Why is Hydration So Important for Runners?
Water is required for the majority of chemical reactions during athletic performance. This water comes from plasma volume, which makes up 50-60 percent of total blood volume. Therefore, when you become dehydrated, the most significant impact is a reduction in your total blood volume.
In the body, blood circulates from the heart, throughout the body and back to the heart through the lungs, and it continuously repeats this circuit. When your blood volume decreases, performance of key bodily functions decrease with it.
Blood has three critical tasks during exercise:
- Assist with the absorption of calories and fluids consumed. Blood is diverted away from the gut to the working muscles during exercise, which makes it more difficult to absorb nutrients from the fuel you eat. In a dehydrated state, this is the first task to be shut down, which can lead to gastrointestinal distress. In other words, hydration promotes digestion.
- Deliver oxygen and nutrients to the working muscles for energy. The faster you run, the more oxygen and nutrients the body demands. In a dehydrated state, this is the second task to be shut down.
- Regulate body temperature through sweat. If your sweat rate decreases as a result of dehydration, your core body temperature will rise. This is the first priority and the last to fail in a dehydrated state. If your body is unable to cool itself, severe hyperthermia (>104 °F) can lead to organ failure and death.