Spin Class

So what's the big deal about spin? Most of us understand that different pitches have different spin, but there is some misunderstanding as to how much the spin affects the flight path of the ball, and above all the effects of gravity.

First off, some background. The Magnus Effect is the phenomenon of a spinning object flying in a fluid (air) experiencing a force perpendicular to the line of motion in which it's flying. As in Figure 1 below, the ball spinning like a fastball or dropball causes the air at velocity V to travel
a little bit faster than V underneath the ball, and a little bit slower than V on top of the ball, causing a difference in pressure. And in accordance to the Bernoulli Principle (google it!), the side of the ball in which the air is traveling slower will experience more pressure than the side with the faster moving air. Thus, the resulting force F will be in the direction of the side with least pressure, the ball drops.

Figure 1: The Magnus Effect on a spinning ball. V is the air's initial velocity, more lines underneath the ball indicate the increase in the air's velocity, and hence less pressure. F is the resultant Magnus force towards the side of least pressure.

Ok, so we know that a ball that has topspin will go down, and a ball that has backspin will stay up. But, what about side to side curveballs and screwballs? The Magnus Effect is not exclusive to the vertical direction, but as far as the limitations of humans are concerned, it's impossible to throw a true curveball or screwball with complete horizontal spin. No matter what, the ball will always have a tilted axis of rotation, this is because your hand is always going to be either under or over the ball. It is impossible for your hand to be completely on the side of the ball to spin it. Therefore, most screwballs and curveballs you see are riseballs or dropballs that have some component of side spin making the ball move in or out. What makes the ball go side to side is how much pressure you apply to one side of the ball. Like pushing a big box across the floor, the only way to push the box straight is to push from directly behind it. Pushing just a little off to the side, will make the box turn or spin.

But even with all these fancy terms and differences in air pressure, we cannot forget about the principle force gravity. The forces on the ball due to gravity greatly outweighs the effects of the forces from the Magnus Effect. Gravity is a powerful thing, it acts on all objects all the time, and accelerates them at 9.8 m/s2 or 32 ft/s2. In fact, ignoring the forces from air pressure, if a pitcher were to throw a pitch at 65 mph from a 37ft release point, by the time it gets to the plate, the ball would drop a total of 29 inches! This is why pitchers must throw the ball upwards to compensate for the drop from gravity so the ball ends up in the strike zone. See Figure 2, the green line always has an upward angle regardless of pitch.

Basically spin can be thought to help or hinder gravity, changing the ball's path just enough to make hitters miss. Dropball spin helps gravity, the ball drop a little bit faster than a fastball would, hence hitters generally swing over them and ground out. Riseball spin hinders gravity, the ball drops a little bit slower than a fastball would, and hitters swing under them and pop up. Take a look at Figure 2, from top to bottom, the pitches are: 1. Fastball 2. Roll drop 3. High Rise 4. Strike Rise 5. Low Rise. The red dots are the path of the ball. As you can see compared to the fastball, the drop has a steeper descent. The strike rise which is aimed higher is not quite on its way down because the upward spin is hindering gravity, making the ball plateau slightly at the top of its flight path. The low rise is aimed lower, and if you look closely it's actually going down.

Figure 2. From top to bottom: Fastball, Roll drop, High Rise, Strike Rise, Low Rise. The red dots are the actual path of the ball, the green line how the ball would travel without gravity, the blue lines are the strike zone.

Along with affecting the movement of the pitch, spin also affects the speed of the pitch. Dropballs are always faster than riseballs for the following reasons: The vector addition of the forces on the ball, a larger radius of circular motion, and the amount of force by the pitcher's fingers in the direction of horizontal motion.

Forces and velocities are vector quantities, or they have direction. If two forces are in the same direction, they are added and the ball speeds up, opposite direction, they are subtracted and the ball slows down. When all the force vectors in all directions on an object are added through vector addition (google it!), an overall velocity can be determined. In our case, once the ball leaves the pitcher's hand, the only forces acting on a pitch are gravity and the Magnus force from the spin. Adding these forces will give us the acceleration and velocity in the vertical direction, then adding the initital horizontal velocity using vector addition, we can determine the overall velocity of the pitch. Therefore, since riseball spin produces a force opposite of gravity, a riseball is traveling in the downward direction at a slower velocity than a dropball. So if we assume the same horizontal velocity for a riseball and dropball, through vector addition we can conclude that the overall net velocity for a riseball will be slower.

Try thinking of vector addition like this. Imagine a North, South, East and West coordinate system drawn on a table. A ball is rolled from one end of the table towards the North. As the ball is rolling, it is nudged slightly from the South-West. As you can imagine, the ball changes direction slightly to the North-East, but it also speeds up. If the same ball traveling North were nudged from the North-East, the ball would change to a more North-West direction, but it would also slow down.

The velocity of an object traveling in a circle is directly proportional to the radius of the path it is traveling. So, the larger the radius of the circle, the pitcher's arm, the faster the ball is going at the point of release. When throwing a dropball, the pitcher releases the ball off of her fingertips with her wrist straight to make the ball have topspin. To throw a riseball, the pitcher must get her hand underneath the ball to create backspin, so her wrist is in a bent position at release, a shorter radius of motion. This bent position versus the straight position of the wrist can be the difference of a couple miles per hour.

Note: If you want to know more about wrist position for different pitches, go talk to a pitcher! Talking to pitchers is a good way to learn more about spins as well. Know how the ball spins, know where it's going, know how to hit it.

Finally, a last contributing factor to the speed of the pitch is how much force you apply to the ball in the direction of motion, the plate. Like the earlier box analogy, if you push from directly behind the box, all your force will be used to push the box in the direction you want to go. Any force a little off of centre will cause the box to turn, you have to push harder to slide the box the same distance as the box that slid perfectly straight. When throwing a peel drop, your hand is completely behind the ball spinning it downwards. For a riseball, all your force is applied underneath the ball on the seam to make it spin in the opposite direction. Again, if you can't understand me, go talk to a pitcher.

So what does this all mean? Well from the earlier 5 questions we can use the spin we see to make an adjustment with our hands to hit the ball square. For those hitters who can't see spin, they are put at a disadvantage because their eyes can only recognize the height of the ball. They then swing to where they assume the ball to end up, however if the ball is spinning in a different direction they might miss. Good pitchers are able to throw the ball that is able to spin up or down, as well as have some component of side spin, a curve rise, or a screw drop for example.

Also, as discussed earlier riseballs are slower than dropballs, therefore you should have more time to hit it right? This is not necessarily true, although the ball is moving slower through the hitting zone, as far as reaction time is concerned you actually have less time to hit a riseball than a dropball. Remember, the golden rule says that higher pitches must be hit more out front, lower pitches farther back in your stance. So, for the simple fact that you must hit a high inside riseball approximately 2 feet farther out in front than that of a low outside dropball, the less distance traveled by the ball provides an illusion of increased velocity. The less distance the ball travels, means there is less time to react, an equivilant to an increase in speed. In fact, if a riseball were to be thrown at 65mph high and inside, you would have to have a quicker reaction time of .021sec, equivilant to an increase in speed of 4mph.

Casting Is Left For The Fish

Casting is often a misunderstood concept. While it's often true that casting is swinging with a straight front arm, it's not the whole story. What actually causes the straight front arm is the top hand going away from the body over the plate, and wrists snapping too early as shown in Figure 1 below. This initial movement outwards is the beginning to a very inefficient swing path.

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Figure 1: Side a) and front b) view of casting. As the top hand starts to go away from the body, it causes the front arm to go straight and the wrists to snap too early. Click to enlarge images.

Snapping your wrists too early, that is before passing the body's centre of gravity, also causes the bat head to move away from the body. Like a boat pulling a water skier, when the boat turns, the skier keeps going in the same direction he was going, restricted only by the rope. The bat head is the skier, wrists and arms are the boat. Now imagine the skier is massive, as he keeps going in the direction he was going, his momentum pulls on the rope and the boat (wrists and arms). This force pulling the boat is called centrifugal force. Centrifugal force is the outward force associated with rotation, the equal and opposite of centripetal force, as shown in the schematic in Figure 2. You've most likely felt this force taking a tight turn in the car, or on the tea cups at the amusement park. This force created by the bat head, pulls the hands away from the body, creating a circular swing. So in general, younger players who have less arm and wrist strength are more likely to cast, because the bat is too heavy relative to their size.


Figure 2: Ball is swung around on a string. Centripetal force is acting on the ball by the string. Click to enlarge image.

Hitters who cast are also more likely to roll over their wrists and ground out. To keep a nice smooth bat path the top hand must stay facing up while rotating (snapping). When the top hand rolls over, the bat head goes up making a hump in the hitter's bat path as shown here. This hump is not very efficient as it doesn't let the hitter's hands reach out as far as possible towards the pitcher.

Note: Although the video is in slow motion and an over exaggeration it is still true! Trust me, if you've ever seen someone smacking themselves in the shoulder on their follow through, this is it. This hitter is subject to many groundballs, and a bruised shoulder.

To avoid casting, the hitter must make sure to load their hands, and slot the elbow close to the body, as shown in Figure 3. Then, hold the wrists in a cocked back position until they pass the centre of gravity of the hitter. Notice that in this position would be ideal for a check swing, because the bat is not over the plate.

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Figure 3: Front view of check swing, and before hitter snaps her wrists a). b) shows when the hitter snaps her wrists, notice her hands have passed her centre of gravity and are in front of her body.

A good drill is to hit off a tee, but place another plate in front of your front foot, as shown in Figure 4. The extra plate is a reference as to where you should snap your wrists for an outside, middle or inside pitch. Once your hands pass over the outside part of the plate, snap your wrists for the outside pitch, middle for middle, inside for inside as shown below.

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b)

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Figure 4: Two plate drill. The second plate in front of the hitter's foot is divided into thirds and represents when the hitter should snap her wrists, a) outside, b) middle and c) inside. Click to enlarge images.

Another drill is to set up a two tee points, one in the middle and one 6-8 inches outside. The outside point is set up higher, while the middle one is lower with the ball set up on it. If the hitter casts, they will hit the outside tee. If they keep their hands in close to their body, they should hit the ball with no problem as seen here.

Squishing Bugs?

We've all heard this one before, "Squish that bug!" referring to pivoting your back foot when swinging. I'm not really sure where it came from, but it seems silly to me making all those unsightly holes in the field. Squishing the bug is an inefficient movement because of the following. First, it moves the center of gravity of the hitter lower and too far back, making it difficult to reach out in front of the plate for extension. Second, it's slow due to the the friction between cleats and ground providing resistance, and not allowing the hips to move as fast as they could. Three, and most importantly, it breaks the kinematic sequence. By squishing the bug, it is impossible to separate the rotation of the hips and shoulders. They instead rotate at the same time, making the hitter use their arms a lot more, resulting in slower batspeed. See what happens when you squish the bug versus kicking <here>. Squishing the bug causes the centre of gravity of the hitter to move backwards over the back foot. Kicking keeps the hitter's centre of gravity in one place, therefore being able to rotate about the hitter's spine. And since the bat head is supposed to move forward towards the pitcher, it is counter productive to have the centre of gravity to be going in the opposite direction towards the catcher. See how much farther the hitter can reach, relative to the tee in Figure 1 below, when the centre of gravity stays still (aka extension).

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b)

Figure 1: Differences in position of centre of gravity in squishing a), and kicking b). In a) the hitter's center of gravity is much farther back than in b), and her bat is therefore not able to reach forward as far relative to the tee. Click to enlarge images.

To overcome friction between cleats and ground, we can avoid it all together by having our back foot in the air! No contact, means no friction, means quicker movement. By "kicking" your back foot forward, it keeps the rotation of your hips tighter aka quicker. Also, by kicking forward, you are driving against your front leg for more power, much like throwing a ball, or pitching.

As mentioned before, it's impossible to separate the rotation of your shoulders and hips when you squish the bug. But why? From the kinematic sequence we know that it starts from the feet, moves to the hips, then shoulders then hands. Squishing the bug is a movement initiated by the hips, in the middle of the sequence. Try wringing a towel out by holding the top still and wringing out the bottom. See how the towels twists gradually starting from the bottom moving up, like a nice kinematic sequence. Now hold the top and bottom still and have someone grab the middle of the towel and start twisting. See how the towel twists above and below the initial rotation at the same time, just like squishing the bug.

Note #1: Even though we're using our hips for power, we're not actually "using" them in the sense that we are using those muscles. We must make sure the kicking action initiates the hip rotation, not the hip rotation causing the kicking. Since the hip muscles are bigger, they cannot move as fast as the foot and knee. By using the hip muscles to kick the foot creates a slower, more sweeping movement with the hips.

Note #2: There is an intermediate movement to kicking the foot and hip rotation called "the elvis." It's when the hips shift forward towards the pitcher before starting to rotate, creating a tilt with the upper body, it's also the start of loading the hands. As the hips shift forward, it makes it easier and almost automatic for the back foot to kick forward. Figure 2 below shows first a hitter's load and then elvis.

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Figure 2: Hitter first loads hands a), then shifts her hips forward b). This shift is called the elvis, and creates a good angle from the front hip to the head. Click to enlarge images

Making Adjustments cont

Continuing with the adjustments theme, if we create a swing which can make adjustments efficiently, it will yield better results. From the previous post we learned that loading your hands back away from the pitcher creates a more gentle slope downwards, thus making it easier to bring them back up as an adjustment. Loading also lets the back elbow be in the right position close to the body when the hips and shoulders rotate around, called "slotting the elbow." This position lets your hands stay still relative to the body for as long as possible. This is an efficient movement because your body can replicate it for every swing no matter where the pitch is, rather than "throwing your hands" at any different pitch in the strike zone, which has a much larger margin for error.

So how do we hit pitches in different locations? We do this by adjusting shoulder and torso angles. Changing the angle of your torso and/or shoulders by a few degrees translates into a much larger change in the angle of your bat as shown in Figure 1. By changing the angle of your torso, your hands don't have to move as far up and down to hit pitches at different heights.


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Figure 1: Adjustment of shoulder and torso angle to low a) and high b) pitches. Note how the hitter's back elbow is slotted, close but not touching the body, and pointing to the pitcher, not over the plate. Click to enlarge images.

Figure 1 a) and b) shows how much of range you can get with your bat just with changing the angle of your torso and shoulders. This angle is first initiated in the hitter's stance, and refers to the line from the belly button to the head leaning in towards the plate as shown in Figure 2. More lean is better for dropballs, less lean is better for riseballs. Referring back to the 5 questions, we know that pitch height is one of the first questions we can answer. Approximately within the first 10 feet the ball has traveled, we can already tell where the ball will end up. At this point, the brain has already decided how much lean the torso needs, and from here adjustments are made by the arms.

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Figure 2: Differences in angle of torso in a hitter's stance. More lean a) is better for dropball pithcers, less lean b) is better for riseball pitchers. Click to enlarge images

Note #1: To make life easier, it's a good idea to start with a lean in your stance like in Figure 2 a), giving you less of a distance to go as the pitch is coming. Trying to lean in and rotate at the same time causes the batter to have too much weight on their toes and fall over. Having a lean in your stance also helps in getting your elbow slotted.

Note #2: By having a stance like this we are somewhat sacrificing not being able to hit the riseball very well. But since the strike zone is from the bottom of the sternum to the knees, we need to be able to hit more low pitches than high. Leaning over in your stance makes hitting dropballs easier because your hands don't have to drop as much to hit the ball. However, to hit a riseball, your hands and elbow must extend upwards faster in order to straighten your shoulders out and get the bat more level with the ground. So, if you're facing a riseball pitcher it would be a good idea to start more upright, making it easier for your hands to get above the ball.

The horizontal plane is much more simple. The only difference in hitting an outside to an inside pitch is how far you let your shoulders rotate before snapping your wrists. Again, see how much range the bat head has just by rotating your shoulders and not moving your hands <here>.

Making Adjustments

The order in which a batter reacts to a pitch is this: the eyes see the ball released, sends a message to the brain telling it where the ball is going, the brain tells the body to swing, then the body swings in the way it was taught, after all those long hours of batting practice of course. But, from the point of release our eyes only have an idea of where the ball is going to be. Only as the ball gets closer can we pinpoint where the ball is actually going to be. Therefore, as the brain processes the information from the eyes (answering the 5 questions) it has to give the body corrections or adjustments from it's original messages. And given a 65mph fastball takes .420sec to get to the plate, this relay of signals often doesn't happen fast enough in order to hit the ball square.

However, if we are able to watch the ball come in, and delay moving our hands, the ball will be easier to hit. Due to inertia, our hands (and the bat) want to keep going in the direction in which they started on, so once our hands start to move forward, it will be harder to change their direction. Those who have ever been fooled by a change up know that once your swing has started coming through it's really hard to slow down to hit the ball. So contrary to popular belief of "throwing your hands at the ball," it's far more efficient to load your hands, keep them still as long as possible, and bring them to the same position every time. Loading your hands, also creates separation between the lower and upper body, aka the X Factor Stretch and more power.

See the difference between loading and not loading your hands <here>. Since the hands, and thus bat head, must drop to hit the ball, not loading your hands creates a sharper angle downwards as shown in Figure 1 below. And what we know from inertia, once your hands start moving down, they're going to want to keep moving down, therefore making it harder to bring them back up fast enough. But, if we create a less steep angle downwards, making the adjustment to bring them back up for a rise ball will be easier.

Figure 1: Flowchart of hands during swing, with and without loading. The blue lines create a less steep angle between each other than the red lines, therefore making it easier to make the adjustment to the higher pitch.

A Hitter's Golden Rules (to date)

These are a hitter's golden rules, these rules are incontrovertible at all times. All mechanics aside, these are concepts based on biomechanics and physics. Can't really argue with those two.

1) The lower and farther outside the ball is, the farther back you must hit it in your stance. Your arms can only reach so far, don't make them reach out front as well as outside unless you want to ground out all day.

2) The faster the ball is going, the less it drops. Therefore, you must swing higher than you think you should to hit faster pitching.

Rule 1 confirms why change ups are most effective when thrown outside and low. Not only must the hitter wait because it's traveling slower, but wait because a low outside change can only be hit hard when hit to the opposite field, or farther back in the hitter's stance. Saying this, the odd change up thrown on the inside part of the plate is not a bad thing either. Often hitter's with circular swings won't be able to keep an inside change in fair territory.

Faster pitchers use these rules to their advantage, as they are more effective in the vertical plane. Such that, a drop ball will be thrown with more velocity because of the combination of gravity and spin [down spin+gravity=drop]. Whereas a riseball won't be thrown with as much velocity because it is fighting gravity. It will still appear to be faster though because it drops less [rise spin+gravity=0]. Therefore a hitter must hit a riseball more out in front (opposite of rule 1), giving less time to react.

So how can slower pitchers be effective? Well, since the ball is moving slower, hitters will tend to be ahead in their timing. In doing so, the bat is already through the "good" contact zone and coming around the body aka rolling over. Rolling over (your wrists) results in hitting the top of the ball and grounding out. Also, slower pitching tends to make hitters lunge at the ball. This lunging action lowers the center of gravity, and in turn, the hands. So, if the bat was going down already, it will go even lower, causing you to be under the ball and pop up. Another thing a slower pitcher can do is make the ball move more. Since the ball is moving slower, gravity has more time to act on it. So, with the combination of spin and gravity, a pitcher can really make that drop ball "fall off the table".

Accordingly, as a hitter it's always a good idea to stand in the back of the box in order to see the ball travel and spin as long as possible. For slower pitchers, to take away the element of waiting, try crowding the plate instead of automatically moving up in the box. While moving up in the box makes the pitcher seem faster, giving you less time to react, crowding the plate lets you hit the ball more out in front of the plate. And since slower pitchers are less likely to throw inside to hitters, getting jammed is a lesser factor to take into account.

Also, as a side note to rule 2, if you succeed in getting your hands high enough on a riseball pitcher and hit a line drive or grounder, that pitcher will be less likely to throw you another riseball, taking away her best pitch. Because if you are able to get your bat over top of the rise, then you're sure able to match it and hit it a long ways.

So we've learned that low outside pitches need to be hit farther back in our stance, and in order to hit faster pitching you must swing higher than you think you need to. So for all you pitchers out there, work batters in sequences of low outside and high inside pitches since those two have the most discrepancy in timing. Whereas low inside pitches and high outside pitches have roughly the same timing.

5 Questions

As the ball is released from the pitcher's hand, before we hit the ball the brain has to process some information in order to react correctly and get the bat in the right position to hit. There are 5 questions the brain answers automatically in this order:

1) How fast is it going?
Is it a change up or fastball? We must see the difference between the two, either from the release seeing the back of the hand, or a change in the pitchers motion in order to not be fooled and transfering our weight too far on the front foot. The quicker one can pick up the change up, the easier he can stop his body and wait (keeping the front heel off the ground).

2) Where is it going?
Is it a high or low pitch? This is the next thing you are able to see, because of the way the ball is (usually) projected. High pitches are easier to see than low pitches from release.

3) How is it going to get there?
Seen from differentiating between spins. Although an artform that requires practice, the skill of seeing spin is one that is most valuable that separates good hitters from great hitters.

4) Where is it going?
Is it an inside or outside pitch? This question is answered last because spin often doesn't dictate location on the plate, and since the plate is only 18 inches wide it's harder to distinguish exactly where the ball is going.

5) Where is the ball going to end up when I am able to contact it?
Finally, after all the other questions are answered you have a pretty good idea where the ball is going to be and whether it is a good pitch to hit. And if it is a good pitch to hit, how to position your body in a way to hit it.

Those who can answer these questions the fastest, or have some of them answered before the pitch occurs (having a pick) are obviously at an advantage. Conversely, the pitcher is at an advantage if she can hide her pitches, keeping her body and arm motions similar, and starting pitches on the same plane, having the spin take the ball in different directions.

So how do we do this? Well personally I like having a pick on the pitcher before I even start (more on how to do that later). If I have the change picked for example, it eliminates the surprise of a slower pitch, and all I have to do is react to location. It also eliminates 1 out of a pitcher's 4 pitches, I like a 1 in 3 chance of guessing what a pitch is instead of a 1 in 4 chance.

Seeing the pitcher's hand at release is also important in gathering information about a pitch. Focus in on the hip at release and differentiate between a rise, drop and change. Catchers should be good at this, and those obsessive batters who stand in on their own pitchers all the time.

Finally, by having a good scouting report on a pitcher or figuring out some tendencies throughout the game can give you some answers to these questions. After all, pitchers are predictable, and will throw what is comfortable to them.