Here is the foundation and practical application of Nikajo/Nikyo. This video is from a Nami ryu seminar in Cologne, Germany. There have been many derivations especially in modern arts that use various methodologies with various degrees of effectiveness and sophistication. When put into true martial perspective it becomes apparent that no muscle, no leverage, no contesting is the effective answer to an immediate and lethal threat. Do not flex your bicep at all! This is a common modern way to implement this technique and will not work unless the opponent is cooperating or incompetent.
James Williams is the creator of a series of tactical knives by CRKT. Learn about his inspiration behind the designs, which are rooted in actual designs crafted by Japanese sword smiths hundreds of years ago. Various review videos will assist you in deciding which knife is right for you.