School of Sport, Exercise and Health Sciences, Loughborough University, Leicestershire, UNITED KINGDOM.
English Institute of Sport, EIS Performance Centre, Loughborough University, Loughborough, UNITED KINGDOM.
Med Sci Sports Exerc. 2021 Oct 1;53(10):2119-2130. doi: 10.1249/MSS.0000000000002695.
This study aimed to investigate the changes in lower limb kinematics, kinetics, and muscle activation during a high-intensity run to fatigue (HIRF).
Eighteen male and female competitive middle-distance runners performed a HIRF on an instrumented treadmill at a constant but unsustainable middle-distance speed (~3 min) based on a preceding maximum oxygen uptake (V˙O2max) test. Three-dimensional kinematics and kinetics were collected and compared between the start, 33%, 67%, and the end of the HIRF. In addition, the activation of eight lower limb muscles of each leg was measured with surface EMG (sEMG).
Time to exhaustion was 181 ± 42 s. By the end of the HIRF (i.e., vs the start), ground contact time increased (+4.0%), whereas flight time (-3.2%), peak vertical ground reaction force (-6.1%), and vertical impulse (-4.1%) decreased (all P < 0.05), and joint angles at initial contact became more (dorsi)flexed (ankle, +1.9°; knee, +2.1°; hip, +3.6°; all P < 0.05). During stance, by the end of the HIRF: peak ankle plantarflexion moment decreased by 0.4 N·m·kg-1 (-9.0%), whereas peak knee extension moment increased by 0.24 N·m·kg-1 (+10.3%); similarly, positive ankle plantarflexion work decreased by 0.19 J·kg-1 (-13.9%), whereas positive knee extension work increased by 0.09 J·kg-1 (+33.3%; both P < 0.05) with no change in positive hip extension work. Hip extensor surface EMG amplitude increased during the late swing phase (+20.9-37.3%; P < 0.05).
Running at a constant middle-distance pace led primarily to the fatigue of the plantarflexors with a compensatory increase in positive work done at the knee. Improving the fatigue resistance of the plantarflexors might be beneficial for middle-distance running performance.
本研究旨在探讨高强度跑步至疲劳（HIRF）过程中下肢运动学、动力学和肌肉激活的变化。
18 名男性和女性竞技中长跑运动员在仪器化跑步机上进行 HIRF，跑步机的速度基于先前的最大摄氧量（V˙O2max）测试，为恒定但不可持续的中长跑速度（约 3 分钟）。在 HIRF 的开始、33%、67%和结束时，比较了三维运动学和动力学。此外，还使用表面肌电图（sEMG）测量了每条腿的 8 块下肢肌肉的激活情况。
疲劳时间为 181±42 秒。在 HIRF 结束时（即与开始时相比），地面接触时间增加（+4.0%），而飞行时间（-3.2%）、峰值垂直地面反作用力（-6.1%）和垂直冲量（-4.1%）下降（均 P<0.05），初始接触时的关节角度变得更（背屈）（踝关节，+1.9°；膝关节，+2.1°；髋关节，+3.6°；均 P<0.05）。在支撑阶段，HIRF 结束时：踝关节跖屈力矩峰值下降 0.4 N·m·kg-1（-9.0%），而膝关节伸肌力矩峰值增加 0.24 N·m·kg-1（+10.3%）；同样，踝关节跖屈正功下降 0.19 J·kg-1（-13.9%），而膝关节伸肌正功增加 0.09 J·kg-1（+33.3%；均 P<0.05），髋关节伸肌正功无变化。在后期摆动阶段，髋关节伸肌表面肌电振幅增加（+20.9-37.3%；P<0.05）。
以恒定的中距离速度跑步主要导致跖屈肌疲劳，膝关节正功增加以代偿。提高跖屈肌的抗疲劳能力可能对中长跑表现有益。
