The nutrient primarily responsible for providing energy during intense physical activity is carbohydrates. Carbs are broken down into glucose, which serves as the body's main energy source during high-intensity exercise. Glycogen, stored in muscles and the liver, is derived from carbohydrates and released during physical exertion, supporting stamina and performance. Although fats and proteins also contribute to energy, carbohydrates are the most readily available source, particularly during demand for quick energy bursts. Thus, they play an essential role in fueling workouts and enhancing athletic performance.