12 Steps to Analyzing Baseball Swing Mechanics

By Nunzio Signore (BA, CSCS, CPT, NASM, FMS)

baseball swing

Hitting an MLB fastball requires the application of a huge amount of energy in the blink of an eye- roughly 130ms to be exact. That’s about a 1/8th of a second. Only through a coordinated series of contractions involving not only muscles but joints and connective tissue traveling up the kinetic chain into the hands and ultimately the bat/ball can we achieve adequate bat speed and quickness to hit a baseball traveling at speeds north of 90 mph. This article is meant to familiarize many of you with the 12 positions in baseball swing mechanics that we look at when analyzing video (it’s not a “how-to” blog on analyzing mechanics). 

A baseball player’s swing mechanics (much like pitching), can be broken down into 2 distinct Phases.

Stride Phase (linear) – The Stride Phase begins at set up and ends when the hitter commits to the pitch (approx. at heel plant):

      1. Setup / Stance
      2. Leg Lift / Negative Move
      3. Center of Mass (Balance and Posture)
      4. Center of Mass / Tempo into Foot Strike
      5. Front Foot Strike
      6. Front Knee Angle / Unstable Base
      7. Stride Length
      8. Peak Hip / Shoulder Separation

Swing Phase (rotational) – The Swing Phase begins as the front leg blocks at heel plant and the body begins to accelerate its rotation against a firm front side ultimately ending at contact:

      1. Front Side Blocking
      2. Hand Position at Launch
      3. Axis of Rotation
      4. Bat Lag

Here we go with the Stride Phase, followed by the Swing Phase further below…

Stride Phase (linear)

1. Stride Phase: Set-Up / Stance – Different strokes for different folks here. Because the set-up is a “pre-swing” position, a hitter’s stance at set-up can be unique to each individual without affecting the ability to adjust to pitches in various locations. Stances can range from narrow to wide as well as open, closed or parallel.

hitting set-up stance

While different players have different styles, they all must position their weight on the inside of the feet in order to eventually load around the rear hip and get ready to fire during leg lift.

baseball swing leg lift

2. Stride Phase: Leg Lift / Negative Move – A player’s individual style again comes into play here during leg lift and is based highly on, not only on stance but, anthropometrics (height/limb length) as well. Adjustments in rhythm and tempo will also play a big part of a successful leg lift. Whether it be a lift or a tap, finding a leg lift that works for the individual is paramount in order to store energy/power in the connective tissue of the back hip and lower torso during the negative move. Failure to do so can cause the athlete to either “hang back” or get “too forward”. Both can lead to not only balance issues but can negatively affect our next position in the linear phase “C.O.M. Balance and Posture” as well.

3. Stride Phase: Center of Mass (Balance and Posture) – The most successful hitters maintain good balance and posture from start to finish. Let’s first talk about the difference between the two.

Balance is controlling the body’s center of mass relative to the base of support from start to finish. Imbalances during stance and stride can negatively affect a hitter’s vision and timing. It can also create an inefficient linear move ultimately transferring into inefficient rotation after foot plant affecting bat speed and bat quickness as well.

Posture is the alignment of the head and trunk relative to the lower half during the linear move. Optimal rotation happens on a vertical axis so maintaining this alignment throughout the entire linear move and int rotation is paramount to maintain rotational efficiency of the body.

hitting posture stride phase

4. Stride Phase: Center of Mass / Tempo into Foot Strike – Too fast of a tempo during the stride usually caused by an early push-off on the back leg or lunging/jumping into the pitch, can send the body’s center of mass traveling at too high a velocity going into foot strike. This can make the baseball appear to have a higher perceived velocity, forcing an early commitment to the pitch and/or create a heavier landing on the lead leg when blocking, thus delaying deceleration as well as the rotational phase of the hitting mechanics.

However, too slow of a tempo usually caused by a weak or short stride can kill any momentum going into foot strike, compromising crucial ground reaction forces needed at foot strike to efficiently transfer energy up the chain and ultimately into the bat.

5. Stride Phase: Front Foot Strike – The ball of the front foot will hit the ground when the ball is approx. 30 ft. (halfway) to the hitter. While the position of the foot can and should be adjusted according to hip mobility, there are limits to how “open or closed” we want the front foot to be. The foot should be open enough to acquire adequate hip rotation into contact BUT:

Too Open or Closed – Landing with the front foot too far open can cause a “soft/heel first” or “collapsed” front side when blocking begins. By the same token, landing with the front foot too closed can severely limit rotation and rob the athlete of much needed hip/shoulder separation and thus power/torque.

Once again, hip mobility will factor in to how open or closed the front foot/leg should be. K-Vest can provide us with some great information on rotation as well as poor accel/decel rates in this regard.

hitting kinematic sequence baseball swing

(K-Motion Example – Poor Pelvic Deceleration)

6. Stride Phase: Front Knee Angle / Unstable Base – Maintaining a slightly flexed (bent) knee at heel plant is crucial to keep the core centered and in control to adequately transition from the stride (linear) phase to the swing (rotational) phase efficiently. This can help ensure a quicker, cleaner transfer of energy to the upper half through the lead leg blocking.

An overly flexed or “collapsed” knee at landing will cause the hitter to hit through his front side, creating an unstable base of support and compromising core stability/positioning, power transfer and vision to the ball.

However, an extended or “locked-out” front knee/leg usually through early hip rotation, will transfer force pre-maturely prohibiting the efficient use of optimal ground reaction forces up the chain creating losses in rotational acceleration and power. Mike Trout (below) does a great job of maintaining a great athletic stance/stable base to rotate from.

Baseball swing stride length

7. Stride Phase: Stride Length – There are all types of theories on what the correct stride length is. My opinion is that it depends on a few things:

Too long – While most  more mature athletes are strong enough to utilize the many benefits of a long stride, most younger athletes who do not possess this required strength, drop their center of mass too low.  This in turn, makes it hard for them to get out of such a low position in order to create good angular velocities. Too long of a stride will also delay the beginning of rotation at foot strike causing everything to happen all at once, which gives us lower rotational numbers and peak velocities into the trunk, arm and ultimately the hand/bat.

hitting stride length too long

Too Short – On the other hand, too short of a stride can compromise forward momentum into foot strike, causing the hitter to “hang back” and/or contribute to less than optimal ground reaction forces up and into the sequence.

hitting stride length too short

(Short Stride / Hanging Back)

8. Stride Phase: Peak Hip / Shoulder Separation – The point between foot strike and heel plant is when the upper half (shoulder line) and the lower half (hips) reaches its peak disassociation and our rope (core) is tightened. This creates the torque necessary to unwind from as the swing begins it’s rotational phase.

An important point to make here is that all athletes have different lengths of rope depending upon body type (limb length) and the type of mover they are “loose” (laxity) or “tight” so, what is an optimal amount of separation for one athlete may be too much for another. This can contribute to different problems further up the chain such as early trunk rotation or even worse, common hitting injuries such as oblique strains.

K-Vest does a great job of calculating separation at Heel Strike, First Move and Contact and placing it into a well-written report.  We just have to keep in mind what type of mover we are dealing with, loose or tight and use good judgement.

k-vest x-factor performance graph

(X-Factor Stretch Report / Performance Graph)

Swing Phase (rotational)

1. Swing Phase: Front Side Blocking – If a hitter’s front leg/front side does not firm up immediately at heel plant, the pelvis will continue to “drift” or slide towards the pitcher. Different players have different degrees of knee flexion and that’s ok, as long as they increase that flexion after heel plant. This can negatively affect a player’s front side stability and ultimately affect lower half angular velocities transferred up the chain as well.

hitting front side

2. Swing Phase: Hand Position at Launch – Bat positions may differ from player-to-player but regardless of style, once we get to foot-plant we like to see the hands at roughly shoulder level, beyond the back shoulder but not beyond the back elbow. This will help contribute to a better “whip” as well as a more effortless bat speed and better bat path through the zone and into the ball.

hitting hand position

3. Swing Phase: Axis of Rotation – Once the lower half has begun to transfer energy after blocking, it’s important that we have a stacked center of mass (COM) starting from the base of support (equal distance between the feet) up through the center of the hips and shoulders in order to quickly achieve full rotation. This is the “driveshaft” of the rotational phase. Optimum rotation takes place on a vertical axis and the more efficient our rotation is the quicker the bat will enter the hitting zone.

hitting axis of rotation

4. Swing Phase: Bat Lag – This is the final link in the rotational phase before the bat is delivered by the hands. Once the hips fully rotate and are roughly parallel with the front edge of home plate, the hands should be forward but the bat should be lagging behind, until we forcefully take the hands to the ball and “snap” the bat head into the hitting zone. This allows for better last-minute decisions on pitch selection.

On the other hand, if the bat rotates too early, we are once again robbing full momentum from being transferred into the bat.

hitting bat lag

See ya’ in the gym…

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