Vázquez Pablo, Hristovski Robert, Balagué Natàlia
Institut Nacional d'Educació Física de Catalunya, Complex Systems in Sport Research Group, Universitat de Barcelona Barcelona, Spain.
Ss. Cyril and Methodius, Faculty of Physical Education, Sport and Health, Complex Systems in Sport Research Group Skopje, Macedonia.
Front Physiol. 2016 Feb 15;7:37. doi: 10.3389/fphys.2016.00037. eCollection 2016.
The aim of this study was to detect qualitative changes in the structure of coordinative variable (elbow angle) fluctuations during a quasi-isometric exercise performed until exhaustion. Seven physical education students performed a quasi-isometric arm-curl exercise holding an Olympic bar (weight: 80% 1RM) with an initial elbow flexion of 90° three times over a period of 4 weeks. They were encouraged to persist, even if the elbow angle was lost, until the fatigue-induced spontaneous termination point (FISTP). Changes in both elbow angles were registered during the task through an electrogoniometer. Detrended Fluctuation Analysis (DFA) was conducted on the initial and final 1024 data points of the series and the associated Hurst exponents were obtained. Multi-way RM ANOVA analyses revealed a significant main effect of the Time on task on the Hurst exponent values but also revealed a significant Trial × Time on task interaction. In the initial (non-fatigue) condition participants tended to produce anti-persistent fBm fluctuations. In the final part before exhaustion a tendency toward persistent fBm was dominant. The trial to trial differences in time-variability structure points to an existence of a long-term variability in control strategies during exercise. The changes in the temporal structure of the elbow angle variability as effort accumulated reflected an increase in low-frequency fluctuations signifying a change in psychobiological mechanisms used to negotiate the task demands. The variability properties of the coordinative variable during exercise may provide information about the dynamic mechanisms that lead to exhaustion.
本研究的目的是检测在进行至疲劳的准等长运动过程中协调变量（肘部角度）波动结构的质性变化。七名体育专业学生在4周的时间内，以90°的初始肘部屈曲角度，手持奥林匹克杠铃（重量：1RM的80%）进行三次准等长臂弯举运动。鼓励他们坚持，即使肘部角度丢失，直到疲劳诱导的自发终止点（FISTP）。在任务过程中，通过电子角度计记录两个肘部角度的变化。对该系列的初始和最后1024个数据点进行去趋势波动分析（DFA），并获得相关的赫斯特指数。多因素重复测量方差分析显示，任务时间对赫斯特指数值有显著的主效应，但也显示出试验×任务时间的显著交互作用。在初始（非疲劳）状态下，参与者倾向于产生反持久的分数布朗运动波动。在疲劳前的最后阶段，持久的分数布朗运动趋势占主导。试验间时间变异性结构的差异表明运动过程中控制策略存在长期变异性。随着努力的积累，肘部角度变异性时间结构的变化反映了低频波动的增加，这表明用于应对任务需求的心理生物学机制发生了变化。运动过程中协调变量的变异性特性可能提供有关导致疲劳的动态机制的信息。
