Assessing Shoulder Joint Kinematics During the Bench Press Exercise in Competitive Powerlifters With Markerless...

Motlagh, JG and Lipps, DB. Assessing shoulder joint kinematics during the bench press exercise in competitive powerlifters with markerless motion capture. J Strength Cond Res XX(X): 000-000, 2026-The barbell bench press is fundamental in strength training and powerlifting, yet shoulder injury risk related to this exercise, especially among female athletes, is understudied. Markerless motion capture provides a scalable approach for examining three-dimensional joint kinematics during athletic maneuvers. This study characterized changes in glenohumeral range of motion throughout a standardized, fatiguing bench press protocol and assessed differences by biological sex. Nineteen competitive powerlifters (10 male and 9 female subjects) completed 3 sets of 8 repetitions of barbell bench press at 73.9% of self-reported 1-repetition maximum, following a standardized warm-up. Shoulder kinematics were recorded with markerless motion capture and analyzed with Theia3D. Primary outcomes included the intra- and interset 3D range of motion of the glenohumeral joint. Repeated-measures ANOVA examined the effects of repetition, set, arm dominance, and sex. Within each set, significant intraset increases in range of motion were observed between the first and second-to-last repetition across all joint axes: plane of elevation (p = 0.002), elevation (p < 0.001), and rotation (p < 0.001). No significant interset changes were found. Female lifters demonstrated significantly greater increases in glenohumeral range of motion compared with male powerlifters in the plane of elevation (p = 0.011) and elevation (p = 0.036) axes but not in rotation. This study found notable intraset increases in glenohumeral range of motion during repeated bench press, with these increases most pronounced in female lifters. The findings underscore the importance of targeted injury prevention strategies and support the value of markerless motion capture for sport-specific biomechanical assessment.