Human adaptability in mechanical ease to move explored in athletes' bodies.

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K17592
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 59020:Sports sciences-related
• Research Institution: University of Tsukuba
• Principal Investigator: Sado Natsuki 筑波大学, 体育系, 助教 (60844983)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: MRI / 形態 / 適応 / 個人差 / 慣性 / 可塑性

Outline of Final Research Achievements

The motion of objects, including human motion, is determined by the relationship between mechanical actions and inertia properties. The muscle morphology of athletes has been examined, which is an aspect of adaptation to mechanical actions. However, inertia properties, i.e., the mechanical difficulty of movement, have not been fully investigated. We analysed the morphologies of sprinters, shot putters and long-distance runners. The lower limb moment of inertia (the difficulty of swinging the leg around the hip joint) in athletes did not differ as much from untrained individuals as did mass, because the increases in lower limb mass, whether muscle or fat, occurs in the proximal region. We showed that proximal-specific mass variability in the lower limb does not relatively increase the mechanical difficulty swinging the lower limb during locomotion in humans in general. Meanwhile, this feature was limited to the lower limb and distal muscles were also well developed in the upper limb.

Free Research Field

バイオメカニクス

Academic Significance and Societal Importance of the Research Achievements

競技者の身体能力を研究する目的で行われる形態学的研究は主に筋サイズに着目してきた。これは力学的作用の一側面であるが、慣性もまた身体運動を決定する要因である。本研究は慣性という形態学的研究の新しい視点を示した。
従来、スポーツ現場では身体を鍛えすぎると動かしにくくなると考えられてきた。これに対する筋を鍛える利点の説明としては、「筋が大きくなることで動かしにくくなる以上に大きな力を発揮できる」というものであることが多かった。本研究ではさらに、そもそも力学的な動かしにくさがそこまで大きくならないことを示すエビデンスを加え、筋量増大による動かしにくさ増大に強く注意を払う必要がないことを示唆している。