There is a specific kind of August morning where the air feels like a wet towel by mile two, and this year I spent most of those mornings with a small plastic pod clipped to my left forearm, listening to it narrate my sweat. Every second, it streamed fluid loss, sodium concentration, and a drink-or-don’t verdict to my phone while I plodded through the humidity. My running partners thought I’d finally gone full lab rat. My coaching clients thought it was hilarious that the woman who preaches “learn your body” had outsourced hydration to a sensor the size of a…
