Validity and Reliability of GPS-Based Running Distance Measurements at Varying Bluetooth Connection Ranges

Accurate and reliable performance monitoring is crucial in elite team sports, where wearable technologies, such as GPS systems, are widely utilized. However, the impact of Bluetooth transmission distance between wearable devices and receiver units on measurement quality has received limited attention. This study aimed to evaluate the reliability and validity of running distance data collected using the Polar Team Pro GPS at three different Bluetooth connection distances—20 m, 50 m, and 100 m—during a standardized 20-meter shuttle run test in elite youth football players (n = 20). Participants were randomly assigned to perform the test at each of the specified distances. Reliability was assessed using intraclass correlation coefficients (ICC), coefficient of variation (CV%), standard error of measurement (SEM), smallest worthwhile change (SWC), and minimal detectable change (MDC). Validity was evaluated through Mean Absolute Percentage Error (MAPE), Mean Absolute Error (MAE), Mean Squared Error (MSE), Root Mean Square Error (RMSE), and Bland–Altman plots. Results showed that data reliability and validity declined substantially as the Bluetooth distance increased, with the highest ICC (0.73) and lowest measurement error occurring at a distance of 20 m. These findings underscore the importance of maintaining close receiver proximity to ensure the accuracy of GPS-derived data in both research and applied athlete monitoring settings.