Prolonged sedentary life is associated with several health risks. Office work is characterized by prolonged sedentary time and contributes significantly to the total sedentary exposure for office employees. This work aims to investigate the combination of casual exergames with gamification, two concepts that can impact behavior change, to decrease the prolonged sitting time for office workers, by interrupting long periods of sitting. A gamified web-based break application for micro-training using casual exergames and movement exercises was designed. A user study with office workers was conducted where workers had access to the application for 45 weeks, during which reward-based gamification was introduced in the application during an 11-week period and usage was compared before, during, and after the introduction of the reward-based game elements. The results showed that participants reported a positive experience of the application and that the breaks during the reward-based gamification period was higher compared to the period before and after the inclusion of the reward-based gamification.