured using ultrasound shear wave elastography. In Study 2, the association of the rs12722 polymorphism with sports-related muscle injury was assessed in 1559 Japanese athletes. Muscle injury history and severity were assessed by a questionnaire. In both Study 1 and Study 2, the rs12722 C-to-T polymorphism in the COL5A1 was determined using the TaqMan SNP Genotyping Assay. RESULTS: Study 1 revealed that the rs12722 polymorphism had no significant effect on range of motion in passive straight-leg-raise and sit-and-reach tests. Furthermore, there was no significant difference in passive muscle stiffness of the hamstring among the rs12722 genotypes. In Study 2, rs12722 genotype frequencies did not differ between the muscle injury and no muscle injury groups. Moreover, no association was observed between rs12722 polymorphism and severity of muscle injury. CONCLUSIONS: The present study does not support the view that COL5A1 rs12722 polymorphism has a role as a risk factor for sports-related muscle injury, or that it is a determinant for passive muscle stiffness in a Japanese population.

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    18
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  • Genetics of flexibility

    Myosotis Massidda, Naokazu Miyamoto, Samantha Beckley, Naoki Kikuchi, Noriyuki Fuku

    Sports, Exercise, and Nutritional Genomics: Current Status and Future Directions     273 - 293  2019.01

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    8
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  • Moderate associations of muscle elasticity of the hamstring with hip joint flexibility

    Miyamoto N, Hirata K

    International Journal of Sports Medicine   40 ( 11 ) 717 - 724  2019  [Refereed]

    Authorship：Lead author, Corresponding author

  • Muscle elasticity under active conditions in human: a methodological comparison

    Miyamoto N, Hirata K

    Translational Sports Medicine   2 ( 3 ) 138-145  2019  [Refereed]

    Authorship：Lead author, Corresponding author

  • Muscle Stiffness of the Vastus Lateralis in Sprinters and Long-Distance Runners.

    Naokazu Miyamoto, Kosuke Hirata, Kakeru Inoue, Takeshi Hashimoto

    Medicine and science in sports and exercise   51 ( 10 ) 2080 - 2087  2019  [Refereed]  [International journal]

    Authorship：Lead author, Corresponding author

    　View Summary

    PURPOSE: The stiffness of muscle-tendon units and of tendons in the lower legs plays important roles in sprinting and long-distance running. However, the association of muscle stiffness with sprinting and running remains unknown. This study aimed to identify the characteristics of muscle stiffness in sprinters and long-distance runners, and to determine how muscle stiffness is related to the performance of these athletes. METHODS: In 22 male sprinters (SPR group), 22 male long-distance runners (LDR group), and 19 healthy untrained control male subjects (CON group), the muscle shear wave speed (a proxy for stiffness) of the vastus lateralis (VL) was measured under passive (resting) and active (contracting the knee extensors at 50% of maximal voluntary contraction) conditions, by using ultrasound shear wave elastography. RESULTS: The passive VL shear wave speed in SPR group was significantly lower than that in LDR group (P = 0.039). The active VL shear wave speed in LDR group was significantly higher than that in SPR (P = 0.022) and CON (P < 0.001) groups. In SPR group, the 100-m race time was negatively correlated to the passive VL shear wave speed (r = -0.483, P = 0.023) and positively correlated to the active VL shear wave speed (r = 0.522, P = 0.013). In the LDR group, the 5000-m race time was positively correlated to the passive VL shear wave speed (r = 0.438, P = 0.047) but not to the active VL shear wave speed. CONCLUSION: The muscles of sprinters and long-distance runners exhibit characteristic stiffness that can be beneficial to their athletic performance. Passive and active muscle stiffness may play different roles in human locomotion, depending on locomotion speeds.

    DOI PubMed

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  • ESR1 rs2234693 Polymorphism Is Associated with Muscle Injury and Muscle Stiffness.

    Hiroshi Kumagai, Eri Miyamoto-Mikami, Kosuke Hirata, Naoki Kikuchi, Nobuhiro Kamiya, Seigo Hoshikawa, Hirofumi Zempo, Hisashi Naito, Naokazu Miyamoto, Noriyuki Fuku

    Medicine and science in sports and exercise   51 ( 1 ) 19 - 26  2019.01  [Refereed]  [International journal]

    　View Summary

    PURPOSE: Muscle injury is the most common sports injury. Muscle stiffness, a risk factor for muscle injury, is lower in females than in males, implying that sex-related genetic polymorphisms influence muscle injury associated with muscle stiffness. The present study aimed to clarify the associations between two genetic polymorphisms (rs2234693 and rs9340799) in the estrogen receptor 1 gene (ESR1) and muscle injury or muscle stiffness. METHODS: In study 1, a questionnaire was used to assess the muscle injury history of 1311 Japanese top-level athletes. In study 2, stiffness of the hamstring muscles was assessed using ultrasound shear wave elastography in 261 physically active young adults. In both studies, rs2234693 C/T and rs9340799 G/A polymorphisms in the ESR1 were analyzed using the TaqMan SNP Genotyping Assay. RESULTS: In study 1, genotype frequencies for ESR1 rs2234693 C/T were significantly different between the injured and noninjured groups in a C-allele dominant (CC + CT vs TT: odds ratio, 0.62; 95% confidence interval, 0.43-0.91) and additive (CC vs CT vs TT: odds ratio, 0.70; 95% confidence interval, 0.53-0.91) model in all athletes. In study 2, hamstring muscle stiffness was lower in subjects with the CC + CT genotype than in those with the TT genotype; a significant linear trend (CC < CT < TT) was found (r = 0.135, P = 0.029). In contrast, no associations were observed between ESR1 rs9340799 G/A and muscle injury or stiffness. CONCLUSIONS: Our results suggest that the ESR1 rs2234693 C allele, in contrast to the T allele, provides protection against muscle injury by lowering muscle stiffness.

    DOI PubMed

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  • Association analysis of the ACTN3 R577X polymorphism with passive muscle stiffness and muscle strain injury.

    N Miyamoto, E Miyamoto-Mikami, K Hirata, N Kimura, N Fuku

    Scandinavian journal of medicine & science in sports   28 ( 3 ) 1209 - 1214  2018.03  [Refereed]  [International journal]

    　View Summary

    Passive muscle stiffness is considered to be a major factor affecting joint flexibility and is thought to relate to the occurrence of muscle strain injury. In skinned muscle fiber experiments, the R577X polymorphism of the α-actinin-3 gene (ACTN3) has been associated with passive muscle stiffness. Our primary purpose was to clarify whether the ACTN3 R577X polymorphism influences passive stiffness of human muscle in vivo. We also examined whether the ACTN3 R577X polymorphism is associated with the occurrence of hamstring strain injury. Seventy-six healthy young male subjects were genotyped for the ACTN3 R577X (rs1815739) polymorphism. Shear modulus (an index of stiffness) of each hamstring muscle (biceps femoris, semitendinosus, and semimembranosus) was assessed using ultrasound shear wave elastography, and history of hamstring strain injury was collected via a questionnaire. The muscle shear moduli of the semitendinosus and semimembranosus were significantly higher in R-allele (RR + RX genotype) carriers than in XX genotype carriers, whereas the shear modulus of the biceps femoris did not differ among the ACTN3 R577X genotypes. Frequency of past hamstring strain injury also did not differ between the 3 genotypes nor between the R-allele and XX genotype carriers. This study indicates that RR and RX genotypes of the ACTN3 R577X polymorphism (corresponding to the presence of α-actinin-3 in type II muscle fibers) are associated with increased passive muscle stiffness of the human hamstring in vivo. However, this altered mechanical property might not affect the risk of hamstring muscle strain injury.

    DOI PubMed

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  • Muscle size-strength relationship including ultrasonographic echo intensity and voluntary activation level of a muscle group

    Ryota Akagi, Momoka Suzuki, Emi Kawaguchi, Naokazu Miyamoto, Yosuke Yamada, Ryoichi Ema

    Archives of Gerontology and Geriatrics   75   185 - 190  2018.03  [Refereed]

    DOI

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    35
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  • Associations of passive muscle stiffness, muscle stretch tolerance, and muscle slack angle with range of motion: individual and sex differences

    Miyamoto N, Hirata K, Miyamoto-Mikami E, Yasuda O, Kanehisa H

    Scientific Reports   8 ( 1 ) 8274  2018  [Refereed]

  • Contributions of hamstring stiffness to straight-leg-raise and sit-and-reach test scores

    Miyamoto N, Hirata K, Kimura N, Miyamoto-Mikami E

    International Journal of Sports Medicine   39 ( 2 ) 110 - 114  2018  [Refereed]

  • No association between passive material property and cross-sectional area in human hamstring

    Hirata K, Miyamoto-Mikami E, Kimura N, Miyamoto N

    Journal of Physical Fitness and Sports Medicine   7 ( 1 ) 35 - 40  2018  [Refereed]

    DOI

  • Causal effect of intra-abdominal pressure on maximal voluntary isometric hip extension torque

    Kota Tayashiki, Fumihiro Mizuno, Hiroaki Kanehisa, Naokazu Miyamoto

    European Journal of Applied Physiology   118 ( 1 ) 93 - 99  2018.01  [Refereed]

    DOI

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    5
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  • Effect of prolonged vibration to synergistic and antagonistic muscles on the rectus femoris activation during multi-joint exercises

    Ryoichi Ema, Hirokazu Takayama, Naokazu Miyamoto, Ryota Akagi

    EUROPEAN JOURNAL OF APPLIED PHYSIOLOGY   117 ( 10 ) 2109 - 2118  2017.10  [Refereed]

    DOI

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    5
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  • Inter- and intramuscular differences in training-induced hypertrophy of the quadriceps femoris: association with muscle activation during the first training session

    Taku Wakahara, Ryoichi Ema, Naokazu Miyamoto, Yasuo Kawakami

    CLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING   37 ( 4 ) 405 - 412  2017.07  [Refereed]

    DOI

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    31
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  • Associations of maximal voluntary isometric hip extension torque with muscle size of hamstring and gluteus maximus and intra-abdominal pressure

    Kota Tayashiki, Kosuke Hirata, Kiraku Ishida, Hiroaki Kanehisa, Naokazu Miyamoto

    EUROPEAN JOURNAL OF APPLIED PHYSIOLOGY   117 ( 6 ) 1267 - 1272  2017.06  [Refereed]

    DOI

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    10
    Citation
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  • Acute effect of static stretching on passive stiffness of the human gastrocnemius fascicle measured by ultrasound shear wave elastography

    Kosuke Hirata, Hiroaki Kanehisa, Naokazu Miyamoto

    EUROPEAN JOURNAL OF APPLIED PHYSIOLOGY   117 ( 3 ) 493 - 499  2017.03  [Refereed]

    DOI

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    49
    Citation
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  • Effects of marathon running on muscle damage in lower limb muscle groups and maximal aerobic capacity in novice recreational runners

    Fuminori Takayama, Kosuke Hirata, Yoshiharu Nabekura, Hiroaki Kanehisa, Naokazu Miyamoto

    Gazzetta Medica Italiana Archivio per le Scienze Mediche   176 ( 3 ) 100 - 109  2017  [Refereed]

    DOI

  • Effects of hamstring stretching on passive muscle stiffness vary between hip flexion and knee extension maneuvers

    N. Miyamoto, K. Hirata, H. Kanehisa

    SCANDINAVIAN JOURNAL OF MEDICINE & SCIENCE IN SPORTS   27 ( 1 ) 99 - 106  2017.01  [Refereed]

    DOI

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    65
    Citation
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  • Effect of abdominal bracing training on strength and power of trunk and lower limb muscles

    Kota Tayashiki, Sumiaki Maeo, Seiji Usui, Naokazu Miyamoto, Hiroaki Kanehisa

    Eur J Appl Physiol   116 ( 9 ) 1703-1713  2016.09

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    40
    Citation
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  • Effect of abdominal bracing training on strength and power of trunk and lower limb muscles

    Kota Tayashiki, Sumiaki Maeo, Seiji Usui, Naokazu Miyamoto, Hiroaki Kanehisa

    EUROPEAN JOURNAL OF APPLIED PHYSIOLOGY   116 ( 9 ) 1703 - 1713  2016.09  [Refereed]

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    40
    Citation
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  • Muscle-specific acute changes in passive stiffness of human triceps surae after stretching

    Kosuke Hirata, Eri Miyamoto-Mikami, Hiroaki Kanehisa, Naokazu Miyamoto

    EUROPEAN JOURNAL OF APPLIED PHYSIOLOGY   116 ( 5 ) 911 - 918  2016.05  [Refereed]

    DOI

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    82
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  • THE SKIN ACTS TO MAINTAIN MUSCLE SHEAR MODULUS

    Yasuhide Yoshitake, Naokazu Miyamoto, Keigo Taniguchi, Masaki Katayose, Hiroaki Kanehisa

    ULTRASOUND IN MEDICINE AND BIOLOGY   42 ( 3 ) 674 - 682  2016.03  [Refereed]

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    24
    Citation
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  • 大学生市民ランナーのマラソンレースが筋損傷指標と有酸素性能力に与える影響

    髙山史徳, 平田浩祐, 森寿仁, 鍋倉賢治, 宮本直和

    ランニング学研究   27   47 - 58  2016.02  [Refereed]

  • Validity of Measurement of Shear Modulus by Ultrasound Shear Wave Elastography in Human Pennate Muscle

    Naokazu Miyamoto, Kosuke Hirata, Hiroaki Kanehisa, Yasuhide Yoshitake

    PLOS ONE   10 ( 4 ) e0124311  2015.04  [Refereed]

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    117
    Citation
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  • Evidence for intermuscle difference in slack angle in human triceps surae

    Kosuke Hirata, Hiroaki Kanehisa, Eri Miyamoto-Mikami, Naokazu Miyamoto

    JOURNAL OF BIOMECHANICS   48 ( 6 ) 1210 - 1213  2015.04  [Refereed]

    DOI

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    63
    Citation
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  • Influence of Muscle Hypertrophy on the Moment Arm of the Triceps Brachii Muscle

    Norihide Sugisaki, Taku Wakahara, Koichiro Murata, Naokazu Miyamoto, Yasuo Kawakami, Hiroaki Kanehisa, Tetsuo Fukunaga

    JOURNAL OF APPLIED BIOMECHANICS   31 ( 2 ) 111 - 116  2015.04  [Refereed]

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    13
    Citation
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  • No Graduated Pressure Profile in Compression Stockings Still Reduces Muscle Fatigue

    N. Miyamoto, Y. Kawakami

    INTERNATIONAL JOURNAL OF SPORTS MEDICINE   36 ( 3 ) 220 - 225  2015.03  [Refereed]

    DOI

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    15
    Citation
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  • Increase in vastus lateralis aponeurosis width induced by resistance training: implications for a hypertrophic model of pennate muscle

    Taku Wakahara, Ryoichi Ema, Naokazu Miyamoto, Yasuo Kawakami

    EUROPEAN JOURNAL OF APPLIED PHYSIOLOGY   115 ( 2 ) 309 - 316  2015.02  [Refereed]

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    26
    Citation
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  • Is graduated pressure profile an essential feature for compression stockings to reduce fatigue development of the plantar flexors?

    Naokazu Miyamoto

    Sports Performance     213 - 221  2015.01  [Refereed]

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    2
    Citation
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  • Neural mechanisms of muscle cramp

    Kento Nakagawa, Naokazu Miyamoto, Kazuyuki Kanosue

    Sports Performance     79 - 90  2015.01  [Refereed]

    DOI

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    1
    Citation
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  • Effect of Pressure Intensity of Compression Short-Tight on Fatigue of Thigh Muscles

    Naokazu Miyamoto, Yasuo Kawakami

    MEDICINE AND SCIENCE IN SPORTS AND EXERCISE   46 ( 11 ) 2168 - 2174  2014.11  [Refereed]

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    31
    Citation
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  • INFLUENCE OF THE INTENSITY OF SQUAT EXERCISES ON THE SUBSEQUENT JUMP PERFORMANCE

    Atsuki Fukutani, Seiichiro Takei, Kosuke Hirata, Naokazu Miyamoto, Hiroaki Kanehisa, Yasuo Kawakami

    JOURNAL OF STRENGTH AND CONDITIONING RESEARCH   28 ( 8 ) 2236 - 2243  2014.08  [Refereed]

    DOI

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    53
    Citation
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  • Effect of conditioning contraction intensity on postactivation potentiation is muscle dependent

    Atsuki Fukutani, Kosuke Hirata, Naokazu Miyamoto, Hiroaki Kanehisa, Toshimasa Yanai, Yasuo Kawakami

    JOURNAL OF ELECTROMYOGRAPHY AND KINESIOLOGY   24 ( 2 ) 240 - 245  2014.04  [Refereed]

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    24
    Citation
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  • Inhomogeneous architectural changes of the quadriceps femoris induced by resistance training

    Ryoichi Ema, Taku Wakahara, Naokazu Miyamoto, Hiroaki Kanehisa, Yasuo Kawakami

    European Journal of Applied Physiology   113 ( 11 ) 2691 - 2703  2013.11  [Refereed]

    DOI PubMed

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    126
    Citation
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  • Non-uniform muscle oxygenation despite uniform neuromuscular activity within the vastus lateralis during fatiguing heavy resistance exercise

    Naokazu Miyamoto, Taku Wakahara, Ryoichi Ema, Yasuo Kawakami

    CLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING   33 ( 6 ) 463 - 469  2013.11  [Refereed]

    DOI

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    25
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  • Further Potentiation of Dynamic Muscle Strength after Resistance Training

    Naokazu Miyamoto, Taku Wakahara, Ryoichi Ema, Yasuo Kawakami

    MEDICINE AND SCIENCE IN SPORTS AND EXERCISE   45 ( 7 ) 1323 - 1330  2013.07  [Refereed]

    DOI

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    14
    Citation
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  • In vivo measurement of human rectus femoris architecture by ultrasonography: validity and applicability

    Ryoichi Ema, Taku Wakahara, Yasuyoshi Mogi, Naokazu Miyamoto, Toshihiko Komatsu, Hiroaki Kanehisa, Yasuo Kawakami

    CLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING   33 ( 4 ) 267 - 273  2013.07  [Refereed]

    DOI

    Scopus

    49
    Citation
    (Scopus)

  • 筋痙攣中のM波振幅の低下

    中川剣人, 宮本直和, 村上雄治, 彼末一之

    東京体育学研究   4   11 - 16  2013  [Refereed]

  • 野球打撃前に行う加重したバットでの素振りがバット速度と正確さに及ぼす影響

    樋口貴俊, 永見智行, 宮本直和, 彼末一之

    東京体育学研究   4   17 - 22  2013  [Refereed]

  • The effect of compression of thigh on knee extension torque evoked by electrical stimuli

      25 ( 1 ) 55 - 60  2013  [Refereed]

    CiNii

  • 大学生市民ランナーのマラソンレースが筋損傷指標と有酸素性能力に与える影響

    髙山史徳, 平田浩祐, 森寿仁, 鍋倉賢治, 宮本直和

    ランニング学研究   27 ( 2 ) 47 - 58  2013  [Refereed]

  • Potentiation of isokinetic torque is velocity-dependent following an isometric conditioning contraction

    Atsuki Fukutani, Naokazu Miyamoto, Hiroaki Kanehisa, Toshimasa Yanai, Yasuo Kawakami

    SpringerPlus   2 ( 1 ) 1 - 10  2013  [Refereed]

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    13
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  • ランニング時のコンプレッションウェア着用およびその圧迫強度が筋疲労の程度に及ぼす影響 MR-T2強調画像による検討

    宮本 直和, 川上 泰雄

    体力科学   61 ( 6 ) 585 - 585  2012.12

  • Potentiation of Maximal Voluntary Concentric Torque in Human Quadriceps Femoris

    Naokazu Miyamoto, Hiroaki Kanehisa, Yasuo Kawakami

    MEDICINE AND SCIENCE IN SPORTS AND EXERCISE   44 ( 9 ) 1738 - 1746  2012.09  [Refereed]

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    17
    Citation
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  • Influence of the intensity of a conditioning contraction on the subsequent twitch torque and maximal voluntary concentric torque

    Atsuki Fukutani, Naokazu Miyamoto, Hiroaki Kanehisa, Toshimasa Yanai, Yasuo Kawakami

    JOURNAL OF ELECTROMYOGRAPHY AND KINESIOLOGY   22 ( 4 ) 560 - 565  2012.08  [Refereed]

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    14
    Citation
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  • Association between regional differences in muscle activation in one session of resistance exercise and in muscle hypertrophy after resistance training

    Taku Wakahara, Naokazu Miyamoto, Norihide Sugisaki, Koichiro Murata, Hiroaki Kanehisa, Yasuo Kawakami, Tetsuo Fukunaga, Toshimasa Yanai

    EUROPEAN JOURNAL OF APPLIED PHYSIOLOGY   112 ( 4 ) 1569 - 1576  2012.04  [Refereed]

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    86
    Citation
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  • Task-Dependent Inhomogeneous Muscle Activities within the Bi-Articular Human Rectus Femoris Muscle

    Naokazu Miyamoto, Taku Wakahara, Yasuo Kawakami

    PLOS ONE   7 ( 3 ) e34269  2012.03  [Refereed]

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    34
    Citation
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  • Twitch potentiation after voluntary contraction and neuromuscular electrical stimulation at various frequencies in human quadriceps femoris

    Naokazu Miyamoto, Atsuki Fukutani, Toshimasa Yanai, Yasuo Kawakami

    MUSCLE & NERVE   45 ( 1 ) 110 - 115  2012.01  [Refereed]

    DOI

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    16
    Citation
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  • Warm-up procedures to enhance dynamic muscular performance

    MIYAMOTO Naokazu

    JPFSM   1 ( 1 ) 155 - 158  2012

    　View Summary

    Warm-up routine prior to sports activities is a customary practice among sporting people and athletes. Although warm-up is done with the expectation that it will enhance subsequent performance, little is known about how one should warm-up. In addition, scientific evidence is lacking on the best procedure that would allow for optimal preparation for a given event, especially for explosive sports activities such as jumping and sprinting. Recently, there has been considerable research on the functional significance of activity-dependent potentiation in dynamic muscular performance. Interest has evolved around whether high-intensity, short-duration muscle contraction as a warm-up procedure can improve such performance, although it remains inconclusive since muscle contractions induce fatigue as well as potentiative effects. In this review, based on evidence from well-controlled studies, proper warm-up procedures for enhancing voluntary dynamic muscular performance are proposed from the perspective of both fatigue and potentiative effects.

    DOI CiNii

  • Effect of pressure intensity of graduated elastic compression stocking on muscle fatigue following calf-raise exercise

    Naokazu Miyamoto, Kosuke Hirata, Naotoshi Mitsukawa, Toshimasa Yanai, Yasuo Kawakami

    JOURNAL OF ELECTROMYOGRAPHY AND KINESIOLOGY   21 ( 2 ) 249 - 254  2011.04  [Refereed]

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    57
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  • TWITCH POTENTIATION INDUCED BY STIMULATED AND VOLUNTARY ISOMETRIC CONTRACTIONS AT VARIOUS TORQUE LEVELS IN HUMAN KNEE EXTENSOR MUSCLES

    Naokazu Miyamoto, Toshimasa Yanai, Yasuo Kawakami

    MUSCLE & NERVE   43 ( 3 ) 360 - 366  2011.03  [Refereed]

    DOI

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    12
    Citation
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  • Characteristics of the passive muscle stiffness of the vastus lateralis: a feasibility study to assess muscle fibrosis

    Maeda A, Yamagishi M, Otsuka Y, Izumo T, Rogi T, Shibata H, Fukuda M, Arimitsu T, Yamada Y, Miyamoto N, Hashimoto T

    International Journal of Environmental Research and Public Health   18 ( 17 ) 8947  2011  [Refereed]

  • The influence of the duration of a conditioning contraction inducing postactivation potentiation on the maximal voluntary concentric plantar flexion torque

    Fukutani Atsuki, Miyamoto Naokazu, Kanehisa Hiroaki, Kawakami Yasuo, Yanai Toshimasa

    Journal of Training Science for Exercise and Sport   23 ( 1 ) 31 - 38  2011  [Refereed]

    　View Summary

    The present study examined the influence of the duration of a conditioning contraction inducing postactivation potentiation on the extent of increase in subsequent maximal voluntary concentric torque. Nine male subjects performed a 6 s or 14 s maximal voluntary isometric plantar flexion as the preceding conditioning contraction. Before and immediately after the conditioning contraction, the twitch torque and maximal voluntary concentric torque were recorded. The twitch torque significantly increased in the 6 s and 14 s conditions. The twitch torque after the 14 s conditioning contraction was significantly larger than that after the 6 s conditioning contraction (p < 0.05). Electromyogram recodings indicated that central fatigue was larger in the 14 s condition. These results suggest a tradeoff of the negative (fatigue) and positive (potentiation) effects that can mask the resultant increase in voluntary torque, when the conditioning contraction is performed beyond a certain duration.

    DOI CiNii

  • EFFECT OF POSTACTIVATION POTENTIATION ON THE MAXIMAL VOLUNTARY ISOKINETIC CONCENTRIC TORQUE IN HUMANS

    Naokazu Miyamoto, Hiroaki Kanehisa, Tetsuo Fukunaga, Yasuo Kawakami

    JOURNAL OF STRENGTH AND CONDITIONING RESEARCH   25 ( 1 ) 186 - 192  2011.01  [Refereed]

    DOI

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    39
    Citation
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  • Influence of muscle anatomical cross-sectional area on the moment arm length of the triceps brachii muscle at the elbow joint

    Norihide Sugisaki, Taku Wakahara, Naokazu Miyamoto, Koichiro Murata, Hiroaki Kanehisa, Yasuo Kawakami, Tetsuo Fukunaga

    JOURNAL OF BIOMECHANICS   43 ( 14 ) 2844 - 2847  2010.10  [Refereed]

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    18
    Citation
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  • Fatigue-induced changes in synergistic muscle force do not match tendon elongation

    Naotoshi Mitsukawa, Norihide Sugisaki, Naokazu Miyamoto, Toshimasa Yanai, Hiroaki Kanehisa, Tetsuo Fukunaga, Yasuo Kawakami

    JOURNAL OF BIOMECHANICS   43 ( 8 ) 1632 - 1634  2010.05  [Refereed]

    DOI

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  • JOINT ANGLE DEPENDENCE OF INTERMUSCLE DIFFERENCE IN POSTACTIVATION POTENTIATION

    Naokazu Miyamoto, Naotoshi Mitsukawa, Norihide Sugisaki, Tetsuo Fukunaga, Yasuo Kawakami

    MUSCLE & NERVE   41 ( 4 ) 519 - 523  2010.04  [Refereed]

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    19
    Citation
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  • Effect of counter-movement on elbow joint extension power-load characteristics

    Miyamoto, N, Wakahara, T, Sugisaki, N, Murata, K, Kanehisa, H, Fukunaga, T, Kawakami, Y

    J. Sports Sci.   3   1 - 8  2010  [Refereed]

  • Effect of countermovement on elbow joint extension power-load characteristics

    Naokazu Miyamoto, Taku Wakahara, Norihide Sugisaki, Koichiro Murata, Hiroaki Kanehisa, Tetsuo Fukunaga, Yasuo Kawakami

    JOURNAL OF SPORTS SCIENCES   28 ( 14 ) 1535 - 1542  2010  [Refereed]

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    5
    Citation
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  • EVIDENCE FOR INTERMUSCLE DIFFERENCE IN POSTACTIVATION POTENTIATION IN THE HUMAN TRICEPS SURAE: A MECHANOMYOGRAPHIC STUDY

    Naokazu Miyamoto, Tetsuo Fukunaga, Yasuo Kawakami

    MUSCLE & NERVE   39 ( 5 ) 703 - 706  2009.05  [Refereed]

    DOI

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    12
    Citation
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  • 段階的弾性圧迫ストッキングの着用が歩行中の足関節底屈筋群の血液量・筋活動および主観的運動強度に与える影響

    光川眞壽, 宮本直和, 平田浩祐, 利光徹哉, 川村明, 福永哲夫, 川上泰雄

    スポーツ科学研究   6   88 - 96  2009  [Refereed]

  • Elastic properties of human in vivo triceps brachii tendon

    Murata K, Sugisaki N, Miyamoto N, Wakahara T, Kanehisa H, Kawakami Y, Fukunaga T

    International Journal of Sport and Health Science   6   162 - 168  2008  [Refereed]

    DOI

  • Effect of joint angle on mechanomyographic amplitude during unfused and fused tetani in the human biceps brachil muscle

    N Miyamoto, S Oda

    EUROPEAN JOURNAL OF APPLIED PHYSIOLOGY   95 ( 2-3 ) 221 - 228  2005.10  [Refereed]

    DOI

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    8
    Citation
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  • Mechanomyographic and electromyographic responses of the triceps surae during maximal voluntary contractions

    N Miyamoto, S Oda

    JOURNAL OF ELECTROMYOGRAPHY AND KINESIOLOGY   13 ( 5 ) 451 - 459  2003.10  [Refereed]

    DOI

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    26
    Citation
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  • <Original>Force Generation During Concurrent Hand Grip and Elbow Flexion or Extension :

    Oda Shingo, Miyamoto Naokazu, Kida Noriyuki

    Advances in exercise and sports physiology   6 ( 4 ) 97 - 105  2000  [Refereed]

    　View Summary

    We investigated maximal isometric force during concurrent contractions for hand grip(HG)and elbow flexion(EF)or extension(EE)in nine healthy human subjects(experiment I). In our second experiments(experiment II)we tested : (1)how elbow flexion or extension forces initially sustained at submaximal levels are affected as a result of ramp contractions in hand grip, and(2)how hand grip forces initially sustained at submaximal levels are affected by the production of ramp force in elbow flexion or extension. Surface electromyograms(EMGs)were recorded from the flexor digitorum superficialis(FDS), extensor digitorum(ED), biceps brachii(BB)and lateral head of triceps brachii(TB). In experiment I the maximal HG forces simultaneously worked with EF or EE were significantly lower than the HG force exerted alone. The EF force that simultaneously worked with HG was significantly lower than the EF force alone. The EE force that simultaneously worked with HG was markedly lower than the EE force alone. In experiment II the EF force that was initially sustained at a submaximal level increased with increasing HG ramp contraction, whereas the EE force that was initially sustained at a submaximal level decreased as a result of HG ramp contraction. The HG force that was initially sustained at a submaximal level increased as a result of EF ramp contraction, whereas it was not affected by the EE ramp contraction. A notable result was that the EE force reductions observed in experiment I and II were not associated with a decrease in agonist TB activities. This result suggests that the EE force reductions might be explained by the net force for elbow flexion resulting from the mechanical interactions of activities in forearm multiarticular muscles.

    CiNii

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Research Projects

  • Creation of empirical research infrastructure for anti-aging that integrate basic science based on engineered skeletal muscle cell culture and applied science

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research

    Project Year :

    2021.04
    -
    2026.03
     

  • 肉離れ受傷リスク予測モデル構築に向けた骨格筋・腱の特性を規定する遺伝要因の解明

    日本学術振興会  科学研究費助成事業

    Project Year :

    2020.04
    -
    2025.03
     

    宮本 恵里, 高澤 祐治, 宮本 直和, 西尾 啓史

    　View Summary

    本研究は、骨格筋や腱の機能的特性（スティフネスや横断面積など）を規定する遺伝要因が肉離れの受傷しやすさに影響しているという仮説を検証することにより、「肉離れに対する遺伝的リスクの予測に必要な遺伝情報を同定すること」および「個人のリスクに合わせた肉離れ予防策構築のための学術的基盤を創出すること」を目的としている。令和2年度は、「研究課題①：ヒト生体における骨格筋のスティフネスを規定する遺伝子多型の同定」および「研究課題②：ヒトの摘出筋・腱における組織特性と遺伝子多型の関連性の検討」という二つの研究課題に取り組んだ。
    研究課題①では、骨格筋のスティフネスを超音波剪断波エラストグラフィーにより計測した約350名の若年成人男女を対象に、唾液から抽出したDNAサンプルを用い、全ゲノム領域の網羅的なSNP（single nucleotide polymorphism）解析を行った。SNP解析には、日本人に特化したジャポニカアレイを使用し、約66万個のSNPについてジェノタイピングを実施した。
    研究課題②では、ACL再建手術を受ける患者を対象とし、手術時に通常破棄される半腱様筋の余剰筋および腱の検体採取と、ゲノム解析用の血液採取を行った。これまでに約50例分の骨格筋、腱、血液検体の採取を終了している。採取した腱検体を用い、荷重変位測定ユニットを使用した引張試験を行い、力－変位関係、初期長、横断面積からスティフネスを算出した。

  • 脳機能亢進に資する骨格筋の「量」と「質」の向上方略策定に向けた挑戦

    日本学術振興会  科学研究費助成事業

    Project Year :

    2020.07
    -
    2023.03
     

    橋本 健志, 宮本 直和

    　View Summary

    加齢に伴う筋量と筋機能の低下は、身体能力や生活の質の低下の誘因となり、代謝疾患や認知症発症を誘発する、超高齢社会における喫緊の課題である。
    代表者は、加齢に伴う筋「量」と「質」の低下と認知機能低下の関連性に着目し、脳機能亢進を狙いとするには、骨格筋の「量」と「質」の向上戦略が有効と仮説を立てているが、その検証は皆無である。本研究は、代表者が明らかにしてきた脳神経活動の栄養源ならびに認知機能亢進作用を有する乳酸に加え、現行のin vitro研究で見出した骨格筋の「量」と「質」向上に効果的と期待される新規外的刺激（酸素濃度や各種機能性食品素材など）を、中高齢者対象にレジスタンス運動と併用することで、骨格筋機能のみならず脳機能の亢進をも引き起こす、健康科学が目指すアンチエイジングへの貢献を可能とする方略策定に挑戦することを目的とするものである。
    本年度も、コロナ禍の影響もあり、想定していた実験を遂行することが困難であった。そこで、健常若年男性を対象に、一過性の有酸素運動と食品素材の認知機能（実行機能と短期記憶）に対する併用効果を検証した。食品素材の摂取により、認知機能が亢進した。当該知見は、現在国際誌に投稿中である。また、健常若年男性を対象に、一定期間の低強度レジスタンス運動と食品素材摂取の認知機能（実行機能と短期記憶）に対する併用効果を検証した。現在、結果の解析中である。
    一方、加齢という変数が骨格筋の「量」と「質」に及ぼす影響について詳細に解析した。この成果は、国際誌に公表された。さらに、中高齢者に対する一定期間のレジスタンス運動が、骨格筋の「量」と「質」に及ぼす影響について詳細に解析した。この成果も、国際誌に公表された。さらに、同研究にて、脳機能に与える効果についても検証した（論文投稿準備中）。この成果は、研究会で発表した。

  • 肉離れが好発する筋・部位・個人の特徴解明に基づく効果的予防策構築のための基盤創出

    日本学術振興会  科学研究費（基盤研究B）

    Project Year :

    2019.04
    -
    2023.03
     

    宮本直和

  • 皮膚の弾性は3次元筋形状および筋パフォーマンスの決定因子であるか？

    日本学術振興会  科学研究費助成事業

    Project Year :

    2019.04
    -
    2022.03
     

    吉武 康栄, 宮本 直和, 金久 博昭

    　View Summary

    本研究では，筋を囲む皮膚を中心とした結合組織が3次元筋形状を決定する因子であるか，またその3次元筋形状が力発揮および調節能力に及ぼす影響を明らかにすることを目的とする．今年度は，筋形状の違いは，素速い力の立ち上がりに影響を及ぼすか，またその影響の度合いは関節角度によって異なるか，を明らかにすることを試みた．健常若齢成人男性16名の右肢の足関節底屈筋群を対象とした．対象者は，仰臥位と伏臥位それぞれにおいて，膝・股関節は完全伸展位に保持し，足関節角度は，背屈位15 （DF15），中間位（N），底屈位15 （PF15）の3条件とした．全ての姿勢および足関節角度において，3Dスキャナを用いて，下腿三頭筋群の筋形状を推定した．本研究では，素速く力を立ち上げる能力は，電気刺激誘発の力で評価した．電気刺激は，すべての運動単位の活動する強度にて脛骨神経に皮膚表面から電気刺激を与え，等尺性の足関節底屈力を誘発した．各姿勢・足関節角度における電気刺激は，2連続，そしてその2秒後に単発の刺激を1セットとし， 5セット行った．電気刺激によって誘発された力から，力の最高値，収縮時間，力の立ち上がり勾配（力の最高値/収縮時間）を算出し，5セットの平均値を代表値とした． 力の最高値は，N，PF15においては，仰臥位が伏臥位よりも有意に高値を示した（P < 0.05）．一方で，DF15では，力の最高値に姿勢間で差がなかった（P > 0.05）．さらに，定量化された姿勢変化による下腿三頭筋群の筋形状の平坦化の度合いは，力の最高値の低下の度合いと正の相関が認められた（r = 0.54，P < 0.05）．筋形状が平坦になると，素速い力の立ち上がりが阻害され，また，その度合いは，底屈位，言い換えると，筋長が短くなるにしたがい増長されることが示唆された．

  • Does exercise training involved with cognitive training improve motor skill and cognitive function?

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research

    Project Year :

    2016.04
    -
    2019.03
     

    Yoshitake Yasuhide

    　View Summary

    The 1st study examined corticospinal excitability during unilateral force-matching tasks of different difficulty. Single pulse TMS was applied to the hemispheres of seventeen young male during force matching tasks with easy (EASY) and difficult (DIFF) task difficulty. MEPs were significantly larger (P < 0.05) during DIFF than EASY. These results indicate that greater task difficulty increases corticospinal excitability of both contralateral and ipsilateral hemispheres.
    The 2nd study tested the effect of the exercise training with task difficulty on muscle and cognitive function. After 3 month-exercise training, exercise training with task difficulty enhanced some cognitive function scores greater than traditional exercise training while exercise training volume evaluated by surface EMG was comparable between training. The results indicated that exercise with task difficulty should be better way to enhance muscle and cognitive function than traditional training regimen.

  • 関節柔軟性の規定因子の解明とセミテーラーメイド型肉離れ予防ストレッチング法の確立

    日本学術振興会  科学研究費（基盤研究B）

    Project Year :

    2016.04
    -
    2019.03
     

    宮本直和

  • Mechanisms for improvement of joint range of motion after an acute bout of stretching exercise

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research

    Project Year :

    2015.04
    -
    2017.03
     

    FUKUNAGA Tetsuo, HIRATA Kosuke

    　View Summary

    The purpose of the present study was to elucidate the factors responsible for the improvement of ankle dorsiflexion range of motion (ROM) after an acute bout of static stretching, using ultrasound shear wave elastography. After the static stretching, the maximum dorsiflexion ROM was significantly increased. The stretching induced a significant reduction in passive stiffness of the medial gastrocnemius, but not in that of the lateral gastrocnemius and soleus. The slack angle of the Achilles tendon was significantly shifted to more dorsiflexed position. Additional experiment revealed that the passive stiffness of the medial gastrocnemius at a given fascicle length was significantly reduced. These findings suggest that both the reduction in passive fascicle stiffness and the shift in slack angle of the Achilles tendon contribute to the increased ROM.

  • Applications of surface EMG and real-time capturing of joint angle for muscle resistance training with music

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research

    Project Year :

    2013.04
    -
    2017.03
     

    Yoshitake Yasuhide

    　View Summary

    The aim of the study was to examine the temporal correlation between rectified EMG and instantaneous MU discharge rate in low frequencies. Healthy young subjects produced steady submaximal force with their right finger. Surface EMG and fine-wire MU potentials were recorded from the first dorsal interosseous muscle in the right hand. Rectified surface EMG and the instantaneous discharge frequency of MUs were smoothed by a Hann-window of 400 ms duration. In each of the identified MUs, the smoothed MU discharge frequency was positively and temporally correlated with the rectified-and-smoothed EMG as confirmed by the distinct peak in cross correlation function. The results indicated that the low-frequency component of rectified surface EMG provide temporal information on the low-frequency oscillations in the MU discharge frequency.

  • Effect of planting lawns in schoolyards on musculoskeletal systems in lower limbs.

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research

    Project Year :

    2013.04
    -
    2017.03
     

    TANAKA Toshio

    　View Summary

    The purpose of present study was to investigate the effect of planting lawns in schoolyards on musculoskeletal systems in lower limbs. Running kinematics , plantar pressure of shoe insole and electromyogram (EMG) activities of lower limb muscles were measured during maximal sprint running at the lawn and earth, respectively.
    As results, higher plantar pressure and EMG activities were observed during sprinting at lawn schoolyards, though sprint running velocity and any sprint running kinematics were not significantly different with these durung sprinting at earth ground. These results suggested that it was necessary to generate higher muscle force and plantar pressure during sprinting at lawn ground compared with that on the earth. Therefore, it may possible that planting lawns in schoolyards may led strengthen musculoskeletal systems in lower limbs stronger.

  • Physiological significance and validity to measure the shear modulus of skeletal muscles with ultrasound shear-wave elastography

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research

    Project Year :

    2012.04
    -
    2016.03
     

    Yoshitake Yasuhide, Kanehisa Hiroaki, Takai Yohei, Miyamoto Naokazu, Fukunaga Tetsuo

    　View Summary

    Recent development of ultrasound shear-wave elastography is expected to solve various problems by yielding muscle shear modulus with simple operations in various experimental settings at relatively low expense. In the present series of studies, we found that 1) it has high repeatability between trials and between days, 2) the probe angle relative to fascicle direction does not strongly affect muscle shear modulus values, 3) muscle shear modulus increased with exerted torque up to 60% MVC, and its rate of increase against absolute torque depended on muscle strength of individuals, 4) the skin is a main contributor for maintaining the muscle mechanical properties among tissues covering the skeletal muscle.

  • 筋肥大を目的とした効果的なトレーニング法の開発：運動時の吸引酸素濃度に着目して

    日本学術振興会  科学研究費（挑戦的萌芽研究）

    Project Year :

    2014.04
    -
    2016.03
     

    宮本直和

  • ウォームアップ効果の生理学的機序の解明と競技特性に合致したプロトコルの確立

    日本学術振興会  科学研究費（若手研究A）

    Project Year :

    2013.04
    -
    2016.03
     

    宮本直和

  • Mechanism and adaptability of human movement performance approached with in vivo measurement of musculotendinous behavior

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research

    Project Year :

    2012.04
    -
    2015.03
     

    KAWAKAMI Yasuo, YANAI Toshimasa, MIYAMOTO Naokazu, WAKAHARA Taku, MITSUKAWA Naotoshi

    　View Summary

    The purpose of this study was to evaluate the adaptability of muscle-tendon unit functions and reveal the mechanisms during human movements through the measurement of biological data. We disclosed dynamics of the muscle-tendon units and their mechanical properties in the lower limb during running by ultrasound apparatus and a three-dimensional motion analysis system. Regarding the phenomenon of post-activation potentiation, the contraction intensity, exercise velocity and intensity of conditioning contraction were found to influence the force-producing capacity of skeletal muscles and movement performances. Furthermore, we found morphological adaptation of the tendinous tissues to muscle hypertrophy by resistance training. This study clarified some important factors of movement performance and the mechanisms of their improvement through in vivo evaluation of the dynamics and adaptability of muscle-tendon units in humans.

  • 二関節筋特有の神経･筋制御および筋硬度の筋内部位差～肉離れ発症メカニズムの解明に向けて～

    公益財団法人中冨健康科学振興財団  研究助成金

    Project Year :

    2013.04
    -
    2014.03
     

    宮本直和

  • なぜ肉離れは二関節筋の特定部位において好発するのか？

    日本学術振興会  科学研究費（挑戦的萌芽研究）

    Project Year :

    2012.04
    -
    2014.03
     

    宮本直和

  • 動的随意筋力に対する筋電気刺激のウォーミングアップ効果

    日本学術振興会  科学研究費（若手研究B）

    Project Year :

    2010.04
    -
    2012.03
     

    宮本直和

  • Pathogenesis and site specificity of delayed onset muscle soreness : toward training modality effective for strength gain while minimizing muscle soreness

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research

    Project Year :

    2009
    -
    2011
     

    KAWAKAMI Yasuo, MIYAMOTO Naokazu, KURIHARA Toshiyuki, WAKAHARA Taku, IWANUMA Soichiro, SAKUMA Jun, HIRAYAMA Kuniaki, SUZUKI Katsuhiko, KANDA Kazue

    　View Summary

    This study investigated the relationships between the degree of muscle fatigue and changes in the delayed onset muscle soreness(DOMS), biochemical markers of muscle damage and joint performance, induced by calf-raise exercises at two different frequencies. The results suggest that 1) muscle fatigue is less by the faster exercise, 2) the degree of DOMS and the amount of muscle damage markers are related with the degree of muscle fatigue and muscle-specific, but joint performance rapidly recovers after fatigue regardless of soreness or retained biochemical changes, and that 3) fascicle and tendon behavior during exercise is altered in relation to the observed changes.

  • 短距離疾走中における“バネ”の役割～一流スプリンターのバネの特徴解明を目指して～

    財団法人上月スポーツ・教育財団  スポーツ研究助成事業

    Project Year :

    2009.04
    -
    2010.03
     

    宮本直和

  • Studies on the mechanisms of exercise-induced muscle soreness and strain : with a perspective to training for muscle functions

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research

    Project Year :

    2006
    -
    2008
     

    KAWAKAMI Yasuo, FUKUNAGA Tetsuo, SAKURAI Sakurai, FUKUNAGA Tetsuo, SAKURAI Tomonobu, MIYAMOTO Naokazu

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Sub-affiliation

  • Faculty of Sport Sciences   Graduate School of Sport Sciences

  • Affiliated organization   Global Education Center

Internal Special Research Projects

  • 瞬発系スポーツ競技前に行う効果的な短時間高強度ウォームアップ法の確立～実施者の筋線維組成およびトレーニング実施の有無に着目して～

    2012  

    　View Summary

    競技選手やスポーツ愛好家は、競技前のウォームアップを習慣的に行っている。しかしながら、実際に行われているウォームアップの内容は経験などに基づいて決められていることが多く、特に瞬発系競技のパフォーマンスを高めるためにはどのようなウォームアップを行えば良いのかについてはほとんど知られていない。近年の研究では、高強度短時間の筋収縮後にみられる活動後増強効果の役割が注目を浴び、ウォームアップとしての高強度短時間の筋収縮が瞬発系競技のパフォーマンスを向上させるか否かについて数多く検討されている（Tillin & Bishop 2009; Miyamoto 2011, 2012）。我々はこれまでに、事前に5～6秒間の等尺性最大随意筋収縮（Maximal Voluntary Contraction: MVC）を行うことにより、その後に行う最大努力の動的筋力が一時的に高まることを報告してきた。しかしながら、短時間と言えど高強度の筋収縮は活動後増強の効果だけではなく筋疲労をも引き起こすため、活動後増強の恩恵を充分に活かし切れていない。そこで本研究では、高強度のレジスタンストレーニングにより筋疲労耐性を亢進させると、筋力増強はより顕著になるのか否かについて検討した。健常成人男性20名（トレーニング群11名、コントロール群9名）を対象に、5秒間のMVC前およびMVC直後、1、3、5分後に、最大努力による等速性膝関節伸展筋力を計測した。トレーニング群は、12週間の介入期間中に80%1RMの強度にて膝関節伸展のトレーニングを行った。その結果、動的筋力は、トレーニング前ではMVC 終了1分後および3分後に有意に増加したのに対し、トレーニング後ではMVC直後にも有意に増加し、MVC終了1分後の増加はトレーニング前と比べ有意に高かった。これらの結果は仮説を支持するものであり、動的筋力に対する高強度短時間のウォームアップ収縮の効果は、高強度レジスタンストレーニングを行っている者ほど顕著であることを示唆している。

  • 反動動作を用いた筋パワー向上のためのトレーニング方法の確立

    2009  

    　View Summary

    INTRODUCTIONDuring the actions involving a counter-movement (CM), the tendinous tissues have been considered to play an important role in energy storage and release. However there are contradictory reports regarding the relationship between the stiffness of tendon and the extent of joint performance enhancement induced by a CM (Kubo et al. 1999, Bojsen-M&oslash;ller et al. 2005). On the other hand, the extent of joint power enhancement by a CM was reported to be influenced by the load intensity against which the task was performed (Miyamoto et al. in submission). Therefore, the purpose of this study was to investigate the relation between the tendon stiffness and the CM induced enhancement of the joint power output against different loads.METHODSNineteen adult participants performed maximal elbow extensions with and without a CM against different loads (0, 2.5, 5.0, 7.5, 10.0, and 12.5 kg) at their maximal effort. The increase in the average joint power by the CM during concentric phase (75-135 deg: full extension=180 deg) was defined as the CM effect for the given load. The tendon stiffness of the lateral head of the triceps brachii muscle was measured using ultrasonography during isometric ramp contraction of elbow extension. The isometric maximal muscle strength of elbow extension and the tendon stiffness were measured with elbow and shoulder joint angles of 90 deg flexed. The storage capacity of elastic energy by tendon was estimated as the integrated area below the tendon force-elongation curve during the ramp contraction. Multiple stepwise linear regression analysis was used to identify independent predictors of the CM effect at each load intensity, employing tendon stiffness, maximal strength, and storage capacity of elastic energy.RESULTS & DISCUSSIONIn both conditions with and without a CM, the average joint power varied across different load intensities, and peaked at 5.0 kg and 10.0 kg in the tasks without and with a CM condition, respectively (Fig. 1). The CM effect tended to increase with the load intensity (Fig. 1). The multiple stepwise linear regression analyses revealed that none of the variables contributed significantly to the prediction of the extent of the CM effect for the loads within 0-5.0 kg whereas the muscle strength at 7.5 kg (r=0.62, P<0.05) and the tendon stiffness at 10.0 and 12.5 kg contributed significantly to the prediction (r=0.60 and 0.67, P<0.05, respectively, Table 1). The results indicate that for the high load tasks the extent of CM effect was greater in subjects with stiffer tendon. In a CM exercise, it has been reported that short coupling time was necessary for enhancing the performance during the concentric phase (Bosco et al. 1981). The increased stiffness causes the recoiling time to shorten, enabling the tendon to transmit the muscle force to the attached bone quickly and effectively. In fact, a significant correlation was reported between the rate of isometric torque development (a key parameter of rapid muscle force exertion) and the tendon stiffness (Bojsen-M&oslash;ller et al. 2005). Taken together, our results suggest that, at least in elbow extension task, for the high load intensity tendinous tissues play an important role to transmit muscle force to the bone quickly and effectively, and thereby, a stiffer tendon could lead to greater extent of joint power enhancement induced by a CM.

  • 伸張－短縮サイクル運動における筋パワー発揮特性に関する研究

    2008  

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    　さまざまなスポーツ競技において、短い時間の中で爆発的に大きな力を発揮することは優れた競技成績をおさめるための重要な運動能力の一つである。このような運動能力は筋パワーとして位置づけられ、パワーが競技パフォーマンスの決定因子の一つであることは疑う余地がない。筋の短縮速度（関節運動の角速度）が増すと発揮できる力は小さくなるため、力と速度の積で表されるパワーは最大筋力の約30%の負荷を与えたときに最大になる（金子ら、 1978）。このことから、競技力向上を目的としたトレーニングにおいては、最大筋力あるいは最大挙上重量の30%の負荷がパワー向上に最も効果的であると考えられている。ただし、これらの知見は、反動を用いない動作を対象として行われてきた研究によるものである。そこで本研究では、反動の有無が負荷－関節パワー関係に及ぼす影響について検討することを目的とした。　健常な成人男性８名が被験者として参加した。被験者は、反動を用いない状態（NoCM条件）および反動を用いた状態（CM条件）で、0, 2.5, 5.0, 7.5, 10.0, 12.5, 15.0kgの負荷に対して最大努力による肘関節伸展動作を行った。その際、上腕三頭筋外側頭および内側頭、上腕二頭筋から筋電図活動を導出した。　CM条件の平均肘関節伸展パワーは、0kg以外の全負荷において、NoCM条件よりも有意に大きな値であった。また、肘関節伸展パワーが最大となる負荷強度は、NoCM条件では5.0kg、CM条件では7.5kgの負荷であった。筋電図活動は、負荷および反動の有無によって有意な変化は認められなかった。　これらの結果は、最大関節パワーを得るための負荷強度は反動の有無によって異なること、また、反動による関節パワーの増強は伸張反射などの筋活動の違いではなく、弾性エネルギーの蓄積・再利用によるものを示唆するものである。本研究から、反動を用いたパワートレーニングには、従来考えられている最大強度の30%よりもさらに高い負荷の方がパワー増強に効果的である可能性が示された。

  • Postactivation Potentiation のメカニズムを探る

    2007  

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    【背景】最大随意収縮（MVC）後の電気刺激による単収縮張力（Pt）はMVC前と比べて増大し（Postactivation Potentiation: PAP）、PAPの程度は測定をおこなう関節角度の影響を受ける。本研究では、筋の電気的活動（M波振幅値）および機械的活動（MMG振幅値）に着目し、関節角度がPAPに与える影響について検討した。また、各関節角度におけるMVC発揮時のvoluntary activatio（VA）についても検討した。【方法】被験者の足関節を0°、20°背屈位、20°底屈位で筋力測定装置に固定した。各足関節角度において10秒間の等尺性底屈MVC前、および直後から10分後まで定期的に超最大強度の電気刺激を脛骨神経に加え、足関節底屈Ptおよび下腿三頭筋各筋のM波振幅値とMMG振幅値を算出した。【結果】各筋のM波振幅値はいずれの足関節角度においても大きな変化が見られなかった。一方、PtとMMG振幅値はMVC後で増加したが、20°底屈位におけるPtの増加率はMMG振幅値の増加率よりも顕著に大きかった。また、VAは関節角度間に有意な差は認められなかった。【考察】本研究の結果は、PAPには各関節角度でのMVC発揮時のVAや単収縮時の筋の電気的活動の変化ではなく、筋の収縮特性の変化が大きく関与しているが、筋長が短い場合にはそれ以外の要因も介入する可能性を示唆するものである。