CSSD Practice Exam 2025 – Complete Study Resource

Creatine is not classified as one of the four main fuel sources for energy in the body. The primary energy sources typically recognized include carbohydrates (stored as glycogen), plasma glucose, fat (in the form of intramuscular triglycerides), and protein (when utilized in extreme circumstances). Each of these sources plays a critical role in energy metabolism.

Glycogen serves as a stored form of glucose primarily found in the liver and muscles, providing a quick source of energy during physical activity. Plasma glucose is readily available in the bloodstream, fueling cellular functions and physical performance. Intramuscular triglycerides act as a significant fat store that muscles can readily access during prolonged or endurance activities.

While creatine is involved in energy production, specifically through the resynthesis of adenosine triphosphate (ATP) in short bursts of high-intensity exercise, it does not serve as a primary fuel source for energy in the same way as the other three options. Instead, it functions more as a supplemental compound that recycles energy rather than a direct fuel source itself.