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Written on March 8, 2009 at 7:42 am, by Eric Cressey
Today, we’ve got a special guest post from Michael Boyle of StrengthCoach.com. This is some fantastic stuff – definitely one of the most comprehensive articles I’ve seen on the topic of interval training
Interval Training- HIIT or Miss?
I think every fat loss article we read espouses the value of interval training for fat loss. In fact the term HIIT (for High Intensity Interval Training) is thrown around so much that many people just assume they know what it is. However, among all the recommendations I see to perform HIIT, very few articles contain any practical information as to what to do or how to do it. I have to confess that I stumbled into this area somewhat accidentally. Two different processes converged to make me understand that I might be a fat loss expert and not know it. In my normal process of professional reading I read both Alwyn Cosgrove’s Afterburn and Craig Ballantyne’s Turbulence Training. What struck me immediately was that what these experts were recommending for fat loss looked remarkably like the programs we used for conditioning.
At the time I was reading these programs, I was also training members of the U.S. Women’s Olympic Ice Hockey team. It seemed all of the female athletes I worked with attempted to use steady state cardio work as a weight loss or weight maintenance vehicle. I was diametrically opposed to this idea as I felt that steady state cardiovascular work undermined the strength and power work we were doing in the weight room. My policy became “intervals only” if you wanted to do extra work. I did not do this as a fat loss strategy but rather as a “slowness prevention” strategy. However, a funny thing happened. The female athletes that we prevented from doing steady state cardiovascular work also began to get remarkably leaner. I was not bright enough to put two and two together until I read the above-mentioned manuals and realized that I was doing exactly what the fat loss experts recommended. We were on a vigorous strength program and we were doing lots of intervals.
With that said, the focus of this article will be not “why,” as we have already heard the “why” over and over, but “how.” How do I actually perform HIIT? To begin, we need to understand exactly what interval training is? In the simplest sense, interval training is nothing more than a method of exercise that uses alternating periods of work and rest. The complicated part of interval training may be figuring out how to use it. How much work do I do? How hard should I do it? How long should I rest before I do it again?
Interval training has been around for decades. However, only recently have fitness enthusiasts around the world been awakened to the value. The recent popularity of interval training has even given it a new name in the literature. Interval training is often referred to as High Intensity Interval Training (HIIT), and it is now the darling of the fat loss and conditioning worlds. Truth is, you can also do low intensity interval training. In fact most people should not start with HIIT but LIIT. HIIT may make you vomit if you don’t work into it.
In case you have been in a cave for the last decade let’s quickly review some research. A recent study, done in Canada at McMaster University and often referenced as the Gibala Study after lead researcher Martin Gibala, compared 20 minutes of high intensity interval training, consisting of a 30 second sprint followed by a four minute rest, with 90 to 120 minutes in the target heart rate zone. The result was amazing. Subjects got the same improvement in oxygen utilization from both programs. What is more amazing is that the 20 minute program only requires about two minutes and 30 seconds of actual work.
A second study that has become known as the Tabata study again shows the extreme benefits of interval training. Tabata compared moderate intensity endurance training at about 70 percent of VO2 max to high intensity intervals done at 170 percent of VO2 max. Tabata used a unique protocol of 20 seconds work to 10 seconds rest done in seven to eight bouts. This was basically a series of 20 second intervals performed during a four-minute span. Again, the results were nothing short of amazing. The 20/10 protocol improved the VO2 max and the anaerobic capabilities more than the steady state program.
Further evidence for the superiority of higher intensity work can be found in the September/October 2006 issue of the ACSM Journal. Dr. David Swain stated “running burns twice as many calories as walking.” This is great news for those who want to lose body fat. I am not a running advocate, but we can put to rest another high intensity (running) versus low intensity (walking) debate.
Do the math. Swain states that a 136-pound person walking will burn 50 cal/mile and proportionally more as the subject’s weight increases. In other words, a 163-pound person would weigh 20 percent more and, as a result, burn 20 percent more calories. This means that expenditure goes from 50 to 60 calories, also a 20 percent increase. Swain goes on to state that running at seven mph burns twice as many calories as walking at four mph. This means a runner would burn 100 calories in roughly eight and one half minutes or about 11 calories a minute. The walker at four miles per hour would burn 50 calories in 15 minutes (the time it would take to walk a mile at four MPH). That’s less than four calories per minute of exercise. Please understand that this is less a testament for running and more a testament for high intensity work versus low intensity work. More intensity equals greater expenditure per minute.
Interval Training Methods
There are two primary ways to performing interval training. The first is the conventional Work-to-Rest method. This is the tried and true method most people are familiar with. The Work-to-Rest method uses a set time interval for the work period and a set time interval for the rest period. Ratios are determined, and the athlete or client rests for generally one, two or three times the length of the work interval before repeating the next bout. The big drawback to the Work to Rest method is that time is arbitrary. We have no idea what is actually happening inside the body. We simply guess. In fact, for many years, we have always guessed, as we had no other “measuring stick.”
Heart Rate Method
With the mass production of low cost heart rate monitors, we are no longer required to guess. The future of interval training lies with accurate, low cost heart rate monitors. We are no longer looking at time as a measure of recovery, as we formerly did in our work-to-rest ratios. We are now looking at physiology. What is important to understand is that heart rate and intensity are closely related. Although heart rate is not a direct and flawless measure of either intensity or recovery status, it is far better than simply choosing a time interval to rest. To use the heart rate method, simply choose an appropriate recovery heart rate. In our case, we use 60 percent of theoretical max heart rate. After a work interval of a predetermined time or distance is completed, the recovery is simply set by the time it takes to return to the recovery heart rate. When using HR response, the whole picture changes. Initial recovery in well-conditioned athletes and clients is often rapid and shorter than initially thought. In fact, rest to work ratios may be less than 1-1 in the initial few intervals. An example of a sample workout using the heart rate method for a well-conditioned athlete or client is show below.
*In a conventional 2-1, time based program the rest period would have been too long for the first three intervals, rendering them potentially less effective. The reverse may be true in a de-conditioned athlete or client. I have seen young, de-conditioned athletes need rest up to eight times as long as the work interval. In fact, we have seen athletes who need two minutes rest after a 15 second interval. In the heartrate method the rest times gradually get longer. Th first interval is 1-.75 while the last interval is 1 to 1.5,
At least 70 percent of the population does not fit into our age-old theoretical formulas. The 220 minus age formula is flawed on two key points: it doesn’t fit a significant portion of the population, and it is not based on research. Even the developer of the now-famous formula admits that his thoughts were taken out of context. The more accurate method is called the Heart Rate Reserve Method or Karvonen formula.
The key to the Karvonen formula is that it looks at larger measures of fitness by incorporating the resting heart rate and is therefore less arbitrary. However, the two twenty minus age formula will suffice for establishing recovery heart rates.
The longer the interval, the shorter the rest period as a percentage of the interval. In other words, short intervals have a high muscular demand and will require longer rests when viewed as a percentage of the interval. Fifteen second intervals will need at least a 2-1 rest to work ration. Three to one will work better for beginners.
Interval Rest Recommendations (Work-to-Rest Based)
Just remember, as the intervals get longer, the recovery time, as it relates to the interval, may not need to be as long. In other words, a fifteen second sprint may require 30-45 seconds rest but a two minute interval may only need to be followed by a two minute rest.
The biggest benefit of interval training is that you can get a tremendous aerobic workout without the boredom of long steady state bouts of exercises. In fact as the Gibala study demonstrated, you can get superior benefits for both fitness and fat loss by incorporating interval training. If the heart rate is maintained above the theoretical 60 percent threshold proposed for aerobic training, then the entire session is both aerobic and anaerobic. This is why my athletes do almost no “conventional” aerobic training. All of our aerobic work is a by-product of our anaerobic work. My athletes or clients can get their heart rate in the recommended aerobic range for 15 to 20 minutes, yet in some cases, they do only three to five minutes of actual work.
Modes of Interval Training
Although most people visualize interval training as a track and field concept, our preferred method of interval training is the stationary bike. Although I think running is the theoretical “best” mode of training, the facts are clear. Most Americans are not fit enough to run. In fact, statistics estimate that 60 percent of those who begin a running program will be injured. In a fitness or personal training setting, that is entirely unacceptable. Females, based on the genetics of the female body (wider hips, narrower knees) are at potentially even greater risk. Physical therapist Diane Lee says it best in her statement, “You can’t run to get fit. You need to be fit to run.”
Interval training can be done on any piece of equipment. However, the most expeditious choice in my opinion will be a dual action bike like the Schwinn AirDyne. The bike allows, in the words of performance enhancement expert Alwyn Cosgrove, “maximum metabolic disturbance with minimal muscular disruption.” In other words, you can work really hard and not injure yourself on a stationary bike.
Fit individuals can choose any mode they like. However, the bike is the best and safest choice. In my mind, the worst choice might be the elliptical trainers. Charles Staley, another noted training expert, has a concept I believe he calls the 180 Principle. Staley advocates doing exactly the opposite of what you see everyone else in the gym doing. I’m in agreement. Walking on a treadmill and using an elliptical trainer seem to be the two most popular modes of training in a gym. My conclusion, supported by Staley’s 180 Principle, is that neither is of much use.
Interval Training Modes in Detail
Additional Treadmill Drawbacks
Stationary Bike Recommendations
Climbers and Ellipticals
Research continues to mount that interval training may improve fitness better than steady state work. The big key is not what to do any more but, how to do it. For maximum effect, get a heart rate monitor and go to work.
One warning. Deconditioned clients may need three weeks to a month of steady work to get ready to do intervals. This is OK. Don’t kill a beginner with interval training. Begin with a quality strength program and some steady state cardiovascular work. The only good use for steady state work in my mind is preparing an athlete or client for the intervals to come.
Michael is a Boston-based strength and conditioning coach and the editor of StrengthCoach.com. You can purchase Mike’s products through Perform Better. The above article is based on the best-selling Interval Training DVD filmed in 2007.
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