Monday, September 3, 2012

Maximal Intra- & Post-Workout Fat Oxidation With Pause or 90min LISS Between 2x40min Incremental Exercise Bouts?

Image 1: You better don't even think about losing fat, while you cycle!
As a regular reader of the SuppVersity  you know that I don't believe in the idea of "working out to lose fat", at least not if that implies that you would actually try to burn the fat while you are working out ... yeah, right! I am talking about the hilarious concept of the "fat burning zone". I was still amazed, when I came across a paper that's scheduled for the October issue of Journal of Applied Physiology Nutrition and Metabolism (thanks to my friend Sean Casey from CasePerformance, who helped me out on this one) and investigates the effects of two different modes of what initially looked like a novel torture method and then turned out to be somewhat of a comparison of a twice-a-day cardio-workout, as you could perform it during a contest preparation to make weight and it's evil twin brother.

Train insane... and for nothing?

Enough of those metaphors, let's take a closer look at what the 15 healthy, moderately trained male subjects (age 27.4 +/-1; BMI 23.1; body fat 14.4%; fat free mass 63.7kg) were put through (note: all subjects performed both protocols in random order; see figure 1):
Figure 1: Outline of the study protocol; the two trials differed only with respect to the medial part, where the heavy group kept on working out, while the "light" group waited for their second incremental exercise trial.
I guess I don't have to tell you that the upper path, with the additional light intensity steady state exercise in-between was the "evil twin", while the lower one with "only" two bouts of exercise to the anaerobic threshold (when the respiratory ratio RER reaches RER=1) was the lullaby version.
Image 2: Train hard, but make it smart!
Parenteral, ... ah I mean SuppVersital Advisory: Please don't take any of the results or the whole discussion here as an incentive to perform either of these protocols on a daily basis for the rest of your life - especially if the only thing you are allowed to consume during and in between the trial which started at 7-8AM fasted is water (it should be said that this was an experimental necessity here, as everything else would have skewed the results). If you do, I can guarantee that you will be joining the rest of the pack who's sitting in your Dr's complaining about low thyroid, chronic fatigue, or whatever other self-diagnose people who don't want to admit to themselves that they are overtraining will be en vogue then.
So what do you expect the outcome did look like? No, wrong. None of the subjects collapsed... or at least the scientists don't mention that. And let's be honest it's not impossible. I know a couple of people who still believe they had to exercise the fat away who follow a similar protocol ;-) That said, let's see if that's even worth it - I mean do you really burn fat at all when you exhaust yourself like that?
Figure 2: Fat oxidation during the 40min incremental exercise bouts on the cycle ergometer at the beginning (Incr 1) and end (Incr 2) of the trial (data based on Chenevière. 2012)
As the data in figure 2 shows, the answer is straight forward: YES! You do. And surprisingly much, in fact. This is by the way partly mediated by the surprising effect the 90min of LISS had on the "fat max" exercise intensity which is now, in the 2nd incremental exercise trial (Incr 2) 60.9 % of the VOmax, while it is in the "low intensity" trial with the 90min PAUSE instead of LISS at 56.9%. This may sound bad at first, but if you can go faster without shifting to glucose as your preferred fuel this does obviously allow you to burn more fat - and that's exactly what the subjects did during the heavy trial: They derived 9% more of their total energy expenditure from fat and burned 34% more total fat minute per minute - that this would have been meager 8g even if they had been cycling at that high intensity for the whole 45min incremental exercise bout is yet further evidence of the futility of trying to "exercise the fat away"...

So if you can't burn it while you train, what can you do to burn more after you train?

By now, I guess I will have convinced all of you that you won't get ripped by burning an additional 8g of fat while you work out, but what about this EPOC thingy... I mean that "burn fat after you workout concept", what about that? Does it make sense to literally run around all do to make use of that?
Figure 2: Respiratory exchange ratio (lower values = higher percentage of fatty acids oxidized), lactate and heart rate after the second incremental exercise bout (Incr 2; data based on Chenevière. 2012)
Well, if we are honest, the post-exercise data collected right after the incremental exercise bout # (Incr 2, figure 1) is even more disappointing. Ok, the respiratory exchange ratio is minimally, yet statistically significantly lower, but the heart rate the exertion and the lactate levels are much higher. Plus, you cannot tell me that any sane individual would keep on fasting after this torture and in the very same moment you start eating your the "RER advantage" will be lost, anyway.

Image 3: These abs were not sculpted in the "fat burning one"! Click here to read the original article I used this image with, the "Fat Loss Support Routine" from the Step By Step to Your own Workout Routine guide.
So what's the bottom line, here? Aside from another primer on the fallacy of trying to do more, more and once again more, instead of simply getting your diet in check and sticking to it, to lose weight, there is actually a take home message you could derive from the results of this study: Let's assume that - hypothetically, of course - you got to make weight fast and still have more than enough time to recover after this quick weight loss fix before your performance must be back to it's usual heights. In a situation like this, and only as a short time intervention, the additional total energy expenditure during the 90min of LISS and the increased fat oxidation, combined, would make the "evil twin" protocol, with its 2x incremental exercise regimen interspersed by 90min of relatively light cycling in the fasted state, an option, you could even  improve on by replacing the 2x 45 min bouts with 2x20min of HIIT + 2x10min cool-down and guzzling some non-gluconeogenic BCAAs (max. 10g-15g / 45min) while you are putting yourself through this torturous regimen.

  • Chenevière X, Borrani F, Droz D, Gojanovic B, Malatesta D. Effects of 2 different prior endurance exercises on whole-body fat oxidation kinetics: light vs. heavy exercise. Appl Physiol Nutr Metab. 2012 Oct;37(5):955-64.