Psychophysiological effects of slow-paced breathing at six cycles per minute with or without heart rate variability biofeedback

Exploring autonomic dysfunction in functional dysphonia: A protocol for a case-control study and a randomized controlled trial

BACKGROUND

Although psychological factors have been implicated in patients with functional dysphonia (FD), conventional voice therapy (CVT) typically targets the aberrant voice symptoms exclusively. Yet, CVT is not always successful, and in view of the significant adverse quality of life impact combined with the financial burden on the healthcare system and society, research is needed to elucidate the underlying psychophysiology of FD and improve treatment outcomes.

OBJECTIVES

The first objective of this research project is to compare the occurrence and frequency of symptoms and/or disorders related to autonomic nervous system (ANS) dysfunction in patients with FD with gender- and age-matched vocally healthy controls, using a case-control study. The second objective is to compare the effects of a novel therapy for FD based on ANS regulation (i.e., ANS therapy: heart rate variability (HRV) biofeedback) on both autonomic function and voice function versus CVT alone or in combination with ANS therapy (i.e., ANS therapy + CVT), using a randomized controlled trial (RCT).

METHODS

Case-control study: Autonomic (dys)function of patients with FD will be compared with gender- and age-matched vocally healthy controls, using both physiological measures (e.g., HRV, skin conductance level) and psychological patient-reported outcome measures (PROMs, e.g., Neuroception of Psychological Safety Scale, Depression Anxiety and Stress Scale). RCT: The FD group will be randomly assigned to the innovative ANS therapy group, the CVT group or the ANS therapy + CVT group. All patients received 1 month of treatment with 20 min of daily practice. Both the autonomic assessment and the voice assessment will be performed pretherapy and immediately after therapy by assessors blinded to group allocation and study phase.

EXPECTED RESULTS

Higher occurrences of symptoms and/or disorders related to autonomic dysfunction are expected in patients with FD compared with vocally healthy controls. Physiological outcomes: lower HRV, lower cardiac pre-ejection period, higher respiration rate and higher skin conductance level are hypothesized in patients with FD compared with vocally healthy controls. Psychological PROMs: higher self-report of feelings/symptoms related to autonomic dysfunction (e.g., perceived stress, anxiety) is expected in patients with FD compared with vocally healthy controls. The autonomic function is hypothesized to improve more after the ANS therapy and the ANS therapy + CVT compared with the CVT only. Voice function is expected to improve more after the ANS therapy + CVT compared with the ANS therapy and the CVT alone.

WHAT THIS PAPER ADDS

What is already known on the subject Autonomic dysfunction is well recognized in the field of psychology but remains understudied in the area of voice. Given that the vagus nerve, innervating the larynx, also helps to regulate the ANS, and psychological symptoms commonly observed in patients with FD may reflect ANS dysregulation, research in this area is needed. There is some preliminary evidence that autonomic dysfunction might indeed be associated with FD. However, physiological ANS measures are needed, as well as validated psychological PROMs. What this paper adds to the existing knowledge The first objective of this study is to investigate the occurrence and frequency of symptoms and/or disorders related to autonomic dysfunction in patients with FD as compared with a gender- and age-matched vocally healthy control group. Autonomic (dys)function will be determined by employing both physiological measures (e.g., HRV, skin conductance level) and psychological PROMs (e.g., Neuroception of Psychological Safety Scale, Depression Anxiety and Stress Scale). The second objective is to compare the effects of a novel therapy for FD based on ANS regulation (HRV biofeedback) versus CVT alone or in combination with ANS therapy. What are the potential or actual clinical implications of this work? Success rates of symptomatic CVT for FD are highly variable. This study is expected to lead to innovative results related to the pathogenesis and psychophysiology of FD, a prevalent voice disorder associated with a significant adverse quality of life impact and a substantial financial burden on the healthcare system and society. The results of this study will lead to crucial new insights into both the diagnosis and treatment of FD, contributing to evidence-based practice in the field of voice.

Do Longer Exhalations Increase HRV During Slow-Paced Breathing?

Slow-paced breathing at an individual's resonance frequency (RF) is a common element of heart rate variability (HRV) biofeedback training (Laborde et al. in Psychophysiology 59:e13952, 2022). Although there is strong empirical support for teaching clients to slow their respiration rate (RR) to the adult RF range between 4.5 and 6.5 bpm (Lehrer & Gevirtz, 2014), there have been no definitive findings regarding the best inhalation-to-exhalation (IE) ratio to increase HRV when breathing within this range. Three methodological challenges have frustrated previous studies: ensuring participants breathed at the target RR, IE ratio, and the same RR during each IE ratio. The reviewed studies disagreed regarding the effect of IE ratios. Three studies found no IE ratio effect (Cappo & Holmes in J Psychosom Res 28:265-273, 1984; Edmonds et al. in Biofeedback 37:141-146, 2009; Klintworth et al. in Physiol Meas 33:1717-1731, 2012). One reported an advantage for equal inhalations and exhalations (Lin et al. in Int J Psychophysiol 91:206?211, 2014). Four studies observed an advantage for longer exhalations than inhalations (Bae et al. in Psychophysiology 58:e13905, 2021; Laborde et al. in Sustainability 13:7775, 2021; Strauss-Blasche et al. in Clin Exp Pharmacol Physiol 27:601?60, 2000; Van Diest et al. in Appl Psychophysiol Biofeedback 39:171?180, 2014). One study reported an advantage for longer inhalations than exhalations (Paprika et al. in Acta Physiol Hung 101:273?281, 2014). We conducted original (N = 26) and replication (N = 16) studies to determine whether a 1:2 IE ratio produces different HRV time-domain, frequency-domain, or nonlinear metrics than a 1:1 ratio when breathing at 6 bpm. Our original study found that IE ratio did not affect HRV time- and frequency-domain metrics. The replication study confirmed these results and found no effect on HRV nonlinear measurements.

Heart Rate Variability Biofeedback as a Treatment for Military PTSD: A Meta-Analysis

INTRODUCTION

Emerging research has provided tentative support for the use of heart rate variability biofeedback (HRVB) as a treatment for several psychological disorders, with meta-analyses providing compelling evidence for HRVB as a promising treatment for anxiety, depression, and PTSD. Given the prevalence of PTSD in military veterans and the comparatively lower benefit and higher attrition rate of traditional psychological treatment for PTSD relative to civilian counterparts, it is important to examine complementary and alternative treatment approaches such as HRVB in this population. Although studies of HRVB for PTSD have been conducted with military veterans, they have involved relatively small sample sizes, limiting interpretation. To address this, the current article presents a comprehensive meta-analysis, consolidating existing literature to more accurately evaluate the efficacy of HRVB in reducing PTSD symptoms within military populations.

MATERIALS AND METHODS

This meta-analysis was conducted according to Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines, and our protocol was registered with PROSPERO to increase review transparency. A literature search of HRVB interventions was conducted using PubMed, PsycINFO, Military Database, PTSDPubs, and EBSCO's Psychological and Behavioral Sciences Collection.

RESULTS

Five studies met eligibility criteria, providing a combined sample size of 95 military services members. For all studies, effect sizes were negative, indicating a reduction in PTSD symptoms. Effect sizes ranged from -1.614 to -0.414, resulting in an overall moderate to large mean effect for HRVB (Hedges's g = -0.557; 95% confidence interval = -0.818 to -0.296; P < .001). Additionally, cumulative attrition was 5.8%, significantly lower than commonly reported rates for evidence-based treatments (16%-36%).

CONCLUSIONS

The present study is the first meta-analysis to examine HRVB as a treatment for military service members with PTSD. Results indicate that HRVB may be a viable treatment approach to reduce PTSD symptomatology. Low attrition rates, ease of accessibility, and favorable participant outlook serve as additional benefits for the use of HRVB.

Pilot randomized controlled trial of biofeedback on reducing psychological and physiological stress among persons experiencing homelessness

People experiencing homelessness report increased exposure to traumatic life events and higher rates of depression, anxiety, and post-traumatic stress disorder as compared with the general population. Heart rate variability-biofeedback (HRV-BF) has been shown to decrease symptoms of stress, anxiety, depression, and PTSD. However, HRV-BF has not been tested with the most vulnerable of populations, homeless adults. The purpose of this randomized controlled trial was to compare the effectiveness of an HRV-BF intervention versus a Health Promotion (HP) active control intervention focused on improving mental health symptoms among homeless adults. Guided by a community advisory board, homeless adults residing in Skid Row, Los Angeles (n = 40) were randomized to either the HRV-BF or an active HP control group and received eight weekly, 30-min sessions over two months, delivered by a nurse-led community health worker team. Dependent variables of HRV, mental health, anxiety, depression, and PTSD were measured at baseline, the 8-week session, and/or 2-month follow-up. All intervention sessions were completed by 90% (36/40) of participants. Both the HRV-BF and HP interventions showed significant increases in HRV from baseline to 2-month follow-up, with no significant difference between the intervention groups. The HRV-BF programme revealed a somewhat greater, although non-significant, improvement in anxiety, depression, and PTSD symptoms than the HP programme. The usefulness of both interventions, focused on emotional and physical health, warrants future studies to examine the value of a combined HRV-BF and HP intervention.

Mindfulness and time perception: A systematic integrative review

Several recent studies have explored the relationships between mindfulness and time perception, an area of research that has become increasingly popular in the last 10-15 years. In this article, we present a systematic integrative review of the evidence on this subject. We also integrate the field's findings into a conceptual framework which considers the multifaceted nature of both mindfulness, and time perception research. To identify the relevant literature, we searched the following databases using relevant keywords: PsycINFO; Medline; EBSCO Host Psychology and Behavioral Sciences Collection; and Web of Science. These searches were last performed on the 4th of May 2022, and additional hand searches were also conducted. To be included, articles had to be in English and contain original data about the potential relationship(s) between mindfulness and time perception. Articles which did not present usable data about the relationship(s) between the variables of interest were excluded. In total, 47 research articles were included in the review (combined sample size of ∼5800 participants). Risks of bias in the selected studies were evaluated using two separate assessment tools designed for this purpose. Through an integrative narrative synthesis, this article reviews how mindfulness may relate to time perception for various reference frames, and for various time perception measures and methods. It also provides new insights by exploring how a wide range of findings can be integrated into a coherent whole, in light of some relevant time perception models and mindfulness theories. Altogether, the reviewed data suggest the existence of complex and multifaceted relationships between mindfulness and time perception, highlighting the importance of considering many factors when planning research or interpreting data in this field. Limitations of the current review include the scarceness of data for certain categories of findings, and the relatively low prevalence of studies with a randomized controlled design in the source literature. This research was partly funded by a grant from the Natural Science and Engineering Research Council of Canada.

Alleviating premenstrual symptoms with smartphone-based heart rate variability biofeedback training: a pilot study

Introduction

Heart rate variability biofeedback (HRVB) is a well-studied intervention known for its positive effects on emotional, cognitive, and physiological well-being, including relief from depressive symptoms. However, its practical use is hampered by high costs and a lack of trained professionals. Smartphone-based HRVB, which eliminates the need for external devices, offers a promising alternative, albeit with limited research. Additionally, premenstrual symptoms are highly prevalent among menstruating individuals, and there is a need for low-cost, accessible interventions with minimal side effects. With this pilot study, we aim to test, for the first time, the influence of smartphone-based HRVB on depressive and premenstrual symptoms, as well as anxiety/stress symptoms and attentional control.

Methods

Twenty-seven participants with above-average premenstrual or depressive symptoms underwent a 4-week photoplethysmography smartphone-based HRVB intervention using a waitlist-control design. Laboratory sessions were conducted before and after the intervention, spaced exactly 4 weeks apart. Assessments included resting vagally mediated heart rate variability (vmHRV), attentional control via the revised attention network test (ANT-R), depressive symptoms assessed with the BDI-II questionnaire, and stress/anxiety symptoms measured using the DASS questionnaire. Premenstrual symptomatology was recorded through the PAF questionnaire if applicable. Data analysis employed linear mixed models.

Results

We observed improvements in premenstrual, depressive, and anxiety/stress symptoms, as well as the Executive Functioning Score of the ANT-R during the intervention period but not during the waitlist phase. However, we did not find significant changes in vmHRV or the Orienting Score of the ANT-R.

Discussion

These findings are promising, both in terms of the effectiveness of smartphone-based HRVB and its potential to alleviate premenstrual symptoms. Nevertheless, to provide a solid recommendation regarding the use of HRVB for improving premenstrual symptoms, further research with a larger sample size is needed to replicate these effects.

Short-Term Effects of Heart Rate Variability Biofeedback on Working Memory

Drawing upon the well-documented impact of long-term heart rate variability biofeedback (HRVB) on psychophysiological responses, this study seeks to explore the short-term effects arising from a single HRVB session during and after paced breathing exercise. The research aligns with the neurovisceral integration model, emphasizing the link between heart rate variability (HRV) levels and cognitive performance. Therefore, a randomized controlled trial employing a between-subjects design was conducted with 38 participants. Each participant was assigned to either the paced breathing intervention group or the spontaneous breathing control group. The study assessed various parameters such as cardiac vagal tone, evaluated through vagally mediated HRV measures, and working memory, measured using the N-back task. Additionally, participants' affective states were assessed through self-reported questionnaires, specifically targeting attentiveness, fatigue, and serenity. The results notably reveal enhancements in the working memory task and an elevated state of relaxation and attention following the HRVB session, as evidenced by higher averages of correct responses, serenity and attentiveness scores. However, the findings suggest that this observed improvement is not influenced by changes in cardiac vagal tone, as assessed using a simple mediation analysis. In conclusion, this study presents promising insights into the impact of a single HRVB session, laying the foundation for future research advancements in this domain.

Influence of Respiratory Frequency of Slow-Paced Breathing on Vagally-Mediated Heart Rate Variability

Breathing techniques, particularly slow-paced breathing (SPB), have gained popularity among athletes due to their potential to enhance performance by increasing cardiac vagal activity (CVA), which in turn can help manage stress and regulate emotions. However, it is still unclear whether the frequency of SPB affects its effectiveness in increasing CVA. Therefore, this study aimed to investigate the effects of a brief SPB intervention (i.e., 5 min) on CVA using heart rate variability (HRV) measurement as an index. A total of 75 athletes (22 female; Mage = 22.32; age range = 19-31) participated in the study, attending one lab session where they performed six breathing exercises, including SPB at different frequencies (5 cycles per minute (cpm), 5.5 cpm, 6 cpm, 6.5 cpm, 7 cpm), and a control condition of spontaneous breathing. The study found that CVA was significantly higher in all SPB conditions compared to the control condition, as indexed by both root mean square of the successive differences (RMSSD) and low-frequency HRV (LF-HRVms2). Interestingly, LF-HRVms2 was more sensitive in differentiating the respiratory frequencies than RMSSD. These results suggest that SPB at a range of 5 cpm to 7 cpm can be an effective method to increase CVA and potentially improve stress management and emotion regulation in athletes. This short SPB exercise can be a simple yet useful tool for athletes to use during competitive scenarios and short breaks in competitions. Overall, these findings highlight the potential benefits of incorporating SPB into athletes' training and competition routines.

Psychophysiological Effects of Slow-Paced Breathing on Adolescent Swimmers' Subjective Performance, Recovery States, and Control Perception

This study examined the effect of a Slow-Paced Breath (i.e., 6 breaths per minute) without Biofeedback (SPB-NoHRVB) protocol on semi-elite adolescent swimmers' psychological and physiological states during a seven-week ecological training period. A linear mixed-effects multilevel regression analysis approach was used with 13 adolescent national-level swimmers. Athletes were randomly assigned to an intervention group (n = 7) and a control group (n = 6). Seven waves of assessments were completed weekly during a seven-week training preparation in ecological conditions. During the protocol, swimmers completed subjective quantitative measures (RESTQ-36-R-Sport; cognitive perceived stress and control states about the training process, training subjective performance, and subjective internal training load) and physiological heart rate (HR) (HR of exercise, absolute and normalized HR recovery during the first 60 s of recovery; HRR60 and nHRR60) and heart rate variability (HRV) (MeanRR, RMSSD, LFnu and HFnu, LF/HF ration) tests (through a submaximal heart rate (5'-5' test) once a week. Results revealed that the SPB-NoHRVB protocol significantly predicts biopsychosocial recovery states, cognitive perception of control, and training subjective performance (i.e., a significant effect of the SPB-NoHRVB protocol with the dependent variables simple time trajectories). However, no significant effects were found for biopsychosocial stress scales, cognitively perceived stress, HR, or HRV markers. Our results suggest that SPB-NoHRVB induces simple evolutions over time for crucial variables in athletes' adaptation to the training process (i.e., cognitive appraisals and biopsychosocial states). In contrast, it highlights that SPB-NoHRVB does not induce better stress states. This specific effect on the resource component is an exciting result that will be discussed in the manuscript.

Examining the relation between emotional experiences and emotional expressions in competitive tennis matches

Introduction

Emotions consist of different components such as the emotional experience, physiological reactions, action tendencies, or emotional expressions. Assessing the relation of these components may help to better understand the role of emotions in sport competitions. Based on the component process model of emotions, the goal of the present study was to assess the relation between emotional experiences and emotional expressions.

Methods

Twenty tennis players (7 female) with an average age of 23.10 (SD = 4.88) were taped during competitive tennis matches. Thereafter, in individual meetings, after having watched themselves on the footage at pre-selected points, the players had to indicate whether, immediately after the end of a rally, they had a positive or a negative emotional experience and, in case they had one, rate its intensity. Moreover, based on their observable behavior, the players were also asked to state whether they could recognize a positive or a negative emotional expression and, in case they recognized one, rate its intensity. The occurrence of emotional expressions was additionally rated by two external coders. Using multilevel models, separate analyses were conducted for positive emotions after won points and negative emotions after lost points.

Results and discussion

For both positive and negative emotions, the results indicated a positive correlation between emotional experiences and emotional expressions. Moreover, the intensity of emotional experiences could predict the occurrence of an emotional expression rated by both the players or external coders. These insights into the relation between emotional experiences and emotional expressions may help players to more effectively regulate their emotions.

Heart Rate Variability Biofeedback in Adults with a Spinal Cord Injury: A Laboratory Framework and Case Series

Heart rate variability biofeedback (HRV-F) is a neurocardiac self-regulation therapy that aims to regulate cardiac autonomic nervous system activity and improve cardiac balance. Despite benefits in various clinical populations, no study has reported the effects of HRV-F in adults with a spinal cord injury (SCI). This article provides an overview of a neuropsychophysiological laboratory framework and reports the impact of an HRV-F training program on two adults with chronic SCI (T1 AIS A and T3 AIS C) with different degrees of remaining cardiac autonomic function. The HRV-F intervention involved 10 weeks of face-to-face and telehealth sessions with daily HRV-F home practice. Physiological (HRV, blood pressure variability (BPV), baroreflex sensitivity (BRS)), and self-reported assessments (Fatigue Severity Scale, Generalised Anxiety Disorder Scale, Patient Health Questionnaire, Appraisal of Disability and Participation Scale, EuroQol Visual Analogue Scale) were conducted at baseline and 10 weeks. Participants also completed weekly diaries capturing mood, anxiety, pain, sleep quality, fatigue, and adverse events. Results showed some improvement in HRV, BPV, and BRS. Additionally, participants self-reported some improvements in mood, fatigue, pain, quality of life, and self-perception. A 10-week HRV-F intervention was feasible in two participants with chronic SCI, warranting further investigation into its autonomic and psychosocial effects.

Validity and Efficacy of the Elite HRV Smartphone Application during Slow-Paced Breathing

Slow-paced breathing is a clinical intervention used to increase heart rate variability (HRV). The practice is made more accessible via cost-free smartphone applications like Elite HRV. We investigated whether Elite HRV can accurately measure and augment HRV via its slow-paced breathing feature. Twenty young adults completed one counterbalanced cross-over protocol involving 10 min each of supine spontaneous (SPONT) and paced (PACED; 6 breaths·min-1) breathing while RR intervals were simultaneously recorded via a Polar H10 paired with Elite HRV and reference electrocardiography (ECG). Individual differences in HRV between devices were predominately skewed, reflecting a tendency for Elite HRV to underestimate ECG-derived values. Skewness was typically driven by a limited number of outliers as median bias values were ≤1.3 ms and relative agreement was ≥very large for time-domain parameters. Despite no significant bias and ≥large relative agreement for frequency-domain parameters, limits of agreement (LOAs) were excessively wide and tended to be wider during PACED for all HRV parameters. PACED significantly increased low-frequency power (LF) for Elite HRV and ECG, and between-condition differences showed very large relative agreement. Elite HRV-guided slow-paced breathing effectively increased LF values, but it demonstrated greater precision during SPONT and in computing time-domain HRV.

The effect of a single-session heart rate variability biofeedback on attentional control: does stress matter?

Introduction

Vagally mediated heart rate variability is an index of autonomic nervous system activity that is associated with a large variety of outcome variables including psychopathology and self-regulation. While practicing heart rate variability biofeedback over several weeks has been reliably associated with a number of positive outcomes, its acute effects are not well known. As the strongest association with vagally mediated heart rate variability has been found particularly within the attention-related subdomain of self-regulation, we investigated the acute effect of heart rate variability biofeedback on attentional control using the revised Attention Network Test.

Methods

Fifty-six participants were tested in two sessions. In one session each participant received a heart rate variability biofeedback intervention, and in the other session a control intervention of paced breathing at a normal ventilation rate. After the biofeedback or control intervention, participants completed the Attention Network Test using the Orienting Score as a measure of attentional control.

Results

Mixed models revealed that higher resting baseline vagally mediated heart rate variability was associated with better performance in attentional control, which suggests more efficient direction of attention to target stimuli. There was no significant main effect of the intervention on attentional control. However, an interaction effect indicated better performance in attentional control after biofeedback in individuals who reported higher current stress levels.

Discussion

The results point to acute beneficial effects of heart rate variability biofeedback on cognitive performance in highly stressed individuals. Although promising, the results need to be replicated in larger or more targeted samples in order to reach stronger conclusions about the effects.

The impact of a guided paced breathing audiovisual intervention on anxiety symptoms in Palestinian children: a pilot randomized controlled trial

BACKGROUND

Children in Palestine may be at high risk for anxiety symptoms. However, access to mental health services is limited. Therefore, the objective of this study was to conduct a pilot randomized controlled trial to examine whether a guided audiovisual paced breathing intervention was feasible, acceptable, and improved anxiety symptoms in Palestinian children.

METHODS

Students (6-10 years old) in an after-school program in Palestine were randomly assigned to the intervention or control condition. All participants completed a pre- and post-intervention measure of anxiety using the Revised Children's Manifest Anxiety Scale. Participants in the intervention completed 24 sessions over 8 weeks and rated breathing ease as well as pre- and post-session relaxation on a 5-point Likert scale. To examine condition differences in post-intervention anxiety, four analyses of covariance were conducted, adjusting for age, sex, and pre-intervention anxiety.

RESULTS

A total of 144 participants (65.3% girls; Mage  = 7.5 ± 1.2; 50% per condition) enrolled in the study. There were no differences in demographics or baseline anxiety between the two conditions (ps > .05). Participants reported that it was easy to breathe during the sessions (Ms = 4.1-4.7, SDs = 0.5-1.1). For all but the first session, participants reported being more relaxed after the breathing session than before (ps < .003). Post-intervention, participants in the intervention reported fewer anxiety symptoms compared to participants in the control condition (ps < .01).

CONCLUSION

A guided paced breathing audiovisual intervention was feasible and had a significant positive impact on anxiety symptoms in Palestinian children compared to a control condition. Future research should examine whether the audiovisual guided breathing intervention significantly improves long-term outcomes.

Interoceptive rhythms in the brain

Sensing internal bodily signals, or interoception, is fundamental to maintain life. However, interoception should not be viewed as an isolated domain, as it interacts with exteroception, cognition and action to ensure the integrity of the organism. Focusing on cardiac, respiratory and gastric rhythms, we review evidence that interoception is anatomically and functionally intertwined with the processing of signals from the external environment. Interactions arise at all stages, from the peripheral transduction of interoceptive signals to sensory processing and cortical integration, in a network that extends beyond core interoceptive regions. Interoceptive rhythms contribute to functions ranging from perceptual detection up to sense of self, or conversely compete with external inputs. Renewed interest in interoception revives long-standing issues on how the brain integrates and coordinates information in distributed regions, by means of oscillatory synchrony, predictive coding or multisensory integration. Considering interoception and exteroception in the same framework paves the way for biological modes of information processing specific to living organisms.

The diving response and cardiac vagal activity: A systematic review and meta-analysis

This article aimed to synthesize the various triggers of the diving response and to perform a meta-analysis assessing their effects on cardiac vagal activity. The protocol was preregistered on PROSPERO (CRD42021231419; 01.07.2021). A systematic and meta-analytic review of cardiac vagal activity was conducted, indexed with the root mean square of successive differences (RMSSD) in the context of the diving response. The search on MEDLINE (via PubMed), Web of Science, ProQuest and PsycNet was finalized on November 6th, 2021. Studies with human participants were considered, measuring RMSSD pre- and during and/or post-exposure to at least one trigger of the diving response. Seventeen papers (n = 311) met inclusion criteria. Triggers examined include face immersion or cooling, SCUBA diving, and total body immersion into water. Compared to resting conditions, a significant moderate to large positive effect was found for RMSSD during exposure (Hedges' g = 0.59, 95% CI 0.36 to 0.82, p < .001), but not post-exposure (g = 0.11, 95% CI -0.14 to 0.36, p = .34). Among the considered moderators, total body immersion had a significantly larger effect than forehead cooling (Q_M  = 23.46, df = 1, p < .001). No further differences were detected. Limitations were the small number of studies included, heterogenous triggers, few participants and low quality of evidence. Further research is needed to investigate the role of cardiac sympathetic activity and of the moderators.

Reducing decision-making deficits in patients with brain injury: effect of slow-paced breathing

Impairments in decision-making have been reported in brain-damaged (stroke/traumatic brain injury) patients with a wide range of lesion sites. Here, we propose that the performances of patients in complex sequential decision-making (DM) tasks can be explained by their negative affectivity, leading to deliberative processing associated with poor DM performances. We assumed that a slow-paced breathing (SPB) training, by reducing negative affectivity would improve performances in a complex DM task. For 24 days, 34 brain-damaged patients (16 males and 18 females; 12 had a hemorrhagic stroke, 17 with an ischemic stroke and 5 with a TBI), practiced either daily SPB or sham trainings for five min, three times a day. Before and after training, we assessed their vagal tone (electrocardiogram-ECG), affectivity (Positive and Negative Affect Schedule-PANAS) and certainty level (Dimensional Ratings Questionnaire-DRQ) and their performance on the Iowa Gambling Task. All participants showed initial weak performance, which improved only for patients in the SPB training condition. These results suggest that DM disorders in brain-damaged patients can be the consequence of their poor information processing strategy rather than an impairment in their DM abilities. Second, we showed that SPB could be efficient to normalize DM processes in brain injury patients.

Acute effects of mindful interval exercise on cognitive performance in a higher education setting

Interval exercise (IE) has been shown to have acute facilitating effects on cognition; however, the existing literature has been limited to laboratory settings and has focused on manipulating the parameters of exercise bouts during IE. This study included two classroom-based experiments to (1) investigate the effect of an acute bout of IE delivering mindfulness activity during its recovery intervals (mindful IE) on cognitive performance, and (2) compare cognitive performance following acute bouts of mindful IE with non-mindful IE. Experiment 1: Using a class-based within-subject crossover design, 59 participants completed the Stroop, d2, and trail-making tests to measure inhibitory control, attention, and cognitive flexibility, after a 30-min non-exercise or mindful IE session on separate counterbalanced days. Experiment 2: Using a similar design, 70 participants were assigned to two groups to receive a non-exercise and an IE session with (mindful) or without (non-mindful) mindfulness-based recovery intervals on separate counterbalanced days. Results from Experiment 1 showed superior d2 performance following the mindful IE than the non-exercise session. Although Experiment 2 found exercise-related decreases in commission error rate during the d2 test in both groups, the non-mindful group showed additional decreases in omission and total error rates. Further, higher scores on the nonreactivity facet of dispositional mindfulness were correlated with larger decreases in omission and total error rates during the d2 test for the mindful IE group. No exercise-related effect was found for outcomes of the Stroop and trail-making tests in both experiments. These findings in the selective improvements in d2 test performance are the first to suggest the feasibility of integrating mindfulness activity into the recovery intervals of IE for enhanced cognitive performance that may depend on individual differences in dispositional mindfulness.

Squeeze the beat: Enhancing cardiac vagal activity during resonance breathing via coherent pelvic floor recruitment

Resonance breathing (RB) has been shown to benefit health and performance within clinical and non-clinical populations. This is attributed to its baroreflex stimulating effect and the concomitant increase in cardiac vagal activity (CVA). Hence, developing methods that strengthen the CVA boosting effect of RB could improve its clinical effectiveness. Therefore, we assessed whether supplementing RB with coherent pelvic floor activation (PRB), which has been shown to entrain the baroreflex, yields stronger CVA than standard RB. N = 32 participants performed 5-min of RB and PRB, which requires to recruit the pelvic floor during the complete inspiratory phase and release it at the initiation of the expiration. CVA was indexed via heart rate variability using RMSSD and LF-HRV. PRB induced significantly larger RMSSD (d = 1.04) and LF-HRV (d = 0.75, ps &lt; .001) as compared to RB. Results indicate that PRB induced an additional boost in CVA relative to RB in healthy individuals. However, subsequent studies are warranted to evaluate whether these first findings can be replicated in individuals with compromised health, including a more comprehensive psychophysiological assessment to potentially elucidate the origin of the observed effects. Importantly, longitudinal studies need to address whether PRB translates to better treatment outcomes.

Single Slow-Paced Breathing Session at Six Cycles per Minute: Investigation of Dose-Response Relationship on Cardiac Vagal Activity

The practice of slow-paced breathing (SPB) has been linked to a range of positive outcomes, such as decreasing symptoms of depression, anxiety, and stress, as well as increasing well-being. Among the suggested mechanisms of action, SPB has been shown to increase cardiac vagal activity (CVA). The present study aimed to investigate whether there is a dose-response relationship modulating the effects of SPB on CVA. A total of 59 participants were involved in this study. In a within-subject design, participants attended the lab five times, and realized SPB at six cycles per minute with different durations (5, 10, 15, and 20 min), as well as a control condition without SPB. CVA was indexed via the root mean square of successive differences (RMSSD). During SPB, findings showed an increase in RMSSD in all conditions compared to the control condition. However, no differences were found in RMSSD among the different session durations, during SPB or during the resting measurement completed immediately after SPB. Noteworthily, session duration showed an influence on the spontaneous respiratory frequency in the resting measurement occurring immediately after SPB. Specifically, respiratory frequency appears to decrease with session duration, thus potentially contributing to additional relaxing effects.