By Dr. Mercola
Do you have an extra 12 minutes a week to spare? Then listen up: spending those 12 minutes engaging in high-intensity interval type training (HIIT) could significantly improve your health. That's right – just 12 minutes a week, or four minutes a day for three days.
With a time commitment this small, virtually everyone can take advantage of this phenomenal form of exercise!
Improvements to Fitness and Blood Pressure in Just 12 Minutes a Week
A new study of 24 inactive overweight men, published in PLoS One showed that short bouts of high-intensity exercise are indeed effective at improving health.1
One group of men followed a protocol known as 4x4 training, completing four intervals of four minutes of high-intensity exercise (16 minutes) three times a week for 10 weeks. The second group exercised three times a week using four-minute high-intensity sessions, for a total of just 12 minutes of exercise a week.
Both groups showed marked improvements. The 4-minute group had a 10 percent increase in maximal oxygen intake (VO2max), a measure of physical fitness, compared to a 13 percent increase in the 16-minute group.
The 4-minute exercisers also experienced decreases in their blood pressure levels at amounts even greater than the 16-minute group. Those who exercised in 16-minute sessions did have greater reductions in cholesterol and body fat than the 4-minute exercisers. However, even 16 minutes of exercise three times a week should be easily attainable by most people.
The researchers concluded:
"Our data suggest that a single bout of… [4-minute exercise] performed three times per week may be a time-efficient strategy to improve VO2max and reduce blood pressure and fasting glucose in previously inactive but otherwise healthy middle-aged individuals."
Evidence Pours in Showing You Can Get Fit in Just Minutes a Day
This PLoS One study is only the latest to show that investing very short amounts of time in exercise can pay off. One study found, for instance, that participants were able to improve their insulin sensitivity an average of 24 percent with as little as three minutes of HIIT per week.2
And according to Japanese research, a mere four minutes of exercise performed at extreme intensity four times a week can improve your anaerobic capacity by 28 percent, and your VO2 max and maximal aerobic power by 15 percent in as little as six weeks. For comparison, those who performed an hour of steady cardiovascular exercise on a stationary bike five times a week only improved VO2 max by 10 percent, and their regimen had no effect on their anaerobic capacity.
There are a large number of variations, but the HIIT routine I recommend involves going all out for 30 seconds and then recovering at a moderate pace for 90 seconds between sprints. The total workout is typically 8 repetitions, but you can certainly do less. If you can do many more, you are likely not going hard enough. When starting, you can do one or two but I would work up to at least six. In all, you'll be done in about 20 minutes, and you only need to perform HIIT two or three times a week.
How Can You Get Fit in Four Minutes?
The evidence 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. But how does it work? Your body has three types of muscle fibers: slow, fast, and super-fast twitch muscles. Slow twitch muscles are the red muscles, which are activated by traditional strength training and cardio exercises.
The latter two (fast and super-fast) are white muscle fibers, and these are only activated during high-intensity interval exercises or sprints. The benefit of activating these fibers is that they will produce therapeutic levels of growth hormone, which many athletes spend over a $1,000 a month to inject themselves with. So there is no need to pay the money or take the health risks of using synthetic growth hormone when your body can produce it naturally through high-intensity exercises.
Getting cardiovascular benefits requires working all three types of muscle fibers and their associated energy systems -- and this cannot be done with traditional cardio, which only activates your red, slow twitch muscles. If your fitness routine doesn't work your white muscle, you aren't really working your heart in the most beneficial way. The reason for this is because your heart has two different metabolic processes:
- The aerobic, which requires oxygen for fuel
- The anaerobic, which does not require any oxygen
Traditional strength training and cardio exercises work primarily the aerobic process, while high-intensity interval exercises work both your aerobic AND your anaerobic processes, which is what you need for optimal cardiovascular benefit. This is why you may not see the results you desire even when you're spending an hour on the treadmill several times a week. So when it comes to high-intensity exercise, less really is more... The health benefits of high-intensity interval training are well established at this point, and include:
|Significantly improving your insulin sensitivity, especially if you're on a low-processed food, low-sugar/low-grain diet
||Optimizing your cholesterol ratios, when combined with a proper diet
||Boosting fat metabolism and optimizing your body fat percentage (as a result of improved conservation of sugar and glycogen in your muscles)
|Virtually eliminating type 2 diabetes and high blood pressure
||Naturally boosting your levels of human growth hormone (HGH)
||Increasing your aerobic capacity
My Favorite Form of HIIT: Peak Fitness
As mentioned, there are many ways to perform a high-intensity workout. Japanese research Dr. Izumi Tabata, for instance, recommends a protocol that 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.
I personally prefer and recommend the Peak Fitness approach of 30 seconds of maximum effort followed by 90 seconds of recuperation, as opposed to Dr. Tabata's more intense routine of 20 seconds of exertion and only 10 seconds of recovery. But some might like his strategy more. His approach may be better suited to athletes who want to kick it up another notch, but may be too intense for most people. For a Peak Fitness 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. (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
I personally modified the Peak 8 to a Peak 6 this year, as it was sometimes just too strenuous for me to do all 8 repetitions. So by listening to my body and cutting it back when necessary, I can now easily tolerate the workout and go full out -- and I no longer dread doing them. I finish my Peak workouts with Power Plate stretches, 10 pull ups, 10 dips and 20 inverted pushups, and call it a day.
Be Careful to Not Overdo It: Less Really Is More
Remember, while your body needs regular amounts of stress like exercise to stay healthy, if you give it more than it can handle your health can actually deteriorate. So it's crucial to listen to your body and integrate the feedback into your exercise intensity and frequency.
When you work out, it is wise to really push as hard as you possibly can a few times a week, but you need to wisely gauge your body's tolerance to this high-intensity stress. 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.
Then, be sure you are leaving yourself adequate time for recovery, meaning a day or two in between sessions. Most HIIT workouts only need to be done two to three times a week, and no more. This is the beauty of high-intensity exercise!