Hold the dumbbells with very slightly bent arms by your side, with palms facing towards the front. Stand tall, but at the same time contract your abs.
Raise your arms not to the side, nor directly in front, but in-between the two (hence the name Y shape). When your arms are parallel to the floor, rather than lower them, perform a shoulder shrug.
At the top of the shrug, hold for a moment and lower back to shoulder position, pause for another moment and the lower back to starting position. However, don't pause at the bottom but immediately start the next rep.
All of the magic happens towards the top of the exercise. If you feel you can cope with the tension, don't lower the weight all of the way down at the end of each rep.