Changes in Throwing Arm Mechanics at Increased Throwing Distances During Structured Long-Toss

Elbow injuries among adolescent baseball players have been outpacing those of college and professional players. In attempts to prevent injuries and maximize return-to-play potential following injury, attention has been focused on "return to throw" programs, which include long-toss throws. Because the few studies that were conducted on long-toss throwing focused primarily on college-aged athletes, it is not known what type of load is incurred at the elbow during interval throwing progression among high school baseball players.

To quantify the change in arm slot, arm speed, shoulder external rotation, and elbow varus torque across increasing throwing distances within a given athlete.

Descriptive laboratory study.

Ninety-five high school baseball players performed a long-toss protocol while wearing an inertial sensor and sleeve. Each participant was tested for 5 throws at distances of 9 m, 18 m, 27 m, 37 m, and 46 m. Linear mixed-effects models and likelihood ratio tests were used to estimate the within-participant relationship between throw distance and arm slot, arm speed, shoulder external rotation, and elbow varus torque.

Arm slot ( P < .01), arm speed ( P < .01), shoulder external rotation ( P < .01), and elbow varus torque ( P < .01) were significantly associated with long-toss throw distance. As the throw distance increased, there was an increase in arm speed and shoulder external rotation and a decrease in arm slot for each distance. However, elbow varus torque increased with each distance up to 37 m and then remained the same at 46 m.

The use of longer distances for conditioning and rehabilitation may be beneficial in increasing shoulder range of motion and arm speed; however, precaution needs to be taken, as throwing longer distances are accompanied by an increase in arm rotation, arm speed, and elbow torque, with a decrease in arm slot.

Return-to-throw programs have been utilized by sports medicine clinicians and coaches to help guide a player during rehabilitation. These programs involve throwing at increased efforts through increased distances with no immediate feedback on elbow stress. This investigation describes arm biomechanical changes during submaximum interval throwing and demonstrates a tool that can be utilized to measure arm stress in real time for clinicians and athletes progressing through an interval throwing program.