In this paper we discuss the importance of feedback in therapeutic exergaming. It is widely believed that exergaming benefits the patient in terms of encouraging adherence and boosting the patient’s confidence of correct execution and feedback is essential in achieving these. However, feedback and in particular visual feedback, may also have potential negative effects on the quality of the exercise. We describe in this paper a prototype single-sensor therapeutic exergame that we have developed and provide some preliminary user feedback regarding enjoyment and perceived competence when using the exergame compared to exercising without the exergame. Our results indicate that all participants found exercising with the game more enjoyable. However, additional work is needed to increase participants’ confidence in their correct execution of the exercise.