Monday, January 31, 2011

Forget Taking It Slow...Let Me HIIT It!

Outline
I.    Introduction
II.   Long-Distance Runners vs. Sprinters
III.  Definition of High-Intensity
IV.  Impact on Body Fat
V.   Potential Mechanism
VI.  HIIT Methods
VII. Bibliography

Key words:  cardio, fat loss, HIIT, weight training, high intensity interval, ab workouts, ab exercises, abs, workout for abs, get abs, sprinting
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I.  INTRODUCTION

First of all, get your mind out of the gutter!  You need to focus.  Why?? It’s because you may be one of the many people searching for a new way to shed some fat. Those remaining pounds just refuse to come off, even after all of those hours on the treadmill…but what other option is there??  Let me present an example that we’ve all seen...
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II.  LONG-DISTANCE RUNNERS VS. SPRINTERS



Long-distance runners train in a manner that is very similar to many people you might see at your local gym.  They might run for a long period of time at a constant, low-intensity, conserving energy for the duration of that X mile run.  Sprinters, on the other hand, train using intermittent periods of high-intensity running, exerting the highest amount of energy for each sprint.  In most cases, a sprinter’s training period is much shorter than a long distance runner’s training period.  Sprinters also burn far less calories during their exercises.  But, look at the major difference in body type.  Long distance runners usually have minimal muscle definition, while sprinters are muscular, lean, and have little to no body fat.  Which body type would a man rather have?  Which body type would a woman prefer for her boyfriend/husband?  So rather than spending hours on end doing low-intensity cardio, why not try high-intensity, interval training (HIIT) instead.  Simply put, HIIT involves alternating between short periods of high-intensity exercise (sprinting, biking at a high resistance, high-intensity plyometrics) followed by short periods of rest or low-intensity exercise.  If the image above doesn’t convince you, let’s also see what research has shown when comparing the benefits of low-intensity cardio with HIIT. 
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III.  DEFINITION OF HIGH-INTENSITY 

But first, let’s define some terms.  An individual’s aerobic capacity is the maximum amount of oxygen that the body can remove from circulating blood for use in exercising muscles.  It can be measured using a VO2 max test, which determines an individual’s aerobic capacity (VO2 max).  This value is used in research to define the intensity of an exercise.  For research purposes, a high-intensity exercise is one in which aerobic capacity is 85-250% VO2 max.  But generally, your VO2 max value directly correlates to your level of cardiovascular fitness.
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IV.  IMPACT ON BODY FAT 

A variety of studies have been conducted describing the benefits of HIIT in sports training.  But for this forum, I will concentrate on one study that identified greater weight loss benefits than low-intensity training.

Tremblay et al., 1994: In this study, the authors investigated the “Impact of exercise intensity on body fatness and skeletal muscle metabolism”.  Young adults took part in either a 20-week endurance training (ET) program or 15-week high-intensity intermittent-training (HIIT) program.   While HIIT had a much lower average total energy cost (57.9 MJ) than the ET program (120.4 MJ), the HIIT program resulted in a NINEFOLD greater reduction in subcutaneous adiposity (skin fat) when compared to ET.  HIIT also resulted in an increase in 3-hydroxyacyl coenzyme A dehydrogenase (HADH), an enzyme found in muscles involved in fat metabolism.  ET, on the other hand, decreased HADH activity. 

Endurance Training = Decreased HADH activity = decreased use of fat oxidation = more fat left on you!
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V.  POTENTIAL MECHANISM 

So what exactly is the mechanism behind this?  From what I’ve read, I was unable to identify anything definitive.  However, there is one theory that could be a potential mechanism.  Studies have shown that a potential method for increasing fat oxidation is to maintain glycogen stores at a low range (Flatt, 1987).  It is also well known that as the intensity of an exercise increases, glycogen (carb) metabolism increases and fat metabolism decreases (Holloszy et al., 1998; Romijn et al., 1993).  In other words:

Low intensity exercise = more fat burned for energy during exercise
High intensity exercise = less fat, more glycogen burned for energy during exercise

So if more fat burned isn’t burned during high intensity exercise, when is it burned?  One theory is after exercise.  Studies have been conducted to investigate this
(Schrauwen et al., 1998; Schrauwen et al., 1997), but their findings did not completely confirm this theory.  Briefly, these studies investigated the amount of fat oxidation following high-intensity exercise.  However, there was no comparison of high-intensity fat oxidation to low-intensity fat oxidation.  That comparison is essential to properly validate this theory.  Nonetheless, I believe the marathon runner/sprinter comparison along with the Tremblay et al. research is enough evidence to give HIIT a try!
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VI.  HIIT METHODS 

So here are some recommendations for ways to try HIIT:

1.  If you have access to a track, sprint the straightaways and walk/jog the curves.

2.  Run sprints on a field, basketball court, or hill with 15-30 second rest periods.

3.  Take classes like spinning or bodypump.  These can be a fun (and sometimes easier) way to take part in some high-intensity exercise.

4.  Using a treadmill, place your feet on either edge and set the speed at a fast pace that you feel comfortable with to run sprints (6-10 mph, adjust depending on your comfort level).  You can also increase the incline to 4-8% and make it more challenging if you feel comfortable with it (5-8% incline).  Sprint for 15-20 seconds, then hop up, with your feet landing on either side of the moving treadmill.  Rest for 20 seconds, then hop back on the treadmill for the next sprint.  After 10-15 minutes, you’ll feel this.

5.  Use the interval settings on a stationary bike.

A couple of other comments:

1.  In no way am I saying that you should never do low-intensity cardio exercises.  I'm simply suggesting a different type of exercise for those who are looking for new things to try.

2.  I wouldn't do HIIT before, on, or the day after a leg weight-training day.  Your legs will need time to recover from both HIIT and your leg day, and doing them too close together will not provide necessary recover time.

Go HIIT It!!

Dr. O
"I don't live to eat...I eat to live!"
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VII. BIBLIOGRAPHY

Flatt JP. 1987. The difference in the storage capacities for carbohydrate and for fat, and its implications in the regulation of body weight. Ann NY Acad Sci 499:104-123.
Holloszy JO, Kohrt WM, Hansen PA. 1998. The regulation of carbohydrate and fat metabolism during and after exercise. Front Biosci 15(3):1011-1027.
Romijn JA, Coyle EF, Sidossis LS, Gastaldelli A, Horowitz JF, Endert E, Wolfe RR. 1993. Regulation of endogenous fat and carbohydrate metabolism in relation to exercise intensity and duration. Am J Physiol 265:E380-E391.
Schrauwen P, Lichtenbelt WD, Saris WHM, Westerterp KR. 1998. Fat balance in obese subjects: role of glycogen stores. Am J Physiol 274:E1027-E1033.
Schrauwen P, Van Marken Lichtenbelt WD, Saris WHM, Westerterp KR. 1997. Role of glycogen-lowering exercise in the change of fat oxidation in response to a high-fat diet. Am J Physiol 273:E623-E629.
Tremblay A, Simoneau JA, Bouchard C. 1994. Impact of exercise intensity on body fatness and skeletal muscle metabolism. Metabolism 43(7):814-818.


6 comments:

Jesse said...

Awsome Blog! I'll be a regular reader, keep it up.

Jesse said...

My story is the same as yours, but about 6 years later! Last June I really started to put the work in and to date I've gone from 300lbs to 238lbs as of this morning.

angela said...

I needed a different burning calorie method.I will definitely try (Hit method #4 for two weeks or more).

Dozie Onunkwo, Ph.D. said...

Jesse, man that's great news! Keep it up! And I'm glad you find the posts useful!

Angela, let me know how that works for you!

Anonymous said...

This might be nit-picking, but I took issue with this question you ask..."Which body type would a woman prefer for her boyfriend/husband?" I don't know if survey data (see link below) agrees with your insinuation that women prefer men who are "muscular, lean, and have little to no body fat." In fact, women prefer "runners, cyclists, climbers" compared to body-builders according to the survey data here: http://quirkology.com/USA/Experiment_sport.shtml

I realize HIIT can be done by both types of athletes (strength and endurance), but to suggest the women do not prefer "minimal muscle definition" of the long distance runners may not be accurate.

Sandra B. said...

Great post! I like the HIIT ideas that can be applied at the gym. I will definitely apply them. And I've done hill sprints with my trainer. Love them!

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