The autonomic nervous system plays a crucial role in regulating physiological processes including heart rate variability (HRV) and glucose metabolism. Higher glucose levels have been associated with reduced vagally mediated HRV. Resonance frequency breathing (RFB) with HRV biofeedback (HRV-BF) has been shown to enhance vagally mediated cardiac autonomic modulation in healthy adults. However, it remains unclear whether such training alters cardiac autonomic responses during acute metabolic stress. We investigated whether four weeks of the RFB-HRV-BF intervention modifies autonomic response dynamics during a metabolic challenge in 28 healthy adults (n = 16 females, mean age: 25.68 ± 3.66 years; mean body mass index 22.77 ± 3.01 kg/m2). Cardiac autonomic responses were assessed using the HRV parameters root mean square successive differences between normal heartbeats (RMSSD) and standard deviation of all normal-to-normal intervals (SDNN) during the first 30 min of a 75 g oral glucose tolerance test (OGTT), corresponding to peak postprandial glucose levels, before and after the intervention. Piecewise linear mixed-effects models revealed a less pronounced decline in logarithmic naturals transformed RMSSD (lnRMSSD) and SDNN (lnSDNN), during the early postprandial phase of the OGTT following the RFB-HRV-BF intervention, indicating an intervention-related modification of cardiac autonomic response dynamics. Taken together, these findings indicate that RFB-HRV-BF attenuates early vagal withdrawal during acute metabolic stress. By demonstrating effects on cardiac autonomic dynamics during a standardised metabolic challenge, the present study extends previous work on RFB beyond resting conditions and underscores the relevance of context-dependent autonomic assessment for understanding interactions between autonomic regulation and metabolic health.
The increasing complexity of vocal training, particularly in the control of internal physiological processes, necessitates the integration of technologies capable of enhancing sensorimotor learning and self-regulation. Traditional vocal pedagogy remains limited in accessing and monitoring underlying physiological mechanisms, resulting in a gap between subjective perception and objective performance control. The present study aimed to evaluate whether an immersive training environment integrating virtual reality and multimodal biofeedback could improve short-term physiological, acoustic, and cognitive outcomes during vocal training compared with conventional instruction. A randomized controlled pre–post design was implemented across three universities in China (Beijing). The sample comprised 107 students (aged 18–30 years), randomly assigned to a control group (n = 53) and an experimental VR group (n = 54). The findings indicate significant improvements in the VR group: a reduction in muscle activity (− 6.29 vs. −2.93 in the control group; p < 0.001; d = 0.71) and respiratory variability (− 0.048 vs. −0.022; p < 0.001; d = 1.05). Additionally, increased pitch stability (4.91 vs. 2.37; p < 0.001; d = 0.78) and reduced shimmer were observed. A negative correlation was identified between vocal awareness and EMG (r = − 0.273; p = 0.004). Participants receiving VR-based multimodal biofeedback demonstrated greater short-term improvements in physiological, acoustic, and subjective outcomes than those receiving conventional instruction. These findings are consistent with enhanced sensorimotor adaptation during training within an information-rich learning environment. Although further studies are required to evaluate long-term retention, transfer of learning, and the independent contributions of VR and biofeedback, the proposed approach may complement existing vocal pedagogy by providing learners with additional physiological information during practice.
Chronic pain patients often exhibit altered processing of internal bodily sensations, especially in the musculoskeletal domain, and impaired body awareness. This case-control study investigated the association between resting electromyographic (EMG) activity, musculoskeletal tension discrimination and body awareness in chronic headache (CH) patients compared to healthy controls (HC). Twenty-one patients diagnosed with chronic headache and 22 matched healthy controls performed a muscle tension discrimination task while EMG was recorded from the frontalis (pain-related) and biceps brachii (pain-unrelated) muscles. Questionnaires assessed body awareness and pain-related cognitive and affective factors. Compared to HC, CH patients showed higher resting muscle activity (β = 1.32; p < 0.001) and lower discrimination (β = -0.12; p = 0.007) only in the pain site. CH patients exhibited reduced body awareness (η²p = 0.19; p = 0.003), higher anxiety (β = 3.10; p = 0.032), catastrophizing (η²p = 0.30; p < 0.001), and helplessness (η²p = 0.19; p = 0.004). Notably, lower muscle tension discrimination was associated with both higher resting frontalis EMG (ρs = -0.31; p = 0.043) and catastrophizing (ρs = -0.39; p = 0.009). Patients with CH exhibit a site-specific deficit in muscle tension discrimination, accompanied by elevated resting pericranial muscle tension, reduced body awareness, and maladaptive cognitive coping strategies. The association between catastrophizing and impaired discrimination highlights the interplay between cognitive-affective factors and psychophysiological dysregulation in CH. These findings underscore the importance of multidimensional assessment in patients with CH in order to identify targeted psychophysiological treatment.
Grounded in the Neurovisceral Integration Model (NVIM), this study examines the acute effects of two respiratory architectures—4–7-8 (exhalation-focused) and Nadi Shodhana (alternate-nostril breathing)—on stress, affect, and cardiac autonomic regulation in university students. This analyst-blinded, randomized crossover study included 34 participants (19 male, 15 female) who completed three 10-min conditions (4–7-8, Nadi Shodhana, and resting breathing) in a counterbalanced order (with a 1-week washout period between conditions). Subjective outcomes were assessed using the Perceived Stress Scale (PSS), Positive and Negative Affect Schedule (PANAS), and Visual Analog Scale (VAS). Heart rate variability (HRV) was recorded via Polar H10 (1000 Hz) and analyzed using Kubios with artifact correction. HRV parameters (SDNN, RMSSD, LF/HF) were evaluated using 3 × 2 mixed-design ANOVAs with Bonferroni correction. Significant condition × sex interactions were observed for subjective outcomes. The 4–7-8 technique was associated with reduced stress and negative affect in women, whereas Nadi Shodhana showed greater reductions in men. No significant main effects of condition were observed for conventional HRV indices. However, a significant main effect of sex was found for RMSSD (F(1, 33) = 10.19, p < 0.01, η2 = 0.24). No other HRV effects reached statistical significance. Brief respiratory interventions differentially modulate subjective emotional states in a sex-dependent manner, whereas acute autonomic changes remain limited. These findings suggest a temporal dissociation between rapid affective regulation and short-term cardiac autonomic responses, consistent with with an NVIM-based interpretation. However, the present findings do not establish specific neurovisceral mechanisms or demonstrate longer-term autonomic adaptation, which should be examined in future longitudinal studies.
Box breathing, also referred to as square breathing or four-square breathing, consists of equal phases of inhalation, breath retention, exhalation, and post-exhalation hold. It is widely promoted as a simple breathing technique for stress reduction and autonomic regulation; however, evidence from randomised controlled trials (RCTs) specifically evaluating box breathing remains limited and fragmented.To systematically identify and synthesise evidence from randomised controlled trials assessing the effects of box breathing on stress-related, autonomic, and selected clinical outcomes. This systematic review was conducted in accordance with PRISMA 2020 guidelines. Electronic databases including PubMed, Scopus, Web of Science, and ClinicalTrials.gov were searched for randomised controlled trials published up to 2025. Studies were included only if they explicitly investigated box breathing (equal-phase inhale–hold–exhale–hold pattern) as the primary intervention. Data extraction and methodological quality assessment were performed using the Cochrane RoB 2 tool. Due to substantial heterogeneity in populations, interventions, and outcome measures, findings were synthesised narratively. A total of eight eligible randomised controlled trials that were eligible were found. The studies encompassed both healthy adults and clinical cases such as postpartum women and women recovering from surgery. In several studies, box breathing was shown to have short-term benefits on perceived stress, perceived anxiety and mood in a non-uniform manner. There were also mixed physiological responses, s with decreases in respiratory rate seen in some studies and changes in heart rate and heart rate variability in others. There is also more recent evidence that box breathing reduces certain acute stress responses, such as heart rate, state anxiety and salivary alpha-amylase, but not HRV or cortisol. Clinical results were a decrease in postpartum pain and an enhancement in some lactation-related outcomes. Of the 29 RCTs, there were no RCTs that directly measured spirometric lung function or maximal aerobic capacity. Randomised studies in the literature have been conducted in recent years to evaluate the efficacy of box breathing on a wide range of autonomic functions; although it appears to be effective for short-term stress and emotional self-regulation, its effects on wider autonomic functions are inconsistent. The evidence available is limited due to a small number of studies, variable protocols and populations, and a limited long-term assessment. More carefully conducted randomised trials with uniformly prescribed breathing regimens and physiological measures of outcome are needed before more widespread clinical uses can be determined.
