ECG response to submaximal exercise from the perspective of Golden Ratio harmonic rhythm

Abstract

Abstract Background The Golden Ratio (GR), derived from the Fibonacci sequences, has multiple representations in nature, as expressions of the repetition of specific geometric shapes called fractals. Methods The aim of the study focused on investigation of the cardiovascular homeostasis, at rest and during effort testing, with determination of the validity of the GR at the level of variables extracted from serial ECG. We used a group of 230 young subjects (average age 19.21 ± 1.87), each subject performing a 6 min submaximal exercise ergometer test (Astrand & Rhyming Protocol). We were interested in estimate the ratio between the electrical diastole and electrical systole (TQ/QT) and between the cardiac cycle and electrical diastole (RR/TQ), which has been much discussed as being related to GR value. Results We proposed using a new synthetic fractal indicator (SFI), with dynamic nonlinear evolution and we determined the intervals of acceptability for SFI. The mean values of the SFI of our subjects were significantly close to GR value, aspect that suggests the presence of harmonic rhythm, under different conditions of existence and adaptation of the human organism (rest and submaximal effort). The SFI and the heart rate values had very strong correlations, at rest (R = 0.88, p Conclusions Our results show a fractal dimension of the ECG interval dynamics for the study group. The proposed SFI imposes itself as a relatively simple parameter for assessing heart’s electrical functionality during cardiac cycle that can be applied both at rest and exercise.