Intellectual Stimulation. It's not surprising so many people with advanced degrees are attrackted to Aikido. The main difference between this type of exercise and other types of exercise is that because Aikido is so interesting. Every class is different. The importantance of the challenge, weather mental, physical or both makes Aikido interesting and to stay interesting over time. Therefore, even in twenty, thirty or forty years, Aikido can stay interesting and different all the time, and you can gain not only rank, but you can keep your mind sharp and your body limber, without over doing it. At least the body part!