## 1 Introduction  
Changes of direction (CoDs) are one of the most common movements during soccer [1]. As studied by [PERSON] et al. (2022) [2], approximately 20% of goals are preceded by a CoD in the English Premier League (EPL). In addition, [3] analyzed sprints in competition in ten EPL matches and showed that a third of sprints started from a non-linear action. Contextually, CoDs can serve as a transitional move between the offensive phase to create space and the defensive phase to pressure opponents or pull back [1, 4]. From a biomechanical point of view, incorrect mechanics of a CoD could lead to injury to the knee's anterior cruciate ligament [5, 6]. Pre-CoD angulation and speed are two variables that greatly influence the technical execution of movement, proportionally increasing muscle activation and load on the knee as the CoD is performed faster and at a more acute angulation [7]. If such variables can be quantified through portable technology and integrated into the load management model, performance improvement strategies as well as effort recovery strategies could be optimized. Although different methodologies have been used to record changes of direction during competition, little information has been published to date [1; 8; 9; 10]. For this reason, it is not easy to reach a consensus on how many CoDs a soccer player performs in a match, as well as the angulation that is performed. When the observational methodology was used, without considering the intensity of the actions, the number of CoDs recorded was very high, reaching 600 CoDs between 0 and 90\({}^{\circ}\) and 100 CoDs between 90 and 180\({}^{\circ}\)[1]. Using a similar observation classification, but distinguishing the actions into low and high intensity, the number of CoDs decreased, registering over 231 CoDs at 0-90\({}^{\circ}\) and 69 above 90\({}^{\circ}\)[10]. When a pre-CoD minimum speed of 4 m/s was established, the number dropped to 80 CoDs between 45 and 135\({}^{\circ}\) and 20 CoDs over 135-180\({}^{\circ}\). On the other hand, with more modern technologies, new CoD registration methodologies have emerged during competition. The use of infrared laser (LiDAR), for the detection of CoDs in EPL players has shown a significant decrease in the number of CoDs in relation to observational methodology (\(\sim\)300-700 CoDs vs. 20-40 CoDs), with more CoDs recorded in the angulation of 120-180\({}^{\circ}\)[8]. However, both methodologies make it extremely difficult to approach the study of CoDs in a precise, immediate, and sustainable way, given the logistics and the number of people necessary to record the data and subsequently treat it. Over the years, micro-electromechanical systems (MEMSs) that include inertial sensors such as accelerometers, gyroscopes, and magnetometers have served as an alternative for evaluating movement, enabling a quantitative analysis of the variables, as well as reinforcement between research and training [11; 12; 13]. Thus, there are several investigations that have shown acceptable precision identifying the turning angle during a CoD [14]. In this sense, the integration of three inertial sensors in what is known as an \"Inertial and Magnetic Measurement Unit (IMMU)\" has made it possible to obtain the spatiotemporal orientation of a body with greater precision, compared to when only one or two inertial sensors in isolation are used [15]. This has been possible due to the constant development of different algorithms and filtering steps, which have made it easier to merge the information obtained from the different sensors [15; 16; 17; 18]. In a recent investigation, thanks to the information obtained from an IMMU and its processing by means of a specific algorithm, it was possible to be highly precise in detecting CoDs at different angulations, compared to high-resolution video recording [19]. To the authors' knowledge, only five studies have quantified CoDs during competition using inertial sensors, namely in players of basketball [20; 21], handball [22; 23], and soccer [24].