By Dr. Mercola
Increasingly, fitness experts are moving away from the outdated recommendations that suggest you need 30 to 60 minutes of moderate daily activity.
What is now known is that vigorous activity may be far more beneficial for most people, and when you exercise intensely, you only need to do it for a fraction of the time.
In some cases, even five minutes of vigorous activity is enough to provide significant benefits, which is really quite remarkable when you think about it. An entire high-intensity interval training (HIIT) workout, for instance, takes just 20 minutes but the actual vigorous sprinting portion may only be four minutes long.
I can tell you from experience that, in the first three months alone after I switched from lengthy long-distance running to HIIT, I dropped 5 percent body fat without ever touching a treadmill, and with putting in less total exercise time than before.
The science also clearly backs this up, including one new study that found less may, in fact, be more when it comes to running.
Reduce Your Risk of Death from Heart Disease with 5 Minutes of Running a Day
A large observational study involving data from more than 55,000 adults found that runners had a significantly reduced risk of death from all causes and from cardiovascular events compared to non-runners.
However, the benefit – a 30 percent reduction in risk of premature death and a 45 percent reduction in the risk of cardiovascular death – was the same regardless of the duration, speed, or frequency of running.1
In other words, those who ran as little as five minutes a day got the same benefit as those who ran for much longer. All runners in the study enjoyed reductions in risk of death that equated to a three-year increase in life expectancy.
And although the study was observational, which means it can’t conclusively prove that running was responsible for the reported benefits, it is in line with other recent research, including some showing that too much exercise can backfire.
Lead author Duck-chul Lee of the College of Human Sciences at Iowa State University in Ames told Reuters Health:2
“The (World Health Organization) guidelines recommend at least 75 minutes per week of vigorous aerobic activity such as running… However, we found mortality benefits in runners who ran even as little as 30 to 60 minutes per week.”
How Do Short Bursts of Vigorous Activity Get You in Shape?
A study published in the journal Cell Metabolism showed that when healthy but inactive people exercise intensely, even if the exercise is brief, it produces an immediate change in their DNA.3
While the underlying genetic code in the muscle remains unchanged, exercise causes important structural and chemical changes to the DNA molecules within the muscles.
This contraction-induced gene activation appears to be early events leading to the genetic reprogramming of muscle for strength, and to the structural and metabolic benefits of exercise. 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 proteins. Besides lowered body fat, other benefits associated with high intensity interval training include:
- Improved muscle tone
- Firmer skin and fewer wrinkles
- Higher energy levels
- Improved athletic speed and performance
- Heightened sex drive
Part of what makes brief, vigorous activity like HIIT so effective is that it engages far more of your muscle tissue than conventional aerobic cardio exercise, such as slow, steady jogging or walking. You have three different types of muscle fibers: slow, fast, and super-fast.
Only one type of these muscles, the super-fast fibers, will impact your production of human growth hormone (HGH), which is key for strength, health, and longevity. HGH has been shown to significantly improve insulin sensitivity, boost fat loss, and increase muscle growth.
The vast majority of people, including many athletes such as marathon runners, only train using their slow muscle fibers. In fact, neither traditionally performed aerobic cardio nor strength training will work anything but your slow muscles. These are the red muscles, which are filled with capillaries and mitochondria, and hence a lot of oxygen.
The fast type of fiber, which is also red muscle that oxygenates quickly, is five times faster than the slow fibers. Power training, or plyometric burst-type exercises, will engage these fast muscles. The super-fast ones are the white muscle fibers. They contain far less blood and less densely packed mitochondria. These muscle fibers are what you use when you do anaerobic, short burst exercises like HIIT. They're 10 times faster than slow fibers, and activating them is the key to producing growth hormone (also known as your “fitness hormone”).
Impressive Research Supports HIIT as the Ideal Form of Exercise
At first, it may sound too good to be true that you can get fit in just minutes a day, but the research on this is solid (and, just because it’s short doesn’t mean it isn’t hard work, as you’ll be exercising at very hard intensity). Dr. Izumi Tabata’s HIIT protocol, for instance, calls for just 20 seconds of all-out effort, followed by a mere 10 seconds of rest. This intense cycle is repeated eight times. According to Dr. Tabata:4
“All-out effort at 170 percent of your VO2 max is the criterion of the protocol. If you feel OK afterwards you've not done it properly. The first three repetitions will feel easy but the last two will feel impossibly hard. In the original plan the aim was to get to eight, but some only lasted six or seven.”
When 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.
I personally feel that the Tabata protocol is far too intense with not enough time for recovery between reps. I would advise people to avoid it. I have no doubt that it works, and if you are a highly competitive athlete, it might make sense. However, for the rest of us, I firmly believe that it is unnecessarily intense and similar benefits can be achieved with less intense workouts. I still think it is wise to push as hard as your can to your limits, but when you push to the point where you want to throw up, it seems to me that you are ignoring your body’s feedback.
Previous research has found that performing high-intensity exercises for just minutes per week can significantly improve important health indices. One such study found that just three minutes of HIIT per week for four weeks improved participants’ insulin sensitivity an average of 24 percent. This truly is amazing, and while aerobic fitness is indeed important, improving and maintaining good insulin sensitivity is perhaps one of the most important aspects of optimal health. Other research includes:
- A study published in the Journal of Obesity 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.5
- 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).6
- A follow-up study also found that interval training positively impacted insulin sensitivity. 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.7
Too Much Exercise Can Damage Your Heart and Your Health
More is not always better, and that is certainly the case with prolonged endurance exercise. While most Americans would be well served to exercise more, there's no need to work out for more than 45 minutes at a time, and if you exercise effectively, your workouts should be even shorter, as mentioned. So what’s the potential problem with too much exercise? Any of the following can occur when you exercise too much or too hard:
- Your body can enter a catabolic state, in which your tissues break down
- Excess cortisol (a stress hormone) can be released, which not only contributes to catabolism but also to chronic disease
- You can develop microscopic tears in your muscle fibers (which may fail to heal if you continue over-exercising) and increased risk for injuries
- Your immune system may be weakened
- You may develop insomnia, especially if your workout is in the afternoon or evening
However, the most serious risk involves damaging your heart—or worse yet, sudden cardiac death. High-endurance training puts extraordinary stress on your heart. Although stressing a muscle usually makes it stronger, extremely high stress can have the opposite effect—and your heart muscle is no exception. Long-distance running leads to high levels of oxidative stress, inflammation, and damage to your heart tissues, producing acute physiological responses that can trigger a cardiac event.
For instance, according to a study presented at the Canadian Cardiovascular Congress 2010 in Montreal, regular exercise reduces cardiovascular risk by a factor of two or three, but the extended vigorous exercise performed during a marathon raises your cardiac risk seven-fold! Extreme exercise also causes your heart to massively increase cardiac output, which it may have to sustain for several hours, depending on the duration and intensity of your activity. Your heart pumps about five quarts of blood per minute when you’re sitting. But when you’re running, it goes up to 25 to 30 quarts, and it wasn’t designed to do this for hours on end, day after day.8
It enters a state of “volume overload” that stretches the walls of your heart muscle, literally breaking fibers apart. Then, because many endurance athletes don’t allow their bodies to fully recover between sessions, they often live in a perpetual post-workout state, which basically resembles chronic oxidative stress.9 Repeated damage to the heart muscle increases inflammation, which leads to increased plaque formation, because plaque is your body’s way of “bandaging” the lining of your inflamed arteries. Over time, as more damage is inflicted, your heart enlarges (hypertrophy) and forms scars (cardiac fibrosis). MRIs of long-time marathoners typically reveal abundant scarring all over their hearts.
A Sensible, Effective, and Efficient Workout Plan
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 last 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. 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.
If you have a history of heart disease or any medical concern please get clearance from your health care professional to start any exercise programs. 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. This intense program should only be done two to three times a week to allow your body plenty of time for recovery.
Ideally, intense exercise should be balanced with strength training, proper stretching, core strengthening, stress reduction, restorative sleep, and good nutrition. You'll find much more information about HIIT and other types of exercise in the fitness section of my website.
I really enjoy Dr. Doug McGuff’s super slow workouts and seek to do them once a week. They are easier to do for me and are still intense. A good clue that you are doing them intensely enough is that you are sweating pretty hard after doing them. Unless you have a thyroid issue, lack of sweating is a strong indication that you aren’t pushing yourself hard enough. I am convinced that building muscle mass is an important part of a comprehensive exercise program, and I don’t know of a better approach than Super Slow training for that. When putting together your exercise routine, I recommend incorporating the following:
- Stand Up Every 15 Minutes. Compelling research now tells us that prolonged sitting can have a tremendously detrimental impact on your health, even if you exercise regularly. Your body needs to interact with gravity in order to function properly, and this has to be ongoing, throughout your day. Whenever you have a chance to move your body, do so! I invite you to look at our list of 30 videos for ideas about what you can do when you stand up.
- Interval Peak Fitness (Anaerobic) Training: Interval training involves alternating short bursts of high-intensity exercise with gentle recovery periods, and are central to my Peak Fitness routine.
- Strength Training: Rounding out your exercise program with a one-set strength training routine will ensure that you're really optimizing the health benefits of your fitness program. You can also "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 body, and strengthening them can help protect and support your back, make your spine and body less prone to injury, and improve your balance and stability. Foundation Training, created by Dr. Eric Goodman, is an integral first step of a larger program he calls "Modern Moveology," which consists of a catalog of exercises.
- Stretching: My favorite type of stretching is Active Isolated Stretching (AIS). 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 allows your body to repair itself and prepare for daily activity. You can also use devices like the Power Plate to help you stretch.