The Challenges of Hydration

There's now a really robust body of literature out there that basically says if you're relying on thirst, you're going to end up consuming about 50% of the fluids you've lost. The second one with weigh ins is actually the gold standard of measuring sweat rate and fluid needs. But it's completely useless when you're out in the fields. And we see certain trends by age, gender, fitness level, or heat acclimatization.