By Dr. Mercola
By now you may have heard the good news: exercising at very high intensity interspersed with periods of moderate rest, a program known as high-intensity interval training (HIIT), is one of the best ways to get in shape.
That's good news because the workouts are considerably shorter than you're probably used to and involve as little as four minutes of intense activity combined with rest for a total workout of only around 20 minutes.
Because HIIT is so intense, you should only do it two to three times a week, max, making it a workout that even the most time-crunched individuals can fit in their schedules.
Interval Training 101
If you're wondering what HIIT is all about, Greatist has summed it up nicely in the interval training infographic that follows.1 From explaining the benefits and why it works to how to perform a variety of different HIIT workouts, this is the place to start if you want to give HIIT a try.
Research Overwhelmingly Supports HIIT
Compelling and ever-mounting research shows that the ideal form of exercise is short bursts of high intensity exercise.
Not only does it beat conventional cardio as the most effective and efficient form of exercise, it also provides health benefits you simply cannot get from regular aerobics, such as a tremendous boost in human growth hormone (HGH), aka the "fitness hormone."
One study published in the Journal of Obesity2 reported that 12 weeks of HIIT not only can result in significant reductions in total abdominal, trunk, and visceral fat, but also can give you significant increases in fat-free mass and aerobic power.
Other research published in the journal Cell Metabolism3 showed that when healthy but inactive people exercise intensely, even if the exercise is brief, it produces an immediate measurable change in their DNA.
Several of the genes affected by an acute bout of exercise are genes involved in fat metabolism. Specifically, the study suggested that when you exercise your body almost immediately experiences genetic activation that increases the production of fat-busting (lipolytic) enzymes.
Yet another study found that unfit but otherwise healthy middle-aged adults were able to improve their insulin sensitivity and blood sugar regulation after just two weeks of interval training (three sessions per week).4 A follow-up study also found that interval training positively impacted insulin sensitivity. In fact, the study involved people with full-blown type 2 diabetes, and just ONE interval training session was able to improve blood sugar regulation for the next 24 hours!5
Which HIIT Workout Is Right for You?
There are a large number of variations when it comes to HIIT. The infographic outlines three of them, including the Tabata Method, which calls for just 20 seconds of all-out drop-dead effort, followed by a mere 10 seconds of rest. This intense cycle is repeated eight times.
When the Tabata Method was performed four times per week for six weeks, participants in one experiment increased their anaerobic capacity by 28 percent, and their VO2 max (an indicator of cardiovascular health) and maximal aerobic power by 15 percent. This is in contrast to the control group, who performed an hour of steady cardiovascular exercise on a stationary bike five times a week. These participants improved their VO2 max by just 10 percent, and their regimen had no effect on their anaerobic capacity.6
As the infographic explained, this protocol is likely best for those who are extremely fit have very little time. I have not even attempted this protocol as I know how hard Peak Fitness is, which has a 90-second recovery. I shudder to think how painful the Tabata protocol is with only 10 seconds to recover… that said, if you're looking for an extreme intensity workout, this may be it. For those of you just starting out with HIIT, you may want to try Peak Fitness first.
One of My Workouts of Choice Since 2010
For the past couple of years, I've encouraged the use of high-intensity interval training as a key strategy for improving your health, boosting weight and fat loss, promoting HGH production, and improving strength and stamina. I've been doing it myself since April 2010 after meeting fitness expert Phil Campbell (author of Ready Set Go), so I can also vouch for its effectiveness from personal experience.
The HIIT approach I personally prefer and recommend is the Peak Fitness method of 30 seconds of maximum effort followed by 90 seconds of recuperation. I personally modified the number of repetitions from 8 to 6 this year, as it was sometimes just too strenuous for me to do all 8. So by listening to my body and cutting it back to 6 reps, I can now easily tolerate the workout and go full out. Plus, I no longer dread doing them.
Another tweak I made is to incorporate Buteyko breathing into the workout, which means I do most of the workout by only breathing through my nose. This raises the challenge to another level. I will discuss more of the benefits of this in a future article, as I do believe it has many benefits. I then finish my Peak Fitness workout with Power Plate stretches, 10 pull ups, 10 dips and 20 inverted pushups, and call it a day.
When you're first starting out, depending on your level of fitness, you may only be able to do two or three repetitions of Peak Fitness. That's okay! As you get fitter, just keep adding repetitions until you're doing eight. And if six is what your body is telling you, then stop there. If you have a history of heart disease or any medical concern please get clearance from your health care professional to start this. Most people of average fitness will be able to do it though; it is only a matter of how much time it will take you to build up to the full 8 reps, depending on your level of intensity. For a demonstration using an elliptical machine, please see the video above. Here are the core principles:
- Warm up for three minutes
- Exercise as hard and fast as you can for 30 seconds. You should be gasping for breath and feel like you couldn't possibly go on another few seconds. It is better to use lower resistance and higher repetitions to increase your heart rate
- Recover for 90 seconds, still moving, but at slower pace and decreased resistance
- Repeat the high-intensity exercise and recovery 7 more times. (When you're first starting out, depending on your level of fitness, you may only be able to do two or three repetitions of the high-intensity intervals. As you get fitter, just keep adding repetitions until you're doing eight during your 20-minute session)
- Cool down for a few minutes afterward by cutting down your intensity by 50-80 percent
Rounding Out Your Exercise Program
In most cases, HIIT workouts should only be done two or three times a week. But that doesn't mean you should take all the other days off. Switching up your workouts will ensure your muscles continue to be challenged and prevent plateaus in your fitness growth. You want to avoid overtaxing any one area of your body, too, and having a varied workout program helps you to do this naturally. I recommend incorporating the following types of exercise into your program on days when you're not doing HIIT:
- Strength Training: If you want, you can increase the intensity by slowing it down. You need enough repetitions to exhaust your muscles. The weight should be heavy enough that this can be done in fewer than 12 repetitions, yet light enough to do a minimum of four repetitions. It is also important NOT to exercise the same muscle groups every day. They need at least two days of rest to recover, repair and rebuild.
For more information about using super slow weight training as a form of HIIT, please see my interview with Dr. Doug McGuff.
- Core Exercises: Your body has 29 core muscles located mostly in your back, abdomen and pelvis. This group of muscles provides the foundation for movement throughout your entire body, and strengthening them can help protect and support your back, make your spine and body less prone to injury and help you gain greater balance and stability.
Exercise programs like Pilates, yoga, and Foundation Training are great for strengthening your core muscles, as are specific exercises you can learn from a personal trainer.
- Stretching: My favorite type of stretching is Active Isolated Stretching (AIS) developed by Aaron Mattes. With AIS, you hold each stretch for only two seconds, which works with your body's natural physiological makeup to improve circulation and increase the elasticity of muscle joints. This technique also allows your body to repair itself and prepare for daily activity. You can also use devices like the Power Plate to help you stretch.
- Non-Exercise Activity: One of the newest recommendations I have is based on information from NASA scientist Dr. Joan Vernikos, who I recently interviewed: simply set a timer when you are sitting and stand up every 10 minutes. I even modify this further by doing jump squats at times in addition to standing up. This will help counteract the dangerous consequences of excessive sitting.
You can prevent, and to a great degree, delay the damage associated with a large portion of biological aging, especially the most crippling, which is pain with movement and loss of flexibility that you had as a youth. To do so, FIRST you need to make sure you're engaging in more or less perpetual non-exercise movement, as this is an independent risk factor. You then want to add structured exercise on top of that to reap all the benefits associated with exercise.
Going to the gym a few times a week for an hour simply isn't going to counteract hours upon hours of chronic uninterrupted sitting, which essentially mimics a microgravity situation, i.e. you're not exerting your body against gravity. Only frequent non-exercise movement will do that. The key point is to move and shift position often, when you're sitting down. Meaning, you want to interrupt your sitting as often as possible.