The vagus nerve: a cornerstone for mental health and performance optimization in recreation and elite sports

Figures

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  Figure 1. Psychophysiological models of human performance. Several models describing the effects of psychological and physiological variables on performance can be described by an inverted-U function. (A) The illustration is an adaptation of the canonical Yerkes-Dodson law, where performance is regulated as an inverted-U function of pressure, stress, or sympathetic arousal (Yerkes and Dodson, 1908). (B) Task-based performance can also be described by an inverted-U function of locus coeruleus (LC) and norepinephrine (NE) activity. It has been shown that low-frequency tonic activity of LC neurons occurs during periods of inattentiveness, while higher frequency tonic activity of LC neurons occurs during periods of hyperarousal when attention is labile (Aston-Jones and Cohen, 2005). As illustrated, during periods of peak task-based performance, LC neurons fire in a phasic manner (Aston-Jones and Cohen, 2005). Other data convincingly show that transcutaneous vagus nerve stimulation (tVNS) can tune arousal by modulating LC/NE activity across this performance curve as a function of several different stimulus variables (cyan inset). These tVNS variables that differentially influence autonomic…

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  Figure 2. Central and peripheral mechanisms of autonomic arousal and the vagal brake. (A) The schematic shows the critical relationship between the environment, mind, and body as mediated by several cranial nerves, including the vagus (CN X), as similarly described by Polyvagal theory (Porges, 2009). The figure shows afferent (blue) and efferent (orange) connectivity between muscles and organs relay to several brainstem regions including the nucleus ambiguous (NA), the dorsal motor nucleus (DMN), and regions of the reticular activating system (RAS) like the locus coeruleus (LC) and nucleus of the solitary tract (NTS). Cranial nerve activity is transmitted to cardiorespiratory and upper-airway effectors while receiving afferent feedback that ultimately reaches cortical centers. These pathways are responsible for the real-time tuning of autonomic nervous system responses, including heart rate, respiration rate, and emotional reactivity to internal visceral states and environmental stimuli. (B) The figure illustrates how resonance-frequency breathing (black; ≈ 6 breaths · min−1) produces large, phase-locked oscillations in heart rate (HR; red) and blood pressure (BP; purple) separated by a ≈…

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  Figure 3. Transcutaneous electrical nerve stimulation methods of non-invasive vagal modulation. Modern non-invasive vagus nerve stimulation methods enable the targeting of vagal fibers through the skin using compact, user-friendly embodiments of transcutaneous electrical nerve stimulation (TENS) devices designs. These TENS-like devices deliver low-intensity (< 10 mA) pulsed electrical currents through the skin to safely modulate vagal activity. (A) Shown are photographs of a transcutaneous auricular vagus nerve stimulation (taVNS) device (BRAIN Buds; IST, LLC) that utilizes conductive hydrogel earbud electrodes to access the auricular branch of the vagus lining the acoustic meatus of the external ear enabling comfortable and precise self-administration (Tyler, 2025). (B) A transcutaneous cervical vagus nerve stimulation (tcVNS) device (GammaCore; ElectroCore, Inc.) is shown applied to the neck to stimulate the cervical branch of the vagus nerve using metal contact electrodes (Silberstein et al., 2016). Together, these examples illustrate the shift toward modular, portable neuromodulation tools for clinical and human performance applications.

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  Figure 4. Modulation of autonomic arousal by heart rate variability biofeedback training. (A) The line plots illustrate the specificity of resonance frequency breathing (RF) on autonomic regulation. The top panel shows that participants in the RF group exhibited the greatest increase in LF/HF ratio during the breathing phase, indicative of optimized baroreflex resonance, while the RF+1 and control groups showed minimal or negative changes. The bottom panel shows systolic blood pressure (SBP) trends, where both RF and RF+1 groups exhibited reductions during training, but only the RF group maintained attenuated blood pressure reactivity during a subsequent stressor (Steffen et al., 2017). (B) The line plots illustrate the cumulative neurophysiological effects of HRVBFT across training sessions. The top panel shows increases in HRV amplitude over four sessions in the HRVBFT group (HRV), with little change in the progressive muscle relaxation (PMR) control group. The bottom panel shows significant increases in heartbeat-evoked potential (HEP) amplitude, an EEG marker of interoceptive engagement, only in the HRVBFT group, suggesting enhanced brain-body integration and vagal afferent signaling…

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  Figure 5. Contemplative practice reduces psychophysiological responses to stress. (A) The line plots illustrate how long-term contemplative practice modulates both the hypothalamic pituitary axis (HPA) and autonomic responses to psychosocial stress. The top panels show cortisol levels and subjective stress ratings while the bottom panels illustrate heart rate (HR) and heart rate variability root mean square of successive differences (RMSSD) in response to active and placebo Trier Social Stress Tests (TSST). (B) The histograms illustrate differences in cortisol concentrations for experienced meditation practitioners compared to naïve controls in response to stress (top) and during the recovery period (bottom). The data show acceptance-based coping strategies from meditation experience result in faster cortisol recovery (Taublieb, 2018). The figures are adapted from Gamaiunova et al. (2019). **p < 0.05.