Run Like the Wind, Then Walk: Interval Training and the Heart

by Ellen

The newest trend in exercise is something that has been around for quite some time — interval training.  But there’s a new twist.  Some people are now completely replacing their longer endurance cardiovascular workouts with short, more intense exercise intervals and improving their cardiovascular health by leaps and bounds.

Can interval training replace my longer workouts?

The answer is looking like a surprising, “yes!”

Many people claim they simply don’t have the time to fit exercise into their routines.  What if they only needed to exercise ten to fifteen minutes a few times a week?

The New York Times reported the results of a study comparing subjects engaging in longer duration, moderate endurance exercise with those exercising in short bursts of intense exercise:

Researchers at McMaster University in Canada recruited 20 healthy men and women whose average age was 23. All of the study subjects rode stationary bikes. Some exercised five days a week, doing 40 to 60 minutes of moderate-intensity cycling. Others did four to six sets of 30-second sprints on the cycle, allowing 4.5 minutes of recovery time between sets; their total exercise time was about 15 to 25 minutes just three days a week.

After six weeks, the researchers found that the intense sprint interval training improved the structure and function of arteries as much as traditional, longer endurance exercise.¹

What are the benefits of interval training?

We’ve all been told to get out and exercise for better health.  There is no denying that regular moderate aerobic exercise can make us more “fit” in many ways.  Benefits include increased stamina, greater immunity, elevated mood, better sleep, lower blood pressure, lower blood sugar, etc.

However, endurance fitness may not help us when we need it most.  Al Sears, MD, author of The Doctor’s Heart Cure, describes why long-duration exercise (like running for 30-60 minutes three or four times a week) isn’t going to help shield us from a heart attack:

When you exercise continuously for more than about 10 minutes, your heart adapts by becoming more efficient. It achieves this efficiency through downsizing. Long-duration exercise makes the heart, lungs, and muscles smaller so that they can go longer with less energy, but there’s a trade-off. The cardiovascular system becomes very good at handling a 60-minute jog, but it gives up the ability to provide you with big bursts of energy for short periods. Far from protecting your heart, this loss makes you more vulnerable to a heart attack.²

That’s where Dr. Sears grabbed my attention.  You see, I would love to make my heart as strong as possible, especially after years of heart unhealthy behaviors such as:

  • eating too much sugar (raises insulin levels)
  • getting too little sleep (also raises insulin levels )
  • drinking too much caffeine (insulin, again!)
  • consuming too much unhealthy vegetable oil (corn, soybean, canola, sunflower and safflower) found in many processed and restaurant foods.
  • being exposed to life’s stresses

Dr. Sears explains that heart attacks usually occur when a person is at rest or when there is a sudden demand on the heart due to a stressful event, like heavy lifting or an emotional blow. While athletes trained to have good endurance can go the distance, their hearts are not as well equipped to deal with a sudden demand for increased oxygen.

He goes on to say:

Dr. Stephen Seiler recently compared 20 minutes of running on a treadmill to running for 2 minutes followed by 2 minutes of rest for five cycles.  He reported at the American College of Sports Medicine that interval exercise improved maximal cardiac outputs while continuous exercise did not.  Intervals also produced another important improvement not seen with continuous exercise, the development of quicker cardiac adjustments to changes in demand. The interval trainees also achieved “higher peak stroke volumes.”  Think of peak stroke volume as the horsepower of your heart.  It is the highest volume of blood your heart can pump per beat when challenged.³

The best way to “bulletproof” your heart, in Dr. Sears’ opinion, is to train it to adjust quickly to changing demands.  That’s where interval training comes in.  He dubs his plan “PACETM,” which stands for “Progressively Accelerating Cardiopulmonary Exertion.TM”

Dr. Sears says that interval training will not only make the heart stronger, but will also increase lung capacity, improve cholesterol ratios, maintain healthy testosterone levels, and burn more body fat.

How to get started

First of all, talk to your health care provider.  (Please see my disclaimer!)  Interval training is intense and only you and your doctor can determine if it’s right for you.

Also, there are lots of different approaches to interval training.  Some have  you jump right in, while others proceed more systematically, like Dr. Sears’ PACE program.

Interval training can work with a variety of different exercises and routines.   You can run, cycle, swim, row, work out on a elliptical trainer, cross-country ski — choose the aerobic exercise you enjoy and vary the intensity.  Or, you can add some sort of a challenge to your routine, like hill-climbing, trying to keep your speed up.  Some classes combine aerobics with short bursts of high-impact exercises like skipping or jumping rope quickly enough to get the heart rate up.

Being impatient, I started out with a bang.  I went out there the first day and sprinted as fast as I could, then walked some, using telephone poles and mailboxes as my targets.  I kept up this routine for about two miles, then came home decided to slow it down a bit the next time!

My husband loves his daily 5-mile run.  He’s not giving it up; he’s just adding in some intervals of faster running.  Running longer distances has never been as easy for me, so it’s worth it to me to push harder and then get to ease way off.  So you might see me out there pounding the pavement, then moseying along…

Read more:


1)  For Heart Health, Sprints Match Endurance Training, by Tara Parker-Pope. New York Times, June 5, 2008.

2,3)  The Doctor’s Heart Cure, by Al Sears, M.D. Dragon Door Publications, Inc., St. Paul, 2004.

updated 5/6/11

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Jen April 2, 2010 at 9:01 pm

This is thrilling news! I’ve always felt like if I couldn’t do at least a 30 minute run, what was the point…

Thank you for sharing ~ you keep me so well-informed. :)

P.S. Any chance you might do a post sometime on caffeine? Is moderate consumption of coffee good for you or not??!! I’ve read a couple of articles about the many benefits but am curious about the insulin factor you mentioned.

BodyEarth April 3, 2010 at 6:11 am

Thanks, Jen!
Funny you ask about caffeine as I’m having my morning coffee. I will definitely try to write something about the caffeine/insulin link, since it is a problem. It’s one of those things where there are millions of opinions for and against, since there are both benefits and risks.

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