I have discussed previously how upper body barbell or dumbbell exercises done with a 2 inch or thicker handle will increase forearm strength and provide wrist strengthening.
The thicker handle puts your fingers in a stretched position that moves the center of gravity of the bar, requiring greater forearm strength to hold the bar.
When done with the palms down, the wrist ligaments, the thumb flexors and wrist extensors have a much greater force placed on them than when a standard bar is used.
The same is true when doing specific forearm exercises.
Before using the thick handle for the basic forearm exercises, the forearm should be conditioned by doing the exercises with the standard bar, and the wrist and forearm should be conditioned by doing some upper body exercises with the thick handled barbell.
The new stimulation that occurs from using the thick handle during wrist curls, reverse curls, Zottman curls, hammer curls or reverse biceps curls will be very productive.
Not all of these forearm exercises should be done at once, but appropriate ones chosen to develop the area of strength needed.
You should use less weight and/or do fewer reps or sets than you used for the same exercise with the standard bar.
As you get stronger, you can use more weight and do more work.
Another piece of forearm equipment, the wrist roller, is far more effective when it is 2 inches or more in thickness than when it is a standard one inch.
The thick handled version can be used free hand, as is frequently demonstrated for the standard wrist roller.
But when it is placed on a power rack or similar support, the wrist roller can be used for a variety of exercises to strengthen not only flexion and extension of the wrist, but also pronation and supination.
It can even be used to strengthen the small hand muscles.