Pulled air balls are the most effective batted balls but they are not easy to achieve. Last year in mlb the average pull side LA was just 5.8 degrees, vs 9.2 to center and a whopping 24.4 to opposite field.
But which factors make pulling the ball in the air so hard?
One is pitch selection. https://www.fangraphs.com/community/effect-of-pitch-selection-on-launch-angle-and-exit-velocity/ Pulling outside pitches yields lower lauch, the same applies to lower pitches, especially down and away.
But also hitting the inside pitch also has some problems. One problem is simply that the body is in the way. The sweet spot of the bat is like 20 inches away from the hands and the inside of the plate is closer to the body than that.
Because of this to hit the inside pitch you need to create space.
1. Create space ahead of the body
This is the first way. Every hitting instruction, traditional or modern teaches to hit the inside pitch out front more.This means the hands are slid across the chest slightly so the hands are more in front of the belly button instead of besides the body
2. Create Space laterally
The out front method is good but it also has issues if overdone. First of all raking the hand across the chest is breaking the kinetic chain, it creates some kind of „push“. This is needed to hit some inside pitches but it also can reduce exit velo, which is shown even in mlb were up and in leads to the lowest EV of all zone locations.
Also a too circular swing that is too wide around the body leads to a strong right to left component which can create top spin and roll overs (same applies to too far out front contact when bat starts to arc out of zone).
Pro tennis players actually use that across swing actively to generate topspin
However in baseball topspin is of course not wanted unlike tennis. Because of this it can help to make the path to the inside pitch more linear. It is still curved of course, but not as big of a curve.
To achieve this you simply need to increase the distance between the inside of the plate and the body. This is achieved by maintaining hip hinge a little longer and also using side bend to pull away from the plate.
Trout is excellent at this creating space under his right shoulder to create a more direct path. This means he has to hit the inside pitch less out front and rake the hands less across the chest even allowing him to hit balls on the inside black over the fence to straight center.
If you have created space laterally and bring the hands really tight forward under the right shoulder you can bring the path a little straighter to the pitch and hit the ball straighter too.
This is an extreme case though and most hitters will need a combination of both methods to hit the inside pitch.
The third adjustment is horizontal bat angle. A horizontal bat angle of zero means the bat is parallel to the front of the plate. Negative means it points slightly to the catcher and positive means it slighlty points to the pitcher. A positive horizontal angle moves the sweetspot more to the inside and leads to more pulling of the ball. In conjunction with vertical bat angle a positive horizontal bat angle also can help creating more loft. DK Willardson calls this implicit loft in his book quantitative hitting because the forward and down pointed bat can act a little like a ramp.
Too much horizontal bat angle will lead to foul balls though, Willardson mentions a HBA of about 15 degrees for inside pitches.
Maintaining VBA also helps to hit the ball straighter and less of a chance for topspin. A common mistake is to let vba get flatter out front causing topspin. Keep bat tip below the hands as long as possible.
Video of Altuve maintaining his vertical barrel angle (VBA) through the zone. VBA is a very important metric that the common bat sensors can measure. Usually VBA is about -20 to -45 depending on pitch height with good hitters. Too flat can cause low pitch issues@FlatgroundBats pic.twitter.com/iiWJ7idQaA
— dominikk85 (@dominikkeul) October 3, 2019
So to summarize to hit pull side bombs, pick the right pitches to pull (inside pitches or middle pitches that are slightly elevated) and create space to pull the ball without going across it too much.
A common mistake that blocks off the inside pitch is a too wide arc to it that causes to hook the ball and also the hips coming toward the plate to soon. Found this golf drill to correct that. Don’t let hip extension occur until they are fully turned.
Fixing Early Extension is as much about creating new movement patterns as it is about addressing physical limitations.
Dr. Trenton Civello uses a band that requires him to resist early extension in a medicine ball toss, helping teach him to keep his hips back in the golf swing. pic.twitter.com/41hJBd9SA2
— TPI (@MyTPI) November 27, 2018