9 Best Cardio Exercises for Small Spaces (No Equipment Needed)

4. High Knees

High knees are a great running-in-place substitute that works well in limited square footage. Stand tall with core engaged, and drive one knee up toward hip level while pumping the opposite arm, then switch quickly. Keep the rhythm brisk and shoulders relaxed. For quieter options, march with high knee lifts—focus on lifting the knee deliberately and maintaining good posture rather than speed. As a beginner, slow the cadence and ensure your pelvis stays neutral. Common mistakes include leaning back or forward, doing shallow lifts that don't engage the hip flexors, and neglecting arm swing; these reduce effectiveness and can make the movement feel awkward. High knees help improve coordination and increase heart rate without needing more than a step or two of space. Use them as a warm-up or insert them into a circuit for a quick cardio boost.