Migi or hidari hanmi

The back hand is near a hip (as on a photo)

Carrying out impact the step forward (ayumi ashi) is made...

... Thus the back hand begins movement of impact only during that moment...

... When the back leg crosses a line on which there is a forward leg...

Impact is rendered by a fist in area of a breast - a stomach with active movement of a hip...

At the moment of drawing impact the second hand makes reversive (return) movement back...

Due to it (and due to movement of a hip) stronger impact turns out.

Watch a fist... The Fist and a forearm should make a direct line, differently You can "break" wrists...

Watch also that at drawing impact you did not straighten an elbow of a beating hand.

Impact should be made easily, without a pressure of the top humeral belt.