Based on the study of virtual learning systems, motion learning theory, and instructional design theory, a virtual fitness trainer app named TRAINIME has been developed to be used as one of the tools to teach exercise for fitness education programs. This paper describes the design and development as well as the evaluation of the developed app. The methodology can be divided into two parts, first the design and development activity, and then the evaluation activities. The design and development process were guided by the motor learning theory and focused on the application of observation and random practice learning strategies in teaching fitness exercise. The app contains five virtual fitness trainers that show different movements that target different fitness levels. The effectiveness of the app in terms of the students' motivation is measured using the Situational Motivational Scale (SIMS) and tested with a group of 54 students from a local higher institute of learning. Their engagement with the activities is measured with a structured interview. The results showed that the students had the motivation to do fitness activities after being in the practice session with the virtual fitness trainers. The respondents found that the activities were interesting, fun, and made them feel good. They were also motivated to follow the activities because they agreed that they had to do it and the activity was important for them. Most of the respondents agreed that the activities had a good effect on their fitness level and easy to follow for their physical activities. The interview revealed that the movements shown to them by the virtual trainers were very useful in engaging them with fitness activities. There are additional recommendations and added functions that should be included before the app can be fully deployed in a bigger market.