As you probably know, exercise may well be the single most important health habit.  Drinking water, eating well, using supplements properly, avoiding toxins, sleeping, working on your attitude and relationships are all also vitally important.  However, even beyond its power to prevent and treat disease, exercise may well provide the greatest wellbeing boost of any of the essential health habits.

Whether exercise is “number one” or not, it is huge though, and getting people to exercise can be an equally huge problem.  The number one obstacle for most people is time.  Sure, our heritage is to be physically active all day long, sometimes vigorously so.  Just as we are omnivorous eaters, consuming just about anything, our bodies need all kinds of physical activity and thrive on the greatest diversity.  We need to work on our muscular strength (especially as we get old).  We need aerobic activity to strengthen our heart and lungs.  Flexibility and balance are also necessary.  Our bodies, including our brains, need all of this physical activity, but where can one find the time?

Like many in sports medicine, I am very excited about recent discoveries about one form of exercise that can shorten your time commitment, while simultaneously providing you with even greater benefits than those long, slow, time-consuming physical activities pursued by so many.

This magical form of exercise is called High Intensity Intermittent/Interval Training (HIIT).  Many of you will recall the crushingly intense sprint work your coach or PE teacher used to train/punish you with long ago.  HIIT is a bit like that, but NOT torturous.  In fact, when patients in intensive care with heart disease where given a choice of walking on a treadmill or a HIIT workout, the great majority preferred HIIT.

That’s right, ICU patients encouraged to engage in a workout that would seem to be a good way to kill them off.  I am almost as impressed by the fact that these latest studies using very sick hospitalized patients were approved by human subjects committees, as I am with the remarkable impact of the HIIT regimens.

When the first studies came out on this approach less than 10 years ago, they were small but impressive, conducted on young, often already well-conditioned athletes.  HIIT seemed like it might prove to be a way for these athletes to kick up their fitness after a layoff, or in the lead up to a big competition.  After more and more results came in, showing how efficacious this approach could be, researchers decided to try it out on other populations.

Amazingly, we have now built up research evidence ranging from the basic sciences (cellular and physiological changes) to clinical trials of old and young, fat and thin, trained and out of conditioned individuals.  The bottom line: It’s all good.

In only two to three weeks of 2-4 short sessions of HIIT each week, just about every measure we have of fitness improves, often markedly so. It also improves blood tests associated with long-term risk of heart disease, diabetes, cancer and Alzheimer’s.  Also, forget the long, slow activity and the “fat burning” heart rate zones you see posted on exercise equipment.  HIIT gets fat burning better than low intensity exercise, and keeps it going for hours after your workout ends.

One of the incontestable failings of age is that our maximal oxygen uptake drops year after year, beginning in our late 20s.  We just don’t have the aerobic capacity we used to. HIIT has been shown now to improve oxygen uptake, the most essential fuel for our cells, regardless of age, gender or previous fitness.

This is all great news, but it gets better. HIIT, with the rest intervals between the intense exertion intervals, is unlike the sprint training you might have endured long ago, and not just because it is less unpleasant.  The only research comparing HIIT to that sprint-sprint-sprint-till-you-drop torment, shows that HIIT actually works better.  Yay!

With one exception, I cannot remember any similar wave of research on a specific treatment.  That one exception, vitamin D, is an almost perfect comparison.  The evidence suggests vitamin D levels are linked to improvements in nearly every human health trouble.  Similarly, HIIT does almost everything we have learned that exercise can do.  Although there are fewer studies of HIIT than vitamin D, the quality of evidence might actually be even stronger than the vitamin D studies to date, because the of the way HIIT studies can be designed (intervention versus observation).

Okay, so how do you do it?  Very simple.  Warm up a few minutes (5-10).  Then alternate working hard and easy.  How long?  The easiest way is probably to go hard for a minute and then easy for one minute, repeating that cycle a total of 10 times.  Some studies used a four minute hard interval followed by three minutes of easy, for a total of four cycles.  We do not know if some duration will prove to be better than another.  All the studies, using whatever interval, show that it works.  Consequently, I’d say it is up to you.

My son, for example, lives in a high rise building in a big city.  He wanted to work out climbing stairs as he does not have any cardio equipment and gyms are extremely expensive where he lives.  The plan we worked out was for him to climb up for 4 minutes, which gets him near the top of the 30 stories, take the elevator back down then do it three more times.

You can walk, going faster and then slower.  You can do the same with swimming cycling or whatever activity you prefer.

How hard is hard?  90% of your maximal heart rate.  Maximal heart rates are very scientific but they can be annoying to use as a measure, because you have to monitor your heart rate and figure out what 90% of MHR is for you.  Maximal heart rate is different for different people, men versus women and it changes with age.  It also differs by what you are doing.

My advice is to do this by how hard it feels to you.  90% = panting.  Go hard enough so that you are breathing heavily and then go easy.  As you go through the cycles, you will probably learn that, keeping your effort at the same level of intensity, you are going at a slower pace.  That is fine.  Do not try to maintain the same pace unless you feel about the same level of exertion.  The point is your effort, how it feels to you. Do not thrash yourself.  Start out being careful not to push yourself too much, and as you do it for a while you can get a better sense of what your limits are.  You do need to approach those limits, to push yourself, to get the maximum benefit from this.  If you have any questions about this, please come in to talk about your individual circumstance.

I will add that there are some HIIT regimens that make the hard exertion interval much longer than the easy, recovery interval.  I do not like that for anyone who is not already quite fit.

My own experience with HIIT may be of interest.  In years past I trained in this way to build fitness, partly because it was closer to the most demanding physical work I did.  Refereeing semipro men’s soccer games, at times sprinting to keep up with athletes 20 years younger than I, was not at all like jogging for an hour or two.  More recently, as problems leading to my knee surgery became increasingly troublesome, I dropped all of my longer aerobic sessions.  My knee just would not tolerate them.  I experienced much of the same energized but relaxed sensations of the longer aerobic work, but with considerably less pain in my knee.  One conclusion from this is that HIIT can have an important role to play when a person has a chronic or acute joint problem, limiting the stress his/her body can endure.


Written by 

Michael Carlston, MD is an internationally recognized authority in the integration of conventional and complementary medicine in clinical practice, as well as medical education, research and organizational consulting. Practicing in Santa Rosa, California, Dr. Carlston was voted “Best General Physician In Sonoma County, California” by readers of the Sonoma County Independent newspaper and also named one of the outstanding physicians in the Bay Area by San Francisco Focus Magazine. With 30+ years in private practice, his expertise is in nutrition, homeopathy and sports medicine.

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