Introduction Martial arts, like Taekwondo, stress the glenohumeral (GH) joint during high-force movements like punches [1-4]. The middle direct punch (momtong jireugi) generates substantial GH joint reaction forces (GHRF), yet quantitative GHRF analyses, especially in elite athletes, are limited. Musculoskeletal modeling, like OpenSim, can estimate these forces [5-10]. While validated in throwing, its application to martial arts is lacking. Existing punch research neglects internal joint forces across punch phases. This study uses musculoskeletal modeling to quantify three-dimensional GHRF during middle direct punches in elite Taekwondo athletes. Research Question How do glenohumeral joint reaction forces during a middle direct punch vary in various anatomical directions? Methods Twenty elite Taekwondo athletes (10 males, 10 females; age: 25.5 ± 4.5 years; mass: 65.35 ± 8.5 kg; height: 174 ± 4.50 cm; training experience: 13 ± 4 years). 12 Vicon motion captures (100 Hz) tracked 14 markers on bony landmarks during static (anatomical pose) and dynamic Trials (5 maximal punches at sternum height, dominant hand) separated by 5-minute rest. The musculoskeletal model of the shoulder was selected as a base model and scaled by scaling tools of OpenSim software via marker data of static posture for each subject. Inverse kinematics and Static Optimization were used to calculate the joint kinematics and muscle forces, respectively. Joint Reaction Analysis was used to calculate three-dimensional GHRF via kinematics and muscle forces data. Results Figure 1 shows mean (line) and SD (shaded) glenohumeral joint reaction forces (GHRF, N/BW) during a Taekwondo middle punch in AP, SI, and ML directions. Distinct GHRF patterns were observed. Peak anterior force (1.36 ± 0.63 N/BW) occurred at 40 ± 5% (contact). Superior forces dominated pre- and post-contact; minimum superior force was at contact. Peak medial force (1.37 ± 0.32 N/BW) occurred late (88 ± 5%), with lateral forces during retraction. Acceleration (0-40%) showed rapid AP/SI force increases (shoulder flexion). Impact (40-60%) had force peaks (joint compression). Follow-through (60-100%) showed declining forces with posterior deltoid activation. Discussion This study uses OpenSim to analyze 3D glenohumeral joint reaction forces (GHRF) during the Taekwondo middle punch. Results show anterior force dominates at contact, exceeding superior and medial forces. These forces, though 20-30% lower than boxing, confirm anterior shoulder vulnerability. Superior forces indicate joint compression, potentially causing labral injuries. Strengthening the posterior cuff and emphasizing trunk rotation may reduce injury risk. This quantifies GH joint loads, informing targeted training and technique modifications. Future research should examine different punches and fatigue.
© Copyright 2025 Gait and Posture. Elsevier. Alle Rechte vorbehalten.