# Review on Wearable Technology in Sports: Concepts, Challenges and Opportunities
## 7 Applications of Wearables in Sports
### Team Sports  
Team sports are sports in which two or more opposing teams face each other. WT plays an important role in team sports to monitor the performance of players and teams, improve tactics and prevent injuries. In team sports, the functioning or harmony of the team as a group is monitored as well as the individual situations of the athletes, therefore positioning sensors are frequently used. Some sample studies for team sports are summarized in Table 2.  
The Local Positioning System (LPS) (Kinexon) was used by the European Handball Federation in the Champions League Final Four (VELUX EHF FINAL4) to identify the field-based demands of a total of 40 handball players and their specific demands based on player position during both offensive and defensive plays [109]. WT was placed between the player's shoulder blades using a pouch sewn onto the player's jersey. As a result, it was reported that there were differences in player positions during both offensive and defensive plays, and considering these differences in designing training programs would positively impact individual and team performance. Kinexon was used to simplify the external load measurements obtained from IMU data through Principal Component Analysis (PCA) and to determine if the PCA results were sensitive to load demands based on different player positions [110]. Ten male college basketball players were included in the study throughout a competition season. Prior to the matches, IMUs were placed in a sleeve sewn onto the shorts and positioned on the right posterior superior iliac spine for each player. The analyzed data set only included the external load data obtained during active playing minutes, including total mechanical loads (totMECH; a.u. ), jump loads (totJUMP; J), accelerations (totACC; count), decelerations (totDEC; count), average speed (avgSPD; mph), and maximum speed (maxSPD; mph). The output values of the study indicated that, as suggested by the authors, maxSPD, totDEC, totJUMP, and totMECH were the most sensitive to positional differences and best characterized the demands of the matches. [PERSON] et al. used 2 IMU sensors attached to the gastrocnemius muscles of the athletes and GNSS (ZEPP Play Soccer) to analyze both internal and external training loads and tactical actions during small-sided games (20 \(\times\) 15 m, 25 \(\times\) 20 m, and 30 \(\times\) 25 m) [97]. Zepp's computer software V4.8.0 was used to calculate external training loads (total distance covered (m), walking (\(\leq\)9 km/h), jogging (9-18 km/h), high-speed running (>18 km/h), sprint count, maximum sprint speed (km/h)) and tactical assessments (number of passes with dominant and non-dominant foot (ball touches) and maximum pass speed (km/h)). The output values of the study demonstrated that in U23 soccer players, larger playing areas with more players involved resulted in higher intensity runs, while in the same area with fewer players, more tactical individual actions were performed. Additionally, it was noted that smaller playing areas reduced the game speed in low-player systems. [PERSON] et al. demonstrated the differences between training and match physical demands in beach volleyball players using an elastic harness placed between the shoulder blades and a GNSS device (Vector-Catapult) worn under their playing attire [111]. During official matches, the players' playing time, PlayerLoadTM, total jumps, total distance covered, and the number of direction changes performed in the right and left directions were evaluated during the warm-up section, training, and technical-tactical sessions. Regardless of player position (defense or block), the players showed higher activity values during official matches compared to warm-up and training sessions. Tactical-technical training sessions exhibited higher values for all variables compared to official matches, except for the total jumps performed by the blocker.