Effects of a Dynamic Arm Stabilizer on Varus Elbow Torque, Arm Speed, and Velocity in Collegiate Baseball Players: A Pilot Study

Abstract

Purpose: The purpose of this study was to assess the effect a dynamic arm stabilizer had on varus elbow torque, arm speed, and throw velocity during baseball throwing. Methods: 8 collegiate baseball players (age= 20 ± 1 years, height= 183.5 ± 6.5 cm, weight= 85.6 ± 7.7 kg) participated in this study. Participants were randomly assigned to throw their first set of 25 throws at 90 feet wearing a dynamic arm stabilizer or throw their second set of 25 throws at 90 feet not wearing a dynamic arm stabilizer. After completing the first set of throws, the participants threw a second set of 25 throws at 90 feet in the opposite condition. Elbow varus torque and arm speed were measured using a wearable inertial measurement unit, and throwing velocity was measured in miles per hour using a handheld radar gun. Pearson’s correlations were performed to determine relationships between varus torque, arm speed, and velocity during activity with and without the dynamic arm stabilizer. Then, paired samples t-tests were performed to determine differences between varus torque, arm speed, and velocity with and without the dynamic arm stabilizer. Results: Significant correlations were found between varus torque and arm speed, varus torque and velocity, and arm speed and velocity when wearing the dynamic arm stabilizer. Other correlations found were between varus torque and velocity, and arm speed and velocity when not wearing the dynamic arm stabilizer. Significant differences were found between throwing with the dynamic arm stabilizer and not wearing the dynamic arm stabilizer in varus torque (stabilizer = 45.80 ± 8.12 Nm, no stabilizer = 51.85 ± 8.87 Nm, p < .001), arm speed (stabilizer = 857.39 ± 59.64 degrees per second, no stabilizer = 876.58 ± 82.74 degrees per second, p < .001), and throwing velocity (stabilizer = 70.95 ± 5.21 mph, no stabilizer = 71.77 ± 5.68 mph, p < .001). Conclusions: Use of a dynamic arm stabilizer results in a decrease in varus elbow torque when throwing on flat ground at 90 feet. The dynamic arm stabilizer also resulted in a decrease in arm speed and throwing velocity when compared to throwing without a dynamic arm stabilizer. Further research is needed to determine the clinical meaningfulness of these findings in order to determine the best application for a dynamic arm stabilizer in baseball players.