Department of Physical Therapy, Ithaca College, Ithaca, NY 14850, USA; Department of Human Physiology, University of Oregon, Eugene, OR 97403, USA.
Department of Human Physiology, University of Oregon, Eugene, OR 97403, USA; Department of Kinesiology, Iowa State University, Ames, IA 50011, USA.
J Biomech. 2022 Jun;138:111132. doi: 10.1016/j.jbiomech.2022.111132. Epub 2022 May 10.
A repetitive sit-to-stand (STS) task is often used as a fatiguing protocol. Although post-fatigue reductions in muscle strength have been frequently used to indicate fatigue, little is known about changes in body movement during the fatiguing process. This study examined changes in variability of hip-knee and knee-ankle coordination during the STS fatiguing course in 15 young (age: 26.7 ± 5.8 years; 9 females, 6 males) and 15 older adults (age: 69.3 ± 5.7 years; 9 females, 6 males). Participants were asked to perform repetitive STS movements until exhaustion or for 30 min at a self-selected pace. Motion data from 3 consecutive STS cycles were extracted from every minute during the entire fatiguing course and time normalized to STS duration and dummy coded as five stages: 0-20, 20-40, 40-60, 60-80, and 80-100% of the course. Outcome variables were hip-knee and knee-ankle inter-joint coordination variabilities. A 2*5 mixed-effect ANOVA was used to examine changes in variability during different stages of the course in young and older adults. No Age × Time interactions were found in either hip-knee or knee-ankle coordination variability. The hip-knee coordinative variability significantly increased along the STS fatiguing course regardless of age, and the knee-ankle variability from standing to sitting was also higher at the ending, when compared to the beginning, of the fatiguing protocol. The impact of fatigue during repetitive STS protocol is not only limited to a force production decline but also manifested as increased coordinative variability, which could be considered as a fatigue indicator.
一个重复性的坐站（STS）任务通常被用作疲劳协议。尽管肌肉力量在疲劳后会减少，这通常被用来表示疲劳，但对于疲劳过程中身体运动的变化知之甚少。本研究在 15 名年轻（年龄：26.7±5.8 岁；9 名女性，6 名男性）和 15 名老年人（年龄：69.3±5.7 岁；9 名女性，6 名男性）中检查了 STS 疲劳过程中髋关节-膝关节和膝关节-踝关节协调的变异性变化。参与者被要求以自我选择的速度进行重复的 STS 运动，直到疲劳或 30 分钟。在整个疲劳过程中，从每一分钟提取三个连续 STS 周期的运动数据，并将时间归一化为 STS 持续时间并以哑变量编码为五个阶段：0-20%、20-40%、40-60%、60-80%和 80-100%。结果变量为髋关节-膝关节和膝关节-踝关节的关节间协调变异性。使用 2*5 混合效应方差分析来检查年轻和老年人在课程不同阶段变异性的变化。在髋关节-膝关节或膝关节-踝关节协调变异性中，均未发现年龄与时间的交互作用。无论年龄大小，髋关节-膝关节协调变异性在 STS 疲劳过程中均显著增加，并且与疲劳协议开始时相比，站立到坐下时的膝关节-踝关节变异性也更高。在重复 STS 协议期间的疲劳不仅会导致力量产生下降，还会表现为协调变异性增加，这可以被认为是疲劳的一个指标。
