Which two types of reserves are primarily used for fuel during exercise?

During exercise, the body primarily relies on carbohydrates and fats as its main sources of fuel. Carbohydrates are stored in the muscles and liver as glycogen, which can be readily converted into glucose to provide quick energy for high-intensity activities. Fats, on the other hand, serve as a significant energy source during prolonged, lower-intensity exercise, where the body taps into fat stores for fuel.

Proteins also play a role in energy metabolism but are generally not a primary fuel source during exercise. They are more commonly used for repairing and building tissues than for providing immediate energy. Vitamins, minerals, and water, while essential for overall health and proper physiological functioning, do not serve as direct energy sources during exercise. Thus, carbohydrates and fats are the two main types of reserves used for fuel during physical activity.