**1. Introduction**

Since the monitoring of match performance is now considered a fundamental part of contemporary team sport's players development, professional soccer clubs invest significant amount of money to nurture elite players [1]. Overall, the quantification of both internal and external training and match load are useful in a practical context to aid game understanding and decision making in relation to individual and collective physical training content and prescriptions [1, 2].

Today, training load monitoring is made thanks to Electronic Performance and Tracking Systems (EPTS) [3, 4], which are classified into three types based on different technologies: Global Positioning Systems (GPS) or Global Navigation Satellite Systems (GNSS) [5–7], semi-automatic video camera systems (VID) [8], and Local Positioning Systems (LPS) [9]. The fact that GPS/GNSS and LPS were not allowed during official competition, together with VID are non-invasive technologies, were the main reasons to VID has been the most used EPTS before 2014. However, the acceptance of the use radio-frequency based technologies during competitions, some installation difficulties of VID, and the possibility to add additional microelectromechanical sensors (MEMS) makes that radio-frequency technologies have become most common in team sport settings [4]. However, since some scientific validity and reliability studies have compared LPS and GPS/GNSS based EPTS [10–12], and they have shown high precision measures using LPS, the use of LPS seems to grow in the future [4, 13, 14].

Indoor positioning wireless technologies are classified into infrared, radiofrequency (Radio frequency identification (RFID), Wi-Fi, Bluetooth and ultrawide band [UWB]), and ultrasound systems [13]. Among different types of wireless indoor positioning systems, UWB is a promising technology for indoor positioning and tracking [13] and also for outdoor venues where there is no possibility of the surrounding infrastructure interfering in the results [3, 13, 14]. Therefore, the aim of this review was to make an update about UWB technology in sport.
