Shimojo et al. (2019) demonstrated the direct relationship between physical exercise and vagal activation. They demonstrated that swimming for 1 h a day for seven consecutive days attenuated serum levels of tumor necrosis factor (TNF) in the spleen of mice compared to the control group in an endotoxemia model, an effect that was prevented by vagotomy bilateral. In humans, an inverse association was observed between the vagal tone and TNF-alpha level in Crohn’s disease patients (Pellissier et al., 2014). Here, TNF is linked to Crohn disease.