Sit on the peck deck machine back to front, with your chest on the pad. Reach forward and hold the bars. With slightly bent elbows, pull the weight backwards until your hands travel past your upper body and you cant move any more.
Squeeze the shoulder blades together as if you were trying to hold a piece of paper between them. After a few moments slowly let the bar go back to the beginning. But don’t let the weight hit the stack, immediately start the next rep before touch down.