HIIT alternates short bursts of maximum-effort exercise with brief recovery periods. Work intervals may include sprints, burpees, kettlebell swings, or box jumps. The intense effort raises heart rate rapidly and creates an afterburn effect, where the body continues burning calories for hours post-workout. HIIT is time-efficient, improves cardiovascular capacity, and can be adapted to any fitness level through work-to-rest ratio adjustments. Classes are usually 20 to 45 minutes long and often include a warm-up and cool-down. It is ideal for busy people who want maximum results in minimum time.