Intra-Workout Supplementation: Increased Carbohydrate Oxidation with L-Arginine, Lower Fat Oxidation with Glucose & Lowest Rate of Perceived Exertion with Plain Water

Image 1: This bird certainly knows about the importance of adequate hydration ;-)

Have you been at the gym today? If so, what kind of beverage have you been sipping in the rest-periods between your sets, your sprints or during your regenerative (not fat burning ;-) "classic" cardio exercise? Was it Funky XYZ the latest and greatest intra-workout product on the market? If so, you better check out its ingredients, who knows maybe the "latest and greatest" turns out to be quite counterproductive towards the goals you have been setting after reading one of the last two installments of the Intermittent Thoughts? Let's assume you are the "Peter Griffin"-type of chubby - in that case, I hope that your Funky XYZ did not contain glucose, maltodextrin, waxy maize, or any other of the sugars of which the supp companies are going to tell you that they "superior" to the white poison your granny uses in her delicious muffins. Why? Well, according to a soon to be published study by scientists from the Massey University in Wellington, New Zealand, as little as 12g of glucose will reduce the amount of endogenous fatty acid (i.e. the stuff your body is using to hide your abs ;-) oxidation by -22%! Sounds terrible, doesn't it? Well, let's look at some details to decide whether those -22% will really make a difference and what effects the presence of l-arginine and l-glutamine in your intra-workout supplement could have had.

150 min @ 177 Watt + Glucose + (Glutamine or L-Arginine) = ???

Figure 1: Composition of the intra-workout supplement; sodium citrate base + 12g glucose (glucose) and additional 1g l-glutamine (Glu + L-Glutamine) or 0.1g l-arginine (Glu + L-arginine)

It stands out of question that adequate hydration is of utmost importance, when it comes to maximizing athletic performance (incidentally, the same is true, when it comes to "burning fat"). What athletes should drink before (pre-hydration), during (hydration) and after your workouts (re-hydration) is thusly one of the classic topics of exercise science and the recent study by D.S. Rowlands et al. is thusly probably #1001 on the never-ending list of investigations into the optimal mineral and nutrient composition of intra-workout drinks. For us, it is of interest, because it is one of the few which investigated the differential effect of the amino acids l-arginine and l-glutamine on substrate utilization, plasma glucose, lactate and sodium levels and rates of perceived exhaustion in eight male cyclists and triathletes during 150min (!) of cycling at 50% of the individually predetermined peak power (this is noteworthy, because 50% of their peak power equalled 177 W, which is not exactly "light" exercise), in the course of which the athletes consume 150ml of a fluid containing a 0.95g sodium base and either 12g of glucose alone or a combination of glucose and either 1g of l-glutamine or 0.1g of l-arginine (cf. figure 1).

Figure 2: Oxygen consumption (L/min) and substrate utilization (g/min) in 8 trained cyclists / triathletes during 150 min of cycling at 177W with 150ml of four different intra-workout drinks (data adapted from Rowlands. 2011)

As a seasoned student of the SuppVersity, it should not surprise you that the exogenous (i.e. from the outside) supply of glucose produced a -22% shift in substrate oxidation from fatty acids to the now more readily available carbohydrates (cf. figure 2). What you have probably not expected, though, is that the addition of the minuscule amount of l-arginine (which is btw. about what you will get with many of the proprietary blends in the still incredibly popular "NO-boosters") would promote this shift by increasing the total amount of oxidized carbohydrates by another ~10% over the 12g glucose solution alone.

Figure 3: Comparison of total / relative substrate utilization for the 12g glucose + 0.1g arginine, the 12g glucose and the water + sodium citrate groups (data adapted from Rowlands. 2011)

Now you are stunned, hah? So after all it is yet not your fault that you cannot see your abs. It's your NO-suppement! Well, not exactly. I mean take a look at the way I arranged the data in figure 3. You will probably acknowledge that the 12g glucose + 0.1g l-arginine group "burned" more energy - if you want it in calories (remember this is stupid ;-) 0.68kcal/min or 102kcal during the whole session and then come back to the -22% reduced fatty acid oxidation and lament: "But Dr. Andro, they burned 22% less fat than the water-only group! Now I know why I don't get lean." If that is your train of thought, I would invite you to continue the idiotic kcal number crunching and calculate on how much fat the poor l-arginine group would have missed to burn... well, it's the "exorbitant" amount of 170mg/min or - for the whole session 25.5g! While this may be more than one tablespoon of coconut oil, I guess you will probably admit that this probably is not the reason your abs are still covered by a thick layer of flabby adipose tissue, won't you?

Arginine reduces oxygen cost at the expense of glucose

Now, the real interesting findings of the studies are thusly not the changes in substrate utilization but rather the profound impact the addition of the two amino acids had on the lactate levels during the 150min of cycling (cf. figure 4) and the rates of perceived exertion (RPE).

Figure 4: Plasma lactate levels (mmol/L) in 8 trained cyclists / triathletes during 150 min of cycling at 177W with 150ml of four different intra-workout drinks (data adapted from Rowlands. 2011)

The latter (RPE), and this is actually quite surprising, were minimal in the water + sodium citrate group and maximal in the 12g glucose + 1g l-glutamine group (0.8 pts greater on a 0-7 scale). The RPE values of the arginine group, on the other hand, were only marginally elevated and that despite the significant increase in glucose clearance, which, by the way, has also been observed by McConell et al. (McConell. 2006) and Linden et al. (Linden. 2010). 

In view of recent studies such as Greer et al. (Greer. 2011), who observed a small, but statistically significant decreases in endurance during a strength training circuit in response to Arginine-Alpha-Keto-Glutarate (AAKG) supplementation, it is yet very unlikely that the observed effects of an arginine-enriched glucose containing intra-workout supplement observed in this study "have the potential to benefit endurance exercise performance" (which is what the scientists, much to my surprise, conclude). Another thing is yet more than likely, I would even say it is 100% certain: Neither the results of this nor of any future study will change the sales ranks on Bodybuilding.com & Co., where the purported NO-Boosters (and factual stimulants) still are the front-runners of the "TOP 10 selling products" ;-)