Stand in front of the cable weight stack about a foot away from the apparatus. Grip the short straight bar with your palms down (reverse grip) at shoulder-width apart. Tense the cable a bit and lean back just a touch. This is your starting position.
Curl the weight up until your forearms are almost completely vertical. Then lower it back down to the starting position but don't fully straighten your arms. You should always keep tension in your biceps/arms for maximum muscle development. Finally, repeat this entire movement for the desired or prescribed number of repetitions.
Perform this exercise in a smooth and fluid motion
Don't extended your arms completely on the downward portion of the movement
SPECIAL NOTES & LEVEL of DIFFICULTY VARIATIONS
To increase the level of difficulty, slow down the movement or increase the weight.
This exercise is especially suitable for beginners because it's fairly low impact on the wrists. The cable motion provides for a stable and smooth movement. One thing to point out is that this exercise requires a strong grip. Such is the case with all reverse grips.
Thus, if you feel the bar slipping from your hands then you may need to adjust by selecting a lighter weight. The good news is that gripping strength increases very quick. Therefore, after a few weeks of doing this exercise you will find that your grip has become stronger. Then you can increase the weight and further challenge your forearms.