bradd80 said:
There is never myth in any of my posts, they're always backed by cold hard scientific facts.
Focusing on the pics I posted and pointing out that the black sprinters are jacked just because they're black while the marathon runners are lanky and thin just because they're white is ignoring the fact that pretty much all sprinters - whether white or black - are well muscled while pretty much all marathon runners - whether white or black - are lanky and thin.
To state that fat burning efficiency depends on a variety of factors isn't very helpful. All one has to do is look at marathon runners, who are almost universally very thin and almost sick looking, and compare them to the vast majority of sprinters who are jacked and you can see the difference in muscle development. And you reading about fat burning in your text book confirms what we already knew: that running burns fat. But it doesn't compare running to sprinting in order to conclude
which one burns fat more efficiently and effectively.
Your claim that fat burning efficiency depends on blood glucose levels prior to training etc ignores the single most important fact here: that short intense bursts of sprinting burns fat far more effectively and releases more muscle-building HGH (human growth hormone) than conventional running.
See
http://www.metabolismjournal.com/article/0026-0495(94)90259-3/abstract
and I quote directly from the study:
"The impact of two different modes of training on body fatness and skeletal muscle metabolism was investigated in young adults who were subjected to either a 20-week endurance-training (ET) program or a 15-week high-intensity intermittent-training (HIIT) program."
The study's conclusion:
"Despite its lower energy cost, the HIIT program induced a more pronounced reduction in subcutaneous adiposity compared with the endurance training program."
also:
"the decrease in the sum of six subcutaneous skinfolds induced by the HIIT program was ninefold greater than by the endurance training (ET) program."
Not to mention:
"the activity of muscle glycolytic enzymes was increased by the HIIT program, whereas a decrease was observed following the ET program. The enhancing effect of training on muscle 3-hydroxyacyl coenzyme A dehydrogenase (HADH) enzyme activity, a marker of the activity of β-oxidation, was greater after the HIIT program. In conclusion, these results reinforce the notion that for a given level of energy expenditure, vigorous exercise favors negative energy and lipid balance to a greater extent than exercise of low to moderate intensity. Moreover, the metabolic adaptations taking place in the skeletal muscle in response to the HIIT program appear to favor the process of lipid oxidation."
The results are similar in older people:
http://www.theglobeandmail.com/life...ng-is-better-in-the-long-run/article17329544/
See also this study,
http://www.hindawi.com/journals/jobe/2011/868305/, which confirms everything I have stated.
There is no doubt that, all else being equal, HIIT-style sprinting is far better for burning fat (up to 9 times better!) and for releasing HGH which builds muscle than low to moderate running. Now whether one is actually willing to do and stick to sprints over endurance running is up to the person performing the exercise..
Those are some decent references, but your post is bordering on the tautological. You basically restated everything we both just said (minus addressing my points on why photo comparisons are misleading, which still stand) in your own lawyer-esque way.
In my first post I said:
Colossus said:
...sprinting has been shown to utilize more fat for fuel for the time spent in exercise;
..which concurs with your references.
To state that fat burning efficiency depends on a variety of factors
IS very helpful, because those factors make a big difference in efficacy. Nutrient timing, exercise duration, and baseline fitness are a few.
Me saying sprinting>running for fat burning is a "myth" is probably inaccurate; but I
do think it is an oversimplification.
There a few reasons why:
1. The issue of meal timing and insulin levels with regards to HIIT-induced lipolysis has not been addressed by science. We know that a meal within 3-6 hours of an endurance exercise bout will blunt fat metabolism (1), so it is not unreasonable to assume that it may have a similar blunting effect in HIIT or MIIT.
2. Endurance training (ET) and HIIT produce similar physiologic benefits and adaptations (2,3). The main difference between the two is time spent in training; in other words, rate.
3. The studies you referenced have fairly low quantitative power, examining only a few individuals. The results are promising, sure, but I can give you a study (4) with similar statistical power that showed NO significant difference in body composition was seen after 10 weeks of HIIT and ET, only a difference in rate.
4. Also worth considering is the modality of these studies; almost all of them use a
cycle ergometer, NOT sprinting. Your reference states that in the conclusion.
5. Additionally, to restate my point above about the jacked sprinter photos, those are extreme examples of PRO athletes who train for their sport all day, every day. So not only is it obvious they will look different (akin to comparing the physique of a swimmer and an olympic weightlifter), but it just has no relevance to average bros.
So I think we can agree at this point that,
for equal time spent in exercise, HIIT (and even MIIT) appears to be superior for lipolysis. But there are some limitations in the current body of knowledge, and I wouldn't go so far as to state it's a "cold hard scientific fact". Similar adaptations can be achieved with ET (2,3), with lower risk of injury and CNS fatigue.
The take-home message is, if you want what appears to be superior fat-burning potential for the time spent in exercise, and can tolerate the demands of sprinting (or cycling, or whatever) HIIT seems to be the way to go. If you want all of those benefits but have more time to jog or just enjoy it more than sprinting, moderate endurance training is fine.
For most of us non-pro athletes who are just trying to look lean and muscular, be strong, and have healthy hearts, some combination of both is probably best.
REFS
1. Exercise Metabolism, Hargreaves and Spriet, 2nd Ed; 2006. pp 8-11, 89-93, 172.
2. Joyner and Coyle 2008; Pavlik et al. 2010
3.
http://www.ideafit.com/fitness-libr...durance-training-battle-of-the-aerobic-titans
4.
http://scholarworks.gsu.edu/kin_health_diss/7/
