Resonance Frequency Breathing Intervention Modifies Cardiac Autonomic Response During a Metabolic Challenge

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/m 2 ). 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.