Nothing gets me sweatier than mowing the lawn. When my wife and I bought a home on a lot with a generous yard last year, I immediately went all out: new mower, new trimmer (with a swiveling head for edging along the driveway and the entrance walkway), battery-operated hedge clippers—the works. And after the first time hitting the lawn last summer, I was dripping with so much sweat that I had to peel the “Sky’s Out, Thighs Out” long-sleeve shirt off my body. Mission accomplished, baby.

Sweat, naturally, is seen as a sign of hard work, a physiological currency of its owner that proves some type of hard work was accomplished. You see it in Gatorade commercials. You see it in the weather-worn faces of suburban dads everywhere. You see it on podcaster Joe Rogan’s Instagram feed, where he makes it a point to post the puddles of sweat he makes after an intense workout. “Sweat Tents,” miniature, pop-up saunas, are all the rage in the Make America Healthy Again world for improving blood pressure. But what does getting sweaty really mean?

A new cottage industry is here to find out. Companies large and small now produce specialized sensors, no bigger than a slice of lemon, that measure our sweat rates and composition: how fast we throw water off the body, and what’s exactly in those little beads. According to them, these new wearables are important because sweat is the most ignored biomarker, and understanding it will lead to better hydration, better performance, and a better life.

“Most athletes are left to go by thirst alone, which is proven to be unreliable,” said Meredith Cass, founder of Boston-based Nix Biosensors, whose own sweat sensors have been tried by SEC college football players, in 2022. “We believe hydration management is a fundamental human need.”

I figured I needed to try it out for myself. I bought a Gatorade sweat patch—a one-time, disposable sticky pad that you affix to your arm—to try out, but I also spoke to experts, researchers, and, yes, Gatorade, to try to understand everything I didn’t understand about the science of sweat. As I discovered, it turns out body type, fitness, our tolerance to heat, even our genetics dictate how much (and how well) we sweat. But the underlying truth, it seems, is the same.