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The aim of this study is to define absolute and relative reliability of spectral indices of cardiovascular autonomic control in the supine position in women with fibromyalgia syndrome (FMS). Twenty-three women with FMS (age 48 ± 7 years) took part in the study. ECG, finger blood pressure, and respiration were continuously recorded in all participants at rest in baseline 1 (BL1) and after 15 days from BL1 (BL2). The power spectrum analysis provided two oscillatory components: low frequency (LF, 0.04-0.15 Hz) and high frequency (HF, 0.15-0.4 Hz) from the heart period (HP) variability and the LF oscillatory component from SAP variability (LF). Absolute and relative reliability were rated by 95 % of the limit of random variation and intraclass correlation coefficient (ICC), respectively. No significant differences were observed between BL1 and BL2 for the spectral indices of HP and SAP variabilities. The 95 % limit of the random variation of these indices indicated that the values of repeated measurements were between 22 % higher and 0.2 % lower (more reliable parameter; average of HP variability) and 912.9 % higher and 0.2 % lower (less reliable parameter; LF) than BL1. Conversely, the index of relative reliability (ICC) ranged from 0.23 to 0.70 indicating a good reliability. The spectral indices of cardiovascular autonomic control in women with FMS seem to present good relative reliability. Therefore, these indices can be useful as parameters to quantify if a variation was consistent and accurate in the retest besides adding crucial information for clinical research and clinical evaluation of FMS patients. [ABSTRACT FROM AUTHOR]

Objective: The effect of 12 weeks of high-intensity intermittent exercise (HIIE) on cardiac, vascular, and autonomic function of young males was examined. Methods: Thirty-eight young men with a BMI of 28.7 ± 3.1 kg m and age 24.9 ± 4.3 years were randomly assigned to either an HIIE or control group. The exercise group underwent HIIE three times per week, 20 min per session, for 12 weeks. Aerobic power and a range of cardiac, vascular, and autonomic measures were recorded before and after the exercise intervention. Results: The exercise, compared to the control group, recorded a significant reduction in heart rate accompanied by an increase in stroke volume. For the exercise group forearm vasodilatory capacity was significantly enhanced, P < 0.05. Arterial stiffness, determined by pulse wave velocity and augmentation index, was also significantly improved, after the 12-week intervention. For the exercise group, heart period variability (low- and high-frequency power) and baroreceptor sensitivity were significantly increased. Conclusion: High-intensity intermittent exercise induced significant cardiac, vascular, and autonomic improvements after 12 weeks of training. [ABSTRACT FROM AUTHOR]

The paper focuses on the most important application problems commonly encountered in spectral analysis of short-term (less than 10 min) recordings of cardiovascular variability signals (CVSs), critically analysing the different approaches to these problems presented in the literature and suggesting practical solutions based on sound theoretical and empirical considerations. The Blackman-Tukey (BT) and Burg methods have been selected as the most representative of classical and AR spectral estimators, respectively. For realistic simulations, 'synthetic' CVSs are generated as AR processes whose parameters are estimated on corresponding time series of normal, post-myocardial infarction and congestive heart failure subjects. The problem of resolution of spectral estimates is addressed, and an empirical method is proposed for model order selection in AR estimation. The issue of the understandability and interpretability of spectral shapes is discussed. The problem of non-stationarity and removing trends is dealt with. The important issue of identification and estimation of spectral components is discussed, and the main advantages and drawbacks of spectral decomposition algorithms are critically evaluated. [ABSTRACT FROM AUTHOR]