BACKGROUND: Injuries to the ulnar collateral ligament are increasing among baseball players at all levels. Little is known about the loads experienced by the medial elbow during baseball hitting. The purpose of this study was to describe the stress experienced by the medial elbow of the trail arm during baseball hitting. We hypothesized that the biomechanical comparison of hitting will demonstrate greater elbow varus torque of the trail arm for wood vs. aluminum bat and inside vs. other swing locations. METHODS: Thirteen healthy National Collegiate Athletics Association Division 1 baseball players were analyzed hitting plastic balls from a tee at 4 different swing locations (dry [no contact], inside, middle, and outside) using 2 different bats (wood and aluminum). Biomechanical models were generated for each subject from video motion capture data and the peak elbow varus torque and bat swing velocity were calculated for each trial. RESULTS: The average peak elbow varus torque during hitting was 22.15 ± 4.79 N-m. There were no interactive effects between bat type and swing location type (P = .99) and no effect of bat type on peak elbow varus torque (P = .85) or swing velocity (P = .81). Swings to the outside location generated greater elbow varus torque than dry swings or swings to the inside location (P <
.01). Greater swing velocities were observed for swings to the outside location compared to other locations (P <
.01). CONCLUSION: The peak elbow varus torque on the trail arm during a baseball swing is lower than both the throwing and ultimate load to failure of the ulnar collateral ligament. Additionally, both elbow varus torque and swing velocity were greatest when swinging to the outside location.