|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.|
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)|
- HIIT (HIIT), or
- Continuous Moderate Intensity (CONT)
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)|
- increases in VO2 (=cardiovascular fitness)
- loss of body fat, and
- compensation for the daily activity you don't get,
- 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
|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)|
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).
- 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.