Transcutaneous Vagus Nerve Stimulation (tVNS) for Improved Recovery After Exertion.

The proposed study aims to advance the understanding of Post-COVID treatment using a randomized cross-over design to evaluate the taVNS-induced changes over 12 weeks. A hundred twenty patients diagnosed with Long/Post-COVID are randomly assigned to one of three groups related to the two arms of the study ("Monitoring with low/high-intensity stimulation" vs. Monitoring without stimulation"). In the treatment group, forty patients will start with high-intensity taVNS for 6 weeks, then switch to low-intensity stimulation for an additional 6 weeks. Another 40 patients begin with low-intensity stimulation for 6 weeks, followed by high-intensity taVNS stimulation. The control group ("Monitoring without stimulation") is able to receive taVNS after participation in the study. The treatment group and the control group will participate in the same monitoring procedures. All participants will attend an initial laboratory session to complete several baseline assessments, including questionnaires, measuring energy expenditure via indirect calorimetry and completing a body silhouette task. Blood samples are taken at every session to evaluate changes in metabolic and inflammatory markers. To assess the motivation to work for rewards, the investigators employ an effort-based-cost-benefit paradigm (Effort Allocation Task). All these lab assessments will be repeated after 6 and 12 weeks to evaluate stimulation-induces changes in primary and secondary outcomes. In addition, all participants are given a cardio bracelet to monitor physiological parameters (e.g. heart rate, heart rate variability, breathing, skin conductance, step counts) over the study period. Over the 12 weeks, the treatment group will self-administer taVNS for four hours daily in a targeted manner, anticipating forthcoming exertion and stimulating in anticipation of an effortful event to enhance the patients' motivational drive and recovery. Another essential part of the study is the monitoring over the 12 weeks. All participants will complete daily ecological momentary assessments via smartphone to monitor their mental states. In addition, participants will perform once a day one of two discounting games (effort or temporal discounting task) to investigate changes in their decision behavior over time. The effort discounting task is essential to assess the motivation of post-COVID patients to pursue subjectively effortful situations over the 12 weeks.