Mino Soushi, Yoshizawa Nobuhiro, Teshima Takanori, Kubo Keitaro
Department of Life Science, The University of Tokyo, Meguro, Tokyo, Japan.
Sports Medical Department, Nihon Kogakuin College of Hachioji, Hachioji, Tokyo, Japan.
Physiol Rep. 2025 Aug;13(15):e70500. doi: 10.14814/phy2.70500.
The purpose of this study was to investigate the effect of the repeated bout effect induced by eccentric exercises on joint stiffness endurance. Twelve males performed fatigue tasks (5 sets of 50 hopping) three times: first fatigue task on one side (FFT), second fatigue task on the same side 2 weeks after FFT (SFT), and opposite fatigue task on the contralateral side (OFT). Ankle joint stiffness and electromyographic activities of the plantar flexor and tibial anterior muscles during drop jump using only the ankle joint were measured before and after the fatigue task. Active muscle stiffness was calculated according to changes in estimated muscle force and fascicle length during fast stretching after submaximal isometric contractions. After FFT and OFT, joint stiffness and active muscle stiffness significantly decreased, whereas the electromyographic activities of the plantar flexor and tibial anterior muscles during pre-landing, eccentric, and concentric phases did not change. After SFT, joint stiffness decreased slightly, whereas active muscle stiffness did not. Furthermore, the relative changes in joint stiffness and active muscle stiffness were significantly lower in SFT than in FFT and OFT. These results suggest that joint stiffness and active muscle stiffness endurance are significantly enhanced 2 weeks after repeated eccentric exercises produced muscle damage.
本研究的目的是探讨离心运动诱发的重复运动效应（repeated bout effect）对关节僵硬度耐力的影响。12名男性进行了三次疲劳任务（每组50次单脚跳，共5组）：第一次在一侧进行疲劳任务（首次疲劳任务，FFT），在FFT后2周于同一侧进行第二次疲劳任务（同侧疲劳任务，SFT），并在对侧进行相反的疲劳任务（对侧疲劳任务，OFT）。在疲劳任务前后，测量仅使用踝关节进行纵跳时的踝关节僵硬度以及足底屈肌和胫骨前肌的肌电图活动。根据次最大等长收缩后快速拉伸期间估计的肌肉力量和肌纤维长度的变化计算主动肌僵硬度。在FFT和OFT后，关节僵硬度和主动肌僵硬度显著降低，而在着陆前、离心和向心阶段，足底屈肌和胫骨前肌的肌电图活动没有变化。在SFT后，关节僵硬度略有下降，而主动肌僵硬度没有下降。此外，SFT中关节僵硬度和主动肌僵硬度的相对变化显著低于FFT和OFT。这些结果表明，在重复离心运动导致肌肉损伤2周后，关节僵硬度和主动肌僵硬度耐力显著增强。
