Author(s): BOURDILLON, N., ROCHAT, A., WEYDERT, S., MIKELSON, J., MILLET, G.P., Institution: UNIVERSITY OF LAUSANNE, Country: SWITZERLAND, Abstract-ID: 453

INTRODUCTION:
Arterial baroreflex function and respiratory sinus arrhythmia (RSA) constitute two key feedback mechanisms governed by interactions between sympathetic and parasympathetic activity. As respiratory frequency (Rf) increases, vagal efferent mechanisms progressively lose their ability to track respiration-related oscillations, resulting in a reduction in RSA, whereas lower Rf enhances RSA. Slow paced breathing (SPB) is therefore expected to promote health benefits through an increase in RSA; however, previous findings remain inconsistent. The present study aimed to compare a personalized SPB condition with a placebo condition to differentiate the specific effects of SPB from those attributable to breathing awareness or attentional distraction alone.
METHODS:
Twenty-four healthy young adults completed a six-week intervention consisting of either personalized SPB (n = 12) or a control condition involving spontaneous breathing (CON, n = 12). Baroreflex sensitivity (BRS), pulse waveform (PWF) and heart rate variability (HRV) were assessed under laboratory conditions before and after the intervention (labPRE and labPOST). Additionally, three times per week during the intervention, participants completed an at-home orthostatic test (5 min supine [sup] followed by 5 min standing [stand]) before (hPRE) and after (hPOST) each SPB or CON session. Personalized SPB corresponded to the breathing frequency producing maximal RSA, reflecting optimal synchronization between respiration and heart rate. HRV indices included heart rate (HR), root mean square of successive differences (RMSSD), and spectral power in the low- (LF) and high-frequency (HF) bands; PWF indices include: stiffness index (SI), augmentation index (AI), and systolic/diastolic amplitudes and timings and were interpreted as indicators of combined central and peripheral vascular adaptations to SPB training.
RESULTS:
From labPRE to labPOST, BRS (12.8 ± 3.2 vs. 15.2 ± 2.8 ms/mmHg p = .030), RMSSDsup (45.9 ± 12.6 vs. 62.9 ± 19.4 ms, p = .014) and HFsup (1062 ± 687 vs. 1469 ± 905 ms2, p = .040) increased only in the SPB group. Large artery SI (161+/-28 vs. 137+/-13 mmHg/s, p = .027) and AI (2.52+/-0.43 vs. 2.15+/-0.28, p = .026) decreased only in the SPB group and were significantly lower than CON at labPOST. From hPRE to hPOST, LFsup decreased more in SPB than in CON, whereas RMSSDstand increased more in CON than in SPB. Toward the end of the intervention, LFstand showed a greater reduction in SPB than in CON, whilst HFstand increased more in SPB.
CONCLUSION:
Six weeks of personalized SPB training induced greater parasympathetic modulation of cardiac function and improved vascular compliance compared with spontaneous breathing, supporting the health benefits of prolonged SPB practice. Additional research is needed to further elucidate the physiological mechanisms underlying these adaptations.