Montull Lluc, Balagué Natàlia, Petelczyc Monika, Marszalek Karol, Vázquez Pablo
Complex Systems in Sport Research Group, National Institute of Physical Education of Catalonia (INEFC), University of Lleida, La Seu d'Urgell, Spain.
Complex Systems in Sport Research Group, National Institute of Physical Education of Catalonia (INEFC), University of Barcelona, Barcelona, Spain.
Eur J Appl Physiol. 2025 Jul 21. doi: 10.1007/s00421-025-05871-6.
The time-variability of physiological and kinematic variables, extracted at mesoscopic and macroscopic levels, respectively, has shown potential in detecting changes in exercise workload and associated fatigue effects. However, the sensitivity of microscopic variables -such as muscle oxygen saturation, which reflect the dynamics of muscle metabolism-remains unexplored. This study aimed to compare the time-variability structure of the tissular saturation index (TSI) during a graded maximal exercise performed until exhaustion. Nineteen participants started running at 8 km/h with the speed increasing by 1 km/h every 100 s until they could not keep the prescribed velocity. The time-variability of TSI, recorded from the quadriceps, was analyzed using Detrended fluctuation analysis (DFA) and Sample entropy (SampEn) over the first and last 2048 recorded data points (corresponding to 204 s each). Wilcoxon test and Cohen's d were used to compare the initial and final parts of the test. Results revealed a significant decrease in the Hurst (H) exponent (from H = 0.84 ± 0.21 to H = 0.49 ± 0.10; p < 0.01; d = -1.57) and a corresponding increase in SampEn (from 1.12 ± 0.20 to 1.40 ± 0.13; p < 0.01; d = 1.17). These findings indicate a shift towards uncorrelated white-noise as exhaustion approached, suggesting reduced efficacy of oxygen transportation with increasing workloads. The time-variability of muscle oxygen saturation appears to be a) a promising measure for assessing exercise intensity, and b) allow the study of physiological network interactions extracted from different levels (from microscopic to macroscopic).
分别在介观和宏观水平提取的生理和运动学变量的时间变异性，已显示出在检测运动负荷变化及相关疲劳效应方面的潜力。然而，微观变量的敏感性——如反映肌肉代谢动态的肌肉氧饱和度——仍未得到探索。本研究旨在比较直至力竭的分级最大运动过程中组织饱和度指数（TSI）的时间变异性结构。19名参与者以8公里/小时的速度开始跑步，每100秒速度增加1公里/小时，直至无法维持规定速度。使用去趋势波动分析（DFA）和样本熵（SampEn）对记录的股四头肌TSI的时间变异性进行分析，分析前2048个记录数据点（每个对应204秒）和后2048个记录数据点。采用威尔科克森检验和科恩d值来比较测试的初始部分和最终部分。结果显示赫斯特（H）指数显著下降（从H = 0.84 ± 0.21降至H = 0.49 ± 0.10；p < 0.01；d = -1.57），样本熵相应增加（从1.12 ± 0.20增至1.40 ± 0.13；p < 0.01；d = 1.17）。这些发现表明随着力竭临近，向不相关白噪声转变，提示随着工作量增加氧运输效率降低。肌肉氧饱和度的时间变异性似乎a）是评估运动强度的一个有前景的指标，b）允许研究从不同水平（从微观到宏观）提取的生理网络相互作用。
