Grab a pair of dumbbells with your palms facing towards you and bend over until your upper body is at about a 45% degree angle. Hold the dumbbells in front of you and let them hang freely. This is your starting position.
Raise the dumbbells up until they are in the same line as your lower-to-mid stomach. Then, lower them back down again to the starting position.
Repeat entire movement for the desired or prescribed number of repetitions.
Perform this exercise in a smooth and fluid motion
Don't arch your back
Don't jerk the dumbbells in an attempt to lift them; this may result in lower back injury
SPECIAL NOTES & LEVEL of DIFFICULTY VARIATIONS
To increase the level of difficulty, slow down the movement or use heavier dumbbells.
This is a great exercise for the back. If you want to put on muscle you will need to select heavier dumbbells. If your goal is muscle definition you should go with lighter dumbbells.
One thing to point out is that your lower back needs to be reasonably strong for this exercise. Thus, this may not be the best exercise for complete beginners. This movement is best for those that have a year or two of weightlifting under their belt.
Last but not least, make sure you take your time in executing this movement. This exercise is most effective if it's not rushed.