Clarification of the mechanism of muscle fatigue: a shear wave ultrasound elastography study

• Project/Area Number: 16H05918
• Research Category: Grant-in-Aid for Young Scientists (A)
• Allocation Type: Single-year Grants
• Research Field: Sports science
• Research Institution: Shibaura Institute of Technology
• Principal Investigator: Akagi Ryota 芝浦工業大学, システム理工学部, 准教授 (20581458)
• Research Collaborator: Ema Ryoichi 静岡産業大学, 講師 (10768196) ; Hirata Kosuke 芝浦工業大学, 大学院・日本学術振興会, 特別研究員 (00835746)
• Project Period (FY): 2016-04-01 – 2019-03-31
• Project Status: Completed (Fiscal Year 2018)
• Budget Amount: ¥26,260,000 (Direct Cost: ¥20,200,000、Indirect Cost: ¥6,060,000); Fiscal Year 2018: ¥2,730,000 (Direct Cost: ¥2,100,000、Indirect Cost: ¥630,000); Fiscal Year 2017: ¥4,810,000 (Direct Cost: ¥3,700,000、Indirect Cost: ¥1,110,000); Fiscal Year 2016: ¥18,720,000 (Direct Cost: ¥14,400,000、Indirect Cost: ¥4,320,000)
• Keywords: 筋剛性率 / 膝関節伸展筋群 / 足関節底屈筋群 / 等尺性収縮 / 強度依存性 / 活動交代 / 末梢性疲労 / 中枢性疲労 / 筋力 / 中強度 / 高強度 / 筋疲労 / 超音波剪断波エラストグラフィ / 筋の剛性率 / 下肢 / 低強度 / 下腿三頭筋

Outline of Final Research Achievements

When performing sustained low-intensity contractions, the two findings were obtained in this study as follows: 1) The difference in the extent of fatigue of each plantar flexor synergist corresponds to the difference in the frequency of alternate muscle activity between the synergists (the synergist muscles are activated in an alternating pattern of activity and silence). 2) The sex difference in fatigability of the knee extensors is explained by that in peripheral fatigue, particularly the degree of peripheral fatigue of the lateral vastus muscle.

Academic Significance and Societal Importance of the Research Achievements

本研究では，超音波剪断波エラストグラフィ（SWE）法という新しい手法を用いて，これまで長年に亘って果たされていない筋疲労の機序の全容解明に向けて取り組んだ．実際に骨格筋を疲労させるにあたり，低強度で長く運動させた場合と，強度を高くして短い運動で疲労させた場合とでは，SWE法の適用可否が異なってしまったが，少なくとも前者の運動に関しては，これまで明らかにすることができなかった機序の一端を掴むことができた．人々が日頃から疲労感を感じず，充実した生活を送るためには，疲れに強い体作りや日常のケアの方法を確立することが不可欠である．そのような面で，今回得られた知見が役立つことを期待する．

Research Products

• [Journal Article] Muscle size-strength relationship including ultrasonographic echo intensity and voluntary activation level of a muscle group (2018)
  • Author(s): Akagi Ryota、Suzuki Momoka、Kawaguchi Emi、Miyamoto Naokazu、Yamada Yosuke、Ema Ryoichi
  • Journal Title: Archives of Gerontology and Geriatrics Volume: 75 Pages: 185-190
  • DOI: 10.1016/j.archger.2017.12.012
  • Peer Reviewed / Open Access
• [Journal Article] Effects of sex and joint action on voluntary activation (2018)
  • Author(s): Ema Ryoichi、Suzuki Momoka、Kawaguchi Emi、Saito Itaru、Akagi Ryota
  • Journal Title: PeerJ Volume: 6 Pages: e5968-e5968
  • DOI: 10.7717/peerj.5968
  • Peer Reviewed / Open Access
• [Journal Article] Muscle Shear Moduli Changes and Frequency of Alternate Muscle Activity of Plantar Flexor Synergists Induced by Prolonged Low-Level Contraction (2017)
  • Author(s): Akagi Ryota、Fukui Takahito、Kubota Masato、Nakamura Masashi、Ema Ryoichi
  • Journal Title: Frontiers in Physiology Volume: 8 Pages: 708-708
  • DOI: 10.3389/fphys.2017.00708
  • Peer Reviewed / Open Access
• [Presentation] Individual differences in knee extensor fatigue induced by sustained middle-level contraction (2019)
  • Author(s): Hirata N, Hirata K, Akagi R
  • Organizer: XXVII Congress of the International Society of Biomechanics
  • Int'l Joint Research
• [Presentation] Can low-intensity squat exercise improve knee and hip flexion and extension strength simultaneously? (2019)
  • Author(s): Sato S, Hirata N, Tanimoto H, Imaizumi N, Ando R, Hirata K, Akagi R
  • Organizer: XXVII Congress of the International Society of Biomechanics
  • Int'l Joint Research
• [Presentation] 足関節底屈における瞬発的な筋力の加齢変化をもたらす要因：神経筋活動の筋間差という視点から (2018)
  • Author(s): 江間諒一，川口恵実，鈴木桃香，赤木亮太
  • Organizer: 日本体育学会第69回大会
• [Presentation] 低強度での持続的な関節トルク発揮に伴う筋剛性率変化から協働筋間の活動交代を考える－足関節底屈筋群を対象として－ (2017)
  • Author(s): 赤木亮太，江間諒一
  • Organizer: 日本体育学会第68回大会