Oom Yung Doe (음양도; 陰陽道) is a line of martial arts schools founded by John C. Kim (Grandmaster "Iron" Kim). In addition to teaching a broad
range of physical movements and self-defense, the training also incorporates meditation, philosophy, and the use of herbal formulas and equipment. Some students describe substantial
benefits including self-defense skills, mental and physical health, and improvements in conditions such as asthma, diabetes, rheumatoid arthritis, and blood pressure.Critics, however,
accuse the school's founder and instructors of unethical behavior, charging large fees, and pressuring students to commit to long-term contracts.