Maximum Strain on Ulnar Nerve During Throwing

Cubital tunnel syndrome from pressure on the ulnar nerve at the elbow is a common problem in baseball. Professionals on down to Little League pitchers, catchers, and infielders are affected most often. This study shows that repeated strain on the ulnar nerve when throwing the ball puts the nerve at the limits of what it can handle.

Researchers from Sapporo Medical University in Japan conducted a study of the movement and strain on the ulnar nerve during the throwing motion. They used cadavers to measure how much the nerve stretches with each phase of throwing. They also used a gauge to record strain on the nerve. All measurements were taken at the cubital tunnel where the ulnar nerve passes through the elbow.

The results showed the ulnar nerve was stretched to capacity when the elbow was flexed 45 degrees or more. Most of the nerve movement took place during the wind-up phase of the pitch or throw. Most of the strain on the nerve occurred up until the early acceleration phase of the throw.

The scientists also found that the maximum strain on the ulnar nerve at the elbow was about 13 per cent. This is close to the 15 per cent elastic or circulatory limits. At 15 per cent damage to the structure of the nerve can occur.

The authors point out that their results may not mimic live, healthy, young baseball players. The measurements were all taken on older cadavers. The cadavers may not have the same mobility as young athletes. Future studies are needed to look at this more closely.

References: Mitshuhiro Aoki, MD, PhD, et al. Strain on the Ulnar Nerve at the Elbow and Wrist During Throwing Motion. In The Journal of Bone and Joint Surgery. November 2005. Vol. 87-A. No. 11. Pp. 2508-2514.