Thirst during exercise is a poor indicator of how much you actually need to drink. By the time you feel it, performance has likely already taken a hit. Research is pretty clear on this: people left to drink on their own volition during exercise consume only about half the fluids they need. The body's thirst signal lags well behind actual fluid loss, especially in the cold, where you often don't feel thirsty at all despite sweating steadily. The numbers compound fast. A 185-lb person loses 1% of body weight at just under two pounds of fluid. Lose 2%, and physical performance drops 10%. Skill-based performance – accuracy, reaction time, coordination – deteriorates even before that. Generic advice like "drink 8 glasses a day" doesn't account for body size, sweat rate, heat, or effort. Hydration during exercise needs a concrete target. We built a free calculator to help you figure out the right amount of fluid you need. performpodcast.com/tools/hyd…