Effects of Autonomic Nervous System Modulation by Heart Rate Variability Biofeedback Training With Resonant Frequency Breathing on Glucose Metabolism in Individuals With Prediabetes

During training, a ball that expands (breathe in) and shrinks (breathe out) on the screen specified the breathing frequency goal to a value of six cycles per minute (five seconds inspiration, five seconds expiration). The HRV was visualized by new symbols varying in color depending on the respectively measured values, which appeared every ten seconds. When the participants achieved the specified breathing frequency, resulting in an increased sinus arrhythmia, the symbols appearing on the smartphone display were green. When the participants did not achieve the specified breathing frequency, the symbols appeared in yellow (non-significant deviation), orange (significant deviation), or red (very significant deviation). The participants were instructed to adjust their breathing frequency to reach emergence of as many green symbols as possible for the entire training session.

The mobile system eSense Pulse from Mindfield Biosystems is used for the digital anti-stress program. To do this, the participants put on a chest strap with a sensor and can start training via the eSense app. The anti-stress program is carried out using a procedure generated for the study. During the anti-stress program units, the participants receive application-related information and tips to better understand the topic of stress, identify stressors in their own lives and reduce stress. The active control intervention of the anti-stress program was selected to investigate the effect of a specific stress level reduction without the direct modulation of physiological mechanisms of action as with HRV-BF-RFA.