You can have the heart, muscles and lungs, but if you don’t have the fluids, you won’t get anywhere at your athletic event. Your body is nearly two-thirds water, and even a small loss through your sweat can start to affect your performance. Since you’ve probably tasted your sweat before, you know it is not simply water, but also sodium and electrolytes. If you are an athlete exercising at an intense pace, you will need to replace these needed nutrients, too. Always talk to your doctor about the right amount of fluid replacement for you before adjusting your fluid intake.