Abstract
BACKGROUND: Transcutaneous auricular vagus nerve stimulation (taVNS) is a potential treatment for cardiovascular disease, but data on its effects on physiological function during exercise are lacking. We investigated the effects of taVNS on hemodynamics and autonomic nervous system function during exercise stress tests. METHODS AND RESULTS: Sixteen healthy volunteers underwent exercise stress tests with and without taVNS in this study, with a randomized crossover design and with a washout period of at least 7 days. taVNS was set to a frequency of 100 Hz and maximum current intensity without causing discomfort. Hemodynamics and autonomic nervous system function were evaluated using plethysmography and heart rate (HR) variability, respectively. After exclusion of an outlier, data of 15 participants were analyzed. In tests with taVNS, HR was significantly reduced at maximum exercise (136.0±9.7 vs. 132.0±9.2; P<0.001) and 1 min after exercise (115.0±11.4 vs. 104.0±15.0; P<0.001), with minimal changes in blood pressure. The stroke volume and total peripheral resistance at maximum exercise significantly increased and decreased, respectively. Furthermore, low/high frequency ratio reflecting sympathetic dominance decreased at rest (3.7±2.5 vs. 1.6±1.3; P<0.001) and at maximum exercise (4.5±4.5 vs. 1.2±0.9; P<0.001). CONCLUSIONS: taVNS can reduce HR with minimal effect on blood pressure by inducing parasympathetic dominance during exercise stress tests.