Effects of a cardiorespiratory synchronization training mobile application on heart rate variability and electroencephalography in healthy adults

Cardiorespiratory synchronization training (CRST) uses diaphragmatic breathing to increase balance in the autonomic nervous system and reduce negative emotions. CRST integrated with high-technology mobile applications affords innovative and convenient home-based training. This study examined the effects of a CRST mobile application on heart rate variability (HRV) and electroencephalography (EEG) parameters in healthy adults. Ninety-six participants were randomly assigned to the CRST, relaxation training (RT; active control group), and control (C) groups. The CRST group received paced breathing training using a wearable device connected to a mobile application and received feedback on the HRV indices. The RT group received muscle relaxation training using a wearable device connected to a mobile application and received feedback on heart rate (HR). The training program was conducted for 1 h per week for 4 weeks. The C group did not receive any wearable device, mobile application, or psychological intervention. Psychological questionnaires on depression and anxiety and physiological measurements of the breathing rates, electrocardiography (ECG), and EEG were measured at the pretest and posttest. The CRST group showed significantly higher HRV indices and lower breathing rates at the posttest than the RT and C groups. There were no significant interaction effects on EEG parameters at pretest and posttest among the three groups. Use of a CRST mobile application increased balance in the autonomic nervous system at the resting state. This clinical evidence-based technologically advanced mobile application could be implemented in future clinical practice.