This exercise increases biceps mass.
Unlike the barbell curl, dumbbell curls let your wrists extend more and work the biceps better.
Stand up straight, grasp the dumbbells with a reverse grip.
Slightly bend your elbows.
From the starting position, as you exhale, lift the dumbbells up slowly without moving or swinging your body.
Without pausing at the top, slowly return to the starting position as you inhale.
If the weight is too heavy, you will also use your back and legs, that shifts the load to the waist.
Do not use a weight belt - you should keep your back straight by contracting the muscles of your back and abdomen.
You can lift both hands together or alternatively.