Resistance training using the proper rep and set scheme can help you gain one inch in your forearms if you utilize the right exercises. The National Strength and Conditioning Association and National Academy of Sports Medicine recommend that three to four sets be performed for each exercise, with a total of 8 to 12 repetitions per set for muscular growth and hypertrophy. The three key muscular areas in your forearms are your wrist flexors, wrist extensors and brachioradialis muscle. Training these three areas with distinct exercises will allow the entire circumference of your forearms to grow, which will help you increase them by one inch.

Dumbbell Wrist Extension

The dumbbell wrist extension exercise allows you to work your wrist extensor muscles, which are responsible for pulling your wrist toward your body. Start this exercise by grabbing a pair of dumbbells and sitting on the edge of a bench or chair. Place the middle of your forearms on your knees and turn your hands so that your palms face the floor. Flex your forearms, bend your wrist and curl the weight toward your body. Once this position is reached, allow your wrists to relax and lower the weight toward the floor.

Barbell Wrist Flexion

The barbell wrist flexion exercise works your wrist flexors, which are located on the palm side of the forearm. This time, grab a barbell with an underhand grip, with the distance between your hands equaling six to eight inches. Place your forearms on your knees so that your wrists lie over the end of your knees. Relax your wrists and allow your hands to move toward the floor. Now, curl the barbell upward until your hands, wrists and forearms form a straight line. Hold this position for a brief moment, then allow your hands to lower back toward the floor.

Reverse Curl

The barbell reverse curl exercise is traditionally used because it not only works your biceps, but also targets your brachioradialis muscle located near your elbow joint. Grip the barbell with an overhand grip so that your hands are shoulder width apart. Curl the bar toward your shoulders by bending at your elbows. Once the bar touches your shoulders, allow your arms to naturally return to extension.

Farmer's Walk

The farmer's walk exercise trains some of the smaller muscles in the forearm that are responsible for gripping objects. These muscles also help contribute to the size of your forearm and should be trained as well. Grip a heavy pair of dumbbells and turn your hands so that your fingertips are touching the sides of your body. Now walk with the heavy dumbbells in hand. Continue squeezing the dumbbells and walk with them in your hands until your forearms become fatigued. When your forearms are tired, set the dumbbells down and rest for 30 seconds, then pick up the dumbbells and repeat.