The alternate dumbbell preacher curl is a good exercise for isolating the biceps and making them work independently.
- Adjust the height of the seat on the preacher bench so that when you sit on it, the back of your upper arms rest comfortably flat on the padding.
- Grab a set of dumbbells and sit on the preacher bench.
- Your arms should be resting on the padding and be around shoulder width apart.
- Allow the weight to drop and the arms to fully extend. This is the starting position for the exercise.
- Starting with your weakest arm, slowly curl the dumbbell up, squeezing the bicep at the top of the movement.
- Lower the weight back until your arm is fully extended, and then repeat for the other arm.
- This is one rep, now repeat to complete the set.