What Is HIIT?
High Intensity Interval Training involves alternating between very intense bouts of exercise and low intensity exercise. For example, sprinting for 30 seconds, then walking for 60 seconds is high intensity interval training. HIIT can be used both anaerobically (in the gym with weights) and aerobically with cardio.
How does it work?
Most endurance workouts, such as walking, running, or stair-climbing—are performed at a moderate intensity, or an exertion level of 5-6 on a scale of 0-10. High-intensity intervals are done at an exertion level of 7 or higher, and are typically sustained for 30 seconds to 3 minutes, although they can be as short as 8-10 seconds or as long as 5 minutes; the higher the intensity, the shorter the speed interval. Recovery intervals are equal to or longer than the speed intervals.
High-intensity interval training is done at a submaximal level; around 80-95% of maximal aerobic capacity. Sprint interval training (SIT) is a type of high-intensity interval training that pushes beyond this level to 100% or more of maximal aerobic capacity, or an exertion level of 10.
Benefits of HIIT
Super-efficient HIIT is the ideal workout for a busy schedule—whether you want to squeeze in a workout during your lunch break or to get in shape for a fast-approaching event. Research shows you can achieve more progress in a mere 15 minutes of interval training (done three times a week) than the woman jogging on the treadmill for an hour. (A 10-minute fat-blasting cardio routine that burns more calories than a half hour on the treadmill!) And according to a 2011 study presented at the American College of Sports Medicine Annual Meeting, just 2 weeks of high-intensity intervals improves your aerobic capacity as much as 6 to 8 weeks of endurance training.
Not only do you burn more calories during a HIIT workout, but the effect of all that intense exertion kicks your body’s repair cycle into hyperdrive. That means you burn more fat and calories in the 24 hours after a HIIT workout than you do after, say, a steady-pace run.
3. Healthier Heart:
Most people aren’t used to pushing into the anaerobic zone (that lovely place where you can’t breathe and you feel like your heart is trying to jump out of your chest). But in this case, extreme training produces extreme results. One 2006 study found that after 8 weeks of doing HIIT workouts, subjects could bicycle twice as long as they could before the study, while maintaining the same pace.
4. No Equipment Necessary:
Running, biking, jump roping, and rowing all work great for HIIT, but you don’t need any equipment to get it done. High knees, fast feet, or anything plyometric like jumping lunges work just as well to get your heart rate up fast. In fact, some equipment like dumbbells can make HIIT less effective because you want the focus to be on pushing your heart to its max, not your biceps.
5. Lose Weight, Not Muscle:
Anyone who has been on a diet knows that it’s hard to not lose muscle mass along with fat. While steady state cardio seems to encourage muscle loss, studies show that both weight training and HIIT workouts allow dieters to preserve their hard-earned muscles while ensuring most of the weight lost comes from fat stores. Win/win!
6. Increase Metabolism:
In addition to increased fat burning and more muscle preserved, HIIT stimulates production of your human growth hormone (HGH) by up to 450 percent during the 24 hours after you finish your workout. This is great news since HGH is not only responsible for increased caloric burn but also slows down the aging process, making you younger both inside and out!
7. Do It Anywhere:
You can do it in a boat, you can do it with a goat. You can do it here or there, you can do it anywhere! Dr. Seuss would have loved HIIT. Since it’s such a simple concept—go at maximum effort for a short period of time followed by a recovery period and repeat—you can adapt it to whatever time and space constraints you have.
This is not a workout you can do while reading a magazine or chatting with your friend. Because it’s so short, you will be working hard the whole time. The trade-off is this format offers seasoned exercisers a new challenge and new exercisers a quick way to see results. You may be in pain, you may be sucking wind, but you definitely won’t be bored!
Recovery after HIIT
Have you ever completed a particularly difficult HIIT session and found your muscles to be a little shaky afterwards (more common when weights or strength training is incorporated)? This is when you know you’ve definitely depleted your glycogen stores, which is the primary fuel your muscles use during a workou). That’s good. That’s what we want.
But, how do we restore those levels? Well, your body will eventually do this on its own but if you want to speed up the process, then you need to focus on taking in the right ingredients within 20 minutes of your completed exercise. The body’s ability to turn carbs into useful glycogen declines in the hours following your workout. This is why many people choose to carb-load immediately following the completion of their workout.