## 1 Introduction  
Load carriage is an essential part of training and on-duty protocol tasks for special populations, including the military [1, 2] and police [3]. Although important, it has been observed that such a load may impact the musculoskeletal system, causing an increased risk of lower limb injury [4] and decreased physical performance [5, 6] Moreover, recent studies have observed a negative trend in load weight, often surpassing the recommended level of 45% body mass [7, 8]  
When carrying heavy loads, gait and posture characteristics often tend to change and adapt [9]. From a biomechanical point of view, heavy equipment during walking may impact balance, movement and overall postural stability, leading to greater torques in hip and trunk areas and alternatively causing alternations in body control [10]. The majority of previous evidence has tried to examine the effects of load carriage on foot parameters during gait; however, little evidence has been provided regarding carrying heavy loads and foot stability during a quiet stance [1, 11, 12, 13]. By carrying a load, a physiological component of increased energy cost and fatigue has often been observed, increasing the risk of injuries and strains [14, 15]. For quiet standing, deviations in the center of pressure may be able to predict future risks of injury and postural instability [16], especially in the lower extremities [17]. Both cross-sectional [18] and longitudinal [8,19] studies have shown that different load distributions may have even larger negative effects and can increase the level of asymmetry. Studies conducted during quiet standing have concluded that heavier loads increase the center of pressure velocity and contact area between the foot and the ground, directly affecting ground reaction forces beneath different foot regions [1,20].  
The population of police officers needs to be at a high level of preparation [21]. Their primary role includes serving and protecting civilians against crime, and they are engaged in high-risk situations [21]. However, by carrying an uneven load for a long period of time, one could expect significant biomechanical gait changes, especially in a standing position. A unilateral load may affect postural sway, which occurs by shifting the body mass center away from the actual center and leaning forward, producing greater forces beneath the different foot regions [1]. Police recruits encounter carrying a specific external load for the first time, which may have negative effects on their body posture and related biomechanical parameters. Such loads may be responsible for pain and discomfort and a few compensatory mechanisms, especially in the contralateral directions [20]. Since relatively little is known on this topic, it is necessary to examine spatiotemporal foot changes and relative ground reaction forces during quiet standing following a standardized load carriage. By examining such changes, policymakers would be able to act towards re-positioning and re-designing police equipment. The intention behind newly developed equipment would be to increase the possibility of being more efficient in the field during high-risk situations.  
Therefore, the main purpose of the study was to examine differences in foot characteristics while standing still under two conditions: (i) 'no load' and (ii) 'a 3.5 kg load'. We hypothesized that heavier loads would exhibit greater biomechanical foot changes and impaired balance compared to the 'no load' condition.