Forearm exercises are needed in order to strengthen your forearms, not only for size gains, but also for the added benefits stronger forearms will contribute to almost every other upper body exercise.
The stronger your forearms become, the stronger your grip will be. Having a stronger grip will enable you support more weight while performing bicep curls, dead lifts, bench press, etc.
The overall strength increases associated with developed forearms should be reason enough to make sure you do not neglect your forearms as part of your weight lifting routine.
In order to achieve maximum forearm muscle and strength gains you will need to work all areas of the forearms.
You can effectively exhaust your entire forearm by performing a single forearm lift. However, many people have problems achieving significant muscle gains in their forearms.
If you are one of these individuals, I suggest implementing a second forearm lift to further stimulate your forearm muscles.
I personally only implement one forearm exercise, but adding a second lift to your routine will help speed up your forearm muscle gains.
Forearm Lift #1: Palm Up Forearm Curls
Targeted Muscles: Lower and Middle Forearms
Auxiliary Muscles: Upper Forearms
Holding either a curl bar or barbell with both hands, sit towards the end of a flat bench. Bracing the rear of your forearms on the end of the bench with your wrists and the bar hanging over the edge of the end of the bench, curl the weight upwards using only your wrists.
Make sure to move your wrist through its full range of motion to ensure that you are sufficiently stimulating your forearms. If you do not have access to a curl bar or barbell, you may perform this exercise using dumbbells. If you use dumbbells, you will want to train each forearm individually, alternating between your right and left forearm until all sets have been completed.
Optional Forearm Lift #2: Palm Down Forearm Curls
Targeted Muscles: Upper Forearms
Auxiliary Muscles: Middle and Lower Forearms
This lift will be performed exactly as the palm down forearm curl movement; except that you will bring your wrists from a palm down hanging position upwards as far as you can go.
I find it more comfortable to perform this lift using dumbbells, but you are free to use a barbell if you prefer.
If your forearms are lacking in strength, it can inhibit you from increasing your weights on other upper body exercises and will ultimately hinder your ability to gain new muscle on your entire upper body.
Performing these forearm exercises will fully exhaust your forearms and quickly strengthen and build your forearm muscles. Weight lifting is only one part of a successful bodybuilding program and in order to achieve rapid muscle gains, you must also follow an effective muscle building diet and implement the right muscle confusion techniques.