During enduring physical activity, the body primarily relies on stored energy sources, such as glycogen and fat. Initially, glycogen stored in muscles and the liver is broken down into glucose for energy. As activity continues, the body shifts to metabolizing fat for fuel. This process is essential for prolonged efforts, as glycogen stores are limited. Efficient energy utilization is crucial for maintaining performance during endurance events, and training can enhance the body’s ability to use fat stores, thereby delaying fatigue and improving stamina.