By Dr. Mercola
If you have a difficult time fitting exercise into an already crammed schedule, you'll be excited to know you can reap truly remarkable results in a very limited amount of time. Can you carve out 20 minutes two to three times a week?
If so, you can dramatically improve your overall fitness and health – as long as you engage in high-intensity interval training, that is.
Research presented at the Integrative Biology of Exercise VI meeting1, 2 in Colorado last October 10-13, demonstrated that high-intensity interval training burns more calories in less time – a mere 2.5 minutes, divided into five 30-second sprint intervals at maximum exertion, each followed by four minutes of light pedaling to recuperate, can burn as much as 220 calories.
According to lead researcher Kyle Sevits:3
"You burn a lot of calories in a very short time... Nearly all the calories are burned in those 2.5 minutes; you burn very few during the rest period."
Besides burning more calories, high-intensity interval training, which is part of my total Peak Fitness program, has also been shown to produce greater health benefits overall than conventional aerobic training, such as increasing insulin sensitivity and glucose tolerance – both of which are critical components of optimal health. Back in April, I reported on a study that found doing just three minutes of high-intensity exercise per week for four weeks, could lead to a 24 percent improvement in insulin sensitivity.
Another important benefit of high-intensity interval training is its ability to naturally increase your body's production of human growth hormone (HGH), also known as "the fitness hormone." HGH is a synergistic, foundational biochemical underpinning that promotes muscle and effectively burns excessive fat.
It also plays an important part in promoting overall health and longevity. This too is something you cannot get from conventional, aerobic endurance training. Other benefits associated with high-intensity interval training include:
Decrease in body fat Improved muscle tone Improved athletic speed and performance Ability to achieve your fitness goals much faster Increase in energy and sexual desire Firmer skin and reduces wrinkles
Are You Maximizing the Health Benefits from Your Fitness Routine?
The key that unlocks the many health benefits associated with exercise is intensity. To perform anaerobic exercises correctly, regardless of how you do them (sprinting outdoors, using a stationary bike or elliptical machine, or using weights), you'll want to raise your heart rate to your anaerobic threshold, and to do that, you have to give it your all for those 20 to 30 second intervals.
Different studies will use different intervals of exertion and recuperation. For example, in the featured study, 30-second bouts of exertion were separated by four-minute rest intervals. I use and recommend the program developed by Phil Campbell, where you go all out for 30 seconds, followed by 90 seconds of recuperation. If you do the recommended eight repetitions, you'll be done in 20 minutes or less.
Depending on your level of fitness when you're first starting out, you may only be able to do two or three repetitions of the high-intensity intervals. That's okay. As you get fitter, just keep adding repetitions until you're doing eight during your 20-minute session. Here's a summary of what a typical interval routine might look like using an elliptical:
- 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
Greater Intensity = Greater Need for Recovery
To optimize results, do these types of peak exercises twice or three times a week. Again, you only need about 20 minutes per session, and you don't even need a gym membership to do them. If you have beach access, you may want to take to sprinting barefoot by the water's edge. However, before you give it a go, make sure to review some basic safety guidelines, which I discussed in depth in my previous article, Proper Sprinting and Warm-Up Techniques to Optimize Your Workout and Avoid Injury.
You can also turn your weight training session into an anaerobic exercise by following the guidelines presented by Dr. Doug McGuff. The key that turns strength training into a high-intensity exercise is the speed. Reducing the speed increases the intensity.
Whichever way you choose to do them, you do not need to do high-intensity exercises more frequently than three times a week. In fact, doing so can be counterproductive, as your body needs to recover between sessions. The importance of recovery should not be overlooked, as your body needs time to rebuild itself in order to function optimally. As explained by Dr. Jeff Spencer:
"To achieve the most beneficial effects from your workouts in the shortest time it's essential to understand the concept of total load. Total Training Load refers to the total amount of training 'strain' on the body over time. For example, one single super-hard workout can strain the body as much as several moderate intensity workouts done back to back can.
The Total Training Load can be increased by increasing the number of exercise repetitions, resistance, length of workout sets and by increasing the speed of repetitions and, also, by shortening the rest interval between exercise sets. If the Total Training Load is in excess too long, the body breaks down, and illness, over-training, burnout, and injury occur."
Recovery also includes giving your body the proper nutrients it needs in the recovery phase, as your post-workout meal can support or inhibit the health benefits of exercise. For instance, fast-assimilating protein such as high-quality whey protein, eaten within 30 minutes of your workout, will essentially "rescue" your muscle tissue out of the catabolic state and supply it with the proper nutrients to stimulate repair and rejuvenation.
The Synergy Between Exercise and Diet, and Boosting Results with Intermittent Fasting
It's well worth noting that your choice of breakfast food may play a significant role in altering your metabolic functioning, which can either improve or deter weight loss. For example, eating carbohydrates for breakfast will inhibit your sympathetic nervous system (SNS) and reduce the fat burning effect of your exercise. Instead, it activates your parasympathetic nervous system (PSNS), which promotes storage of fat – the complete opposite of what you're aiming for.
Avoiding fructose and other grain carbohydrates is a critical element of a successful weight loss strategy. This includes sports or energy drinks and fruit juices (even if they're freshly squeezed). Exercise cannot counteract the harmful effects of a high-fructose diet. It's also important to remember that if you consume fructose within two hours before or after high-intensity exercise, you effectively negate the ability of the exercise to produce HGH – one of the MAJOR benefits of interval training.
If you're ready to take your fitness routine to the next level, you may even want to consider skipping breakfast altogether and work out on an empty stomach. You can review the article I recently wrote on this here. This is a form of intermittent fasting and I believe it's one of the most profound new developments in weight loss management. This can radically improve your ability to shift to fat burning mode and effectively burn fat rather than glucose.
Also, exercising in a fasted state can help your cells rebuild and repair, keeping them biologically young. I've previously interviewed fitness expert Ori Hofmekler on the issue of fasting and exercise. According to Ori, fasting actually has the surprising benefit of helping you reconstruct your muscles when combined with exercise. This is due to an ingenious preservation mechanism that protects your active muscle from wasting itself.
In a nutshell, if you don't have sufficient fuel in your system when you exercise, your body will break down other tissues but not the active muscle, i.e. the muscle being exercised. That said, neither Ori nor I advocate starvation combined with rigorous exercise. It's important to be sensible. And you need to consume sufficient amounts of protein in order to prevent muscle wasting. While most people need to address the foods they DO eat before considering skipping meals, intermittent fasting can provide you with many benefits, and is another tool you can experiment with to help you reach your goals. Research has shown that the combined effect of intermittent fasting (IF) with short intense exercise may help you to:
Turn back the biological clock in your muscle and brain Boost growth hormone Improve body composition Boost cognitive function Boost testosterone Prevent depression
Being Fat-Adapted Can Help Improve Your Health
If you follow the recommendations mentioned above, which include:
- High-intensity interval training
- Avoiding grain carbs and sugars, especially fructose
- Exercising in a fasted state
Another side effect will eventually become apparent: you'll become increasingly "fat-adapted." Fat-adaption describes the ability to burn fat directly via beta-oxidation. It is the normal, preferred metabolic state of the human body, in which your body burns fat rather than glucose as its primary source of energy. Sadly, the bodies of many, if not most, Americans operate in a state of sugar-dependency, which is an abnormal metabolic state that inevitably results in insulin resistance and related chronic disease. Signs that you're a sugar-burner and are heading down a path of disease include:
- Low satiety
- Persistent hunger
- Carb cravings
As Mark Sisson explains in a recent article, if you are fat-adapted, you:
- Can effectively burn stored fat for energy throughout the day.
If you can handle missing meals and are able to go hours without getting ravenous and cranky (or craving carbs), you're likely fat-adapted.
- Are able to effectively oxidize dietary fat for energy.
If you're adapted, your post-prandial fat oxidation will be increased, and less dietary fat will be stored in adipose tissue.
- Can rely more on fat for energy during exercise, sparing glycogen for when you really need it.
Being able to mobilize and oxidize stored fat during exercise can reduce an athlete's reliance on glycogen. This is the classic "train low, race high" phenomenon, and it can improve performance, save the glycogen for the truly intense segments of a session, and burn more body fat.
According to Sisson, once you can go three hours or more without feeling hungry, you're on your way toward being fat-adapted. If you can handle exercising without having to carb-load, you're probably fat-adapted. And if you can work out effectively in a fasted state, you're definitely fat-adapted.