Rogers Bruce, Giles David, Draper Nick, Hoos Olaf, Gronwald Thomas
College of Medicine, University of Central Florida, Orlando, FL, United States.
Lattice Training Ltd., Chesterfield, United Kingdom.
Front Physiol. 2021 Jan 15;11:596567. doi: 10.3389/fphys.2020.596567. eCollection 2020.
The short-term scaling exponent alpha1 of detrended fluctuation analysis (DFA a1), a nonlinear index of heart rate variability (HRV) based on fractal correlation properties, has been shown to steadily change with increasing exercise intensity. To date, no study has specifically examined using the behavior of this index as a method for defining a low intensity exercise zone. The aim of this report is to compare both oxygen intake (VO) and heart rate (HR) reached at the first ventilatory threshold (VT1), a well-established delimiter of low intensity exercise, to those derived from a predefined DFA a1 transitional value. Gas exchange and HRV data were obtained from 15 participants during an incremental treadmill run. Comparison of both VO and HR reached at VT1 defined by gas exchange (VT1 GAS) was made to those parameters derived from analysis of DFA a1 reaching a value of 0.75 (HRVT). Based on Bland Altman analysis, linear regression, intraclass correlation (ICC) and testing, there was strong agreement between VT1 GAS and HRVT as measured by both HR and VO. Mean VT1 GAS was reached at 39.8 ml/kg/min with a HR of 152 bpm compared to mean HRVT which was reached at 40.1 ml/kg/min with a HR of 154 bpm. Strong linear relationships were seen between test modalities, with Pearson's values of 0.99 ( < 0.001) and.97 ( < 0.001) for VO and HR comparisons, respectively. Intraclass correlation between VT1 GAS and HRVT was 0.99 for VO and 0.96 for HR. In addition, comparison of VT1 GAS and HRVT showed no differences by testing, also supporting the method validity. In conclusion, it appears that reaching a DFA a1 value of 0.75 on an incremental treadmill test is closely associated with crossing the first ventilatory threshold. As training intensity below the first ventilatory threshold is felt to have great importance for endurance sport, utilization of DFA a1 activity may provide guidance for a valid low training zone.
去趋势波动分析（DFA）的短期标度指数α1（DFA a1）是基于分形相关特性的心率变异性（HRV）的非线性指标，已被证明会随着运动强度的增加而稳步变化。迄今为止，尚无研究专门考察将该指标的行为用作定义低强度运动区的方法。本报告的目的是比较在第一通气阈值（VT1）时达到的摄氧量（VO）和心率（HR），VT1是公认的低强度运动界定值，与从预定义的DFA a1过渡值得出的VO和HR进行比较。在递增式跑步机跑步过程中，从15名参与者获取气体交换和HRV数据。将通过气体交换定义的VT1（VT1 GAS）时达到的VO和HR与通过DFA a1分析得出达到0.75值时的参数（HRVT）进行比较。基于布兰德-奥特曼分析、线性回归、组内相关系数（ICC）和检验，在通过HR和VO测量的VT1 GAS和HRVT之间存在高度一致性。达到平均VT1 GAS时的摄氧量为39.8毫升/千克/分钟，心率为152次/分钟，而达到平均HRVT时的摄氧量为40.1毫升/千克/分钟，心率为154次/分钟。在测试方式之间观察到很强的线性关系，VO和HR比较的皮尔逊相关系数值分别为0.99（P<0.001）和0.97（P<0.001）。VT1 GAS和HRVT之间的组内相关系数，VO为0.99，HR为0.96。此外，VT1 GAS和HRVT的比较通过检验未显示出差异，也支持该方法的有效性。总之，在递增式跑步机测试中达到DFA a1值0.75似乎与越过第一通气阈值密切相关。由于低于第一通气阈值的训练强度被认为对耐力运动非常重要，利用DFA a1活动可为有效的低训练区提供指导。
