Improving cardiovascular fitness without running involves incorporating alternative aerobic exercises that elevate your heart rate. Try activities such as cycling, swimming, brisk walking, hiking, or using cardio machines like the elliptical or rowing machine. High-intensity interval training (HIIT) workouts, circuit training, or dance-based cardio classes can also effectively boost cardiovascular endurance. Consistency and gradually increasing intensity are key to seeing improvements in cardiovascular fitness regardless of the specific activity chosen.