"Zone 2" refers to a specific heart rate training zone that is often used in endurance training. It typically represents 60-70% of an individual's maximum heart rate. Training in this zone helps improve aerobic capacity and endurance, making it beneficial for athletes and fitness enthusiasts. In Zone 2 training, the body primarily uses fat as a fuel source, promoting efficient energy use. This zone is ideal for long, steady workouts, such as running, cycling, or swimming, allowing individuals to build stamina without excessive fatigue.