Stand up with you back to the cable apparatus. You should be roughly a foot away from the weight stack. Grip the short straight bar with your palms up at shoulder-width apart. Tense the cable a bit and lean forward just a touch. This is your starting position.
Curl the weight up with your wrists as much as the natural range of motion allows. Then curl back down to the starting position. Finally, repeat this entire movement for the desired or prescribed number of repetitions.
Perform this exercise in a smooth and fluid motion
Don't allow the weight to jerk your wrists down as this may result in injuryl; always be in complete control of the weight
SPECIAL NOTES & LEVEL of DIFFICULTY VARIATIONS
To increase the level of difficulty, slow down the movement or increase the weight.
This is a very effective exercise for working on forearm muscles. It's low impact on the wrists and the motion of the cable provides for a smooth and stable movement.
The key to performing this exercise is the slight lean forward. In other words, if you don't lean forward to counter-balance the pull of the weight, you will tip backwards.
Thus, leaning forward and getting into the right position before you start this exercise is very important. Take a moment to set up right and this exercise will be that much easier and more effective to execute.