The purpose of this work is to investigate the influence of biofeedback, implemented through controlled slow breathing and rhythmic contraction of skeletal muscles at the frequency of baroreflex resonance, on the physiological parameters of the body.

Methods. To achieve this goal, an analysis of breathing signals, heart rate variability (HRV), and photoplethysmography was conducted. Statistical and spectral analyses were employed, as well as the calculation of nonlinear interaction measures such as phase coherence and the total percentage of phase synchronization.

Results. The study showed that slow breathing in the frequency range of baroreflex resonance (around 0.1 Hz) leads to a statistically significant increase in the amplitude of heart rate variability oscillations and the power of sympathetic and parasympathetic regulation processes of heart rhythm. An increase in phase coherence between breathing and heart rate variability was also observed, as well as phase synchronization of the sympathetic regulation circuits of circulation.

Conclusion. A resonant frequency-selective response of the autonomic regulation systems of heart rhythm to slow breathing was identified. The effects observed during slow breathing were significantly more pronounced compared to rhythmic contraction of skeletal muscles at the same frequency, highlighting the differences in the biophysical mechanisms of these methods’ impact on the circulatory
system.