Clarification of mechanisms of strength gains induced by resistance training

Research Project

Project/Area Number	18K17837
Research Category	Grant-in-Aid for Early-Career Scientists
Allocation Type	Multi-year Fund
Review Section	Basic Section 59020:Sports sciences-related
Research Institution	Ritsumeikan University
Principal Investigator	Maeo Sumiaki 立命館大学, 総合科学技術研究機構, 研究員 (60774586)
Project Period (FY)	2018-04-01 – 2021-03-31
Project Status	Completed (Fiscal Year 2020)
Budget Amount *help	¥4,160,000 (Direct Cost: ¥3,200,000、Indirect Cost: ¥960,000) Fiscal Year 2020: ¥1,040,000 (Direct Cost: ¥800,000、Indirect Cost: ¥240,000) Fiscal Year 2019: ¥2,210,000 (Direct Cost: ¥1,700,000、Indirect Cost: ¥510,000) Fiscal Year 2018: ¥910,000 (Direct Cost: ¥700,000、Indirect Cost: ¥210,000)
Keywords	筋力トレーニング / 中枢神経系 / 骨格筋 / 皮質脊髄路の可塑性 / レジスタンストレーニング / 筋線維 / 肥大 / 増殖 / 経頭蓋磁気刺激 / 運動誘発電位
Outline of Final Research Achievements	Training-induced strength gains are often attributed to adaptations in the central nervous system and skeletal muscles, but it is poorly understood what modifications specifically occur in these sites. In this study, we reported that cortico-spinal excitability is lower (transmission is higher) in long-term resistance trained males than untrained males, but there is no difference in motor cortical representation, during submaximal contractions. In addition, we found that long-term resistance trained males had larger muscle cross-sectional area than untrained males, and it was associated with size and number of muscle fibres and myofibrils, as well as myofilament packing density.
Academic Significance and Societal Importance of the Research Achievements	トレーニングによる筋力の増加には、骨格筋の変化だけではなく、大脳運動野をはじめとする中枢神経系の機能的変化も寄与していると考えられてきた。本研究により、長期的なトレーニングを実施している鍛錬者は非鍛錬者と比較して、より多くの筋線維および筋原線維を有することや、最大下の力発揮中では皮質脊髄路の興奮性が低い（伝達効率が高い）ことが示唆された。本研究で用いた手法や得られた結果は、今後、より直接的な縦断的研究（トレーニング介入実験）や、最大筋力発揮中における測定を行ううえで重要な知見となるため、学術的意義は大きいと考えられる。