Fractal correlations and linear analyses of heart rate variability in healthy young people with different levels of physical activity

Abstract

Changes in cardiac autonomic regulation, expressed by increased sympathetic activity and decreased heart rate variability, have an important relationship with the onset of lethal cardiac phenomena. Therefore, we aimed to evaluate the cardiac autonomic behaviour in young people according to their level of physical activity. Through the International Physical Activity Questionnaire, 55 healthy young non-smokers with no history of previous diseases and whose parents did not suffer from metabolic syndrome were assessed and divided into groups: sedentary (n=12), insufficiently active (n=16), active (n=14), and very active (n=13). We collected respiratory rate, systolic and diastolic blood pressure at rest, and body mass index. Subjects remained supine at rest, and without mental stress for 15 minutes in a controlled environment. Using a cardiofrequency meter (Polar® RS800CX), data were analysed in the time domain, frequency domain, and detrended fluctuation analysis. For the sedentary group, the mean RR and rMSSD were significantly lower, and the insufficiently active group showed higher means, but significantly only for rMSSD. The insufficiently active group showed in the detrended fluctuation analysis that α2 was significantly lower compared with the sedentary, active, and very active groups. We conclude that young, healthy, sedentary individuals present an increased heart rate and that insufficiently active individuals present a decreased fractal correlation and increased parasympathetic activity.

Non-linear analysis of heart rate variability for evaluating the acute effects of caffeinated beverages in young adults

“…Heart rate variability analysis is a mostly preferred method since it divulges information about the influence of the autonomic nervous system activity on the heart and it is a reliable, informative, and applicable tool in daily practice. 16 The most important step is the extraction of the features containing all the relevant information about the system dynamics. 32 Time-domain, frequencydomain, and non-linear methods are generally used for this procedure.…”

“…Furthermore, we investigated the detrended fluctuation analysis parameters which quantify the absence or presence of fractal correlation properties in RR intervals. 16 In many studies, detrended fluctuation analysis parameters were investigated and the researchers suggested this analysis as an ideal way to have more accurate information about the complexity of heart rate variability. 16,25 However, there are very few studies related to the non-linear analysis of heart rate variability signals after caffeine consumption.…”

“…16 In many studies, detrended fluctuation analysis parameters were investigated and the researchers suggested this analysis as an ideal way to have more accurate information about the complexity of heart rate variability. 16,25 However, there are very few studies related to the non-linear analysis of heart rate variability signals after caffeine consumption. Papaioannou et al 15 reported a significant increase in long-term scaling exponent α after caffeine ingestion, while the placebo induced no significant change.…”

“…28 For healthy subjects, α1 tends to 1 (unity) and is bigger than α2 value. 16 In this study, heart rate variability time series was analysed by detrended fluctuation analysis. Both short-term (α1) and longterm (α2) exponents were calculated in order to have detailed information about the fractal characters of the system.…”

“…14 In the literature, there are some studies which investigated heart rate variability time series with detrended fluctuation analysis and reported the accuracy of the method. 15,16 To our knowledge, there are no reports in the literature on non-linear analysis of heart rate variability used to investigate the acute effects of caffeinated beverages on cardiovascular system. For this reason, our study will be the first for this subject in the literature.…”