A biomechanical characterization of the gymnastics round-off back handspring first contact and implications for upper extremity orthopedic injury
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INTRODUCTION: Women’s gymnastics has the highest injury incidence rates for NCAA female college athletes. Gymnastics maneuvers may require support and transfer of the entire body weight from the feet to the hands. Such motions cause excessive loading and stress across joint surfaces which on occasion can exceed the mechanical strength of upper limb joints and supportive musculoskeletal structures, resulting in injuries ranging from acute fractures to chronic overuse injuries like osteochondritis dissecans. Recent technological advances have only now made it possible to analyze the complex and simultaneous motions in multiple planes required for evaluation of even the most basic gymnastic maneuvers like the round-off back handspring (ROBHS). OBJECTIVES: There is a paucity of data characterizing upper extremity injury causation and biomechanical risk factors in the small number of gymnastics studies conducted. The first hand contact for any gymnastics skill has never been quantitatively assessed. Therefore, the primary objective of this study is to perform a detailed 3D biomechanical characterization of the round-off back handspring (ROBHS) first hand contact and evaluate any potential correlations to upper extremity injury determinants. METHODS: A 3D motion capture camera and force plate system captured the relative positon of reflective markers affixed to 62 anatomical positions on subjects during performance of an ROBHS. A virtual model of each subject was constructed using Nexus C-motion software. Programming with Visual3D and MATLAB software was used to calculate desired force, kinematic and kinetic variables such as joint torques and angles. Past medical history questionnaires were administered, and clinical range of motion and strength measures were assessed. RESULTS: Compared with other factors analyzed, hand contact order appeared to have the highest degree of influence on upper extremity biomechanics at both the time of initial contact and throughout the entire movement sequence. The second contact limb was correlated with a larger average ground contact force, whereas while the first contact limb was related to a shorter time to peak force development and larger magnitude rotational kinematic variables, especially at the elbow—the primary site of upper extremity injury. For the first hand contact, torque development at the elbow and shoulder appeared to be related, and wrist and shoulder variables were presumably related to ground reaction force (GRF) development. The proposed literature elbow injury mechanism may need some adjustment to reflect the impact of elbow flexion angle on GRF and elbow valgus torque, key variables tied to chronic elbow joint capsule overload injuries. CONCLUSIONS: The novel information provided by this study can be used to guide future recommendations for the prevention of upper extremity injury in gymnastics training and competition. Improved understanding of associated force, kinetic, and kinematic biomechanical variables like joint torque could have implications for movement specific body positioning with the potential for extrapolation to gymnastics moves with similar loading patterns. Possible protective technique interventions based on study findings include increasing second hand elbow flexion during the round-off phase of motion or minimizing the time between hand contacts.