ISSA Nutritionist Practice Exam 2026 – Comprehensive All-In-One Guide to Exam Mastery!

The correct choice is interstitial fluid, as it is the fluid found in the spaces between cells in tissues. This compartment serves as a reservoir for various substances, including electrolytes and waste products, and plays a crucial role in maintaining homeostasis. When the body begins to sweat during exercise, it primarily draws water from the interstitial fluid.

During physical activity, the body's temperature rises, and sweating becomes a vital process for thermoregulation. The interstitial fluid provides the necessary water and electrolytes that make up sweat, which evaporates from the skin surface to help cool the body down.

The other fluid compartments mentioned have specific roles that are not directly related to the production of sweat. Intracellular fluid is located within the cells and is critical for cellular processes. Intravascular fluid refers to the blood plasma within blood vessels and is more involved in circulation and transport of nutrients and gases. Extracellular fluid encompasses interstitial fluid and intravascular fluid but does not specifically indicate the fluid utilized for sweating, which is more accurately defined by the interstitial component.