The study involved the development of a web-based system integrated with a prototype credential decoder using Radio Frequency Identification (RFID) to manage access to the strength training club of an educational institution. The problem addressed was the need for efficient and secure access control, ensuring data privacy and protection. The objective was to create an integrated solution that automated attendance registration and improved the user experience. The methodology included applied research with a qualitative approach, using observation and interview techniques. The development was divided into two phases: the first, based on the Extreme Programming (XP) methodology, focused on the web system with user roles and specific modules, employing a client-server architecture, the Model-View-Controller (MVC) pattern, and technologies such as PHP and the CodeIgniter 4 framework; the second phase used prototyping methodology for the construction of the credential decoder, integrating Arduino Mega and RFID sensors. The results demonstrated effective integration between both components, enabling automated access management with differentiated roles (athlete, administrator, and manager) and real-time attendance registration. Average attendance registration time was reduced from 45 s to 2.3 s with the RFID system, measured in 200 tests. The conclusions highlighted the success in automating access control, security, and ease of use, recommending future improvements in sensors and the expansion of functionalities to adapt to technological changes.