Dave Schultz is an exceptionally skilled angler, and his casting stroke is one of the most fundamentally sound that you’ll ever see.
As with all expert casters, Dave’s stroke begins with the large muscles of the arm and finishes with the small. Just as in throwing a baseball, football, or hitting a golf ball, the sequential movement of the arm from shoulder to wrist is a key to efficiency and power. Note, too, the vertical movement of Dave’s elbow—up on the backcast, down on the forward cast. This movement, present in all expert casters, helps prevent tailing loops and sets the proper default trajectory of the cast—high in the back, low in the front.
Dave uses his wrist during every stroke, at the end of each stroke. Saving the wrist until the end of the stroke allows the speed it creates to be additive to the speed already built up with the upper arm and forearm. This is a hallmark of the efficient caster. (One of the most common casting flaws is using the wrist at the wrong time during the stroke, and using it excessively.)
At his age (80), Dave notes that he has lost a lot of strength in his arm. That may hurt his distance casting, but it certainly doesn’t affect his casting at normal fishing distances. If you’re wondering what a professional level casting stroke looks like, this is one.