Exergames, which combine physical activity and video games, present an innovative approach to promoting health and well-being. This paper aims to identify key game design elements contributing to the successful integration of physical activity and a fun gaming experience. The objective is to propose more effective and engaging game elements applicable to therapeutic activities. The paper discusses the development and results of an experiment exploring how design elements can alter the player’s perception of fun. In a previously conducted systematic literature mapping (SLM), a diverse range of elements that impact the perception of fun was revealed. These findings served as the foundation for modifying an exergame, SIRTET, by incorporating selected elements. Thirthy one responses were received from experts, with the majority holding a Ph.D. These responses indicated a consensus on the importance of the Feedback element, which was identified as the primary contributor to fun. However, there was uncertainty regarding the contribution of the Control Device to fun, which was recognized as a minor contributor.