In this short tutorial Sensei Amos explains the first move of Shotokan kata Jion. Sensei talks about contracting the muscles on both sides of the body when preparing and the expanding sharply as the move is executed.
Try and keep the body weight forward and drive the left leg back sharply. In the video below, Sensei Amos explains the arm positions at the start of the Kata when coming to yoi and driving the downward block down and forward like a punch, with the same feeling on the uchi uke block, driving the uchi uke forward rather than around in an arc.
Short Video Tutorial On The 1st Move Of Kata Jion