How To do 21’s (see video above)
First you will need to pick a weight on a barbell or ez-curl bar that will be moderately challenging for you. Maybe about 70% of the weight you use for regular sets of 10. For example, being able to curl 110 pounds 10 times may require you to drop down to about 80 pounds for this particular exercise.
The exercise is best described as doing 3 exercises back to back, isolating different parts of you biceps.
The first movement you will be making is basically half of a curl. Have the bar at your waist and lift until your forearms are parallel to the floor, stop, lower the weight and repeat 7 times.
Without rest, after your 7th rep, start in the position that you ended with in the last movement (forearms parallel to the floor) and then bring the bar to your neck, back down to the starting position and back up to your neck for 7 reps. This movement is basically the top half of the typical curl whereas the previous step was the bottom half.
Now you have totaled 14 reps and your biceps should be on fire but its not over yet. To complete this exercise, finish it off with 7 more full motion curls to make the total 21 reps (Hence the name). Good Luck!
For best results, make sure you follow a good total body routine and diet (you get both in my workout plan). It may also help to try a good fat burner like TEA REXX, it is what I use to help me stay ripped.