Critical Distance

Critical distance = the distance between you and your opponent that allows you the most effective strike. Everyone's critical distance is different and it must be dealt with differently when you work with different opponents. It is important to know your critical distance and to be able to draw on it within a fight. Moment by moment you need to know if you are outside your critical distance, at or in closer than it. Your actions will differ depending on where you are in relation to your critical distance.

How to determine Critical Distance
Before you can use or learn to recognize your critical distance, you will need to know how to determine it. If you were to make a fist and hold your arm straight out so that your knuckles are against a punching bag, this is normal extension - but it is not your critical distance. Punching to this distance could cause you to hyper-extend your elbow. At this distance, your puch has already lost most of its power and you will have to 're-fill' before you punch again. If you move about a fist or two closer to the target, this is your critical distance. You want to visualize your strikes going past the surface you are striking.

You will also need to be able to figure out your opponent's critical distance. If they have greater reach than you do, you will enter their critical distance before they enter yours. You will be vulnerable before you can strike them.

Terminology
This article deals with critical distance as it is taught in my Kung Fu school. Other styles might define critical distance different. For instance:

In the My Self Defense blog, it is defined as the point where enter your opponent's kicking or punching range. In my system this would be 'outside your opponent's critical distance'. You may encounter other definitions as well.