For those of you who are not familiar with this exercise I will explain it as Vince Gironda describes in his course "The Vince Gironda Workout Bulletin."
(IronMan Magazine Jan 1977 Vol. 36 No. 2)
Use a parallel bar set up which permits you to have a spacing of 33" wide. Remember that the elbows must be wide and straight out from the shoulders. The head is down chin on chest and the back rounded forward. The feet are under the face or slightly in front. Dip as far down as possible and return as high as you can.
Never change this position as this isolates the pectoral muscle and does not bring the triceps into play as in the elbows back style.