BIOMECHANICS OF THROWING

Overuse injury in baseball result most often from pitching. To investigate this problem, the American Sports Medicine Institute (ASMI) has focused on pitching biomechanics. Kinematics (motions) and kinetics (forces and torques) are computed with a four-camera 200 Hz automated motion analysis system. Since 1989, ASMI has conducted 600 throwing tests. Because of its high risk of injury, baseball pitching has been the focus of much of the research.

Pitching Motion (Flash 4 movie)

A left-handed pitching motion was recorded and presented in a flash 4 movie. Key frames were presented with explainations of good mechanics. Click here to see.

The Six Phases of Pitching

To make the biomechanics easier to understand, the pitching motion can be divided into six phases: windup, stride, arm cocking, arm acceleration, arm deceleration, and follow-through. Click here for more.

Factors related to ball speed

It is generally believed that pitchers with good mechanics throw harder than pitchers with poor mechanics. The most important mechanical factor was the timing of maximum arm velocity. Click here for more.

Pathomechanics of Elbow Injuries

Near the end of arm cocking, the shoulder is in extreme external rotation, the elbow is flexed approximately 90°, and the forearm is in a valgus position. To resist valgus stress, a large varus torque is produced at the elbow (Figure 2). Tension in the ulnar collateral ligament (UCL) provides nearly half of this varus torque. This high tension is near the ultimate tensile strength of the UCL, leaving the UCL susceptible to injury. Click here for more.

Pathomechanics of Shoulder Injuries

Extreme external rotation during throwing makes the shoulder prone to injury. As the shoulder externally rotates, the humeral head translates anteriorly. At maximum external rotation, the posterior rotator cuff may become impinged between the glenoid labrum and the humeral head. This "over-rotation" injury can cause degeneration of both the superior labrum and the rotator cuff. Click here for more.

Relationship between poor mechanics and chance of injury

Improper mechanics are believed to increase the stress on the throwing shoulder and elbow, resulting in increased chance of injury. Click here for more.

The Interval Throwing Program

Flat ground throwing and partial effort pitching are often used in rehabilitation programs like the "Interval Throwing Program." The purpose of these programs is to reinforce proper mechanics while systematically increasing joint loads. Click here for more.

Differences between fastball, changeup, curveball, and slider biomechanics

Fastball, changeup, curveball, and slider mechanics were measured and compared for 16 college pitchers. Both the curveball and the changeup had slow trunk rotation. Elbow extension and shoulder internal rotation were relatively slow in the curveball and changeup. Click here for more.

Football throwing

The biomechanics of football passing and baseball pitcher were compared. In general, football passing looked similar to baseball pitching, but without a high leg lift in the windup. Click here for more.

Flat-ground throwing

While pitchers throw from a mound, all other players throw from flat ground. To identify differences between these throws, 27 college pitchers were tested throwing from flat ground (60, 120, 180 ft) and pitching from a mound (60.5 ft). The crow-hop technique (similar to an outfielder's throwing motion) was used for all flat ground throws. Click here for more.

Windmill softball pitching

Eight active and former collegiate softball pitchers were studied with ASMI's motion analysis system and force plates. To simplify the interpretation of data, the pitching motion was separated into four phases: windup, stride, delivery and follow-through. Click here for more.

Youth Pitchers

Pitching biomechanics were compared for 23 youth (age range: 10-15 yrs), 33 high school (15-20), 115 college (17-23), and 60 professional (20-29) level athletes. Even when normalized by bodyweight and height, all joint forces and torques increased with competition level. Ball and joint velocities also increased. Click here for more.

Benefits/risks of increasing mound height

In order to reduce offense and speed up the game, Major League Baseball is considering raising the pitching mound from 10 inches to 13 inches. To help make the decision, Major League Baseball commissioned ASMI to compare biomechanics for the two mounds. This study found insignificant differences between the two mounds, implying that raising the mound would not increase the risk of injuries to pitchers. Click here for more.