Take hold of some suitable weight dumbbells. Lay down on a bench inclined at around 45 degrees. Your core is tight and your feet planted firmly on the ground. Your arms hang down outstretched on the sides of your body, perpendicular to the floor, taking the weight of the dumbbells, palms facing each other. This is the starting position.
Commence the movement by curling the dumbbells up from the elbow joint and squeezing your biceps. The elbows should work like a hinge with the forearm being the only moving part. Twist the wrists from palms facing inward to palms facing up and toward the body, as you approach the top of the curl. Exhale through the movement. Do not use momentum to throw the dumbbells up.
When your biceps are at maximum contraction, squeeze for a second and then reverse the movement by extending the arms to the starting position, inhaling as you do.