Analysis of tachograms from subjects on stress test, a multifractal approach.

The multifractal spectra analysis of time series has been used for several applications, for example, in tachograms, that are the graph of the time intervals between heartbeats throughout a monitoring, there are differences between the complexity of the tachograms of healthy and young subjects and the tachograms of elderly or subjects with heart disease. Recent research has shown that parameters of the multifractal spectrum of tachograms, such as width (degree of multifractality) and curvature of the spectrum around the maximum, could be used to classify the health status of a subject. On the other hand, tachograms obtained from stress test subjects decrease in complexity compared to those obtained at rest, and this can also be characterized with multifractal analysis. In this work, we created a database of 131 electrocardiographic signal recordings and tachograms of subjects at rest for one hour and in a stress test for 30 minutes, and we performed the analysis of the aforementioned multifractal spectrum parameters. The results of the multifractality analysis confirmed that the complexity in the tachograms of the stress tests decreases significantly with respect to the series at rest, especially in the series of subjects who reported a sedentary lifestyle. Therefore, these parameters could be useful to classify the physical condition of a subject. [ABSTRACT FROM AUTHOR]