Why the heel of the left foot is raised in kendo
Kendo has developed over many hundreds of years to be as efficient in dispatching an opponent as humanly possible. One efficient method is moving the sword out its scabbard with the thumb just before an attack, it is said this move is designed to prevent the tightly fitting blade from sticking, I believe that this move also allows and gives you an extra inch time advantage for your sword to completely clear the scabbard. Yet another kendo method is keeping the heel of the left foot raised, it is said this allows for strong push with the left foot, I also believe keeping the heel of the left foot raised before stepping also gives us a fraction of a second time advantage in a forward motion, enough time advantage when both opponents measure a killing strike in fractions of a second.