"This 'windup set' will be slow to the plate, even combined with the slide step. It has to be, as the body must rotate. In the stretch, the shoulders and hips are already properly aligned."
I will grant you that it will likely be slower to the plate than a slide step from the Set position. However, since it eliminates the knee lift I would argue that it's probably no slower than going from the standard Set position with a knee lift.
What's more, going from the Wind-Up Set position gives you several advantages over both the slide step and going from the standard Set position.
1. You don't have your back to the runner.
2. You can move to 1B faster. Just step and throw.
3. It changes the read. No more going or getting back depending on what knee cracks.
All of this will tend to hold runners closer to the bag.
"If using windup & stretch is a problem (e.g., too much variation), then a pitcher can throw only from the stretch (as some do)."
Agreed. I do this right now with my guys who use the traditional pitching motion.
"The different slide step mechanics do violate the KISS principle. And from that standpoint there is an inherent problem."
Agreed. This is especially a problem with younger pitchers.
"Flail and arm slots are not linked. Pitchers can flail and use any arm slot."
I'm not exactly sure what you mean by the term "flail". Please elaborate.
"Regarding your study, correlation does not mean causality. And again, all you have to do is feel it yourself. Even with no flail at all, a person can feel greater stress in the rotator cuff and triceps when taking the arm back fully extended as opposed to arm circles. I certainly can feel it. Have you tried it?"
Yes, and it doesn't cause me any discomfort if I bring my arm out in line with my shoulders (and I do it routinely now). Did you ever have any shoulder problems in the past? That could be part of the problem. Otherwise, you could be confusing discomfort due to soreness (due to using new muscles) that will go away over time with something that consistently causes pain.
"The overhead slot is very stressful on the shoulder. I can't think of a young pitcher I coached who used the overhead slot that didn't have shoulder pain. I always advised them to go to overhand. The ones that went from overhead to overhand saw the pain go away."
This is a very widely-held misconception.
What about Sandy Koufax? He pitched from a very high arm slot and never had shoulder problems.
This is safe as long as you tilt the shoulders so that the pitching arm side elbow doesn't go significantly above the plane of the shoulders (aka abduction < 100 degrees).
"But there will be less horizontal movement on the ball."
Precisely. Research into the human perceptual system indicates that people have the hardest timing judging the motion of an object that is moving at them in a purely vertical manner. This explains why the hardest ball for an outfielder to catch is one hit directly at them, why the hardest curveball to hit is a 12-6, and the illusion of the rising fastball. For more information Google "illusion rising fastball" or go to...
- Rising Fastball Presentation
"And with regard to where the forearm is at release, many pitchers use the three quarter slot. Not even overhand, much less overhead."
But that doesn't mean it's the best slot to use. Again, look at Sandy Koufax.