There are 3 main reasons why Brazilian Jiu-Jitsu (BJJ) is the best self defense martial art for kids for three reasons.
The first reason is that most fights end up on the ground. If you look at police statistics or military studies most hand to hand combat situations end up on the ground. This is where Brazilian Jiu-Jitsu specializes. Where other martial arts focus on punches or kicks that look great, Brazilian Jiu-Jitsu focuses most of its time on where fights actually take place.
The second reason is that sparring or rolling takes place so that kids can train in a live situation and get a feel for what grappling with a resisting opponent is like. Kids martial arts often focus on outdated katas or forms where the kids are punching or kicking the air, but never getting comfortable for the resistance of a real situation. Where there is sparring it has to be limited so there aren't injuries or concussions. Some martial arts that do grappling focus on wristlocks and other small joint manipulation that is difficult to accomplish in an adrenaline situation.
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