Aragón Institute of Engineering Research, IIS Aragón, Spain.
IEEE Trans Biomed Eng. 2013 Jul;60(7):1796-805. doi: 10.1109/TBME.2013.2242328. Epub 2013 Jan 23.
The analysis and interpretation of heart rate variability (HRV) during exercise is challenging not only because of the nonstationary nature of exercise, the time-varying mean heart rate, and the fact that respiratory frequency exceeds 0.4 Hz, but there are also other factors, such as the component centered at the pedaling frequency observed in maximal cycling tests, which may confuse the interpretation of HRV analysis. The objectives of this study are to test the hypothesis that a component centered at the running stride frequency (SF) appears in the HRV of subjects during maximal treadmill exercise testing, and to study its influence in the interpretation of the low-frequency (LF) and high-frequency (HF) components of HRV during exercise. The HRV of 23 subjects during maximal treadmill exercise testing is analyzed. The instantaneous power of different HRV components is computed from the smoothed pseudo-Wigner-Ville distribution of the modulating signal assumed to carry information from the autonomic nervous system, which is estimated based on the time-varying integral pulse frequency modulation model. Besides the LF and HF components, the appearance is revealed of a component centered at the running SF as well as its aliases. The power associated with the SF component and its aliases represents 22±7% (median±median absolute deviation) of the total HRV power in all the subjects. Normalized LF power decreases as the exercise intensity increases, while normalized HF power increases. The power associated with the SF does not change significantly with exercise intensity. Consideration of the running SF component and its aliases is very important in HRV analysis since stride frequency aliases may overlap with LF and HF components.
分析和解释运动期间的心率变异性（HRV）不仅具有挑战性，因为运动的非平稳性质、时变的平均心率以及呼吸频率超过 0.4 Hz 的事实，而且还有其他因素，例如在最大循环测试中观察到的以蹬踏频率为中心的分量，这可能会混淆 HRV 分析的解释。本研究的目的是检验一个假设，即在最大跑步机运动测试中，受试者的 HRV 中出现一个以跑步步频（SF）为中心的分量，并研究其对运动中 HRV 的低频（LF）和高频（HF）分量的解释的影响。分析了 23 名受试者在最大跑步机运动测试中的 HRV。不同 HRV 分量的瞬时功率是从调制信号的平滑伪魏格纳-维尔分布中计算出来的，假设该调制信号携带来自自主神经系统的信息，该信息是基于时变积分脉冲频率调制模型估计的。除了 LF 和 HF 分量外，还揭示了一个以跑步 SF 为中心的分量及其别名的出现。与 SF 分量及其别名相关的功率代表所有受试者总 HRV 功率的 22±7%（中位数±中位数绝对偏差）。随着运动强度的增加，归一化 LF 功率减小，而归一化 HF 功率增加。与 SF 相关的功率随运动强度的变化没有显著变化。考虑到跑步 SF 分量及其别名在 HRV 分析中非常重要，因为步频别名可能与 LF 和 HF 分量重叠。
