Item from One-Punch Man by ONE & Yusuke Murata
The biological ceiling on growth that every living being has — except Saitama, who broke his, and Garou, who was breaking his through sheer willpower and pain.
The Limiter theory is the series' closest thing to an explanation for Saitama's power. Dr. Genus theorized that Saitama's mundane training routine (100 push-ups, 100 sit-ups, 100 squats, 10km run) was so persistently done despite being painful that it broke through the natural limit on human growth. The result: infinite physical capability. Garou's arc involves approaching the same breakthrough through combat damage and monsterification — getting stronger every time he's pushed to his breaking point. The difference: Saitama broke his Limiter quietly and completely. Garou's was cracking dramatically and incompletely. The Limiter is the series' most important piece of worldbuilding because it explains why Saitama is unique — not through special training or genetic gifts, but through the stupid, boring persistence of doing something every day when it hurts.
The Limiter is not a physical object — it's a concept. Dr. Genus (House of Evolution) theorized that every organism has a limit to how strong they can become, a built-in ceiling that prevents indefinite growth. Breaking the Limiter removes this ceiling entirely.
Also known as: The Limiter, Limiter