The goal of one of my first exergame studies was to quantify the amount of moderate to vigorous physical activity (MVPA) in youngsters who play DDR. While playing DDR for 45 minutes, the youngsters were in the MVPA range for over 33 minutes (~73%) and the average heart rate was 142 beats per minute.
Yang, S.P., Graham, G. (2005). Project GAME (Gaming Activities for More Exercise). Research Quarterly for Exercise and Sport, 76(1 Suppl), A-96.
Note: I am now an Assistant Professor at SUNY Cortland. Click here for my profile.