Post-exercise auricular vagus nerve stimulation modulates autonomic and recovery responses in physically inactive young adults: a randomized controlled trial.

Efficient post-exercise recovery largely depends on rapid parasympathetic reactivation of the autonomic nervous system. Auricular transcutaneous vagus nerve stimulation (taVNS) has emerged as a non-invasive neuromodulatory approach with the potential to facilitate autonomic recovery following physical exertion. This study aimed to investigate the acute effects of auricular transcutaneous vagus nerve stimulation applied immediately after exercise on autonomic nervous system activity and recovery-related physiological, metabolic, and perceptual parameters in healthy young adults. This cross-sectional study with an acute intervention bout included sixty physically inactive healthy young adults (18-35 years) who were randomly allocated to an exercise + taVNS group (n = 30) or an exercise-only control group (n = 30). All participants completed a standardized 30-minute treadmill walking protocol. Immediately after exercise, the intervention group received 20 min of bilateral taVNS, while the control group underwent a matched recovery period. Autonomic function was assessed using heart rate variability indices, including the root mean square of successive differences (RMSSD), a time-domain indicator of parasympathetic activity, and the low-frequency/high-frequency (LF/HF) ratio, which reflects sympathovagal balance, together with cardiovascular, metabolic, and perceptual recovery markers. Both groups demonstrated recovery-related improvements following exercise. However, the taVNS group showed greater reductions in systolic and diastolic blood pressure compared with the control group (p = .003 and p = .004). The parasympathetic nervous system index increased significantly more in the taVNS group (p = .009). Blood lactate concentration decreased more markedly in the taVNS group (- 4.90 ± 3.02 mmol·L⁻¹) than in the control group (- 1.38 ± 0.97 mmol·L⁻¹; p < .001). Participants receiving taVNS also demonstrated a greater reduction in perceived fatigue scores (p < .001). In contrast, heart rate variability parameters such as heart rate, RMSSD, and LF/HF ratio showed comparable recovery patterns between groups (p > .05). Auricular transcutaneous vagus nerve stimulation applied immediately after exercise appears to enhance parasympathetic reactivation and improve cardiovascular, metabolic, and perceptual recovery beyond spontaneous post-exercise recovery. These findings suggest that taVNS may represent a feasible non-invasive strategy to support acute post-exercise recovery in healthy young adults when applied under appropriate stimulation parameters (ClinicalTrials.gov: NCT07371676).