The late Vince Gironda, the originator of the Perfect Curl (or complete curl) described how to do it in the following manner.
The first part of “The Perfect Curl” (using a straight bar and a shoulder width hand spacing) begins with the elbows resting on the pelvis or hip bones with the arms hanging straight and the upper torso inclined with the head and shoulders just back of the hips.
This particular starting position will actively stimulate the lower insertion of the biceps as the barbell is curled upward the first 10-12 inches.
The second part of “The Perfect Curl” kicks in as the barbell is continuing to be curled upward and the upper torso (head and shoulders) begins to travel forward to an erect (or vertical) position. This part of the curl involves the belly of the
biceps.
The third part of “The Perfect Curl” concludes with the upper torso (head and shoulders) moving slightly forward from an erect (or vertical) position and the bar is curled upward to completion. When the torso is slightly forward from vertical at the completion of the upward phase of the curl it creates a maximum peak contraction in the biceps.
Cramp the barbell into the top curl position and contract the biceps for all they are worth for a second and then reverse the procedure as you lower the barbell to the starting position.
This completes one rep!
Each rep should take approximately 6 seconds to complete.
Always use poundage that you can handle in the form described above, perhaps with about 60 percent of your maximum single barbell curl.
Vince suggested doing one of the following sets and reps schemes; 6 sets of 6 reps, or 8 sets of 8 reps and finally 10 sets of 10 reps.
Rest-pause, 20-30 seconds between each set of the chosen set and rep scheme.