Assessment of Shoulder Biomechanics during Pull-up Techniques

Abstract: CrossFit® has gained popularity as a functional training method that caters to individuals with varying levels of fitness, including those with little to no athletic background. Regardless, shoulders represent the highest injury rate in this sport, most frequently associated with pull-up variations. Therefore, ensuring safety during these movements is crucial. This thesis utilized optical motion tracking, force sensors, and Electromyography to measure nine experienced non-professional CrossFit® athletes performing three pull-up techniques used in CrossFit® (strict, kipping, and butterfly). Data were used in musculoskeletal modeling to assess and compare kinematics, kinetics, and muscle activations. Findings were then associated with common injury factors observed in overhead athletes. The novel dataset generated in this study demonstrated excellent repeatability and revealed significant differences between the techniques for most kinematic and kinetic variables, while variations in muscle activations were less systematic. Results indicated shoulder joint angles linked to impingement risk, with the kipping pull-up displaying more prominent risk factors. The butterfly pull-up exhibited extreme angular velocities and negative joint powers; however, direct associations with injuries could not be established. Notably, shoulder joint moments were high in all three techniques, suggesting significant muscle stresses. These results underscore the importance of individualized training load management to mitigate the risk of overuse injuries. Furthermore, the evidence presented in this study supports the importance of maintaining proper mechanics and developing strength before attempting kipping and butterfly pull-ups. The high joint moments, combined with severe positions and velocities observed during these techniques, highlight the necessity of prioritizing foundational strength and technique to minimize injury risks.