Last month, we reviewed the infamous Tommy John surgical procedure — namely, what it is and what its risk factors are.
To recap: Tommy John surgery is a ligament repair procedure for the medial ulnar collateral ligament (MUCL) of the elbow. Many athletes can be at risk of injuring their MUCL, but it’s most commonly seen in baseball players and pitchers due to the nature of the sport. Some risk factors include a large carrying angle of the elbow, higher pitch counts, and higher throwing velocities.
But, there is one risk factor that is more substantial (and complex) than the rest: improper pitching mechanics.
The aforementioned risk factors are important considerations, but pitching mechanics are by far the most necessary training aspect to focus on, as it’s a modifiable, trainable skill that can go a long way for injury prevention.
Let’s dive in.
The 6 Phases of Pitching
In order to catch improper pitching mechanics, we first have to understand what PROPER mechanics look like!
Some people are surprised to learn that there are 6 phases involved in a single pitch, but that’s what it takes to build the kind of power and velocity needed for a strong throw.
Phase 1: The Wind-Up
The very beginning phase of a pitch is referred to as the wind-up phase. It begins when the pitcher starts moving, shifting their weight onto the stance leg and lifting the other foot off the ground. This initial phase continues until the point where the pitcher is balanced and fully bearing weight on their stance leg, with their leading knee at maximum height.
With a standard pitch over the home plate, the wind-up phase takes a bit more time, as you need to build as much force as possible. But, if you’re pitching from the stretch to a runner on base, your wind-up will be much quicker. In either case, the arm moves very little in this initial stage, so injuries to the elbow are rare during wind-up.
Phase 2: Stride
The stride phase is exactly what it sounds like. It’s the stage of pitching where you stride forward and move your leading leg outwards until it hits the ground — but this is where the research gets specific about certain biomechanics.
For the most ideal pitch, your stride length should extend as far as 83% of your body height. Additionally, the knee flexion in your leading leg should be 45 degrees, your pelvis should be rotated 33 degrees towards the batter, and your shoulders should only be about 15 degrees open.
As you’re moving into the pitching motion, your arms will move in opposite directions so that your throwing shoulder moves up, abducting by 93 degrees and externally rotating by 56 degrees. At this point of your throw, your elbow should be flexed at 90 degrees.
Phase 3: Arm Cocking
Here is where your body starts to build some of that pitching power!
This phase starts from the moment your lead foot makes contact with the ground to the point of maximum external rotation (MER) in the shoulder. Visually, this is when your arm is brought as far back behind you before moving into the forward swing of your pitch.
Your MER can reach as much as 181 degrees, and the degree of external rotation is directly correlated to the velocity of the ball. Unfortunately, the extent of this rotation is also one of the most common points of injury during a pitch.
Form is a key player during the arm cocking phase — rather than solely depending on the arm and shoulder, pitchers need ample trunk rotation. You should be pulling your gloved hand in towards your body as you rotate, as this helps accelerate the rotational forces and velocity that travels from your hips, through your upper trunk, and into the shoulder.
Phase 4: Arm Acceleration
As you can probably infer from the name, this phase is where the velocity really kicks in.
Your arm acceleration phase begins from the point of peak shoulder external rotation until you fully release the ball. When propelling your arm forward, you’re moving into rapid shoulder internal rotation with velocity that can reach up to 7,500 degrees per second. (And when your elbow moves into extension, the joint may tolerate up velocities up to 2,450 degrees per second.)
With those kinds of statistics, it’s no surprise that both your shoulder and elbow joints are vulnerable to injury, right?
And the biomechanics continue to remain important, even after the ball leaves your hand! When releasing the ball, your trunk should be leaning forward by 36 degrees and to the side by 23 degrees, and your leading knee should be flexed to 35 degrees.
Phases 5 and 6: Arm Deceleration and Follow-Through
Now, your body has to manage the aftermath of this rapid force production — as the ball is released, your arm begins decelerating and the shoulder starts to rotate internally. Your rotator cuff has to work eccentrically to resist the forces and prevent them from interfering with the deceleration process.
The follow-through phase follows immediately after deceleration, when your shoulder is at peak internal rotation. It continues through to the end of your pitching motion as your arm naturally swings across your body.
Risk Factors for Elbow Injury in Pitching
These phases describe the mechanics of a picture-perfect pitch: but, there’s a lot of room for possible movement deviations that increase a player’s injury risk.
Research has shown that there are 4 primary risk factors with overhead throwing that increase stress on the MUCL. They’re a bunch of big, almost daunting words, but don’t worry — we’re here to break it down for you.
Shoulder Abduction During Acceleration
Abduction refers to any movement that brings a body part away from the midline of your body. With the shoulder joint, the angle of horizontal abduction measures how far out your arm moves away from your shoulder blades. (In the context of a pitch, an excessive angle of abduction presents as the elbow joint trailing behind your shoulder while throwing.)
This is also referred to as “hyperangulation.” The larger this angle is, the more valgus stress is being placed on the inner part of your elbow. Hyperangulation occurs during the arm cocking phase, when your leading foot first makes contact with the ground, and it can carry all the way through the arm acceleration phase.
Elbow Flexion at Peak Valgus Stress
Proper pitching form always has a point of “peak valgus stress”: it’s the moment where your elbow joint tolerates the most force during a throw. This peak alone is not an injury risk — but its corresponding degree of elbow flexion is.
During the arm acceleration phase, a flexed elbow helps reduce the valgus forces in the joint. On average, your elbow should be bent about 98 degrees through this phase to help mitigate the amount of force traveling through the arm.
Unfortunately, many pitchers sustain injury as a result of insufficient flexion. The straighter your elbow is during acceleration, the more force builds in the joint and stresses the MUCL.
Torque at Peak Shoulder External Rotation
Just like peak valgus stress, peak shoulder external rotation is a natural part of proper pitching mechanics — the risk of injury happens as a result of the torque in your shoulder at this point.
Torque is the rotational force that brings your arm backwards during the arm cocking phase and beginning part of the acceleration phase. Professional pitchers will average 111 Newton-meters of torque, which is a crazy amount of force for one joint to tolerate repeatedly. (And unfortunately, it’s not possible to assess torque through visual observation alone; it requires state of the art equipment that can measure specific angles and velocities in real-time.)
Angular Velocity at Peak Shoulder Adduction
Adduction is the inverse movement of abduction: it’s when you bring a body part towards the midline of your body. In the case of pitching, your shoulder joint simultaneously adducts your arm while also bringing it forward during the acceleration phase.
The angular velocity of this movement specifically measures how quickly you bring your arm forward. On average, elite level pitchers hit a velocity of 933 degrees of adduction per second. (Yet another impressive degree of force that your body has to sustain!) Just as with torque, angular velocity has to be assessed in a clinic with the necessary equipment to attain an accurate measure.
Pitching is Complicated!
You probably already knew that pitching was no easy task — but now you understand just how nuanced it can be, on top of it being such an explosive, dynamic movement. There’s a lot that can’t be easily measured or quantified when it comes to the biomechanics and physics of a solid pitch.
At least, not without the proper equipment.
Find a movement specialist who has the right technology to measure your biomechanics and physiology! (If they also work with high-level athletes like our clinic, that’s an even better opportunity to ensure specialized care for sport-specific recovery and injury prevention.)
Check out the third and final blog of our series, where we dive into the best set of exercises for preventing elbow injury and Tommy John Surgery altogether.
