High intensity interval training (HIIT) is the no. 2 fitness trend in the world, according to the 2015 American College of Sports Medicine's Worldwide Survey of Fitness Trends. If you're just starting out, the technical term for the casual-paced interval training you're probably doing is fartlek. For example, sprint as fast for as long as you can, rest, run, then walk. HIIT is more advanced because you get more specific, such as one minute of sprints followed by 30 seconds of recuperation, then repeat. Also, you’re working full anaerobic and aerobic thresholds. The more advanced you are at HIIT, the longer the work periods become and shorter the rest periods become.
Intervals of aerobic HIIT have been shown to increase VO2max compared to continuous aerobic training, even though HIIT workouts take less time to complete. Furthermore, a 2013 Journal of Strength and Conditioning study found that four weeks of HIIT rowing burned more body fat than traditional rowing. Effective HIIT training will help you torch calories, build lean muscle, lose fat, improve heart health, push your limits, and increase efficiency.
With all of that said, the real magic of HIIT lies in its ability to keep you burning fat even after you leave the gym. In short, your body isn’t able to bring in enough oxygen during periods of hard work. Therefore, you accumulate a “debt” of oxygen that must be repaid post-workout in order to get back to normal. The result: your metabolism is revved for hours after you leave the gym. Trainers refer to this phenomena as excess post-exercise oxygen consumption, or EPOC. The biggest way to use it to your advantage is to make short, intense exercise bouts a regular piece of your workout regimen.
HIIT workouts can be done with body weight, dumbbells, kettlebells or medicine balls, but for compound barbell movements, longer rest periods are generally warranted for injury prevention and full recovery between sets. If you’re a HIIT beginner, try these two muscle-building, fat-burning bodyweight interval workouts.