How to do dumbbell regular 21 curls to preacher curls

Learn how to do dumbbell regular 21 curls to preacher curls. Presented by Real Jock Gay Fitness Health & Life.
Benefits
Bicep curls shouldn't always go from hip to shoulder; using half of your range of motion demands greater control within your muscles' working range of motion. For these curls, you'll do half curls (bottom to middle and middle to top), and wind up with a set of full curls against a preacher bench to further isolate the bicep muscle.
Starting Position
Stand upright with arms at your side and a dumbbell held in each hand with your palms facing forward.
Exercise
1. From the starting position, lift the dumbbells up simultaneously until you are halfway through a full bicep curl, pause, then lower your arms back to starting position. Do a total of seven of these lower-half bicep curls.
2. After you have finished seven of the lower-half bicep curls, you are ready to move on to upper-half biceps curls. Lift the dumbbells up to a starting point that is halfway through a full range bicep curl, with your elbows at a 90-degree angle and the dumbbells held out in front of you. Curl the dumbbells up together to the top of a bicep curl, but lower down only until your elbows are back at the 90-degree angle. Do a total of seven of these upper-half biceps curls.
3. After you have finished seven of the upper-half bicep curls, keep your arms bent in the top position of the final repetition and walk over to a preacher bench. Sit down and lower the weights until your arms are fully extended along the preacher bench with your palms facing up. Lift the dumbbells up simultaneously and do seven full range of motion biceps curls. When you have finished seven of these curls, you have completed one set.