Watch Les Mills Combat - Power HIIT 1 (2012) : Full Movie Online Free Power HIIT 1 workout includes High-intensity interval training (HIIT). This is a form of fitness training that integrates short intense periods anaerobic exercise to get the heart rate really pumping high and then is followed by a less-intense recovery period. This form of cardio vascular exercise improves your athletic conditioning, endurance and also improves fat burning.