Final answer:
Sweat evaporates from the skin during running, removing heat and cooling the body. Adequate fluid intake is necessary to sustain this process, especially since high humidity can reduce sweat evaporation efficiency. In tandem, the cardiovascular system helps regulate temperature by adjusting blood vessel width.
Step-by-step explanation:
During running or any strenuous activity, thermoregulation is critical for maintaining the body's core temperature. Sweat plays a significant role in this process. When the body's temperature rises, sweat glands secrete fluid onto the skin's surface. As this sweat evaporates, it carries a large amount of heat away from the body, effectively cooling it down. This loss of energy, or evaporative cooling, is a key aspect of temperature regulation during exercise.
In high humidity conditions, sweat does not evaporate as efficiently, leading to a less effective cooling process. To ensure proper sweating and cooling, it is essential to maintain adequate fluid intake to replace the water lost through sweating. The cardiovascular system also participates in thermoregulation by dilating blood vessels, which increases blood flow to the skin, aiding in heat dissipation to the environment.