2025 Volume 52 Issue 2 Pages 43-50
To improve the efficiency of individualized resonance frequency search for heart rate variability biofeedback (HRV-BF), we focused on the phase match between respiratory and heart rate waveforms. The resonance frequencies of 32 male experimental participants were determined using BREASSIST® (made by TOYOBO Co., Ltd.), an application that adjusts the time gap between the peak of successive heart rate changes and the peak of the respiratory waveform by simultaneously measuring heart rate and respiratory sensors. The results showed that the average determining time was 3 minutes 20 seconds, with the shortest taking 2 minutes 28 seconds and the longest 5 minutes 40 seconds. The average resonance frequency for each search time was 6.3 times a minute (0.105 Hz), with a mode and median of 6.5 times a minute. Resonance frequencies ranged from 5.0 to 7.5 times a minute, which tended to be slightly faster than the known resonance frequency range of 4.5 to 7.0 times a minute. Analysis of HRV-BF training conducted at the determined resonance frequencies (n＝30) showed a significant increase (p＜0.001) in RMSSD, which represents parasympathetic activity during paced breathing, compared to resting breathing, statistically confirming the increase in parasympathetic activity, and suggested that paced breathing with resonance frequency reduces mental stress. In addition, SDNN, which represents autonomic nervous activity, was significantly higher after the HRV-BF training than before the training, and the mean heart rate was also significantly lower in the same comparison. From the above results, it was found that the method of adjusting the time gap between the peak of heart rate change and the peak of respiratory waveform at the paced breathing by simultaneous measurement of the heart rate sensor and the respiratory sensor could efficiently determine the resonance frequency, and this method was comparable to the effects of conventional HRV-BF.
