## 1 Introduction  
Carrying heavy loads represents a crucial task in a special population of military and police personnel [1; 2; 3]. Such loads are often required for protection and providing lifesaving equipment needed for specific operations [1; 2]. Although necessary for performing fundamental tasks, evidence suggests that heavy loads often exceed a threshold of 45% of body mass recommended for long distances [4; 5]. For the past years, the magnitude of the absolute load being carried has dramatically increased, showing an alarm negative trend that affects energy expenditure costs during walking [6] and increases the risk of musculoskeletal injuries [7].  
Carrying an excessive load can also impact the biomechanics of human locomotion [6; 8]. During carriage, the extra load requires gait compensations to minimize decrements in maximal performance [8; 9; 10]. Most parameters associated with gait include spatiotemporal data, kinematics, ground reaction forces, and electromyography [11]. Amongthem, previous studies have shown that load carriage significantly impacts gait kinematics, kinetics, and electromyography [11]. In terms of kinematics, evidence suggests that during the loaded conditions, increases in hip [12; 13], knee [12; 14], neck [15], and trunk [12; 15] flexion, ankle dorsiflexion [12] and hip [15; 16], knee [15; 16] and ankle [12; 14; 16] range of motion are observed, followed by decreases in trunk sway [17] and trunk range of motion [18]. Compared to unloaded conditions, average and peak plantar pressures [19; 20] increase with loaded conditions, along with increased muscle activity [14; 17; 21; 22]. On the other hand, past findings have shown inconclusive results, where the added external mass can impact spatiotemporal gait parameters [6; 8] or have no proven effects [11]. For example, previous systematic reviews have shown that external weight may lead to a reduced stride length and an increased cadence during walking [6; 8]. However, the most recent systematic review has demonstrated that load carriage had no significant effect on any of the spatiotemporal gait parameters, including walking speed, step or stride length, cadence, step width, and double or single support time [11].  
Along with different findings, most of the studies have been conducted among military personnel [11], while the population of different types of police has been less studied. Compared to active-duty soldiers, intervention police officers are often engaged in more vigorous-intensity tasks throughout the day, possibly being at more risk for injuries and sprains [23]. All these activities are accompanied by even heavier load carriage exceeding >50% of body mass on a daily basis, compared to military personnel [23; 24]. This would imply that heavier load carriage and the nature of everyday tasks may have different effects on spatiotemporal gait parameters in intervention police officers. Due to these changes, previous findings on military personnel may not be applicable to this population [11].  
Therefore, the main purpose of the study was to investigate whether different loading conditions might impact spatiotemporal gait parameters in a representative sample of intervention police officers. Based on one previous study conducted on special police officers [25], which showed non-significant changes in spatiotemporal data under different loading conditions, we hypothesized that heavier loads would lead to statistically unchanged values in both spatial and temporal gait parameters.