There's a lot of different martial arts that you can train inside. In the past, the most common practices were kung fu, karate, tae kwon do, and similar options. With the rise of MMA fighters, and the popularity of events that come within the fighting world, many are starting to look at a variety of different solutions as the way to go with self defense and more. With that in mind, you may want to look at a few options that fit your needs, but one of them should be Judo. There are several reasons why this is a good option to learn how to grapple, but honestly, you may narrow them down to 3 full reasons.
Learn Body Movement (Momentum)
There are several elements that you will learn with Judo. However, the main focus is on movements of the body. What that means, is that the goal is to use the momentum and body weight of others, to subdue them for defense. When someone moves against, tries to strike you, the goal is not to be offensive, but rather defensive, and Judo allows for that. Of course, there are other focoes here, but the main focal point is found within the framework of momentum and the use of bodily shifts, without having to use your own strength.
The Balance Factors
Judo teachers balance above many other things. For skateboarders, surfers, and those that are into action sports, training in this martial art becomes an important thing. You see, when you are working within this defense element, you're going to learn to have a stance that allows you to move people over your body, and to use your own muscle system to create incredible defense mechanisms. This is done without having to strike, without being proactive, but rather, reactive. Your balance will improve, and if you're an action sports fan, you will see your balance rise through the roof because of it. You will also learn to control your muscles across your shoulders, arms, legs, and hips.
Anyone Can Learn Judo
Perhaps the best thing about learning self defense, specifically that of Judo, is that anyone can learn. You can be in a wheelchair, you can be an old lady, you can be a young man, or a woman of any shape, size, and even children. All of these individuals can learn how to defend themselves with this type of form. It's meant to help anyone learn the techniques of peaceful defense, and fighting, without having to go with just strikes, kicks, and offense that you may think of when you consider martial arts.
As far as a peaceful, focused, energy based solution, Judo is hard to compare to others. It's a solution that you will no doubt want to explore as a top option for learning defense.