# The Impact of Draw Weight on Archers' Posture and Injury Risk Through Motion Capture Analysis
## 4 Discussion

Table 3: The correlations between trunk flexion/extension and other factors. more of a work cycle can predict chronic or recurrent shoulder issues. Likewise, internal and external shoulder rotations beyond 70\({}^{\circ}\) can strain the rotator cuff and cause joint instability [49]. Some studies [50,51] suggest a connection between hand and shoulder muscle activity, with high static handgrip forces, especially in elevated arm positions, imposing additional load on shoulder muscles. This load is more likely to affect stabilizing muscles like the rotator cuff than larger muscles such as the deltoid and trapezius. As a result, movements that combine abduction and external rotation, especially during the draw phase with a high handgrip force, should be kept within moderate ranges to avoid impingement or overuse injuries. For the analysis of trunk flexion/extension and rotation, positive values indicate flexion and body rotation to the right, while negative values indicate extension and body rotation to the left. Trunk movements also highlight gender-specific adaptations. Females demonstrate approximately 10 degrees more trunk extension and rotation when using heavier bows, particularly the 32-lb bow. This pattern reflects their reliance on trunk adjustments to compensate for left arm drooping and elbow extension, which may result from insufficient muscle strength [52]. Males, on the other hand, exhibit smaller variations in trunk movements, maintaining a more upright posture across all draw weights and distances. During the draw phase, the trunk should maintain a neutral posture with minimal flexion and extension [53]. A slight trunk rotation is recommended to align the hips and shoulders, ensuring an even distribution of load. Lateral flexion should be avoided to reduce the risk of imbalanced stress on the lumbar spine [54]. Interestingly, the left elbow angle reveals contrasting strategies between genders. Males tend to maintain a more neutral posture, while females often rely on the elbow joint's supporting force to assist the left arm in bearing the bow's pulling force [55], which may cause pain because of the locked elbow on draw [56]. For optimal elbow mechanics, the drawing arm should maintain a flexion angle between 90\({}^{\circ}\) and 120\({}^{\circ}\) to avoid hyperflexion, which can strain the biceps and joint capsule [57,58]. The bow arm should maintain a slight flexion of 5\({}^{\circ}\) to 10\({}^{\circ}\) when holding the bowstring to prevent joint locking, as hyperextension increases the risk of ligament strain and joint instability [59]. In this posture, the average angles of several joints involved in drawing the bow remain within the physiological range, including right shoulder flexion and rotation, as well as left shoulder angles. However, the average right shoulder abduction exceeded 90\({}^{\circ}\), and the average right elbow flexion was approximately 155\({}^{\circ}\). Notably, during the draw phase with a 32-lb bow, the left elbow exhibited hyperextension (negative angle), which increases the risk of ligament injury. As for trunk flexion, extension, and rotation, the angles increased while drawing the 32-lb bow. Given that the draw weight of some bows can reach up to 100 lbs, these joint angles may exceed recommended limits, potentially leading to injury. For the analysis of R values, the relationship between compressive force and trunk flexion/extension exhibits an increasing trend as the bow was changed from 20 lbs to 32 lbs. This indicates that as the body leans back, the compressive force on the back decreases. This explains why males experience greater compressive force compared to females. This difference is attributed to their relatively smaller trunk extension. Previous studies [39,41] have highlighted the sensitivity of trunk flexion to compressive force on the back. However, in this study, the trunk is predominantly in an extended state. Consequently, the variations in compressive force are minimal.