High-intensity interval training (HIIT) causes rapid changes in endurance capacity, maximal oxygen consumption, muscle glycogen levels, and oxidative enzyme activity. Creatine monohydrate supplements increase the capacity for high-intensity exercise, and promote recovery from repeated bouts of interval training. Kristina Kendall and colleagues from the University of Oklahoma in Norman found that the effects of HIIT and creatine might be more effective than either treatment alone. Creatine plus interval training increased critical power (the theoretical power output that can be maintained indefinitely), but had no effect on peak power output. The results were small, and might not be practically significant. However, the technique might be more effective in highly-trained athletes. (Journal Strength Conditioning Research, 23: 1663-1669, 2009)