Wednesday, February 12, 2014

Continuous Exercise But Not High Intensity Interval Training Improves Fat Distribution in Overweight Adults - Really!?

Sled pulling in the sand?! For someone with her height, but twice or thrice the weight with a primary on fat loss, on the other hand, it's suboptimal.
"HIIT", about a year ago this was the buzzword in the health and fitness industry. Doing anything but "hiiting it hard" was thought to be a waste of time and the acronym "LISS" [Light Intensity Steady State] became synonymous with "lose" as in loser.

As a SuppVersity reader you're immune against hype and constant overgenerealization. You are aware of the "specificity principle", and the usefulness of all type of exercise. And you know that there is a place and time for each form of cardio training: Light, moderate and high intensity (interval) training.

Speaking of cardio,...

... if your main concern really is your myocardium (=the large heart muscle), what type of exercise do you have to perform then? Right! "CARDIO" = Light exercise as a replacement for the daily activity most of us pencil pushers are lacking and HIIT as a means to actually train your heart.

In the end, it doesn't really depend on your current fitness level. The "no pain, no gain" principle is true for everyone. And with "light" always being defined against your current VO2max (the standard measure of cardio-respiratory fitness) - "light" exercise such as the Continuous Endurance Training (CONT) program, 13 out of the 38 subjects in a recent study by Shelley E. Keating and her colleagues from the University of Sydney and the University of Sydney is always defined relative to the your personal fitness level.

Table 1: Frequency, intensity, work : recovery ratio, no. of intervals (INT), duration of continuous work (DUR) and total session time per week (in min; incl. warm-up, cool-down, etc.; Keating. 2014)
For the 38 inactive (exercising <3 days/week) and overweight (BMI 25 to 29.9) 18- to 55-year-old year-old slackers (7 men and 31 women) who were randomly assigned to receive three sessions/week for 12 weeks of
  • HIIT (HIIT), or
  • Continuous Moderate Intensity (CONT)
training or a sedentary control group (PLA). As you can see in the tabular overview below, the researchers made sure to gradually increase both the volume and intensity of the workouts.

When I am talking to people who complain about not seeing the results they want (strength, size,  conditioning and fat loss - it does not matter), not making "progress" an obligatory part of their training regimen is second only to eating processed foods (no fat loss) and eating way to little (no performance and size increases), when it comes to the most "popular" ;-) reasons for failure.

Don't make either of these mistakes!

What kind of mistakes? Well, the first one is not to acknowledge the progressive overload principle and its reign in both endurance and strength training. You will probably remember the bottom line from the "block peridization article" (see "Block Periodization - Impressive Performance Gains in Pro-Athletes: Revolutionary Training Concept, Or Just a Good Way to Eventually Break Out of the Comfort Zone?" | read more): There is no progression without progression! In other words, if you ain't willing to kick your own ass, you better hire a trainer to do that for your or content yourself with mediocrity.
Figure 1: Changes in body composition (left) and conditioning parameters (right) after 12 weeks (Keating. 2014)
As the results from the study at hand show (see Figure 1), progression is fine and dandy, but without specificity and the blind faith that there was one training method that would deliver it all, i.e
  • increases in VO2 (=cardiovascular fitness)
  • loss of body fat, and
  • compensation for the daily activity you don't get,
... you are off the track. Seriously. Doing only HIIT will help you compensate for the daily activity you don't get, it will also help you lose body fat. However...
  • HIIT is not a sensible way to compensate for the lack of daily activity in the long term (specifically for people who lift weights and have another highly CNS taxing type of workout in their routine), and
  • HIIT is neither the most effective way to shed body fat for those who need it the most
I know that you will read the exact opposite on all kinds of websites, but the study at hand clearly demonstrates that exercise-induced weight loss, which is what most people want to achieve, when they're hitting the gym. Is not going to happen with HIIT, alone. The data in figure 1 does also leave no doubt that the lack of weight loss in the HIIT group of the Keating study is not a consequence of increases in lean mass.

Figure 2: Greater mass and fat gains in the CONT group are not what the slowly abating hype around HIIT would have you expect (from Keating. 2014)
As the b/w figures on the right hand side of this paragraph reveal (Figure 2), it's actually quite the opposite: The lean mass gains in the "average subject" of the continuous exercise group were (albeit non-significantly) more pronounced than than those of the 13 "HIITer" (2 dropouts in both groups).

In the absence of differences in total energy intake (p = 0.44) or the macronutrient ratios (33% | 42 % | 25% from fat, carbs and protein, respectively), identical sedentary times, a similar energy total expenditure per day (~10,000kJ/day), the training modalities, i.e. CONT vs. HIIT are the only parameter to explain why this "first study to examine the efficacy of HIIT versus that of continuous aerobic exercise training on body fat levels in previously inactive, overweight adults" (Keating. 2014 says: If you want to lose body fat without dieting, you better stick to (relative) low intensity steady state exercise.

Don't worry, HIITers! There is more to it...

... if your goal is a different one, though - in other words, if you aspire to achieve maximal fitness in minimal time, you will appreciate that the HIIT group achieved similar improvements in cardio-respiratory fitness (VO2max) with only "50–60% of the time taken for the same gain in fitness via
continuous aerobic exercise (60–72 versus 108–144 minutes per week)." (Keating. 2014).
Fitness, yes - fatness, no! The fitness effects of the HIIT regimen do not negate the fact that the data from the study at hand clearly demonstrates that continuous aerobic exercise, but not HIIT,
reduces total body fat and android fat in previously inactive, overweight adults.

Tabata is about HIGH intensity as it gets and a perfect means to get in shape for people who are already lean  | learn more
In spite of the fact that Keating et al. rightfully state that their results suggest that HIIT is not as "effective for the management of body fat levels", as previously suggested (e.g. Tremblay. 1994; Tjonna. 2009; Heydari. 2012 - all without CONT, control). You just have to make one minor change to the study protocol that could turn the results upside down. You have no idea what this change could possibly be? Well, if you want to shed fat effectively, you better diet (if you are already lean you must diet) and in this scenario, you've read about that in countless previous SuppVersity articles (read more), short and intense exercise regimen are a suitable means to propel (in this case) diet induced fat loss.
  • Keating, Shelley E., Elizabeth A. Machan, Helen T. O'Connor, et al., "Continuous Exercise but Not High Intensity Interval Training Improves Fat Distribution in Overweight Adults". Journal of Obesity, vol. 2014. 2014. Article ID 834865. 
  • Heydari, M., J. Freund, and S. H. Boutcher. "The effect of high-intensity intermittent exercise on body composition of overweight young males." Journal of obesity 2012 (2012).
  • Tjonna, A., et al. "Aerobic interval training reduces cardiovascular risk factors more than a multitreatment approach in overweight adolescents." Clinical science 116 (2009): 317-326.
  • Tremblay, Angelo, Jean-Aimé Simoneau, and Claude Bouchard. "Impact of exercise intensity on body fatness and skeletal muscle metabolism." Metabolism 43.7 (1994): 814-818.