Which macronutrient is most readily used by the body during high-intensity activities?

• A. Fats
• B. Proteins
• C. Carbohydrates
• D. Vitamins

Answer: (C)

During high-intensity activity the body needs energy rapidly. Carbohydrates provide quick energy because they’re stored as glycogen in muscles and liver and can be rapidly broken down to glucose and used in glycolysis to generate ATP quickly, even before oxygen delivery catches up. This fast energy pathway supports short, intense efforts like sprinting or heavy lifting. Fats, while a larger energy store, yield energy more slowly and require more oxygen, making them less suitable when effort is maximal. Proteins aren’t a primary energy source during brief, intense work, since their breakdown for fuel is less efficient and not the body’s preferred route. Vitamins aren’t energy sources themselves; they act as cofactors in reactions that help energy production. So carbohydrates are the best answer for the most readily available energy during high-intensity activities.