HIIT is a cardio session arranged as short bursts of very hard work. The whole point of high-intensity training is to kick up the intensity of your cardio. In order to qualify as true HIIT, you’ll need to push yourself to the max during every set. That’s why they’re short—anywhere from 20 to 90 seconds, typically. It’s the opposite of going for a long run where you ration your energy in order to sustain the activity for longer. Numerous studies have shown that working your hardest is key when it comes to boosting endurance, increasing metabolism, regulating insulin levels, and losing body fat. “All exercise helps burn fat by burning calories. HIIT can be a more effective way of getting shredded, HIIT routines that involve bodyweight work (e.g. push-ups) or added weight, such as kettle bells, medicine balls, or dumbbells, will tone your muscles while spiking your heart rate. “HIIT is effective on multiple fronts. It’ll improve your endurance, it will complement your strength development, and it’ll help you get shredded,”