Kiai - Kendo's Fire

Raise your Ki means, Get fired up. Be intensely alert. Ki means spirit.
When we make a loud yell in Kendo, we call this kiai. We're purposely using a bloodcurdling yell to transform our physicality. Our blood chemistry changes. Our oxygen levels go up when we kiai. We expel carbon dioxide. New hormones are introduced to the blood stream. The brain works faster. Where else can we get this fired up? There are so few places in our western society where we are actually encouraged to belt out a battle cry. The Kendo Dojo is where we stoke our fire.

[optimusmaximus]

So I guess you can't do kendo if you are mute or have bad laryngitis.