I thought I knew how to hydrate during workouts. A sweat test showed I was making 3 big mistakes.

I thought I knew how to hydrate during workouts. A sweat test showed I was making 3 big mistakes.

The Gatorade Sports Science Institute offers exercise testing for elite athletes. I put my sweat to the test as an amateur roller derby athlete.Clark Hodgin for BI"It's HOW hot in here?"I'm no stranger to sweating. As a competitive roller derby athlete, I spend hours a week racing around the track and smashing into my friends (and rivals), often amid sweltering NYC summers.But this time, I was locked in, literally harnessed to a giant industrial…