Interval training involves alternating periods of high-intensity exercise with low-intensity recovery or rest periods. This method enhances cardiovascular fitness, improves metabolic rate, and can lead to greater calorie burn in shorter durations. Commonly used in running, cycling, and circuit workouts, interval training effectively builds strength and endurance while keeping workouts engaging. The variation in intensity also reduces boredom and can prevent plateauing in fitness progress, making it a popular and effective training method.