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