Strength

• Most activities in which you bend your wrist are working the upper forearm. These are some exercises to increase strength:
  Curling a dumbbell with your fingers. Grip a dumbbell in front of you with your arm bent at the elbow at a right angle to your body. With your palm up, let the weight to roll down to your fingertips and curl it back up again.
  Extending and flexing your wrists back and forth.
  Squeezing a flexible object like a tennis ball, or hand-grip exercise device.
  Hanging on a chin-up bar until you can't hold on any more. Rest, then repeat.
  
  

Flexibility

• To prevent injury, keeping forearm muscles flexible as they get stronger is imperative. Here are two good flexibility exercises:
  Hold your the arm straight out with the palm facing down. With the opposite hand, pull the fingers back toward the body pointing them upward. The muscles on the bottom of the arm should feel the stretch.
  Again, with your arm straight out and palm down, pull the fingers downward. The muscles on the top of the arm should feel a stretch.
  
  

Stamina

• To build stamina in the forearm, work it with continuous low stress exercises. With the strength exercises noted above, use lighter weights and resistance than would be used for strength training and do more repetitions. Another good exercise for upper forearm strength is called "quick fists:" clench your fists as tightly as possible and then unclench them. The idea is to make as many quick fists as possible in the course of a minute by opening and closing your hands. Increase to the time by 30 seconds as stamina improves.