Regular rotation, corresponding rotation. The hip and arm going in the same direction.

Koshi Kaiten means Hip Rotation and it’s a very important and basic part of generating power in karate for both kicking and striking. With proper hip rotation (Jun Kaiten) and reverse rotation (Gyaku Kaiten) you will generate more snap and more power. Jun Kaiten means to rotate with the techniques, this would be similar to rotating the hip into the techniques and Gyaku Kaiten away from a technique. It actually has little to do with position (hanmi, Shomen and Gyaku hanmi). Jun Kaiten is when your hip rotates with the movement. So when you are performing Gyaku zuki or reverse punch you will rotate your hip into the movement by rotating the back hip along with the arm into the target. This generates a great deal of power as you rotate and also use the back leg to push with off the floor. This power full technique will generate a huge amount of power as you move from position to position.

Some JKA groups suggest that Gyaku zuki will move from Hanmi to Shomen as you punch some groups barely move into Hanmi when they start the punch and others stay Shomen when moving and punching. I advocate a full range of motion from Hanmi to Shomen and finishing in Gyaku Hanmi. This serves multiple purposes from martial power improvement to a more natural movement process and also strengthening and creating flexibility in the hips. This is a great example of un Kaiten, the hip is going the same direction as the technical movement.