Evaluation of Heart Rate Variability and Application of Heart Rate Variability Biofeedback: Toward Further Research on Slow-Paced Abdominal Breathing in Zen Meditation.

This review summarizes my own involvement in heart rate variability (HRV) and HRV biofeedback studies, as a tribute to the late Dr. Evgeny Vaschillo. I first review psychophysiological studies on behavioral stress and relaxation performed in my laboratory using an assessment of cardiac parasympathetic activity. Although magnitude of high-frequency (HF) component of HRV corresponding respiratory sinus arrhythmia (RSA) is widely used as an index of cardiac parasympathetic function, a respiratory confound during stress or relaxation may have interfered with the proper assessment of the HF HRV. An enhanced method under frequency-controlled respiration at 0.25 Hz provided a reliable assessment of cardiac parasympathetic activity. I then review findings from HRV biofeedback research in my laboratory. Based on the hypothesis that RSA measured as an HF component of HRV represents cardiorespiratory resting function, it was demonstrated that HRV biofeedback before sleep enhanced the magnitude of HF HRV during sleep, a cardiorespiratory resting function. Moreover, by focusing on the spectral peak of the low-frequency (LF) component of HRV, paced breathing at the LF-peak frequency was shown to increase baroreflex sensitivity. Finally, I describe the potential of slow-paced abdominal breathing (i.e., Tanden breathing) performed in Zen meditation. The concept of Tanden breathing as described in a regimen from early modern Japan is introduced, and recent research findings on slow-paced abdominal breathing are summarized. Future research directions of slow-paced abdominal breathing are also discussed.

History and Recent Advances of the Japanese Society of Biofeedback Research.

This article provides an overview of the history of the Japanese Society of Biofeedback Research (JSBR) and presents some of its recent advances. Most of the research papers published in the JSBR journal (Biofeedback Kenkyu) have been written in Japanese, and therefore have had very few opportunities to reach global readers. We would like to present some of important findings previously published there. First, we present the history of the JSBR. Secondly, we will focus on paced breathing, which is instrumental in achieving relaxation in heart rate variability biofeedback (HRV-BF). We will look back on the origin of slow-paced breathing in Japan, that could be attributed to the concept of Tanden breathing (abdominal paced breathing) practiced in Zen meditation. Thirdly, we will introduce some of the current research progresses of JSBR, especially focusing on the development of a non-contact sensing technology and relaxation device. Finally, we will explain about a very recent trial, the "Suu-Haa" Relaxation Technique, which we hope may be useful for helping people cope with the SARS-CoV-2 (COVID-19) crisis.

Efficacy of Paced Breathing at the Low-frequency Peak on Heart Rate Variability and Baroreflex Sensitivity.

We developed a simple method for identifying resonance frequency by focusing on the spectral peak of the low-frequency (LF) component of heart rate variability (HRV) and examined the hypothesis that paced breathing at an accurate resonance frequency increases HRV and baroreflex sensitivity (BRS). We assessed a peak frequency of the LF component of the resting HRV by using power spectral analysis under respiratory control at 0.25 Hz, and a resonance frequency, which was evaluated by using the standard breathing maneuver (Lehrer 2007). We examined the effects of paced breathing at the peak frequency of the LF component (Spectral condition) and paced breathing at the resonance frequency as determined by the standard breathing maneuver (Standard condition) on HRV and BRS in 28 healthy college students and young adults. Electrocardiogram, respiration, and noninvasive continuous blood pressure was recorded during a 5-min baseline, followed by a 5-min paced breathing session. Results indicated that the BRS increased during the breathing session under both conditions, but the increase in BRS under the Spectral condition was higher than the Standard condition (p < .05). The LF amplitude increased during the breathing session under both conditions (p < .001), although the difference between the conditions was not significant. These results suggest that paced breathing at the peak frequency of the LF component enhanced the autonomic baroreflex function. Moreover, assessment of the LF-peak may provide more accurate information on resonance frequency for paced breathing during HRV biofeedback.

[Development of a short-form self-report measure to assess relaxation effects].

The present study aimed to develop a short-form self-report measure to assess relaxation effects (S-MARE). Participants (N = 190) responded to a questionnaire comprised of 45 items assessing relaxation and non-relaxation based on the Relaxation Inventory (Crist et al., 1989). Exploratory factor analysis identified three factors: physiological tension, psychological relaxation, and anxiety. Each factor was related to 5 items and each had an acceptable Cronbach's coefficient (alpha = .93, .94, and .85). S-MARE scores pre- and post- relaxation instruction were significantly correlated with the Emotional Relaxation Scale (Tokuda, 2011) (r = .446) and with State Anxiety (r = -.531) (N = 172). There was a significant correlation between the amplitude of the high frequency component of heart rate variability during relaxation instruction and physiological tension scores on the S-MARE (r = .456-.474, N = 24). These results confirmed the reliability and validity of the S-MARE in terms of physiological correlation with cardiac parasympathetic tone, suggesting that the S-MARE is a valid measure of relaxation effects.

Heart rate variability biofeedback improves cardiorespiratory resting function during sleep.

The present study was designed to examine the effect of heart rate variability (HRV) biofeedback on the cardiorespiratory resting function during sleep in daily life. Forty-five healthy young adults were randomly assigned to one of three groups: HRV biofeedback, Autogenic Training(AT), and no-treatment control. Participants in the HRV biofeedback were instructed to use a handheld HRV biofeedback device before their habitual bedtime, those in the AT were asked to listen to an audiotaped instruction before bedtime,and those in the control were asked to engage in their habitual activity before bedtime. Pulse wave signal during sleep at their own residences was measured continuously with a wrist watch-type transdermal photoelectric sensor for three time points. Baseline data were collected on the first night of measurements, followed by two successive nights for HRV biofeedback, AT, or control. Cardiorespiratory resting function was assessed quantitatively as the amplitude of high frequency(HF) component of pulse rate variability, a surrogate measure of respiratory sinus arrhythmia. HF component increased during sleep in the HRV biofeedback group,although it remained unchanged in the AT and control groups. These results suggest that HRV biofeedback before sleep may improve cardiorespiratory resting function during sleep.

Effect of negatively valenced words on deviant P3 during the three-stimulus oddball paradigm.

Attentional bias (sensitization) for negative information was estimated using event-related brain potentials (ERP). We used a three-stimulus visual oddball paradigm that comprised a small diamond standard stimulus (66.7%), a large diamond target stimulus (16.7%), and deviant word stimuli (16.7%) written in Kanji. Furthermore, half the deviant words were negative emotional words (e.g., destruction or scream) and the others half were neutral words (e.g., structure or range). Healthy participants (N = 26) were instructed to press a button after the target appeared while ignoring the other stimuli. EEG was recorded from Fz, Cz, and Pz sites and the average of EEG that time-locked to the onset of stimuli was calculated. Results indicated that the P3 amplitude for the target at Pz was the largest among the three sites, whereas the P3 amplitude for deviant words at Cz and Pz was larger than those at Fz. Furthermore, the P3 amplitudes for negative words increased in comparison to those for neutral words. These results suggest that increased amplitudes to word stimuli are regarded as deviant P3, and changes reflect passive attentional capture elicited by negative emotional information. Implications for using ERPs for estimating attentional bias to threat information are discussed.

Impact of real-world stress on cardiorespiratory resting function during sleep in daily life.

To examine if real-world stress affects the restorative function of sleep in daily life, we studied the impact of college examinations on cardiorespiratory resting function during sleep. In healthy college students, at 1 week before, the day before, and the first day of semester-end examinations pulse wave signal during sleep at their own residences was measured continuously with a wristband-shaped wireless transdermal photoelectric sensor. The cardiorespiratory resting function was assessed quantitatively as the power of a high-frequency component of pulse rate variability, a surrogate measure of respiratory sinus arrhythmia. Changes in anxiety were also evaluated with a state anxiety questionnaire. On the day before the examinations, compared with 1 week before, the score of state anxiety increased and the HF component of pulse rate variability decreased. Among college students, anxiety about college examinations may be accompanied by suppression of the cardiorespiratory resting function during sleep.