Even in shorter races such as a 5K race, medical problems can and do occur, especially if it is a warm or humid day and if you are not in peak running fitness. Heat illness can occur easily with intense effort, manifesting often as nausea, dizziness, and headache. Adequate hydration (drinking 16-24 ounces of sports drink, 1-2 hours before the Run is recommended) allows you to continue to produce sweat, which cools the body as it evaporates from the skin. If you feel sick in any way, please stop and walk so that no one ends up with medical problems.