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

• A. Saturated fat
• B. Amino acids
• C. Starch
• D. Carbohydrates

Answer: (D)

During high‑intensity work, the body needs ATP quickly to power rapid muscle contractions. Carbohydrates provide energy fastest because glucose can be produced from blood sugar and stored glycogen in the muscles very quickly and enter glycolysis, supplying ATP rapidly. This fast pathway works well even when oxygen is limited, which is why anaerobic glycolysis supports short, intense bursts of activity. Fat metabolism, by contrast, is slower and requires more oxygen, so it cannot meet the rapid energy demand of high‑intensity efforts. Amino acids aren’t the body’s go‑to energy source during these brief, intense bouts, and starch is simply a type of carbohydrate that becomes glucose once digested. In short, carbohydrates are the readily available fuel for high‑intensity activities.