Basic Martial Arts
Karate, Boxing, Jujitsu, Aikido... the list goes on and on. At the beginners level, martial arts can be great form of exercise and as such will improve the efficiency of your exercise program. When you reach higher levels, it can sometimes provide a simple form of self-defense. NOTE: The exercise effect from Martial Arts is not cumulative with the effect from Yoga.
You can learn about this skill from the item or book Basic Martial Arts.
You can learn about this skill in a school or university which offers a class in it, or you can learn it from an apprenticeship with a master.
Higher Learning
If you have enough stars in this skill you can learn the following: