The following three pictures are expressing what is regarded as the correct posture, and all these pictures are based on a common view in which straightening up one's back along the vertical axis is justified. As far as I know, almost all of experts engaging in medical-and-fitness-related industry appear to have almost same opinions, and I have an opinion that goes against their widely accepted opinion.
While most experts think like above, they also know that the correct alignment of spine should have four arches as you can see below. Pointing up the importance of standing along vertical axis can hinder a person to make correct S-shape on his spine as he will try to straighten his back. Since thoracic spine draws an arch rising backward, trying to straighten one's back will quite go against favorable result; a person who is directed to straighten his back will rather try to stick out his chest, which will make a reverse curve of correct one on his back.
Here are examples of correct postures that can be defined to be so from an athletic viewpoint. Their spines have well curved shape with thoracic spine making backward curve and lumbar spine making forward curve. (center is Cristiano Ronaldo)
So what is the key element to make this posture? A certain muscle is the answer of it - a muscle called psoas major muscle. Psoas major muscles work to bend the hip joint. So if your psoas major muscles contract in the situation of your legs being fixed to the ground, those muscles will cause your pelvis to tilt forward. Black people have bigger psoas muscles than other races, especially compared to Mongoloid race; Mongoloid race particularly has small psoas muscles. That is the reason why black people have hip-up posture.
Comparison of Psoas Major Muscle: Left is Jamaican sprinter and right is Japanese sprinter.
In Recent MLB scene, one-hand follow through has become common. As far as I know, this trend started in the early 1990s, triggered by some sluggers such as Frank Thomas, Juan Gonzalez, and Mark McGwire. Charlie Lau and Walt Hriniak has been deemed to be essential figures who played important roles for prevalence of this technique.
however, I want to cast a doubt on this trend. Alex Rodriguez and Albert Pujols are typical hitters who are employing it in today's MLB, so please look at the photo below. Their arms are shrinking and the wrists are rolling over at the early stage of their swings. Although, one-hand follow through, at first glance, is likely to prevent the wrists from rolling over, the results actually become opposite as you can see below. As a proof of this, by searching for their names on Google images, you will be able to find a lot of similar pictures of their swings.
For extending your arms fully in the follow through, both of the scapula should be abducted, making an arch on your back. One-hand follow through, however, makes you difficult to keep that position because pulling a bat with the bottom hand makes the same-side scapula adducted.
All of these hitters - Kyle Seager, Josh Willingham, Nelson Cruz, Matt Carpenter - always swing without releasing their top hand. This is the real extension.
So let me cite an example, a home run swing by Jack Cust, and here is the movie containing high-speed slow motion. Although his swing looks like a kind of short stroke one, when we look into the swing with a high-speed movie, we can find it to have an excellent extension as you can see below.
So now, I want to create a conceptual term "effective follow through." The term refers to an amount of the force a hitter can add to the ball in his follow through toward the fair zone, especially toward center fielder's direction.
Hitters who do the one-hand follow through seem to have a large follow through at a first glance, but it is no more than optimal illusion that comes from their finish pose. However, a part of the force they can add to the ball in their follow through is going out of the fair zone as they pull their bottom hands toward the back-stop's direction, extremely speaking. In this case, we can say that their effective follow through are not that large.
Next, watch a movie of Alex Rodriguez' tee batting. In this movie he let his wrist roll over too much early on in his swing, and he clearly have an intention of pulling the bat with his bottom hand. This movie shows us that the one-hand follow through and rolling over of the wrist in early stage of the swing are in correlation with each other.
In fact, hitters who employ one-hand follow through don't carry the ball very far even though they can hit considerable number of home runs. On the other hand, some of the hitters with double-handed follow through can carry the ball surprisingly far. Hitters who can hit really long home run are typically employing double-handed follow thorough such as Nelson Cruz, Giancarlo Stanton, Justin Upton, Cecil Fielder, Bryce Harper, and Edwin Encarnacion. Here is a movie I edited, gathering swing examples that I think have optimal double-handed follow through.
I don't mean, however, that you have to swing always with your both hands until the finish of the swing. There are two types that are the most vulnerable to the failures which I wright about in this article: hitters who use always one-hand followthrough, and hitters who intend to make a large follow through by releasing the top hand, extending the bottom hand intentionally - later type swing is particularly prone to cause excessive bottom-hand pull. In fact, the unfavorable tendencies that are shown in the swings with one-hand follow through can hardly be observed in the swings of hitters who sometimes swing with one hand, and sometimes with double hand, such as Mark Trumbo, Jose Bautista, and Prince Fielder. So I want to recommend hitters who use one-hand follow through to do some kind of drills in which they use double-hand follow through for keeping their swing healthy.
When most coaches teach how to grip a baseball at entry revel, they would say it should be like the photo bellow, but I want to cast a doubt on it. What I'm going to wright about in this article might be useful when you instruct little leaguers as their hands are smaller than adults' ones.
This grip, needless to say, is based on the common notion that throwing four-seam fastball is an essential basic skill for all baseball players. The notion partially stands on the fact that four-seam fastball is the least affected by the gravity force among all kinds of pitches thanks to the Magnus effect.
So what pitches did they throw as their fastball? As you can see, the forearms of Pedro Martinez and Randy Johnson do not stand vertically at their release point, even though they had been throwing fastballs with considerably high velocity. They certainly used to use the so-called four-seam grip, but their each 'four-seam fastball' probably was not the backspin fastball. Such a case should be so common.
However, that is not the only reason why I don't recommend so-called four-seam grip. I have been doubting the validity of it because of its lack of mechanical stability. In the case of four-seam grip, as indicated in the photo below, the force from the index and middle finger can balance with the force from the thumb, but the force from the ring and little finger does not have its counterpart. So in this case, the ball is likely to slip out easily to the direction of vector 'a', and if you try to prevent the slipping out, you might throw the ball to the ground because of the strained grip.
So how should we grip the baseball alternatively? I recommend the way shown below. By shifting the thumb outside on the ball slightly, all the forces can get balanced. There are four points to keep the ball sustained in the hand, and those points make trapezoid.
Of course, shifting the thumb too much outside like the photo below is not proper because this makes the thumb touch the ball with its front face. Thumb must touch the ball with somewhat lateral face of it because if it touched the ball with its front face, you will come to grasp the ball too much strongly.
The way I recommend in this article would allow you to grip the ball more relaxedly and loosely because of its mechanical stability. And it is based on a premise that the back-spin fastball is not the only one correct answer for throwing fastball.
In this clip, pitchers' rear legs cross their front legs in their follow throughs and land the opposite side of their throwing arms. I named this kind of motion 'turn-and-tumble finish'. In the current world baseball scene, especially in the MLB, turn-and-tumble finish seems to have been common, but it probably had been controversial issue even in the MLB. In fact, Leo Mazzone, a former Atlanta Braves' pitching coach being known for having mentored Greg Maddux, Tom Glavine, and John Smoltz, dealt with that issue in his book, 'Pitch Like a Pro'. He stated that pitchers should focus on delivering their best pitch, and if the pitching mechanics is a kind of one in which his rear leg lands the opposite side of his throwing arm, then, he should stick to the mechanics for playing his most important role.
I read the Japanese edition of his book more than 10 years ago, and according to his description, the pros and cons about the 'turn-and-tumble finish' seemed to be existing yet at that point. Since he was a very influential figure in the baseball circle, his opinion also must have been influential. Indeed, turn-and-tumble finish has got majority in current baseball scene.
In my opinion, turn-and-tumble finish is an ideal motion. One advantage of doing it is to be able to avoid the risk of shoulder injuries. As you can see in the photo below, the arm path of the throwing arm is followed and traced by the weight transfer that is unique to turn-and-tumble motion.
Some kinds of shoulder injuries occur when a slowing arm slows down in the follow through, because shoulder muscles suffer tensional force when the acceleration of the throwing arm is stopped. Therefore, the weight shift that follows and traces the arm path in turn-and-tumble motion becomes an effective device for easing the shock that a shoulder suffer in the follow through.
However, turn-and-tumble finish unfortunately has not been accepted in Japanese baseball circle, especially by senior therefore high-standing coaches. They think that it diminishes the accuracy of ball control as well as not allow pitchers to take proper fielding stance. In fact, young pitchers often were 'corrected' their pitching mechanics that have turn-and-tumble finish even in professional baseball teams. Here is a footage of Masahiro Tanaka. His rear leg not only does not cross the front leg, it even does not land beyond the front foot - a most vulnerable mechanics to slowing-arm injuries as the throwing arm is stopped suddenly.
So how about the pitcher in the following clip? Actually, in the case of sidearm mechanics, the rear leg lands on the throwing-arm side because in that case, the pitcher's spine tilts forward (third base direction for right handed pitchers) right after he lifts up the front leg to make the angle for sidearm throwing. So it's correct for him to land his rear leg on the throwing-arm side because his balance inclines to that direction.
Next, how about the pitcher below? I think he has a pretty good mechanics even though he doesn't turn-and-tumble finish. His rear leg jumps up in the springy motion after kicking the ground, which is a proof that he is able to use his lower half effectively, and that is why I think he is not vulnerable to shoulder and elbow injuries. I would not advise a pitcher who has this kind of mechanics that you should change your follow-through.
Wen it comes to base stealing, while most people talk about the motions at the start of it, the most important factor is, I think, the posture at that moment. As you can see in the photo above, Ichiro always lets his right arm down when he takes a lead-off from first base. This is the secret of good start. By putting down the right arm, his torso turns to the first base and it causes his left leg to rotate externally slightly. Since the leg motion with which we kick the ground includes internal rotation, the posture Ichiro shows means being ready for kicking the ground strongly with his left leg. It allows him to turn and accelerate to the second-base direction quickly, kicking the ground strongly. Notice this sprint runner's right leg and the white print on his right thigh. His right leg is rotating internally to kick the ground. That is an automatic motion accompanied by the brain command for accelerating straight forward. So you don't need to rotate your legs intentionally.
Besides, if a pickoff throw comes, you can get back to the first base with the head-first slide easily because your chest is faced to the first base.
As for the sliding to second base, head-first slide is reasonable because first-base runner reach second base in the acceleration phase of sprinting. So if you are to go to third base after passing second base, then you should use leg-first slide.
Considering all above, Dee Gordon's base stealing in the clip below is excellent. The one starting from 0.15 on that clip is particularly wonderful.
Tee drill is one of the most common hitting drills and it is useful especially in the case of personal instruction because instructors can observe hitters and point out their mechanical problems right beside them. Besides, ball location and timing are free to decide for them - an advantage that is suitable for building up and reforming hitting mechanics.
However, there is one noteworthy problem in the tee drill. As you can see in the photo above, hitter's face is directed toward first base. On the other hand, when sluggers hit home runs, as you can see in the photo below, their faces are typically directed toward pitcher's mound.
Let's think of an extreme case. If you swing while keeping your shoulder at the angle of batting stance, the swing should draw a typical outside-in bat path. Because in that case, the bat barrel gets away from your torso right after the swing has started. On the other hand, If you rotate your shoulder while keeping your hands at launch position, then you will see the very inside-out bat path. Since swinging with looking toward first base in the tee drill prevents your shoulder from rotating very well, it will cause you to get outside-in swing if you repeatedly practice it. Following clips show the glimpses of that. Their swings are not the same as ones they show in actual games.
So what should we do? The ubiquitous nature inherent in tee drills is indispensable for many players, especially for those who cannot enjoy sufficient space and assistants. So I would recommend you add a supplemental drill to tee drills in the aim of correcting your swing mechanics. That is the dry-swing which is done with your face looking at a point drawn on the wall or something like that in front of you. The point, of course, must be put in the pitcher's direction so that you can swing with your face facing that direction.
I recommend to do this dry-swing drill about two or three times every three to five swings of the tee drill. That way tee drills can become truly efficient drills.
As far as I see the websites written by instructors and researchers, so-called 'inverted W' has seemed to be considered poor mechanics that could cause pitching arm injuries.
However, as many players or on-site instructors may well know, this kind of form in which both elbows up, leaving those hands down at the same time could never be seen in the mechanics of lower level players. Many of them would show the ones such as pie-throwing arm and javelin-throwing arm. They could never make inverted W. So I think there are 'good inverted W' and 'bad inverted W', and good inverted W should rather be said as an ideal form in the pitching mechanics. Craig Kimbrel's pitching mechanics is one of the good examples for it.
Then, what is the difference between the good and bad one? Good inverted W is that in which both elbows are pulled up at the same time, interlocking with the lower half's movement and harnessing the power of it. On the other hand, Bad inverted W is that in which both elbows are pulled up forcibly by exclusively the power of shoulder muscles and there is no interlocking with the lower half.
Note: Craig Kimbrel has a problem of short stride and it can possibly cause some kinds of pitching arm disease. Yet that should not have something to do with his 'inverted W'.
Mike Piazza showed an epoch-making hitting mechanics at the point of early 90's. He looked like merely standing in his batting stance and started the swing suddenly like an explosion. There seemed to be no load and weight sift at a glance, so it seemed to go against conventional hitting theories such as Charley Lau's it. The existence of that kind of hitting mechanics might cause the argument in which rotational mechanics and linear mechanics were compared. Someone might say piazza's mechanics was that of no-stride, but in fact, his left foot used to be lifted and off the ground slightly. There is a significant difference between his stride mechanics and no-stride mechanics like Pujols' it. Mark McGwire had been employing the same stride mechanics as Piazza's it. Here is the video including Piazza's home run that was hit off Curt Schilling - my most favorite home run in his career -. (from 0.40)
Albert Pujols has been regaining his momentum, collecting 23 home runs as of july 25th, 2015. One reason why he was able to do it is in his effort for improving the swing mechanics. As you can see, he has abandoned no-stride hitting mechanics, which has been enabling him to rotate his hip enough. Although no-stride mechanics has been tried by many sluggers such as Andruw Jones, Mike Sweeney, Nomar Garciappara, Jim Edmonds, etc., there were few hitters who was able to achieve high stats, continuing practicing no-stride mechanics. No-strde mechanics is simply a wrong mechanics, I think, and it even can cause some injuries in back, knees, and sometimes wrist.
First of all, my classification method does not depend on superficial mechanics such as the width of stride or bat's angle at the batting stance. Rather, it refers to essential systems of the arm acceleration, namely, the core of the hitting mechanics. The difference of these systems, however, is so simple and easy-to-understand that even kids players would be able to understand it.
