Pervasive electronic games use innovative mechanics to create immersion and promote user engagement, thus being a potentially powerful tool to promote active lifestyles among the elderly. We describe a pervasive game developed to test how design elements can affect older adults' levels of physical activity, using social interaction as case study. Two variations of the game were developed – including or not social interaction – and a feasibility study was performed to evaluate the proposed design and its potential to affect the levels of physical activity of players.