Elucidata the mechanism of force potentiation by countermovement based on the visualization of the sarcomere length

2022 Fiscal Year Final Research Report

• Project/Area Number: 21K19744
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Review Section: Medium-sized Section 59:Sports sciences, physical education, health sciences, and related fields
• Research Institution: Ritsumeikan University
• Principal Investigator: Fukutani Atsuki 立命館大学, スポーツ健康科学部, 講師 (80722644)
• Co-Investigator(Kenkyū-buntansha): 伊坂 忠夫 立命館大学, スポーツ健康科学部, 教授 (30247811)
• Project Period (FY): 2021-07-09 – 2023-03-31
• Keywords: ミオシン / アクチン / タイチン / サルコメア / 骨格筋

Outline of Final Research Achievements

The isometric force is increased after an eccentric contraction compared to the pure isometric force. This phenomenon is called residual force enhancement. Currently, the mechanism of this force potentiation is considered to be sarcomere length non-uniformity. However, this idea is an estimation based on the theory and not yet experimentally verified. Therefore, the purpose of this study was to examine whether this estimation is correct or not by visualizing the sarcomere length during contractions. As a result, although the force potentiation was confirmed as expected, the variation of sarcomere length was not different between conditions. This result indicates that the widely-used sarcomere length non-uniformity theory could not explain the force potentiation after an eccentric contraction and should be reconsidered.

Free Research Field

バイオメカニクス

Academic Significance and Societal Importance of the Research Achievements

これまで、サルコメア長の変化は均一と考え、「筋線維が10%短縮したということは、各サルコメアが均一に10%短縮した」とみなして、力学現象を説明してきた。しかしながら、本研究によって、サルコメア長の変化は均一ではなく、伸ばされて長くなるサルコメアもあれば、反対に短い状態を維持したままのサルコメアも存在することが明らかになった。サルコメアの長さが均一でないからこそ生じる現象も存在することから、各サルコメア長の実測が必要ということを提唱することは、身体運動の詳細な生成メカニズム解明に向けて当該分野の理解を一歩進めるという点で、学術的意義がある。