This study proposes a structural usability model to identify the relationship between the user interface design and the usability of an exergame system that includes a software system and a separate hardware device. The model consisted of two dimensions: the interface design, which was evaluated using Nielsen's heuristic evaluation method, and the usability, as defined by ISO 9241-11. An empirical study used the iFit exergame system to test the physical fitness of 101 seniors in order to evaluate the model's validity. The results showed a strong correlation between the interface design and the usability of the exergame system. An improved interface enabled users to interact with the system better, and the usability of the whole system was enhanced, including the device and the system itself. The results show that the proposed usability model can be used to evaluate other exergame systems.
Keywords: elderly user; exergame system; interface design; structural equation model; usability.