Effective fitness routines for people with busy schedules can include high-intensity interval training (HIIT), bodyweight exercises, or brief sessions of strength training. These types of workouts can often be completed in 20-30 minutes and can be done at home or in a gym. Incorporating activities like walking or cycling into daily commutes also promotes fitness without requiring additional time. The key lies in consistency and finding enjoyable activities to ensure adherence amidst a packed schedule.