Hammer curls are great for building forearm strength in the upper and outer portion of your forearms as well as working the bicep muscles. This exercise can be done in two variations. The first and most common is to bring the weight directly upward until it approaches your shoulder; the second variation moves the weight in a semi-circular motion across your upper torso bringing the weight to approximately your pectoral muscle on the opposite side.
Take a moderately heavy dumbbell in each hand and stand with your feet at about shoulder width apart. Your arms should be hanging down on each side with the palms facing inward. Press your upper arms inward against your body and keep them motionless throughout the movement.
Use your forearms muscles to pull the weight directly upward in front of the body until it stops in front of your shoulder. Squeeze your forearm and bicep muscles for a moment before slowly lowering the weight back to its starting position with the arm fully extended. Repeat this same motion with the opposite arm, and make sure to do the same number of repetitions for each arm.
A great variation to this forearm exercise is to allow the weight to travel across the body to the opposite shoulder. Bring the weight just in front of your and point your knuckles directly forward instead of out to the sides. Allow the weight to travel in front of your body until it reaches the peak contraction point at approximately your opposite pectoral muscle. Squeeze your forearm and biceps muscles for a moment before lowering the weight back to the starting position. Repeat this same motion with the opposite arm, and make sure to do the same number of repetitions for each arm.
Tips From the Trainer
As with all curl exercises, keeping your upper torso motionless is important to keeping the focus of the exercise on your forearm muscles. If you are having trouble, lean against a wall or sit in an upright bench. Focus on keeping your upper arms motionless so that only the forearm moves, with your elbows acting as motionless hinges moving the weight up and down.