2010). Regular physical activity is typically associated with lower resting heart rate, which is at least partially attributable to an increase in central cardiac vagal outflow (Melanson 2000; Buchheit et al. 2004; Sandercock et al. 2008; Joyner and Green 2009). The type and intensity of exercise determine the level of resting bradycardia and its mechanisms of control (Azevedo et al. 2014). The current study examined the effect of irisin on cardiac-projecting neurons of nucleus ambiguus, a critical site for central parasympathetic cardiac control (Mendelowitz 1999). Here, FNDC5 is linked to Bradycardia.