By Dr. Mercola
Did you know that working out just 20 minutes using interval exercise may provide many of the same benefits of much longer workouts done in conventional "long-duration" style?
A growing body of research shows you may not need to spend as much time exercising as you think -- provided that you are willing to truly put in some effort when you do.
Most recently, a Canadian research team recently 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.1
The participants were asked to undertake a program of cycling intervals -- repeated short bursts of strenuous activity, divided by rest periods.
According to the New York Times2:
"Most of us have heard of intervals, or repeated, short, sharp bursts of strenuous activity, interspersed with rest periods.
Almost all competitive athletes strategically employ a session or two of interval training every week to improve their speed and endurance.
But the Canadian researchers were not asking their volunteers to sprinkle a few interval sessions into exercise routines.
Instead, the researchers wanted the groups to exercise exclusively with intervals."
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 belief is that the brevity of the exercise helps insulate your heart from the intensity.
How Intense is "High Intensity" Training?
The key to make interval training work is intensity. The cycling program developed for the out of shape and ill patients in the featured study3 was a gentler version of the interval training typically used, when you really go all out to reach your maximum heart rate. In this modified routine, the participants did one minute of strenuous effort, raising their heart rate to about 90 percent of their maximum, followed by one minute of recovery.
These intervals were repeated 10 times for a 20 minute long workout.
Your maximum heart rate can be roughly calculated as 220 minus your age. However, to measure the intensity of your effort, you really need a heart rate monitor. It's nearly impossible to accurately measure your heart rate manually when it is above 150. And accuracy is important. There's a big difference between a heart rate of 170 and 174 (or 160 and 164 if you are over 50). Once you reach your maximum heart rate you may feel a bit light headed and, of course, VERY short of breath. But your body catches up quite rapidly and in about 30-60 seconds you will start to feel much better. Most people feel tired but great once they're done.
For the past couple of years, I've heavily promoted 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.
Summary of my Interval Training Program
The interval program created by Phil Campbell also takes about 20 minutes, but here you'll want to push your heart rate up to your anaerobic threshold during the exertion portion. The silver lining is that the actual sprinting totals a mere 4 minutes instead of 10! Here's a summary of what a typical interval routine might look like (for a full demonstration, see the video below):
- 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
- Recover for 90 seconds, still moving, but at slower pace and decreased resistance
- Repeat the high intensity exercise and recovery 7 more times, for a total of 8 repetitions
By the end of your 30 second period you will want to reach these markers:
- 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"
While you may need to slowly work your way up to this point, ultimately you want to exercise vigorously enough to reach your anaerobic threshold as this is where the "magic" happens that will trigger your growth hormone (HGH) release. HGH, also known as "the fitness hormone," accounts for many of the health benefits of interval training.
But be mindful of your current fitness level and don't overdo it when you first start out. Also keep in mind that there's no "magical" speed here. It's entirely individual, based on your current level of fitness. Some may reach their anabolic threshold by walking at a quick pace, while others may need to perform a mad-dash to get the same effect.
The Many Health Benefits of High-Intensity Interval Training
Once you engage in these high-int ensity exercises two to three times a week, most people notice the following benefits:
|Decrease in body fat||Firmer skin and reduces wrinkles||Improved athletic speed and performance|
|Improved muscle tone||Increase in energy and libido||Ability to achieve your fitness goals much faster|
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.
More Supporting Evidence
In a 2008 study published in the Journal of Physiology, Canadian researchers compared the effects of steady versus interval cycling. Active but untrained young men and women were divided into two groups:
- The interval training group performed four to six repeats of 30-second all-out effort, with 4 ½ minutes of recovery between repeats, three days a week
- The conventional cardio group cycled continuously for 40-60 minutes, five days a week
After six weeks, the leg muscles of those in the interval training group exhibited similar physiological changes as seen in those who performed multiple, hour-long sessions each week of steady cycling4. The main difference? Those performing interval training spent just 1.5 hours per week in the gym, compared to about 4.5-5 hours for the conventional group.
Researchers have also concluded that interval training has a significantly beneficial impact on insulin sensitivity. In a study published last year, 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)5. A follow-up study of the featured 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 hours6.
Interval Training is Part of a Balanced Exercise Routine
Exercise is one of the most important tools that you can implement to gain optimal health, but as great as it is, it's still important to include a variety of activities. Otherwise, your body will quickly adapt to your program, and whenever exercise becomes easy to complete, it's a sign you need to work a little harder and give your body a new challenge. So when you're planning your exercise routine, make sure to incorporates the following types of exercise:
- Aerobic: Jogging, using an elliptical machine, and walking fast are all examples of aerobic exercise. As you get your heart pumping, the amount of oxygen in your blood improves, and endorphins, which act as natural painkillers, increase. Meanwhile, aerobic exercise activates your immune system, helps your heart pump blood more efficiently, and increases your stamina over time.
- Interval (Anaerobic) Training: Again, this is when you alternate short bursts of high-intensity exercise with gentle recovery periods.
- Strength Training: Rounding out your exercise program with a 1-set strength training routine will ensure that you're really optimizing the possible health benefits of a regular exercise program.
Here you also have the option of including Super Slow Weight Training, which will give you many of the same health benefits as interval training on a recumbent bike, for example. The only difference is you're doing it with weights. For more information about this, please see my interview with Dr. Doug McGuff. Another benefit of super-slow weight training that makes it ideal for virtually everyone, regardless of age or fitness level, is its safety, as it actively prevents you from accidentally harming your joints or suffering repetitive use injury.
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.
- 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 and yoga 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.
- 1 Physiological adaptations to low-volume, high-intensity interval training in health and disease, The Journal of Physiology, 2012 Jan 30. [Epub ahead of print]
- 2 New York Times February 29, 2012
- 3 Physiological adaptations to low-volume, high-intensity interval training in health and disease, The Journal of Physiology, 2012 Jan 30. [Epub ahead of print]
- 4 Similar metabolic adaptations during exercise after low volume sprint interval and traditional endurance training in humans, Journal of Physiology, 2008 Jan 1;586(1):151-60
- 5 Low-volume interval training improves muscle oxidative capacity in sedentary adults, Medicine and Science in Sports and Exercise, 2011 Oct;43(10):1849-56
- 6 Acute high-intensity interval exercise reduces the postprandial glucose response and prevalence of hyperglycaemia in patients with type 2 diabetes, Diabetes, Obesity and Metabolism, 2012 Jan 23 [Epub ahead of print]