Why You Get Thirsty When You Exercise

When we exercise, our core body temperature rises from a minimum of 37°C to a maximum of 40°C, depending on the intensity. This is because a large amount of heat is generated as your muscles contract. Your brain secretes sweat to prevent your body temperature from rising too much. Sweat is composed of water and salt, causing the body's water to evaporate quickly. As water is lost through sweat, the amount of water in your blood decreases. This thickens the concentration of your blood and causes a slight drop in blood pressure. The thirst center in the hypothalamus of your brain detects these symptoms. This thirst center sends us a strong signal to "drink water," which is what we perceive as thirst.