Anaerobic exercise is 80-90% of your max HR. Benefits include an improved VO2 maximum (the highest amount of oxygen one can consume during exercise) and thus an improved cardio-respiratory system, and a higher lactate tolerance ability which means your endurance will improve and you'll be able to fight fatigue better. Since the intensity is high, more calories will be burned. Although more calories are burned in this zone, 85% of the calories burned are from carbohydrates, 15% from fat and less than 1% are from protein.