Pitching Changes Your Anatomy – For a While

A new study looks at the effects of baseball pitching—a notably strenuous activity—on muscle architecture, strength, and range of motion. Furthermore, the study asks the important question, how long does it take to recover “normal” musculoskeletal architecture, strength, and range of motion post-injury.

The study, “Acute Effect of Pitching on Range of Motion, Strength, and Muscle Architecture,” was published on March 14, 2022, in The American Journal of Sports Medicine.

“Acute adaptations in clinical measures of range of motion and strength have been found after baseball pitching; however, there is a lack of research concerning the physiological mechanism responsible for these changes. Adaptations in muscle architecture of the infraspinatus and teres minor may serve as the structural changes responsible for these clinical measure changes,” the researchers wrote.

For the study, the researchers took a long-term look at the acute changes in range of motion, strength, and muscle architecture of the infraspinatus and teres minor muscles in baseball pitchers after a simulated baseball game. They also analyzed the relationship between muscle architecture and changes in clinical measures of range of motion and strength.

The study participants were 10 non-varsity collegiate club baseball pitchers (mean ±SD; age, 20.1 ± 1.10 years). Each of them was examined pre-pitching, immediately after pitching, and for 5 days after.

The researchers used a digital inclinometer and handheld dynamometer to assess range of motion and strength, respectively. They also used diagnostic ultrasound to assess pennation angle and muscle thickness of the infraspinatus and teres minor at rest and at maximal contraction.

Overall, internal rotation range of motion significantly decreased immediately and did not return to baseline until 4 days after pitching (p ≤ .05). There was also an immediate decrease in external rotation strength which returned on their third day after pitching (p ≤.05).

In addition, the resting pennation angle of the superficial and deep portions of the infraspinatus increased immediately after pitching. The superficial portion returned to baseline on day 4 and the deep portion on day 5 (p ≤.05).

They also found that the pennation angle changes of the infraspinatus and thickness of the teres minor were predictive of the loss of internal rotation range of motion after pitching (R² = 0.419; p ≤ .05).

“This study found diminished internal rotation range of motion and external rotation strength after pitching, with alterations in muscle architecture of the infraspinatus. The pennation angle increase in the infraspinatus at rest is indicative of increased tension in the muscle, which was found to be the underlying mechanism for the clinical loss of internal rotation range of motion. This was demonstrated by the inverse relationship between internal rotation range of motion and the pennation angle of the superficial and deep fibers of the infraspinatus,” the researchers wrote.

Basically, and this is a universal truism, it takes time for the pitcher’s body to recover. “Clinicians should consider recovery time after pitching to prevent chronic losses of shoulder range of motion and strength. Identification of the underlying mechanisms of range of motion loss after pitching allows clinicians to optimize recovery strategies in baseball pitchers.”

Study authors included Nicholas S. Mirabito, MS, LAT, ATC, and Matthew Topley, MS, of Temple University in Philadelphia, Pennsylvania, and Stephen J. Thomas, PhD, ATC., of Thomas Jefferson University also in Philadelphia, Pennsylvania.