'Technical Background Information on Atemi and Kansetsu'
Generally speaking an Atemi Waza was a technique in which you strike the opponent at a physiologically weak point (ie. a vital point) in order to render him unconscious. Kansetsu waza were joint locks that were designed to attack an opponent's joint in order to cause severe sprains or dislocations. Although these techniques do have this dangerous side to them, I feel that if you really understand the fundamentals of these techniques you will see that the resulting concussion or pain is only an incidental part of the technique and can be divorced from the technique proper as such. Even though these techniques were designed by our predecessors to have such dangerous and lethal end results, the main core of the technique could still, nevertheless, be seen as a throw or a hold.
Therefore the striking techniques of Aikido incorporate the idea of balance breaking; the result being that the opponent is brought down due to loss of balance rather than because he was hit on some vital point. Thus it is not necesary to kill or hurt him by using strong impact, nor is it necessary to train your hand or fist to withstand such impact.
In the modern Budo form of Judo, the aim is to break the opponent's balance and throw him by using foot and hip movements without injuring him. Similarly in the Atemi Waza of the modern Budo form of Aikido, the aim should be to take advantage of breaking your opponent's balance and push or strike him down using your hand or arm without injuring him. Most Judo throwing techniques employ the use of force to two points on the opponent's body in two directions at the same time. In Aikido, on the other hand, force is usually used in one direction on one part of the body. "
by Kenji Tomiki