Feasibility and Acceptability of a Mobile Health Exercise Intervention for Inactive Adults: 3-Arm Randomized Controlled Pilot Trial.

BACKGROUND: Objective monitoring of self-directed physical activity (PA) is a common approach used in both fitness and health settings to promote exercise behavior, but adherence has been poor. Newer mobile health (mHealth) technologies could be a cost-effective approach to broadening accessibility and providing support for PA behavior change; yet, the optimal method of delivery of such interventions is still unclear. OBJECTIVE: This study aimed to determine the feasibility and acceptability of an mHealth exercise intervention delivered in combination with objective monitoring in 3 ways: health education emails, asynchronous exercise videos, or synchronous videoconference exercise classes. METHODS: Physically inactive (<30 min/wk) adults (cisgender women aged 31.5, SD 11.3 years, cisgender men aged 34.1, SD 28.9 years, and nonbinary individuals aged 22.0, SD 0 years) were randomized (1:1:1) to 8 weeks of increasing PA behavioral support: level 1 (health education+objective monitoring, n=26), level 2 (asynchronous contact, level 1+prerecorded exercise videos, n=30), or level 3 (synchronous contact, level 1+videoconference group exercise, n=28). Participants used a heart rate monitor during exercise and a mobile app for interaction. Primary outcomes were feasibility (accrual, retention, and adherence) and acceptability (user experience survey). Secondary outcomes assessed at baseline and 8 weeks included resting heart rate, self-reported PA, and quality of life. The exercise dose was evaluated throughout the intervention. RESULTS: Between August 2020 and August 2021, 204 adults were screened for eligibility. Out of 135 eligible participants, 84 (62%) enrolled in the study. Retention was 50% (13/26) in level 1, 60% (18/30) in level 2 and 82% (23/28) in level 3, while adherence was 31% (8/26) in level 1, 40% (12/30) in level 2 and 75% (21/28) in level 3. A total of 83% (70/84) of the study sample completed the intervention, but low response rates (64%, 54/84) were observed postintervention at week-8 assessments. Program satisfaction was highest in participants receiving exercise videos (level 2, 80%, 8/10) or exercise classes (level 3, 80%, 12/15), while only 63% (5/8) of level 1 reported the program as enjoyable. Level 3 was most likely to recommend the program (87%, 13/15), compared to 80% (8/10) in level 2 and 46% (5/8) in level 1. Self-reported PA significantly increased from baseline to intervention in level 3 (P<.001) and level 2 (P=.003), with no change in level 1. Level 3 appeared to exercise at higher doses throughout the intervention. CONCLUSIONS: Only the videoconference exercise class intervention met feasibility criteria, although postintervention response rates were low across all groups. Both videoconference and prerecorded videos had good acceptability, while objective monitoring and health education alone were not feasible or acceptable. Future studies are needed to examine the effectiveness of videoconference exercise interventions on health-related outcomes during nonpandemic times and how asynchronous interventions might maximize adherence. TRIAL REGISTRATION: ClinicalTrials.gov NCT05192421; https://clinicaltrials.gov/study/NCT05192421.

Stress-induced increase in heart-rate during sleep as an indicator of PTSD risk among combat soldiers.

STUDY OBJECTIVES: Discerning the differential contribution of sleep behavior and sleep physiology to the subsequent development of posttraumatic-stress-disorder (PTSD) symptoms following military operational service among combat soldiers. METHODS: Longitudinal design with three measurement time points: during basic training week (T1), during intensive stressed training week (T2), and following military operational service (T3). Participating soldiers were all from the same unit, ensuring equivalent training schedules and stress exposures. During measurement weeks soldiers completed the Depression Anxiety and Stress Scale (DASS) and the PTSD Checklist for DSM-5 (PCL-5). Sleep physiology (sleep heart-rate) and sleep behavior (duration, efficiency) were monitored continuously in natural settings during T1 and T2 weeks using wearable sensors. RESULTS: Repeated measures ANOVA revealed a progressive increase in PCL-5 scores from T1 and T2 to T3, suggesting an escalation in PTSD symptom severity following operational service. Hierarchical linear regression analysis uncovered a significant relation between the change in DASS stress scores from T1 to T2 and subsequent PCL-5 scores at T3. Incorporating participants' sleep heart-rate markedly enhanced the predictive accuracy of the model, with increased sleep heart-rate from T1 to T2 emerging as a significant predictor of elevated PTSD symptoms at T3, above and beyond the contribution of DASS stress scores. Sleep behavior did not add to the accuracy of the model. CONCLUSION: Findings underscore the critical role of sleep physiology, specifically elevated sleep heart-rate following stressful military training, in indicating subsequent PTSD risk following operational service among combat soldiers. These findings may contribute to PTSD prediction and prevention efforts.

Beyond HIV Shame: Effects of Self-Forgiveness in Improving Mental Health in HIV-Positive Individuals in Poland.

Guided by the bio-psycho-socio-spiritual approach, this randomized controlled trial assessed the efficacy of a self-forgiveness intervention among 60 HIV-positive individuals in Poland. Participants underwent a 90-min "Restore: The Journey Toward Self-Forgiveness" session, in contrast to a wait-list control group. The intervention significantly enhanced self-forgiveness, spirituality, mental well-being, and heart rate variability in response to a cognitive stressor (i.e., a mental arithmetic challenge). Significant effects were observed in both between-group and within-subject comparisons. These results support the incorporation of self-forgiveness into psychological rehabilitation programs for HIV to improve quality of life and health outcomes.

The missing piece. Physiological data as a factor for identifying emotions of people with profound intellectual and multiple disabilities.

Introduction: The preferences of people with profound intellectual and multiple disabilities (PIMD) often remain unfulfilled since it stays challenging to decode their idiosyncratic behavior resulting in a negative impact on their quality of life (QoL). Physiological data (i.e. heart rate (variability) and motion data) might be the missing piece for identifying emotions of people with PIMD, which positively affects their QoL. Method: Machine learning (ML) processes and statistical analyses are integrated to discern and predict the potential relationship between physiological data and emotional states (i.e. numerical emotional states, descriptive emotional states and emotional arousal) in everyday interactions and activities of two participants with PIMD. Results: Emotional profiles were created enabling a differentiation of the individual emotional behavior. Using ML classifiers and statistical analyses, the results regarding the phases partially confirm previous research, and the findings for the descriptive emotional states were good and even better for the emotional arousal. Conclusion: The results show the potential of the emotional profiles especially for practitioners and the possibility to get a better insight into the emotional experience of people with PIMD including physiological data. This seems to be the missing piece to better recognize emotions of people with PIMD with a positive impact on their QoL.

Blood pressure/Heart Rate-Derived Ratios, as Indices of Health and Cardiovascular Pathology.

This communication, based on a review of the relevant literature on ratios deriving from blood pressure and heart rate measurements, and their conformance/nonconformance to the mathematical Golden Rule (i.e., 1.681), proposes that such ratios, particularly emanating from large numbers of home blood pressure and heart rate measurements, obtained by the patients themselves or their caretakers, may constitute new risk markers, useful in the assessment of heath and cardiovascular pathologies, prognosis of morbidity and mortality, and implementation to clinical practice and research.

Feedback control of heart rate during robotics-assisted tilt table exercise in patients after stroke: a clinical feasibility study.

BACKGROUND: Patients with neurological disorders including stroke use rehabilitation to improve cognitive abilities, to regain motor function and to reduce the risk of further complications. Robotics-assisted tilt table technology has been developed to provide early mobilisation and to automate therapy involving the lower limbs. The aim of this study was to evaluate the feasibility of employing a feedback control system for heart rate (HR) during robotics-assisted tilt table exercise in patients after a stroke. METHODS: This feasibility study was designed as a case series with 12 patients ( n = 12 ) with no restriction on the time post-stroke or on the degree of post-stroke impairment severity. A robotics-assisted tilt table was augmented with force sensors, a work rate estimation algorithm, and a biofeedback screen that facilitated volitional control of a target work rate. Dynamic models of HR response to changes in target work rate were estimated in system identification tests; nominal models were used to calculate the parameters of feedback controllers designed to give a specified closed-loop bandwidth; and the accuracy of HR control was assessed quantitatively in feedback control tests. RESULTS: Feedback control tests were successfully conducted in all 12 patients. Dynamic models of heart rate response to imposed work rate were estimated with a mean root-mean-square (RMS) model error of 2.16 beats per minute (bpm), while highly accurate feedback control of heart rate was achieved with a mean RMS tracking error (RMSE) of 2.00 bpm. Control accuracy, i.e. RMSE, was found to be strongly correlated with the magnitude of heart rate variability (HRV): patients with a low magnitude of HRV had low RMSE, i.e. more accurate HR control performance, and vice versa. CONCLUSIONS: Feedback control of heart rate during robotics-assisted tilt table exercise was found to be feasible. Future work should investigate robustness aspects of the feedback control system. Modifications to the exercise modality, or alternative modalities, should be explored that allow higher levels of work rate and heart rate intensity to be achieved.

Heart rate deceleration capacity as a marker of perioperative risk: identifying relevant patient phenotypes surgical procedures.

Loss of regulation of the autonomic nervous system is found in many diseases from the age of 50 to 60 yr and even more so in older patients. The imbalance is usually manifested by an increase in sympathetic tone, long considered to be the most deleterious element in terms of cardiac rhythmic risk, but also by a reduction in the effectiveness of short-term regulation of the baroreflex arc (partial loss of parasympathetic control). Techniques for analysing this autonomic disorder by analysing heart rate regulation are widely available in outpatient clinics and provide interesting indicators of cardiovascular and cerebrovascular risk. Deceleration capacity of cardiac autonomic control has been identified for its prognostic role in high-risk patients and in the general population. Further research is indicated to assess the value of this marker in anaesthetic risk management by targeting procedures with greater risk of intraoperative and postoperative autonomic dysfunction.

Heart rate reactivity, recovery, and endurance of the incremental shuttle walk test in patients prone to heart failure.

AIMS: Few randomized trials assessed the changes over time in the chronotropic heart rate (HR) reactivity (CHR), HR recovery (HRR) and exercise endurance (EE) in response to the incremental shuttle walk test (ISWT). We addressed this issue by analysing the open HOMAGE (Heart OMics in Aging) trial. METHODS: In HOMAGE, 527 patients prone to heart failure were randomized to usual treatment with or without spironolactone (25-50 mg/day). The current sub-study included 113 controls and 114 patients assigned spironolactone (~70% on beta-blockers), who all completed the ISWT at baseline and at Months 1 and 9. Within-group changes over time (follow-up minus baseline) and between-group differences at each time point (spironolactone minus control) were analysed by repeated measures ANOVA, unadjusted or adjusted for sex, age and body mass index, and additionally for baseline for testing 1 and 9 month data. RESULTS: Irrespective of randomization, the resting HR and CHR did not change from baseline to follow-up, with the exception of a small decrease in the HR immediately post-exercise (-3.11 b.p.m.) in controls at Month 9. In within-group analyses, HR decline over the 5 min post-exercise followed a slightly lower course at the 1 month visit in controls and at the 9 month visits in both groups, but not at the 1 month visit in the spironolactone group. Compared with baseline, EE increased by two to three shuttles at Months 1 and 9 in the spironolactone group but remained unchanged in the control group. In the between-group analyses, irrespective of adjustment, there were no HR differences at any time point from rest up to 5 min post-exercise or in EE. Subgroup analyses by sex or categorized by the medians of age, left ventricular ejection fraction or glomerular filtration rate were confirmatory. Combining baseline and Months 1 and 9 data in both treatment groups, the resting HR, CHR and HRR at 1 and 5 min averaged 61.5, 20.0, 9.07 and 13.8 b.p.m. and EE 48.3 shuttles. CONCLUSIONS: Spironolactone on top of usual treatment compared with usual treatment alone did not change resting HR, CHR, HRR and EE in response to ISWT. Beta-blockade might have concealed the effects of spironolactone. The current findings demonstrate that the ISWT, already used in a wide variety of pathological conditions, is a practical instrument to measure symptom-limited exercise capacity in patients prone to developing heart failure because of coronary heart disease.

Increased stress burden and electrodermal reactivity in bladder cancer patients in comparison to healthy controls.

The purpose of our study was to assess specific physiological parameters associated with stress responses in bladder cancer (BCa) patients compared to healthy individuals. By examining the transition from a supine to a sitting position, representing a mild physiological load, we investigated the changes in autonomic nervous system (ANS) activity as reflected by alterations in these parameters, indicating shifts in ANS regulation, using non-linear heart rate variability (HRV) parameters (0V%, 2UV%, parasympathetic and sympathetic nervous system - PNS and SNS indices), modified heart rate acceleration (ACmod) and deceleration capacities (DCmod), heart rate (HR), electrodermal activity (EDA), and also their correlations with perceived stress score. Our findings showed that BCa patients (n = 38) exhibited elevated resting HR, heightened SNS index, and increased EDA compared to their healthy counterparts (n = 47), indicating a notable physiological stress burden. The 0V% parameter showed a positive association with the SNS index, ACmod, HR, and EDA parameters, while displaying a negative correlation with the PNS index, DCmod and 2UV%. These non-linear HRV parameters, such as 0V% and 2UV%, offer nuanced insights into the complexities of heartbeat dynamics and autonomic regulation. After the transition from supine to sitting positions, BCa patients displayed higher EDA responses, indicating heightened stress reactivity and ANS sensitivity. These physiological distinctions persisted even when we did not prove differences in the levels of perceived stress between the studied groups. In conclusion, our study emphasizes the significance of identifying cancer patients at risk of ANS dysregulation, paving the way for tailored stress management strategies.

Screening of preoperative obstructive sleep apnea by cardiopulmonary coupling and its risk factors in patients with plans to receive surgery under general anesthesia: a cross-sectional study.

Objective: Preoperative obstructive sleep apnea (OSA) is supposed to be the abnormally high occurrence of OSA the night before surgery under general anesthesia. This study aimed to evaluate the prevalence preoperative OSA using cardiopulmonary coupling (CPC) and its correlation with imbalance of sympathetic/parasympathetic nervous system. Methods: A total of 550 patients with plans to receive surgery under general anesthesia were enrolled. All patients were assigned to wear CPC on the night before surgery until the next day. Sleep quality characteristics, heart rate variation parameters, and apnea-hypopnea index were acquired. The diagnosis of pre-existing OSA was not considered in the current study. Results: According to apnea-hypopnea index, 28.4%, 32.2%, 26.2%, and 13.3% patients were assessed as no, mild, moderate, and severe operative OSA, respectively. Multivariate logistic regression model revealed that higher age [p < 0.001, odds ratio (OR) = 1.043] was independently and positively associated with preoperative OSA; heart rate variation parameters representing the imbalance of sympathetic/parasympathetic nervous system, such as higher low-frequency (p < 0.001, OR = 1.004), higher low-frequency/high-frequency ratio (p = 0.028, OR = 1.738), lower NN20 count divided by the total number of all NN intervals (pNN20; p < 0.001, OR = 0.950), and lower high-frequency (p < 0.001, OR = 0.998), showed independent relationships with a higher probability of preoperative OSA. Higher age (p = 0.005, OR = 1.024), higher very-low-frequency (p < 0.001, OR = 1.001), and higher low-frequency/high-frequency ratio (p = 0.003, OR = 1.655) were associated with a higher probability of moderate-to-severe preoperative OSA, but higher pNN10 (p < 0.001, OR = 0.951) was associated with a lower probability of moderate-to-severe preoperative OSA. Conclusion: Preoperative OSA is prevalent. Higher age and imbalance of sympathetic/parasympathetic nervous system are independently and positively associated with a higher occurrence of preoperative OSA. CPC screening may promote the management of preoperative OSA.

Effect of combined Zhuang medicine treatment on tricuspid annular displacement and heart rate variability in rheumatoid arthritis patients.

Objectives To assess the benefits of Zhuang medicine in treating rheumatoid arthritis (RA), with a focus on cardiac tricuspid annulus displacement and heart rate variability (HRV), thereby providing evidence supporting Zhuang medicine theories. METHODS: This retrospective study analyzed echocardiographic data and HRV of 30 healthy subjects and 60 RA patients. RA patients were divided into two groups for a 6-month treatment: 30 received iguratimod (control group), and 30 underwent combined Zhuang medicine and needle-pricking therapy (test group). Echocardiographic assessments and HRV measures were recorded both before and after treatment. RESULTS: Compared to the healthy group, RA patients showed increased late diastolic tricuspid annular velocity. However, early diastolic tricuspid annular velocity to late diastolic tricuspid annular velocity ratios, tricuspid annular plane systolic excursion (TAPSE), and the standard deviation of average normal RR intervals (SDANN) were significantly lower (all P<0.05). After treatment, the test group exhibited higher clinical efficacy (90% vs. 56.67% in the control group). Significant improvements were observed in TAPSE and HRV indices [SDANN, standard deviation of the RR intervals (SDNN), root mean square of successive RR interval differences (RMSSD), and the percentage of adjacent RR interval differences greater than 50 milliseconds (PNN50)] in the test group (all P<0.05). Additionally, a positive correlation was noted among these measurments. CONCLUSION: Zhuang medicine significantly enhances right ventricular function and autonomic balance in RA patients, thus affirming its therapeutic potential.

Heart rate variability biofeedback enhances cognitive, motor, psychological, and autonomic functions in post-stroke rehabilitation.

Post-stroke patients often experience psychological distress and autonomic nervous system (ANS) dysregulation, impacting their well-being. This study evaluated the effectiveness of heart rate variability (HRV) biofeedback on cognitive, motor, psychological, and ANS functions in sixty-two ischemic stroke patients (43 males, mean age = 60.1) at a Medical Center in southern Taiwan. To prevent interaction, we allocated patients to the HRV biofeedback or control (usual care) group based on their assigned rehabilitation days, with 31 patients in each group. Assessments conducted at baseline, three, and six months included the Montreal Cognitive Assessment (MoCA), Fugl-Meyer Assessment for Upper Extremities (FMA-UE), Perceived Stress Scale, Hospital Anxiety and Depression Scales (HADS), and HRV indices. Mixed-effect models were used to analyze Group by Time interactions. The results revealed significant interactions across all functions. At 3 months, significant improvements in the HRV biofeedback group were observed only in MoCA, FMA-UE, and HADS-depression scores compared to the control group. By 6 months, all measured outcomes demonstrated significant improvements in the biofeedback group relative to the control group. These results suggest that HRV biofeedback may be an effective complementary intervention in post-stroke rehabilitation, warranting further validation.

Cardiac cycle modulates social pain.

Social pain is a painful feeling evoked by social rejection, exclusion, or the loss of other important people. Previous research suggests that physical pain is reduced by increased signals from baroreceptors that monitor blood pressure. This pre-registered study investigated whether social pain is attenuated by increased baroafferent signals, as observed in physical pain. Given that baroafferent signals increase during cardiac systole and decrease during diastole, we hypothesized that feelings of pain induced by social rejection would be lower when exclusion events are presented at the cardiac systole than when they are presented at the diastole. Participants completed the cyberball task, a computerized ball-tossing game involving two other players. In the rejection condition, the ball was rarely thrown to the participant, while the other players kept tossing it to each other. Throws between other players were defined as exclusion events and were presented either at the cardiac systole (a systole condition) or at the diastole (a diastole condition). We found that exclusion events evoked significantly less social pain in the systole condition than in the diastole condition. Furthermore, the effects of cardiac cycle were more pronounced in participants with higher heart rate variability than those with lower heart rate variability. Our results suggest that cardiac afferent signals contribute not only to physical pain but also to social pain.

Treating heart failure by targeting the vagus nerve.

Increased sympathetic and reduced parasympathetic nerve activity is associated with disease progression and poor outcomes in patients with chronic heart failure. The demonstration that markers of autonomic imbalance and vagal dysfunction, such as reduced heart rate variability and baroreflex sensitivity, hold prognostic value in patients with chronic heart failure despite modern therapies encourages the research for neuromodulation strategies targeting the vagus nerve. However, the approaches tested so far have yielded inconclusive results. This review aims to summarize the current knowledge about the role of the parasympathetic nervous system in chronic heart failure, describing the pathophysiological background, the methods of assessment, and the rationale, limits, and future perspectives of parasympathetic stimulation either by drugs or bioelectronic devices.

Effects of Singing on Vascular Health in Older Adults with Coronary Artery Disease: A Randomized Trial.

Background: The impact of singing on cardiovascular health has not been extensively studied. The aim of this study is to investigate the effect of singing on cardiovascular biomarkers in an aging population with coronary artery disease. Methods: Participants had three study visits separated by 2-7 days, according to a randomized, single-blind, cross-over, controlled design: (1) a 30-minute period of coached singing from an in-person music therapist, (2) a 30-minute period of singing along to an instructional video and (3) a 30-minute rest (control). Primary outcomes included macrovascular endothelial function assessed by brachial artery flow-mediated dilation and microvascular function assessed by peripheral arterial tonometry (Framingham reactive hyperemia index; fRHI). Heart rate variability was a secondary outcome. Results: Sixty-five subjects (mean age 67.7± 0.8, 40% women) completed the study. Compared to control, there was an increase in fRHI for the singing video intervention (estimate 0.54, SE 0.25, p=0.005) but not for the coaching intervention (estimate 0.11, SE 0.18, p=0.570). There was no change in macrovascular function with either intervention. The low frequency/high frequency (LF/HF) ratio increased by 2.80 (SE 1.03, p=0.008), and the LnHF power decreased by -0.90 ms2 (SE 0.29, p=0.003) with the video (during to pre-change). When assessing post- to pre- change, the coaching intervention showed a significant change of -0.62 ms2 (SE 0.29, p=0.036) in LnHF power. Conclusions: Singing along to an instructional video for 30 minutes improved microvascular, but not macrovascular, endothelial function, in older patients with CAD. HRV changes with singing are similar to that of exercise. Clinical trial registration: ClinicalTrials.gov, identifier: NCT04121741.

Cardio-respiratory coupling and myocardial recovery in heart failure with reduced ejection fraction.

INTRODUCTION: The interaction between the cardiovascular and respiratory systems in healthy subjects is determined by the autonomic nervous system and reflected in respiratory sinus arrhythmia. Recently, another pattern of cardio-respiratory coupling (CRC) has been proposed linking synchronization of heart and respiratory system. However, CRC has not been studied precisely in heart failure (HF) with reduced ejection fraction (EF) (HFrEF) according to the myocardial recovery. METHODS: 10-min resting electrocardiography measurements were performed in persistent HFrEF patients (n=40) who had a subsequent left ventricular EF (LVEF) of ≤ 40 %, HF with recovered EF patients (HFrecEF) (n=41) who had a subsequent LVEF of > 40 % and healthy controls (n=40). Respiratory frequency, respiratory rate, CRC index, time-domain, frequency-domain and nonlinear heart rate variability indices were obtained using standardized software-Kubios™. CRC index was defined as respiratory high-frequency peak minus heart rate variability high-frequency peak. RESULTS: Respiratory rate was positively correlated with high-frequency (HF) peak (Hz) in both persistent HFrEF group (p<0.001) and HFrecEF group (p<0.001), while respiratory rate was negatively correlated with HF power (ms2) in the healthy controls (p<0.05). CRC index was lowest in the persistent HFrEF group followed by HFrecEF and was high in healthy controls (0.008 vs 0.012 vs 0.056 Hz, p=0.03). CONCLUSION: CRC index was lowest in patients with impaired myocardial recovery, which indicates that cardio-respiratory synchrony is stronger in persistent HFrEF. This may represent a higher HF peak (Hz)/lower HF power (ms2) and abnormal sympathovagal balance in persistent HFrEF group compared to healthy controls. Further work is underway to tests this hypothesis and determine the utility of CRC index in HF phenotypes and its utility as a potential biomarker of response with neuromodulation.

Affective Implications of Human-Animal Relationship on Pig Welfare: Integrating Non-Linear Heart Rate Variability Measures.

The human-animal relationship is crucial for animal welfare. Gentle handling enhances pigs' comfort while rough handling causes fear and stress. This study examined how different human-animal relationship qualities affect the behavior and heart rate variability (linear and non-linear parameters) of 36 nursery pigs. Over six weeks, pigs experienced positive (n = 12), minimal (n = 12), or negative (n = 12) human handling. Their responses to handlers were then assessed in an experimental arena with four phases: habituation, exposure to the handler standing and sitting, and forced interaction. Pigs subjected to negative handling exhibited increased fear-related behaviors, spending less time in contact with the handler. They also exhibited heightened stress responses, with greater LF/HF ratio and Lmean values compared with positively handled pigs. Conversely, gently handled pigs displayed affiliative behaviors, accepting more strokes, and higher parasympathetic activation, indicated by greater RMSSD/SDNN and SampEn values, suggesting a more positive affective state. Minimally handled pigs exhibited some behavioral similarities to gently handled pigs, although physiological data indicated that the interaction was likely more rewarding for the gently handled pigs. These results emphasize the impact of human-animal relationships on pig welfare and highlight the value of incorporating non-linear heart rate variability parameters in such evaluations.

Stress Responses in Horses Housed in Different Stable Designs during Summer in a Tropical Savanna Climate.

Single-confinement housing can pose welfare risks to domestic horses. This study investigated horses' stress responses when confined to single stalls in different stable designs in a tropical savanna region to address a gap in the literature. In total, 23 horses were assigned to a stable with a central corridor and solid external walls (A) (N = 8), a stable with one side corridor and solid external walls (B) (N = 6), or a stable with a central corridor and no solid external walls (C) (N = 9). Air velocity, relative humidity, air temperature, and noxious gases were measured inside the stables, and the heart rate and HRV of the horses were also determined. The relative humidity was lower in stable C than in stable A (p < 0.05), while the air temperature was higher in stable C than in stable B (p < 0.05) during the day. The airflow and ammonia levels were higher in stable C than in stables B and A (p < 0.01-0.0001). Overall, horses' HRV in stable A was lower than in those in stables B and C (p < 0.05-0.01). Horses in stable A tended to experience more stress than those in other stables.

Brief Report: Baseline HRV Time Domain Parameters Predict Trauma and Depression Symptom Change in Veterans with PTSD Undergoing Biofeedback.

Heart rate variability (HRV) is an index of cardiac autonomic function and an objective biomarker for stress and health. Improving HRV through biofeedback has proven effective in reducing symptoms of posttraumatic stress disorder (PTSD) and depression in veteran populations. Brief protocols involving fewer sessions can better maximize limited clinic resources; however, there is a dearth of knowledge on the number of clinical sessions needed to significantly reduce trauma and depression symptoms. We conducted a series of linear regression models using baseline, post-intervention, and follow-up data from intervention group participants (N = 18) who engaged in a pilot waitlist-controlled study testing the efficacy of a 3-session mobile app-adapted HRV biofeedback intervention for veterans with PTSD. Based on Nunan et al. (Pacing and Clinical Electrophysiology 33:1407-1417, 2010) short-term norms, we found that pre-intervention RMSSD in the normal range significantly predicted PTSD and depression symptom improvement. Findings suggest the utility of baseline RMSSD as a useful metric for predicting HRV biofeedback treatment outcomes for veterans with PTSD and comorbid depression. Those with below-normal baseline RMSSD may likely need additional sessions or an alternative treatment to show clinically meaningful symptom improvement.