As a rule of thumb, staying hydrated throughout the day is important for overall health and wellbeing. But as you move more during exercise, your body will work more to regulate its temperature by sending a message to the hypothalamus in the brain to stimulate the sweat glands in your skin. This results in heat being removed as the sweat evaporates from your skin3.
But as you sweat, your body loses fluids. The longer and more intense the workout, the more fluids are lost. On warmer days, your body temperature may already be raised, leading to even more fluid loss and increasing your risk of dehydration. Dehydration occurs when the fluids lost through sweating aren’t replaced and can lead to headaches, muscle cramps, and nausea4. Even if you aren’t feeling thirsty, drink plenty of fluids before, during, and after your workout.