The 30-60-90 rule in the gym typically refers to a time-based interval training strategy used in cardio or high-intensity interval training (HIIT) formats. It’s a method of progressive interval conditioning, where the work intervals get longer and/or more intense, and rest intervals remain consistent or decrease—designed to improve cardiovascular endurance, muscular stamina, and metabolic conditioning. The 30-60-90 workout structure is based on performing three consecutive work intervals that increase in length and require varied intensities: 30 seconds: high-intensity exercise 60 seconds: moderate-to-high intensity 90 seconds: moderate intensity, focused on endurance. Each round (or set) of 30-60-90 is followed by a brief rest period (typically 30–60 seconds), and the cycle is repeated 2–4 times, depending on the individual’s fitness level and training goal. This method is commonly used in: HIIT (High-Intensity Interval Training) Group fitness classes Metabolic conditioning (MetCon) Hybrid bodyweight/cardiovascular workouts. The 30-60-90 format is designed to maximize energy system training by targeting different aspects of performance in a single workout. 30 seconds: taps into the ATP-PC system for explosive, anaerobic effort 60 seconds: shifts into glycolytic energy production, building muscular endurance 90 seconds: emphasizes aerobic metabolism, improving cardiovascular capacity.