Kendo kiai is very different from just a loud voice. But that is the start. So these are the levels you have to go through to increase your kiai strength.
- Be as loud as you can so you will lose your voice.
- Don’t give up there. Squeeze your abs to have more kiai (this will teach you how to use your abs to have a good kiai)
- Make your kiai sharper like an arrow. Still has to be loud. But making it sharp the quality of your kiai will change.
- Learn how to maintain your lower abs filled with energy (start thinking about this when you become 3 or 4-dan).
- You should be able to maintain the same level of kiai even when you are quiet (this probably starts around 6 dan)
