The PKA and the American above-the-waist experiment
American karateka moved from point-fighting into full contact and wrote a rulebook around what they could already do — a decision that shaped, and eventually limited, the whole scene.
American kickboxing developed almost entirely independently of Japan's. From 1974 the Professional Karate Association formalised a code for karateka who wanted to fight full-contact, and the rules they wrote reflected the fighters they had: strikes above the waist only, boxing gloves, foot pads, no clinch, no knees, no elbows.
One rule stands out as unique in combat sports. Because early full-contact bouts had a habit of collapsing into ordinary boxing, the sanctioning bodies imposed a minimum number of kicks per round — commonly eight — with penalties for falling short. No other major ruleset legislates for how a fighter must fight rather than only what they may not do.
What the code produced was a distinctive athlete: upright, mobile, kicking high and often, with no need to defend a lead leg because nobody was allowed to attack it. Bill Wallace retired undefeated as middleweight champion with effectively one functional kicking leg — a career that is only possible inside those rules. The limitation was invisible from the inside, and would take an outsider to expose.