Influence of Manual and Electrical Vagal Stimulation on Autonomic Activity and Other Dysautonomous Symptoms in a Healthy Population.

The objective of this clinical, longitudinal, prospective, randomised (randomised) unmasked study is to analyse whether electrical and manual vagal stimulation produces changes in heart rate variability in a healthy population and it have a beneficial clinical effect in reducing dysautonomic symptoms. The main questions it seeks to answer are: * Will non-invasive (manual and electrical) stimulation of the vagus nerve produce a significant change in heart rate variability, generating effects on the regulation of the autonomic nervous system, increasing the activation of the parasympathetic nervous system and decreasing the activation of the sympathetic nervous system? * Will non-invasive (manual and electrical) stimulation of the vagus nerve have a beneficial clinical effect in reducing dysautonomic symptoms such as fatigue and improving sleep quality? * Will noninvasive (manual and electrical) vagus nerve stimulation improve quality of life? * Are there differences in the level of satisfaction with the treatment after the intervention program received? Two groups of participants will be formed: * Transcutaneous auricular vagus nerve stimulation consists of applying electrical stimulation to the auricular branch of the vagus nerve using a 2-pole stimulation electrode. Stimulation is performed for 1 hour per day for 10 days (5 days per week). * Manual vagus nerve intervention consists of applying a protocol of manual therapy techniques to the vagus nerve and along its path, during 4 sessions lasting 30 minutes, 2 interventions per week.