Antone Matysek is best known for his feat of strength where he lifted a custom made bicycle with three riders using a single hand, as shown in the picture below. He started his teaching career very early, at the age of 18 and won the “Strongest Man in America” at the age of 30.
Matysek wrote a great book on Muscle Flexing which is still very popular. Below are the pictures and an excerpt from the said book on correcting rounder shoulders.
Shoulder Blade Control – How to correct Rounder Shoulders
Place hands slightly below the top of the head and interlap the fingers as shown in the first picture. At this position relax completely. Then begin to contract the upper arms and finish by trying to pull your grip apart. Pull hard for two seconds, then relax, but keep your hands in the original position on the head. After one of two weeks practice you will notice that your shoulder blades begin to move outwards. The second picture indicates about how much your blades will come out after you give this splendid exercises a chance to loosen up the muscles around the shoulder blades and upper back, especially the Latissimus Dorsi, Trapezius and the Deltoids. The arrow indicates the part of the muscle that you are to concentrate upon with every pull. Repeat ten times.