This study focuses on the design, construction, and validation of a digital-adjustable, weight-free home fitness device for muscle training. The research adopted a mixed-methods approach, providing a comprehensive evaluation of the device's performance. Initially, existing equipment and resistance training methods were analyzed, gathering essential information for the preliminary design. Three-dimensional models and prototypes were developed using software such as Rhino Cross 6 and AutoCAD 2018. For validation, the device’s resistance was tested with a digital dynamometer in eight different settings, yielding a high validity with a correlation coefficient of 0.9. The reliability of the device was also assessed across three exercises (seated leg extension, seated chest press, and seated biceps curl) with 10 kg weights, repeated five times, resulting in a reliability coefficient of 0.8. These results indicate the device's high accuracy and consistent resistance. With precise digital adjustments and the capability for varied strength exercises, this device enables users to conduct effective, high-quality workouts at home, contributing to muscle strengthening and improved fitness.
