This is an amazing bicep exercise, and one of my favorites, because of the degree of engagement I feel from the biceps. Whereas, I see people curling both dumbbells at the same time, I prefer to do them individually, slowly, with maximum attention to form. Like the barbell, you can cheat a little, but try to avoid it, and if you do keep it to a minimum.
Find a bench and use your best posture to sit up tall, with your back as straight as possible. Next, with your arms straight with a slight bend at the elbows, hold the dumbbells at your side with your hands facing each other. As you begin the motion also begin rotating your hands to where the palms of your hands are straight up, stopping the movement at the point where your hands are now facing your anterior deltoids and squeeze for a count. Lower the weight, and once the dumbbell is at the starting position begin the motion with the other arm and repeat.
1. Use too much weight. This should be a strict movement, and not the time to go heavy and get sloppy.
2. Drop the weight; instead attempt to move the dumbbell at the same speed going down as you did going up.
3. Swing your body leaning forward and then back to create momentum.
4. Swing the weight backwards at the bottom, to generate momentum at the bottom of the movement.
The next time you’re training biceps, add this movement, but perform the repetitions exactly as described. You might need to drop weight a bit.