Kinematic Sequence More Important Than Pitch Delivery Approach for Preventing Baseball Injuries

There are two primary approaches to a baseball pitch: the traditional windup and the stretch. The conventional wisdom in the baseball community is that pitch delivery from the stretch produces more stress at the elbow and shoulder joints than the windup does.

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Based on biomechanical studies, researchers at Massachusetts General Hospital believe trainers and coaches should concentrate pitch instruction on something different: the kinematic sequence (KS). In this study sample, there were no significant differences in shoulder and elbow torques between the stretch and windup delivery styles. However, there were significant differences across the three most used KS. In the Journal of Sports Science and Medicine, senior sports medicine scientist Donna Moxley Scarborough, PT, MS, PhD, orthopaedic surgeons Luke S. Oh, MD, Eric M. Berkson, MD, and fellows in the Sports Medicine Center, explain their recommendation.

Study Methods

The researchers analyzed data they obtained previously from competitive baseball players. They identified 10 pitchers (six collegiate, four high school; average age 17.6 years) who had thrown from both the windup and stretch delivery. All routinely had in-game roles pitching at least three innings per outing, and they achieved similar fastball velocities using the two pitch approaches.

Previous research and throwing simulation models have theorized that the most efficient KS for a baseball pitcher is a movement pattern transferring energy from the legs to the arms in a sequential fashion. This study evaluated the pattern of transfer of energy in pitches thrown from the windup and the stretch positions. Pitchers threw in a sports biomechanics laboratory, where the researchers used high-speed 3D motion capture analysis to calculate peak angular velocities of each body segment involved in pitching. They then identified KS's for each of 88 pitches.

Kinematic Sequences

Pitchers utilized multiple patterns of energy transfer, or KS, but none of the pitches fit the ideal proximal-to-distal KS. Of the 11 KS's identified, three were most common across all players and both pitch delivery types:

• Modified proximal to distal—Forearm and hand peak simultaneously (n=14 pitches)
• Altered distal arm—Forearm velocity peaks before the hand (n=28)
• Altered proximal arm—Peak arm velocity switches order with that of the hand (n=15)

Other Key Findings

• Comparison of delivery approaches—No significant differences in ball velocity, peak shoulder external rotation torque, shoulder extension torque, elbow valgus torque or time from stride to ball release
• Comparison of the three KS's—Shoulder external rotation torque, shoulder extension torque and elbow valgus torque did vary significantly

Avoiding Injury and Supervising Recovery

Many coaches have young pitchers throw from the stretch, not the windup, when teaching basic throwing mechanics. Using the stretch delivery for instruction theoretically allows for focus on the time from stride to ball release. Because pitchers are taught that throwing from the stretch is a faster pitch, it is speculated that the changes in pitch biomechanics made to throw faster may create greater torque at the shoulder and elbow.

However, this study showed that the KS used influenced torque production at the shoulder and elbow more than the pitch delivery approach does. Instructing baseball pitchers in the ideal KS could protect them from injury to the shoulder and elbow regardless of whether they throw from the traditional windup or the stretch delivery.

The study results also inform rehabilitation strategies for baseball players at all levels of competition.

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