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If you drop onto your hands and toes, keep your back flat, arms straight, and hips low, then push off with both legs as your arms pull forward, you can run on all fours. But human arms are too short compared to legs, so you’d lose speed. Even if your arms were longer, your spine would need to curve deeply—and it’s not built for that. Over time, your shoulders and wrists would take too much strain and get injured. Humans are designed for efficient upright movement and endurance—not speed on four