Color of judo uniform has no effect on winning. Contrary to previous studies and widespread belief, new research on competitive judo data finds a winning bias for the athlete who is first called, regardless of the color of their uniform. Source 2l
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Judo is one of those martial art forms that I never quite understood for practicality. Usually avoiding confrontation but this one encourages you to get up and close. I can see Judo being used as part of the techniques for self-defense but not all on its own.