Story at-a-glance
- The most recent research shows that alternating relatively short bursts of intense exercise with periods of rest, known as high-intensity training (HIT) can deliver many of the health and fitness benefits you get from doing hours of conventional exercise—even if done only a total of a few minutes each week
- HIT can lead to reductions in visceral and total body fat, boost your aerobic power, improve your heart health and insulin sensitivity, and more, with only a small amount of time invested
- While it's theoretically possible to reap valuable results with as little as three minutes once a week, it might be more beneficial doing them two or three times a week for a total of four minutes of intense exertion, as recommended in my Peak Fitness workout
By Dr. Mercola
One of the biggest barriers many people face in sticking with a regular exercise program is the time it takes to do it.How Does High-Intensity Interval Training Work?
Carving out an hour or two to hit the gym can seem daunting, and on some days might be completely unrealistic.
This doesn't have to be your excuse for not exercising, because a growing body of research shows you can get fit in a fraction of the time compared to the "old standard" recommendations of exercising 30 minutes to an hour most days of the week by using high-intensity interval training (HIIT) such as Peak Fitness.
The most recent research shows that alternating relatively short bursts of intense exercise with periods of rest can deliver many of the health and fitness benefits you get from doing hours of conventional exercise – even if done only a total of a few minutes each week.Fat Loss, Aerobic Boosts and More: The Research Speaks for Itself
You don't need a gym to perform high-intensity interval exercises. They can be performed with virtually any type of exercise -- with or without equipment. You can just as easily do interval training by walking or running outdoors as you can using a recumbent bike or an elliptical machine.
While it's theoretically possible to reap valuable results with as little as three minutes once a week, it might be more beneficial doing them two or three times a week for a total of 4-6 minutes of intense exertion, especially if you are not doing strength training, as recommended in my Peak Fitness workout (I'll explain this in detail below).
You do not need to do them more often than that however. In fact, doing it more frequently than two or three times a week can be counterproductive, as your body needs to recover between sessions. The key to making interval training work is, in a word, intensity.
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 loss, promoting human growth hormone (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.Improve Your Heart Health and Your Insulin Sensitivity
Of course, the research on HIIT is just pouring in as well, and it's showing phenomenal results.
One study published in the Journal of Obesity1 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. In this study, in which young overweight males were randomly assigned to either HIIT exercise or a control group, the following health benefits were achieved by the exercising group doing just 20 minutes of high-intensity exercises (only a fraction of the 20 minutes is done at high intensity, the rest is recovery) three times a week for three months:
Other research published in the journal Cell Metabolism,2 showed that when healthy but inactive people exercise intensely, even if the exercise is brief, it produces an immediate change in their DNA. While the underlying genetic code in the muscle remains unchanged, exercise activates important structural and chemical changes associated with DNA expression within the muscles, and this contraction-induced gene activation appears to lead to the genetic reprogramming of muscle for strength, lending a molecular biological explanation for some of the well-known structural and metabolic benefits of exercise.
- Aerobic power increased by 15 percent
- Reduction of total fat mass: Nearly 4.5 pounds
- Visceral fat reduced by 17 percent
Several of the genes affected by an acute bout of exercise are genes involved in fat metabolism. Specifically, the study suggests that when you exercise, your body almost immediately experiences genetic activation that increases the production of fat-busting (lipolytic) enzymes.
Peak Fitness type exercises appear to be better than conventional cardio at burning fat and promoting weight loss, but it also offers additional astounding benefits to your heart and risk of chronic diseases, like diabetes. A Canadian research team gathered several groups of volunteers, including sedentary but generally healthy middle-aged men and women, and patients of a similar age who had been diagnosed with cardiovascular disease.3
The participants were asked to undertake a program of cycling intervals as their exclusive form of exercise.
After several weeks on the program, both the unfit volunteers and the cardiac patients showed significant improvements in their health and fitness. Most remarkably, the cardiac patients showed "significant improvements" in both heart and blood vessel functioning. And, contrary to what popular belief might dictate, the intense exercises did not cause any heart problems for any of the cardiac patients.
The conventional widely held belief is that the short exposure of the exercise actually helps insulate your heart from the intensity!
Equally remarkable were the results of yet another study, in which 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
This truly is amazing, and while aerobic fitness and fat loss is indeed important, improving and maintaining good insulin sensitivity is perhaps one of the most important aspects of optimal health. The fact that you can improve your insulin sensitivity significantly with a time investment of less than one hour a month really should send people straight to the gym en masse...A Simple to Follow HIIT Approach: Peak Fitness
If you are using exercise equipment I recommend using a recumbent bicycle or an elliptical machine for your high-intensity interval training, although you certainly can use a treadmill, or sprint anywhere outdoors. You can also sprint outside but must be very careful about stretching prior to sprinting. Also, unless you are already an athlete, I would strongly advise against sprinting, as several people I know became injured doing it the first time that way. For a demonstration using an elliptical machine, please see the following video.
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**
- Cool down for a few minutes afterward by cutting down your intensity by 50-80 percent
**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. By the end of your 30-second high-intensity period you will want to reach these markers:
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.
- It will be relatively hard to breathe and talk because you are in oxygen debt.
- You will start to sweat. Typically this occurs in the second or third repetition unless you have a thyroid issue and don't sweat much normally.
- Your body temperature will rise.
- Lactic acid increases and you will feel a muscle "burn."
The remarkable effectiveness of interval training makes logical sense when you consider that this type of exertion mimics how our ancestors lived. This is also how animals and young children behave naturally (long-duration exercise really isn't "natural"). By exercising in short bursts, followed by periods of recovery, you recreate exactly what your body needs for optimum health, and that includes the production of growth hormones, the burning of excess body fat, and improved cardiovascular health and stamina.Rounding Out Your Exercise Program
It is wise to use a wide variety of exercises in addition to Peak Fitness in order to truly optimize your health. Without variety, your body will quickly adapt and the benefits will begin to plateau. As a general rule, as soon as an exercise becomes easy to complete, you need to increase the intensity and/or try another exercise to keep challenging your body. I recommend incorporating the following types of exercise into your program:
- Interval (Anaerobic) Training: As explained, this is when you alternate short bursts of high-intensity exercise with gentle recovery periods.
- Strength Training: You can actually "up" the intensity by slowing it down. For more information about using super slow weight training as a form of high-intensity interval exercise, 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. 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. Exercise programs like Pilates and yoga are also 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 stretches developed by Aaron Mattes. With Active Isolated Stretching, 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.
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