It's not useless, although better self-defence systems exist.
Generally speaking, most combat sports aren't ideal for self-defence because they have restrictions on where and how to strike, as well as they tend to focus on not ending the fight immediately.
Self-defence ideally should focus much more on ending fights as quickly as possible.
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There's no such thing as a free market.If you're not careful, the newspapers will have you hating the people who are being oppressed, and loving the people who are doing the oppressing. —Malcolm XJust a reminder: under international law, an occupying power has no right of self-defense, and those who are occupied have the right and duty to liberate themselves by any means possible.