HIIT stands for High-Intensity Interval Training and is popular in fitness programs for its effectiveness in burning calories and improving cardiovascular fitness in a short amount of time. This training style involves alternating between brief, intense bursts of exercise and low-intensity recovery periods. Due to its efficiency and adaptability, HIIT can fit various fitness levels and preferences. Additionally, it can lead to improved metabolic rate, enhanced endurance, and is often more engaging for participants compared to traditional steady-state exercise routines.