Sit down on a preacher bench and rest your elbows and upper arms comfortably on the pad. Grab a hold of the dumbbells and hold them with your palms facing up and arms extended. This is your starting position.
Raise both dumbbells up until your forearms are fully vertical and then, while at the top, twist/rotate the dumbbells 180 degrees until your palms are facing outward and away from you. Then, lower the dumbbells back down to the start position and at the bottom rotate the dumbbells again for 180 degrees until your palms are facing up.
Repeat entire movement for the desired or prescribed number of repetitions.
Perform this exercise in a smooth and fluid motion
Don't twist the dumbbells too fast because it might cause discomfort in your forearms
SPECIAL NOTES & LEVEL of DIFFICULTY VARIATIONS
To increase the level of difficulty, slow down the movement or use heavier dumbbells.