The unconscious mental inhibiting process of human maximal voluntary contraction

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K11532
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 59030:Physical education, and physical and health education-related
• Research Institution: Waseda University
• Principal Investigator: Takarada Yudai 早稲田大学, スポーツ科学学術院, 教授 (70367093)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: goal-priming / unconscious motivation / motor system activity / noradrenergic activity / TMS / pupillometry / maximal effort / shout

Outline of Final Research Achievements

When combined with the term‘maximal'in the consciously visible form, the effect of this subliminal motor-goal priming in inducing pupil dilation and stronger action preparation/execution was abolished without conscious awareness. This is the first objective evidence of motor inhibitory effect-predicting patterns of pupil-linked noradrenergic activity as a signature of a type of mental inhibition underlying the MVC behavioural goal. Meanwhile, shouting significantly increased handgrip maximal voluntary force and reduced the silent period, indicating that shouting increased handgrip voluntary force during sustained maximal exertion effort through the reduced silent period. This is the first objective evidence that the muscular force of shouting during maximal force exertion is associated with the potentiation of motor system activity produced by the additional drive of shouting operating on the motor system (i.e., shouting-induced excitatory input to the primary motor cortex).

Free Research Field

Biological science/Neuroscience/Motivation

Academic Significance and Societal Importance of the Research Achievements

シャウトが最大随意筋力（MVC）を増加させる原因を調べてみると、シャウト自体の運動指令が一次運動野（M1）皮質内抑制を低減させることが分かった。つまり、シャウトによる力増強効果はシャウトによる心理的抑制の除去あるいは軽減（Ikai & Steinhaus,1961）というよりはむしろ、シャウトに関連した運動指令のM1への追加的入力であることが初めて客観的に示された。このようなMVC変動のメカニズム解明は、アスリートのみならず、筋機能改善を目指した中高齢者やリハビリテーション患者の健康・運動性能の適切な評価や再現性の高い測定法の確立に必要不可欠であると考えられる。