L-Arginine infusion increases glucose clearance during prolonged effort

Not entirely sure what to make of this one.

But for the record, from the American Journal of Physiology: Endocrinology & Metabolism, Jan2006, Vol. 53 Issue 1, p60-66, authors McConell, Huynh, Lee-Young, Canny and Wadley (from the Unis of Melbourne and Monash, btw) concluded that "L-Arg infusion had no effect on cycling exercise performance. In conclusion, L-Arg infusion during exercise significantly increases skeletal muscle glucose clearance in humans. Because plasma insulin concentration was unaffected by L-Arg infusion, greater NO production may have been responsible for this effect."

My personal conclusion would be that if you were thinking of 'infusing' yourself with L-Arginine for a specific performance boost, think again. Mind you, the test was only for a 15 minute 'all-out' effort and there may be benefits outside of that scope.

Why are we even thinking about Arginine? Well if you take a protein supplement you are probably already adding Arginine to your diet. It is an amino acid, one of the building blocks of protein and a known precursor of the gas nitric oxide. Arginine is a necessary part of the human diet and you could have a deficiency - but I can't tell and presumably nor can you without a blood test (unless you are displaying some clear signs of immune failure perhaps). It is implicated in hormone secretion, including a probable increase in growth hormone output (a good thing) and the removal of toxic waste products from the body (another good thing). It may have a role in boosting the immune system as well. Indeed, as a precursor of nitric oxide, a trigger for vasodilation, it plays a role in healthy sexual function and general circulation. That can't be bad for a cyclist, can it?

You'll find L-Arginine as a dietary supplement for the above reasons, plus its link to the regulation of salt levels in the body (and thus controlling blood pressure). So if you have a deficiency it may be worthwhile taking some - but don't expect miracles, don't take it unless you get good advice from someone other than me and don't take too much. Too much of anything is too much for me. Please remember I'm not medically qualified, I just bring things to your attention. And I race a bike.