I’ll be honest — when my sports medicine mentor first mentioned the vagus nerve during a continuing education seminar back in 2014, I tuned out. Something about parasympathetic this and autonomic that. I was deep in my track coaching era, obsessed with force production and split times, and “nervous system regulation” sounded like something a yoga retreat would put on a flyer. I was spectacularly wrong, and it took a decade plus a wearable revolution to prove it. The vagus nerve is the longest cranial nerve in your body, running from your brainstem down through your neck, weaving around your…