A series of short, intense cardio intervals provide similar fitness results as long efforts do, but in much less time.

It happens to just about everyone. They hop on the treadmill, elliptical or stairclimber, ready for an invigorating cardio workout but before the machine even gets warmed up, the would-be calorie cruncher is faced with that same old cardio menu option –“Intervals” or “Fat Burning?” Which one to choose? For some it’s a bigger dilemma than “paper or plastic.”

Choosing “Intervals” means hard efforts mixed with easy. Now that’s not a bad option for anyone who is in an aggressive mood and wants a challenge. But what about “Fat Burning?” Who does not want to burn fat? Isn’t “fat burning” one of the reasons a lot of people join the gym in the first place?

Which Program Is Best?

If you are like most people, you have asked the same question. But what is interval training? Or to be more specific, what is the buzz term “HIIT,” aka high-intensity interval training? And what is endurance training at lower intensity, aka “in the fat burning zone?”

The hype with HIIT is from studies that show that a series of short, intense cardio intervals provide similar fitness results as long efforts do, but in much less time. It’s like traveling across country on a jet – a few layovers will get you to your destination faster than one long road trip. For example, a 40-minute HIIT treadmill workout that includes eight three-minute maximum efforts mixed with two-minute recovery periods burns more calories than a long two-hour jog at 60 percent effort. So, simply, the appeal of HIIT is that interval training burns more calories in a shorter time.

While some might think HIIT is a relatively new idea, it’s actually been around for a century – seriously! According to research by Billat in 2001, Finnish long distance runner Hannes Kolehmainen was doing HIIT back in the early 1900s. The “Flying Finn” Kolehmainen must have been on to something because he tallied up four gold medals and one silver medal in the 1912, 1916 and 1920 Olympic Games.

Despite Kolehmainen’s successes 100 years ago, many people still consider the best way to improve performance, burn calories, drop weight and get fit is put in long slow hours in the “fat burning” zone.

Long-effort endurance training (or training in the “fat burning” zone) is typically defined as exercising for more than 20 minutes at a steady intensity. For example, a jog around the park, a recreational bike ride, or exercising at a consistent pace on stairclimber, elliptical, treadmill or any type of indoor machine found in the cardio section of most gyms is considered long-effort endurance training.

What Are the Benefits?

First of all, both endurance training and HIIT training are highly beneficial to cardiac health. Cardio exercise strengthens the heart, which helps push more oxygen-carrying blood to the muscles faster. Cardio exercise also strengthens the skeletal muscles that help return the blood back to the heart.

Typically, people who start a cardio program feel the benefits in a matter of weeks if not days. One way to think of it is this – as the body makes adaptations to the stress of the workouts and as the heart and skeletal muscles grow stronger, the blood circulates more efficiently and the body can handle more stress. So for example, someone who starts an exercise program that consists of jogging on a treadmill one mile, three times a week for two weeks would be more prepared to raise their distance to two miles a day, four times a week than someone of a similar fitness level who has not started an exercise program at all.

In addition to strengthening the heart, cardio also improves metabolism, increases the removal of metabolic waste and increases fat oxidation.

Which One Is Better?

According to studies, HIIT is shown to have similar benefits as endurance training, with less time working out. So for those of us who feel there’s not enough time to work out, the faster route tends to be the better route. In addition to less time in the gym, studies have shown that HIIT not only brought about faster improvements, it also elicited superior cardiovascular benefits than endurance training. Helgerud et al. found that performing four bouts of four-minute running efforts at 90 percent to 95 percent of maximum heart rate, separated by three minutes of active recovery at 70 percent of maximum heart rate three days a week for eight weeks, resulted in a 10 percent greater improvement in the amount of blood pumped from the heart than did endurance training. Slordahl et al. also showed that HIIT strengthened the heart 13 percent more than endurance training.

Research has also shown that HIIT is better than endurance training for improving the body’s maximal aerobic capacity or (VO2 max). Daussin et al. compared a group of men and women who trained for eight weeks doing HIIT to a group of men and women who only did endurance training. The study found that those doing HIIT increased their VO2 max 15 percent, while the group in the endurance training group only experienced VO2 max increase of 9 percent.

Are Low-Intensity Workouts a Waste of Time?

Not at all. Most fitness professionals would agree that presuming that low-intensity workouts are a waste of time is not a very good idea. In fact, many of the findings show that low-intensity workouts are the main foundation of training, and high-intensity interval workouts are not considered anything like the “cornerstone” of that training foundation.

Tips for Starting HIIT

• Before engaging in higher intensity workouts, it is important to have a strong base.

• Instead of getting rid of one training method for another, alternate workouts for more variety.

• Keep the workouts down to two or three per week.

• The effects of HIIT on physiology and performance are fairly rapid, but rapid plateau effects are seen as well. To keep from falling into a rut, increase training volume systematically.

• Keep easy workouts easy and hard workouts hard.

References:

HIIT vs. Continual Endurance Micah Zuhl, MS, and Len Kravitz, Ph.D. February 2012 IDEA Fitness Journal

Aerobic exercise bests resistance training at burning belly fat. Chris Slentz, Ph.D, Lori Bateman, M.S., Willia E. Kraus, M.D., Leslie H. Willis, M.S., A. M.S., Lucy W. Piner, M.S., Victoria H. Hawk, M.P.H., R.D., Michael J. Muehlbauer, Ph.D., Greg P. Samsa, Ph.D., Rendon C. Nelson, M.D., Kim M. Huffman M.D., Ph.D., Connie W. Bales, Ph.D., R.D. Duke University

Intervals, Thresholds, and Long Slow Distance: the Role of Intensity and Duration in Endurance Training. Stephen Seiler and Espen Tønnessen. Sportscience, 13, 32-53, 2009 (sportsci.org/2009/ss.htm)

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