## 3 Results and Discussion
Earlier research has also illustrated that postural stability and stance characteristics play an important role in determining shooting performance [2]. However, standing position often leads to instability, because of the high position of the body's centre of gravity and relatively small body support area with the ground [18]. To be able to perform a correct shot at maximal level, previous evidence has highlighted the importance of physical effort being associated with body stability [19]. A more stable body and rifle stability have been associated with the static and dynamic balancing of the destabilizing forces of gravity and inertia by stimulating the appropriate muscle groups [20]. In that way, the forces generated by muscles compensate for disturbing the stability. Moreover, it has been well documented that the efficiency in shooting strongly relies on the motor ability to 'freeze' during shooting, creating the smallest possible amplitudes and generating lower ground reaction forces, while maintaining the standing [5,21]. Our findings showed that higher absolute and relative ground reaction forces beneath the hindfoot region of the foot were associated with poorer shooting performance. During shooting, the vertical  
Figure 4: The associations between relative ground reaction forces beneath the forefoot and hindfoot region of both feet with shot score in the study participants. projection of the rifle falls out of this area, causing additional movement corrections of the shooter's body posture. In addition, the posture of top-class shooters is often modified by twisting, including maximal support of the body by bones and ligaments and the minimal activation of postural muscle groups [18]. This was supported by our results, since the position of standing by maintaining a stable posture using the hindfoot region could not efficiently amortize the external forces produced by the shoot. It has been highlighted that postural stability during shooting is inversely associated to the distance between the vertical projection of the position of the centre of gravity of the shooter-rifle system and the point of action of ground reaction force vector [18]. Leg muscle activity [22] and foot pressure distribution [23] change somatosensory information and may provide different standing-position perception in the anteroposterior position. When leaning backwards and producing higher ground reaction forces beneath the hindfoot region, a large increase in muscle activity has been observed at about 25% of the foot length from the standing position [24], and upward patellar movement has been detected more frequently while gradually leaning backwards [25]. Thus, higher ground reaction forces under the heel may significantly impact postural stability and shooting efficiency. Our findings also showed that higher absolute and relative forces beneath the forefoot region were associated with better shooting efficiency, even after adjusting for weight and body-mass index. Previous evidence suggests that a challenge for performing a coordination task, such as shooting, is to determine the distribution of the applied forces [26]. This study has a few limitations. First, by using a cross-sectional design, we cannot determine the causality of the associations. Second, a relatively small sample size (\(N=30\)) may have led to insufficient statistical power. Third, no biological and physiological measurements were collected, including blood samples, heart-rate monitoring, fatigue level and sleep deprivation. Fourth, we did not collect, nor include, another variable, which might moderate the associations between forces and shooting performance, such as officer's experience, type of weapon usually used in combat situations, and mental health.